Saturday, July 22, 2006

Electrocardiogram (ECG)

adapted from

So I gave a brief overview of Electrophysiolgoy last time. Now I will give a more comprehensive account of the electrical activity of the heart, including what medical electrophysiology aims to do in terms of monitoring and fixing the defects that sometime exist. As mentioned previously, the heart generates electrical pulses that originate in the SA node. The electrical pulse travels down throughout the atria causing the upper chambers of the heart to contract and push the flow of blood down through the tricuspid and mitral valves. There is an insulating fibrous skeleton of the heart that separates the atria from the ventricles where the electrical pulse would not pass through if it were not for the specially conducting pathway of the AV node and the His-Purkinje system. The electrical pulse is then able to conduct down into both ventricles causing the bottom chamber of the heart to contract and thus pushing the blood through the pulmonary semilunar valve and the aortic semilunar valve. Diagrams of both the gross anatomy of the heart and a schematic of the electrical conduction pathway are shown below for reference.

Heart Anatomy


Conduction System

adapted from

The primary component the the heart's electrical conduction is the action potential. The action potential describes the change in membrane potential that a cell (cardiac in this case) undergoes when it is sufficiently stimulated as is done when an oncoming electrical wave gets close enough. Use the simple diagram below as a guide to the following explanation.

Cardiac Action Potential

Most of the body's cells, cardiac included, have a resting membrane potential that is on the order of -70mV. This means that the inside of the cell is more electrically negative than the outside of the cell. This is achieved by the presence of ion pumps that constantly maintain this gradient by the active process involving the use of ATP energy. But this sort of details is not important. On either side of the membrane exist many different types of ions (charged particles). The distribution of Sodium, Calcium and Potassium are not equal, and the permeabilities of these ions across the membrane is carefully controlled. So for each ion, there exists a chemical gradient tending the push the concentrations of each to an equal value, and there is a electric force which will tend to push the voltage difference to zero. To keep a long story short, there is an equation derived solely to describe this phenomena – the Nernst equation. More about this can be read about in most any mathematically physiology book including Keener and Sneyd 1998. The first upstroke phase (depolarization) of the action potential is achieved by the presence of fast sodium channels in the cell. These channels are voltage sensitive and so when they reach a certain threshold value (to be correct its when the second derivative of voltage change reaches a certain value), they explode open and cause the voltage of the entire cell to rise dramatically. This is seen in the diagram as part 0 of the action potential. They subsequently slam shut, but not before the calcium channel open up as well, which tend to keep the voltage at a high level as can be seen in parts 1 and 2 of the action potential. The potassium channels have also had more than enough time to open up and this current flow across the cell membrane causes the voltage in the cell to drop back down (repolarization) to resting value, as can be seen in phase 3 and early phase 4 of the action potential diagram. Then a resting phase takes place where the channel kinetics are given a chance to reset.

It is important to note that not every part of the heart cell exhibits the same action potential shape. The SA node and AV node have a shallower initial upward sodium dependent slope. The entire action potential duration of the atrial muscle is almost half the size of the purkinje fiber action potential. These differences in action potential characteristics determine the differences in electrical conduction in these different parts of the heart. The shallower initial slope of the SA and AV node means that the adjacent cells will not reach their threshold value for rapid depolarization as fast as they would have meaning that the overall electrical pulse will travel slower in these areas. The SA and AV node are thus referred to as 'slow conducting' parts of the heart.

The characteristics of the action potential dictate the electrical properties observed in an EP study. Most of the time, doctors and researchers refer to the ECG, or electrocardiogram of the heart in order to assess the electrical functionality of the heart. While the action potential gives only very local information about the change in voltage across cell membranes, the ECG gives very global information. An example was given in the beginning of the blog.

The main parts to focus is the P wave, which corresponds to the depolarization of the atria, the QRS complex, which corresponds to the depolarization of the ventricles and the T wave, which corresponds to the repolarization of the ventricles. This global picture of the electrical activity in the heart is very useful to electrophysiologists. I think thats enough information for now, but in my next blog I will hopefully explain more what sorts of things an EP clinician can do.

Thursday, July 20, 2006

Week #3: Opposite ends of the spectrum

Another week in the trenches and a whole new set of cases that have been read in MRI. I think that my experience with Dr. Prince has been a bit different from everyone else's because my focus is on MRI, not speaking to patients and watching surgeries, but that doesn't make it any less interesting!

We're all engineers or at least aspiring to be engineers and MRI is a great example of how scientists and engineers can reshape the medical field. It can all be traced back to Raymond Damadian's original patent filed in 1971 and issued in 1974 (Pat. No. 3789832). Damadian's patent and several journal articles disclosed that he had discovered certain mouse tumors displayed elevated relaxation times compared to normal tissues. This Damadian hypothesized could be used in humans to identify diseased tissue from healthy tissue with much greater contrast than offered by X-ray and Ultrasound. This discovery combined with recent work in cryogenics made possible the construction of large super-conducting magnets necessary for MR-imaging in humans and thus MRI was born.

The story goes that Damadian and colleagues designed and built their own whole-body super-conducting magnet while at the State University of New York. Here is a diagram from Damadian's 1971 patent showing the MRI device that he had envisioned:

(Image taken from U.S. Patent and Trademark Office)

The first commercial scanner named 'Neptune' was installed at the Hammersmith Hospital in London and had a magnet strength of 0.15T (no that isn't a typo). The most common modern day scanner strength is 1.5T which provides many major improvements over the original 'Neptune'. With the involvement of large corporations like Siemens, GE, and Phillips, and collaboration in the medical research field, MRI has come a long way from the first human images ever reported.

As an interesting aside the 2003 Nobel Prize in Medicine was awarded to Paul Lauterbur and Sir Peter Mansfield for their contributions MRI (Lauterbur's contribution was the discovery that gradients in the magnetic field could be used to generate two-dimensional images and Mansfield analyzed the gradients mathematically). The Nobel committee snubbed Domadian, the pioneer and father of modern day MRI by not awarding him a Nobel Prize. Shortly after the committee's decision, Damadian took out expensive, full-page advertisements in major newspapers to protest their decision - the advertisement can be seen here.

The title of my post this week is "Opposite ends of the spectrum" and it comes from my experience last week of two different memorable cases. In the first case, the patient was 100% ignorant about his health and condition as well as why he was being subjected to an MRI. He had such a lack of interest in his condition and had no desire to help himself that he adamantly refused to be scanned. The second patient was the exact opposite, he was informed (both by the physician and through research he had done independently) and was eager to undergo the MRI to begin to fix the problems with his health.

It seems to me that the most difficult problem in the medical field is getting people to understand - and want to understand - their condition and treatment. From my experience in observing patients being scanned it seems that a majority of them have no clue what is being done or even why it is being done. I have found it rare that a patient has a firm grasp of their condition and treatment that they can have an intelligent discussion with the Radiologist or Physician about it.

In the first case, the patient initially agreed to the scan. The technicians setup the machine, put the patient into the scanner, and began to acquire images. Four minutes into the image acquisition the patient got agitated and wanted to get out the machine. While the cylinder inside the magnet is small, his movements were enough to ruin the images that were acquired. The technician operating the machine got on the speaker and tried to calm the patient down and convince him the lie still so they could finish the scan. The patient suprisingly agreed and they continued to scan.

One minute into the new scan the patient begins to move again and this time seems even more agitated than before. The technician gets on the speaker and tries to calm the patient down. Unfortunately this time he isn't successful. He seemed to have the opposite effect - upsetting the patient even more. The man became so agitated that he began to pull the inside of the scanner apart exposing the fiber-optic lighting system. At this point Dr. Prince decided to stop the scan and pull the patient out.

It took 15+ minutes and the assurance of the doctor, multiple technicians, a few residents and fellows, and some drugs to get the patient to agree to finish the scan. It took a lot of effort to convince one man to sit still for 5 minutes because it was going to benefit his health. After getting the coils realigned, and putting the patient back in the scanner, the technician was finally able to finish.

In contrast, the other case was as easy as it gets because the patient knew what is going on and also had a vested interested in following all of the technicians instructions. Unfortunately, most of the cases are more similar to the former than the latter.

I have learned that the sign of a good technician is someone who can communicate with the patient on a personal level to comfort them during the scan. This desired trait is opposed by the fact that operating a scanner is technically complex and generally best suited for someone who is computer savvy. In laymen's terms, the best MRI technician is a nerd with an amazing personality - this is a hard combination to come by. Sorry if that last comment offended anybody but we all know that nerds are generally socially inept and the inverse is true for socialable people.

Until next week, I hope you all had as good a time as I did observing patients and the weird things they do and say.

Week #2: The Transposition of the Great Vessels

I’ve been silent on the blog for a little bit because I have been putting together a post that doesn’t seems to end. Hopefully I’ll be able to get this all out in one breath – bare with me – here goes …

Week #2 has come and gone in a flash, but not without some interesting cases being read in MRI. I spent the week once again split between Cornell and Columbia Presbyterian Hospital watching my mentor, Dr. Prince, read a variety of cases. For example, we saw cases involving:
  • Dilated pancreatic duct
  • Kidney and liver transplants (pre- and post-op)
  • Multiple cases involving vessel stenoses and aneurisms
    • Renal artery
    • Common iliac
    • Femoral artery
    • Profunda
    • Superficial femoral artery (SFA)
    • and many more …
  • Multiple bypass grafts
  • Pancreatic carcinoma
  • Bicuspid aortic valve
  • Hepatic and renal cysts
I am quickly learning that a proficient radiologist must have a thorough understanding of human anatomy and physiology as well as insight into the pathology of diseases affecting all organs and tissues. The radiologist’s job can be boiled down to converting pictures to text in the form of reports, which gives the physicians a clear picture of the patient’s status. Even though a picture is worth a thousand words, it is the radiologist’s job to succinctly convey to the physician what is seen in the MRI and provide quantitative measurements of any observations.

Last week I introduced Contrast-Enhanced MRA and to a lesser extent MRI, which I hope you all are experts in by now. Instead of boring you with more physics and MRI techniques I thought I'd share one of the interesting cases I saw last week: Transposition of the Great Vessels.

Transposition of the Great Vessels is a condition in which the great vessels (the aorta and pulmonary artery) serving the heart are transposed. In a normal heart, the aorta carries blood from the left ventricle to the body and the pulmonary artery carries blood from the right ventricle to the lungs. In a patient with Great Vessel Transposition, the two main arteries serving the heart are switched forcing blood to circulate in only one of two pathways:
  1. Oxygenated blood (“Red” blood) is pumped through the left side of the heart to the lungs and back, without entering the rest of the body.
  2. Deoxygenated blood (“Blue” blood) is pumped through the right side of the heart to the body and back without entering the lungs.
This condition is as serious as it sounds because it destroys the body’s ability to deliver oxygen to the blood serving the entire body. Here is a diagram of the vasculature as it would appear in a patient suffering from Transposition of the Great Vessels:

This is a condition that babies are born with and amazingly, can survive with for a short period of time after birth because of special connections in a newborn heart and blood vessels that help to mix oxygenated and de-oxygenated blood. Generally, babies born with transposition are cyanotic – have blue colored skin, lips, and nail beds – because of low oxygen concentration in the blood.

The first connection present in newborn hearts is the foramen ovale or atrial septal defect (ASD), an opening in the atrial septum between the two atria. Here is a diagram of the location of the foramen ovale:

(Image taken from:

The foramen ovale is used during fetal circulation to speed up the circuit time of blood through the heart. Fetuses don’t use their lungs because they receive oxygen rich blood from the mother via the placenta through the umbilical cord. Blood can therefore be directed straight from the right atria to the left atria without a need to travel through the right ventricle and pulmonary artery.

There is a similar hole in the ventricles referred to as the Ventricular Septal Defect (VSD), which joins the right and left ventricles through a patent hole in the ventricular septum. Just as in the foramen ovale, the VSD helps to mix oxygenated blood into the predominantly deoxygenated blood in the right ventricle and aorta.

Normally, the foramen ovale (and VSD) closes at birth due to increased blood pressure on the left side of the heart. The baby as well as the doctors can take advantage of the foramen ovale to prolong life without the need for major surgery. In some cases where the foramen ovale has already closed, minimally invasive catheterization surgery can be performed to make it patent using a small inflatable balloon similar to balloon angioplasty; The procedure is called a balloon septostomy.

The third life-saving connection in newborns with great vessel transposition is a patent ductus arteriosus, a blood vessel that runs between the aorta and pulmonary artery. Here is a diagram of a patent ductus arteriosus:

As is the case with the foramen ovale, the ductus arteriosus begins to close shortly after the first breath. Generally, the ductus arteriosus completely closes four to ten days following birth. A small connection between the aortic branch and the left pulmonary artery remains after stenosis of the ductus arteriosus and is called the ligamentum arteriosum. Doctors can delay the stenosis of the ductus arteriosus by administering drugs such as Prostaglandin (Reference).

These three connections aside, no patient can sustain life with transposition of the great vessels because even with patent foramen ovale and ductus arteriosus there isn’t an adequate supply of oxygen to the tissue to maintain its viability, especially considering the added strain of the rapidly developing body.

There are two common surgical procedures used to correct for this malformation of blood vessels:
  • Mustard (or Senning) Operation – blood flow is corrected by transposing the pulmonary veins with the systemic veins.
  • Fontain Operation – also referred as the Arterial Switch Operation (ASO) – as the name implies this surgical procedure corrects the blood flow by de-transposing the great arteries of the heart.
Choosing the correct surgical procedure can be difficult because there are drawbacks with each. In the Mustard Operation, the procedure is much simpler surgically because veins are much easier to work with. The problem with the Mustard operation is that since the great vessels are still transposed the right side of the heart does the work of the left and vice-versa.

This becomes a problem when considering that each side of the heart performs a different job. The right side is intended to serve the lungs taking in deoxygenated blood from the systemic blood flow and reoxygenating it via the pulmonary arteries. There is considerable less resistance to flow in the right side of the heart and therefore the muscle is weaker than the left.

The left side has a more mechanically stressful job since it is required to push the blood throughout the body. From the start, each side of the heart is designed for different jobs and this means that ultimately the right side of the heart in a patient who has undergone a Mustard operation will fail under the intense stress of the muscle. These patients, whose hearts generally last for 20-30 years, will eventually need a transplant.

The Fontain or Arterial Switch procedure is more difficult surgically because the surgeon has to separate two major arteries (the aorta and pulmonary artery) from the ventricles and reattach them to the correct ventricle while also moving the coronary arteries, which are significantly smaller (1-2mm in an infant) and very important to proper heart growth and function. The pictures below show the patient’s heart pre- and post-operative. The X denotes the location of surgical stitches.

Normally the coronary arteries originate from the ascending aorta immediately distal from the aortic valve. When a surgeon is performing an Arterial Switch Operation (ASO), they must move the coronary arteries from the right side to the left so that the heart muscle receives oxygen-rich blood. To protect the coronary arteries, the surgeon removes a button of tissue surrounding the coronaries to aid in their attachment to the aorta. Here are two diagrams of the changes that are made during surgery:

Essentially, the surgeon excises the aorta and pulmonary arteries just above the valves and frees the coronaries (with additional muscle around it). Next, the surgeon sutures each coronary into place on the left side with fine precision (this can be seen in steps A-C in the first image above). The aorta is then moved into the correct position on the left side of the heart and sutured, above where the coronary arteries were sutured. Next, the two holes in the right side of the heart from the excision of the coronary arteries are patched with pieces of pericardium and the pulmonary artery is attached to the right side (as shown in the left of the first image above). Finally, the foramen ovale and ventricular septal defect are closed and the patent ductus arteriosus is tied off if open.

The surgery is complete but post-operative status is closely watched as complications such as bleeding, and/or myocardial infarction can occur. The patient who I saw this week was scheduled for routine scans to evaluate the condition of his heart. He had undergone a Fontain procedure as a baby and it is common for the patient’s physician to keep a close watch on the health of his heart.

(PAUSE for a quick breath) I guess I couldn’t get it all out in one breath. I hope that you enjoyed this case, I found it very interesting. Stay tuned for my next novel-length post coming soon!

Ben Hawkins: Week 3

Surgical Observations
I was able to observe two neurological surgical procedures this week, which were both fascinating.

Neurosurgery 1
The first patient was a 6 year old boy with a rare condition called Moyamoya Syndrome. The repair procedure used in this case is described in the link as EDAS (encephaloduroarteriosynangiosis). The syndrome is the results in poor blood flow to the brain, due to blockage in the lower skull. To restore blood flow to the brain, surgeons isolated the two arteries exterior to the skull, excised a section of skull near these arteries and sutured them into the dura (membrane surrounding brain, beneath skull). The excised bone was then replaced. This rerouting of arterial blood flow generally restores oxygenation to affected tissues. Particularly interesting was the manner of located the arteries to be rerouted. A device, termed "doppler" (essentially a sophisticated microphone attached to a speaker), is used to probe for the arteries. Through a speaker the surgeon hears blood flow and isolates the artery by sound.

Unfortunately, in many cases (as in this one) the first indication of the syndrome is stroke, and permanent loss of function often results.

Neurosurgery 2
The second surgery was extremely interesting from a device aspect. The patient, a mid-thirties male, had a cyst growing in his third ventricle. The cyst was discovered over 15 years ago, but was not of significant size to remove, and was asymptomatic. The cyst grew and now required surgical removal. Prior to surgery the patient was fitted with several markers (exterior) and scanned (using CT, MRI, etc.). Then, while in the operating room, a viewing machine was brought in which used stereoscopic imaging to track markers on the patients head and on various instruments that the surgeons used. The imaging was done using reflective spheres attached to various instruments and to the patient. Using a probe tool, surgeons indicate a location on the patients skull and the viewer showed cross sections from the scan in all three axes. The software (and tools) were from a company called BrainLab. In this way, the neurosurgeon determined exactly where create an access hole in the skull. The endoscopic tool used in the proceedure was also fitted with reflective markers, and the endoscope was guided into the third ventricle using only feedback from this tool. Once the endoscope was in the ventricle, a camera was inserted and the procedure was carried out using visual feedback from the camera, now on the tip of the endoscope inside the ventricle. The cyst was incised and drained using this technique. Unfortunately, in attempting to remove the cyst tissue, the patient began to bleed, and the choice was made to use gross, non-endoscopic, procedure to remove the remaining tissue.

Ethics Seminar

Inmaculada de-Melo Martin came and gave a one week ethics seminar to the class. The course discussed what ethics is and how it applies to research, ethical theories, historical case studies of human research abuses, the IRB, vulnerable subjects, the FDA, and stem cell regulations. For more information and powerpoints on the course, see this website

There were some technical difficulties during the first day of class.

Eventually the projector was set up and class began. After introductions, the ethics discussions began.

From left to right: Daniel, Evan, Vishal.
You can tell they are having fun.

Julius listening to the lecture and making sure that it ends on time.

Wednesday, July 19, 2006

Uche in Electrophysiology

Here Uche is observing a procedure for a pace maker implant.

Tuesday, July 18, 2006

Ben Hawkins: Week #3

NICU Rounds
Last week I reported on two patients with interesting conditions/cases. I would like to update their status over the past 7 days.

Patient A
Patient A came to the ICU with difficulty maintaining blood oxygenation. This condition was found (via ultrasound) to be the result of PDA (Patent Ductus Arteriossus). In order to receive treatment for the condition (a simple ligation of the shunt) he must have adequate strength to come off the high frequency oscillatory ventilation system and endure the conventional ventilation for the lenght of the procedure. Steroids and diuretics were administered to help the lungs drain and heal. (In addition to PDA there was significant atelectasis, or liquid closing of the alveoli). The steroid treatment was effective and the ligation was performed this week. Patient A recovered from the surgery and was extubated, he is now receiving nasal CPAP, and is expected to be discharged from the NICU soon

Patient B
As previously reported Patient B suffered from chronic lung disease. He has been treated for this, and is recovering. However, he has failed to gain weight and has several other symptoms of trichothiodystrophy. In order to confirm this diagnosis a complicated genetic analysis must be carried out, which would take a long time and cost a lot of money. Another test, examination of the hair by dermatology, to determine if the child's hair exhibits "tiger-tail banding" was performed instead. This test is not a conclusive positive, but if it comes back negative, then a simple lab test has avoided a more costly and expensive one. The test did come back negative, which leaves everyone still wondering why this child will not grow.

Greetings from the Paparazzi

A Day in the Life of Jun Wu

Before Surgery
Jun and his mentor, Dr. Karwoski, as they wait for the nurses to finish prepping the patient for a vascular surgery. The computers behind them have the patient's information and some controls.

A Busy OR

The nurses prepare the patient for a vascular surgery. Preparation for this patient is more extensive than usual.

<>Jesse and Another Surgery

Jesse can often be sited in this particular attire. Pictured left, Jesse washes his hands before entering the OR for another surgery with Dr. Tewari, his mentor.

The doctor and nurses prepare for a prostate removal. The procedure will be done with a robot, which is located in the far right side of the picture.

The nurse prepares the doctors instruments for him. The doctor prepares to make an incision in the patient's abdomen in order to insert a camera into the patient.

The instruments on the right front side of the table are the arms for the robot. The camera and various other tools and instruments are also on the table for the doctor.

The doctor makes the incision for the camera to be inserted. The screen behind the doctor and nurse shows the camera's view. There are several other screens in the operating room displaying the same thing.

A Trip to HSS

HSS has stricter regulations than WMC, so the camera was not permitted in the OR. Instead, pictured to the right from left to right, Daniel, Robby, and Flor.

Ben Hawkins: Week #3

Thoughts on doctoring...
I continue to attend the resident rounds in the NICU. I am continually fascinated by the methods doctors use. In many cases, decisions about patient care are made in the moment, based only on the most recent data, rather than observation of trends. The attending that I am observing, however, tends to try and base his medical recommendations on more statistical and evidentiary basis. He recently informed me that only 20% of medical decisions are outcome based, meaning that the statistical link between what doctors do and the results they achieve can only be statistically supported in 20% of all cases. I found this number staggering, but then began to consider the amount of information doctors have available and the system which they attempt to understand. In the laboratory, we are used to a completely defined system, or if not, we are used to being able to gather so much information that we can determine and effectively predict a response in every case. The body and its ailments are such complicated systems that it may be impossible to define them so strictly in an engineering sense, which leads to the approach that seems the most central topic of every presentation: homeostasis. Infants and premature babies have underdeveloped immune systems, and as such are not completely able to fight infection or disease. So doctors administer drugs to fight the disease (thats the simple first step), but the next step is managing the continuing status of the child so that it can grow to a point where it can fight on its own. This effectively helps the child to grow to the point where its immune system can understand and fight the ailment. The immune system is as complicated as the system it manages, and is more capable of responding to stresses than a doctor prescribing treatment; so in many cases doctors are reduced to managing symptoms and maintaining homeostasis in order to keep a patient alive until the body develops sufficiently to do what doctors can't. The other side of the coin are a large number of patients who have defects or problems that result in a child who might live, but not for long. Heart defects, genetic conditions, and many other conditions require intervention on the doctors part in order to preserve the life of the patient. But after the intervention, after the condition is ameliorated, its once again up to the body's own systems to heal and deal with the aftereffects. It comes down to this, in my opinion: the more information doctors have, the more accurate it is, the easier it is to access; the better doctors can do their job, whether its managing homeostasis for a recovering patient or intervening at a critical juncture. Diagnostic sytems, chemical test results, imaging techniques, and implantable devices all play a crucial role in the doctors job.

Does it fit?

Following the spinal surgeries I have been lucky to sit it on a total hip replacement and a shoulder stabilization. I am still completely facinated by the ability to perform surgery using the minimally invasive arthoscope. However, this is not what this post is about. During the total hip replacement and the spinal surgery it was aparent that it was necessary for the implant to be sized for the patient. The implant that would work for the 300 lb offensive lineman would not be ideal for my 125 lb grandmother. Despite this fact, implants simply are not customized for each patient, but sizes are available in the same way you buy small, medium, and large clothing. It is of course a more complex system than this however the implants are not custom made. This is one exciting aspect of tissue engineering. With the combination of 3D printing and complicated imaging techniques available customizable 3D implants are a possibility. My time with Dr. Potter has introduced me to software being developed to segment out anatomical structures such as cartilage, the intervertebral disc, and the meniscus from the MRI images. This would be advantageous as the patient needing the implant could have and MRI image taken of them and the tissue needed segmented out and a patient specific implant made for that particular patient. It would be possible for high risk patients such as athletes to have a scan on file so upon injury a model of the needed tissue could be constructed from the MRI image. From this step, a 3D printer could be used to print out the new implant and then implant this back into the patient. This was an exciting tie in between the surgeries and time in radiology. For my particular application, it is necessary to know the ideal pulse sequence to obtain the contrast necessary between the IVD, endplate, and bone. Today I met Dr. Herzong who has been dealing with the IVD for 20 years. I hope to get to talk to him again and pick his brain about what he would view as an ideal pulse sequence for such an application. The ability to produce patient specific implants in my opinion would dramatically increase the success of these implants and revolutionize the industry.

BME 2006 Summer Immersion

Third Week

This week I started branching out a little more into surgeries. In cardiology I saw a pretty good example of a stint being put in. This was more impressive because the block was so bad that on the monitor I could even see where the issue was. They send a dye through the blood, into the heart, then image the dye. This gives a quite impressive view of those blood vessels. In this particular patient It was clear that there was a part of the heart where the blood vessel got really thin, then thick again. Even before having it pointed out I was pretty sure this was the problem area in the heart. Sure enough they send in the stint, and inflate it right where I expected. The differences between before and after the stint were pretty impressive. It went from impeded blood flow, to what looked like normal blood flow.
Other surgeries I watched were a kidney transplant, and bladder removal. The kidney transplant was actually pretty much what I would have expected, although it was the first open surgery I had seen. The bladder removal was a bit more unusual however. After removing the bladder using the Da Vinci robot they took the robot out, and pulled out a section of colon through an incision in his stomach. They then cut out an approximately 4 inch section of this, sewing back together the colon then going to work on the section. After perhaps two hours of sewing(this was a seven hour operation) they construct a"bladder" and sew it into the spot the bladder previously was. Apparently it functions much as a normal bladder.

One of my two projects is essentially done at this point. It was less that I solved the problem, and more that I found someone for which it was hardly a problem. This is the testing of radiation levels
from the CRT display on the robot. Apparently if a crt display has been tested for X ray emissions it should have a label saying it complies with the code of Federal Regulations (CFR), Department of Health and Human services (DHHS), 21 CFR 1020.10. I searched the robot for this label, nothing. This means it is unlikely it was tested for radiation emissions. Of course this is probably because it rarely is an issue, however since the doctor holds his head so close to the display, so long I can understand why he would want to be certain. I was searching the internet looking for an appropriate meter to measure these emissions when it hit me that there must be a radiation safety guy with the gear to measure X rays. Sure enough, I found a physicist by the name of Chris Saganich who seems to have the proper equipment, and is willing to test the robot. That should happen by the end of the week.

The second project has me more confused. As it stands right now I have a 10mm diameter stainless steel pole with a lens at the end that needs heated. This pole has to fit through an 11mm port that is stuck in the patient. I have found some heaters that are 10 thousandths of an inch wide(1mm is about 39 thousandths). However after emailing multiple vendors I am reasonably certain there is no such heater made from materials intended for surgery. I have found some that are teflon, which appears to be rather biocompatible. However, are they really? To be honest I have no clue how to go about testing the safety of any materials that the company did not intend for the use in surgery or similar biomedical applications.
So, with that remaining 29 thousandths of an inch (19 if I wrap the heater around) I need to find some way to encase the heater so it doesn't present a risk. My first thought is to just tape it on. This is pretty temporary, but I may be able to do a proof of principal experiment like that. For perminance I would need to construct something like A stainless steel sleeve. However I have done enough machining to not envy the job of making a tube with ten thousandths thick walls.

My Campus to Campus

I am so glad that you have tuned in for another thrilling episode. Let’s first start by saying that last week was a short one. I was here from Monday to Wednesday evening, when I left for a gruesome trip back to Ithaca. As I left Olin, to catch the bus, it was storming like crazy. There was heavy rain and electricity in the air. As we left, I was thinking that this was going to be a long trip. Sure enough, a few blocks down was some of NYC’s finest, bumper to bumper traffic. The bus driver was insistent about continuing on down the same path so by the time we were out of traffic; I had whiplash and nausea. Upon arriving in Ithaca after about a 6.5 hour trip, I was starving. After grabbing a quick bite, I immediately began working on my daughter’s bedroom. There was a 5 drawer chest with my name all over it. I finished at about 3 AM. I grabbed a few hours of sleep and was off to the lab. My goal for my time in Ithaca was to run 3 experiments to complete my data set for a potential paper. 2 of the 3 went as expected but some monkey threw a wrench into the other experiment. So, after a superficial analysis, the paper is still moving forward but we will have to see what the data has to say.

Rewind: The “Fat Lip”

During this week, there was more of the same and a few once-in-a-lifetime cases. The first was a severe case of the “fat lip.” This patient was seen by a general practitioner as she had a really fluid-filled lip, a fat lip. There were no obvious culprits as she had received no trauma to the region of her face. This case seemed a little “fishy” and I am sure that the first doctor thought of domestic abuse. Well, it turned out to be much more serious. After CT and MRI, it was determined that the patient had an AVM in her lower lip. You can look back to my previous blog to refresh yourself on AVMs. The treatment for this AVM was embolization. It is hoped that the lack of blood supply will result in shrinkage of the surrounding tissue. If not, an option to be excision by a surgeon in Plastic surgery.

Neck Mass

The next interesting case was a neck mass embolization. This patient, located at Memorial Sloan-Kettering Cancer Center, presented with a complication from a C3-c5 fusion. Sometime ago, this patient was in a bad car accident and suffered from whiplash. This incident caused a crack in one of the vertebrae resulting in the fusion. This fusion was done with the aid of a titanium cage and screws that would allow the bone to the metal structure that was in place for support. That operation was a total success. After sometime at a post-operative check-up, the physician noticed some swelling and tenderness. After imaging, the patient was informed that a tumor was growing around and through the metal cage that was implanted to fix his broken neck.

Our job was embolization. Surgeons at Sloan-Kettering were going back in to remove everything which included all metal implants and the entire tumor. Without embolization, chances were very high the patient could bleed out before the surgeons were through. The patient was embolized, using polyvinyl chloride beads, successfully with few complications.

Well, stay tuned for the next episode. We have several interesting cases on the docket for this week. After three weeks of this, I am pretty comfortable and confident watching most procedures and operations. I have read up on and watched the most common cases several times. I find myself explaining to the newcomers just as people helped me before. I am totally enjoying the experience and can't wait for more.

Image of the Bottom Lip AVM (The "Fat" Lip)

Monday, July 17, 2006

3rd Week and it Feels Like Home

So the third week of the summer immersion program has just wrapped up, and the Weill Medical School is beginning to feel like home (a home away from home), but still a home. This feeling of being part of the hospital stems from the daily interaction with the residents on the 8am rounds in 4 North, the group of clinicians that I interact with on a daily basis where we read MRI, CT, SPECT images, and the nurses that recognize me in the different departments where I observe the procedures. The hospital has become a routine to an extent, but each day there is something new to learn and there is always a new experience to be had, which is the main reason that it keeps this job interesting.

Monday and Tuesday were relatively quiet and non-eventful. I started the days off in the cardiology division of the hospital with rounds with the residents at 8am and then moved on to meet with Dr. Weinsaft and read MRI images. Tuesday had something new to the standard MRI images because we had another clinician that joined us and was looking at the lungs that are in the field of view while you image the heart. By looking at the lungs, the clinician was able to diagnose and pick out small nodules that could potentially be lung carcinoma and warn the patient/physician of these growths. Additionally, this same clinician pointed out to me that you can also see variations in the bone structure and can diagnose problems (such as slipped disks which the patient didn't know they had) and then help treat the condition.

One dramatic image from Tuesday was that a patient came in and had a CT scan done and had been complaining of chest paint amongst other symptoms. The patient was also diagnosed and treated for prostate cancer earlier (which I learned from his medical records) and the CT confirmed that the prostate cancer had begun to spread into the liver and bones (bone pain was another symptom that the patient had complained about). The cancer was readily observable on the CT images especially in the liver where normal tissue appeared a light grey, while the cancerous tissue was spherical and dark. The patients heart turned out to be functioning correctly, but from the CT he had to be informed that his cancer had spread. I don't know how much longer the patient had to live, or if he was going to undergo radiation therapy, but the power of the CT scan demonstrated that many of the diseases that a patient has cannot always just be observable from the outside. The technology of the CT machine allows a very rapid way to image the human body and find where the problems exist without having to use invasive procedures.

Wednesday and Thursday began as the other two previous days had, with rounds in 4 North, some more MRI/CT image reading. On Thursday I had a meeting with Dr. Weinsaft and two other doctors that were involved on a paper that had just been submitted to the American Journal of Cardiology. This paper is currently under review, but the project that I am working on builds off of the previous paper. We met as a group to discuss what I had been doing with the database analysis and setup a time where I could work with one of the clinicians to begin tracing the cardiac MRI images that had been acquired. From my database analysis I had found 19 patients that had a normal heart, but their left ventricle walls had increased in size and mass (this can be caused by high blood pressure, genetic predisposition, and coronary heart disease). In the coming week I will take this group of patients and with the help of another clinician begin on generating numerical values that can be used in the statistical analysis to compare against the data that was obtained for the paper.

Friday was a bit different; instead of starting rounds in 4 North as I had been doing for the last two weeks, I headed down the E 55th St MRI building that houses two more MRI machines in the basement of the building. This building is more a clinic rather than a hospital because many patients do not like to attend a hospital to receive treatment. I spent the day observing MRI images, not just of the heart, but also of the brain, the breast, and lower lumbar regions. Each region of the body has a different way in which it is scanned and there is a different program that is used to generate the image. During this time, two graduate students of Dr. Wang's were present and were also running their algorithm on the patients to determine if their imaging programs functioned. These images then could be compared again the images that are currently being used. One thing that I did realize when the patients got off the MRI table was that they wanted their results automatically and the technicians could not tell them what they had found since they were not specialists nor had the power to diagnose what the patient had. However, while the patient was in the machine, the technicians were readily able to pick out what was wrong with the patient (wall abnormalities in the heart, spread of cancer from the breast, aneurysm in the brain), because of the countless scans that these technicians do on a daily basis. Although the technician knows what they see, they cannot let the patient know anything because it brings up the potential of a malpractice lawsuit for a misdiagnosis where a person that is not legally qualified to diagnosis a condition voices their opinion.

Therefore this third week at the medical school has begun to feel like home and although it is becoming routine (with rounds and reading images) there is always something new to observe and a new case that can be examined, so you'll hardly get bored.

Vishal's Third Week

This week I returned to observing Dr. Wong in the Cardiac Catheterization labs. Monday was a slow day, and I only observed one patient receive a stent in the proximal LAD.

On Tuesday, things picked up again, and I saw Dr. Wong perform surgery on a 71 year old female to start. One stent was inserted into the mid right coronary artery (RCA), marking the first time I have seen them work on the right side of the heart in the cardiac catheterization labs. Another stent was inserted into the proximal circumflex. On that day, I also learned about the numbers the doctors shout to the nurses while they are inserting the stent. If they say something like “12-15,” it means that they are inflating at 12 atmospheres of pressure for 15 seconds.

In another interesting case, I saw the doctors inject nitroglycerin into a vessel, which succeeded in reducing the blockage. Dr. Wong explained to me that nitroglycerin relaxes smooth muscle, which in some cases can open the blood vessel on its own. The nitroglycerin did not work in another vessel, so they still inserted a stent into the mid/distal LAD.

I also spoke to Dr. Wong and Dr. Minutello about another possible project. Stent fracture only seems to happen with very long stents. Dr. Wong and Dr. Minutello would like to know if there is a fluid dynamics/hemodynamics explanation for this. However, Dr. Minutello needs to find a way to extract the necessary data. I have also looked at some papers on the subject, and have found that complete physical modeling of hemodynamics is very complicated for the following reasons: (1) Blood flow is pulsatile (unsteady), (2) Blood is Non-Newtonian and inhomogeneous, (3) Blood vessels have some elasticity, (4) Blood vessels have complicated geometry, (5) Some regions of flow are turbulent. Thus, this study would greatly benefit from an in vitro experiment used to gather empirical data.

The last patient I observed on Tuesday was a 77 year old male who had 4 existing bypasses. Dr. Wong first checked to see that all the bypasses were functional through angiography. The bypasses were all fine, but there was a blockage in a native artery. In observing the bypasses, the doctors had injected a significant amount of contrast agent into the patient, so they decided to wait until Thursday to insert a stent.

On Wednesday, I saw Dr. Winchester again, who arranged a meeting for me with Dr. Weinsaft (Jan’s Mentor) to see if he could help me to find a more active project. Dr. Weinsaft said that he would have some work for me to do on Monday.

On Thursday I saw the patient from Wednesday return and receive his stent. Friday was another generally slow day. I saw a 66 year old male receive a stent in the distal circumflex.

A Brief Description of Intravascular Ultrasound (IVUS)

In IVUS, long thin catheters are inserted into vessels and connected to computerized ultrasound equipment. These catheters are of elaborate design, making IVUS relatively expensive. The sound signal is sent from within the blood vessels, allowing visualization from within vessel out through the surrounding blood column, including the inner walls of the vessel. The main advantage of IVUS is the ability to detect atheroma, abnormal buildup of macrophage white blood vessels, which also leads to heart attacks. Most frequently, angiography and IVUS are used in tandem. An example of an IVUS image taken at New York Presbyterian Hospital, with patient identifying information removed, is shown below.

Sunday, July 16, 2006

3rd week- Hospital for Special Surgery

Surgeries at HSS

After all, besides shadowing my clinician at the neuropathology center, I am also part of the summer program at HSS. At the beginning I was very confused and I want to apologize to Yi Wang, if I gave troubles to him, but I didn’t understand either what was happening. Anyway, now I am happy to be able to attend surgeries and meetings at the HSS and learn about neuropathies.

This week, it have been amazing because I was inside the operating room observing the way that doctors, nurses and technology works together for the same goal. My impression after this week is that the human body is more resistant than I have thought and even though science is being developed continuously, I see that still there are many methods that could be improved. In my opinion, surgeons have to take to much bone away, or the oppening that they perform is very big, so is harder and painful for the patient to recover. Endoscopies, seems that have been the solution that allow minimally invasive surgery, but it can not be applied to all types of surgeries.

The surgeries that I attended were:

Spinal Surgeries

Lumbar spinal decompression:

This surgery was kind of hard to see because doctor, fellow and resident were working on the patient, basically they removed a portion of the bone or disc to give the nerve root more space. The surgeon has to be very careful, because as can you imagine, if the spinal cord get damaged while they are removing the bone and lamina close to it, the effects on the health could be irreversible. It was a great experience to see the spinal cord just 20 cm from me. In Real!! No in pictures!

Spinal fusion:

After the lumbar spinal decompression, we observed part of a spinal fussion. The goal of this surgery was to obtain a union between two or more vertebrae. This involve placement of a bone graft between the vertebrae and the use of two screws to hold them together.

During these surgeries the doctor consults the MRI and the X-Ray slides frequently.

Shoulder stabilization

In this operation they use arthroscopy so we were able to observe on the screen with the doctors what was going on inside the body. But I should said, that even though they use this technique, three small holes were performed in to the patient's shoulder, and at the end the shoulder was very swallen.

The aim of the surgery is to tighten and repair the shoulder joint, that has been loosen. They try to reattach a torn tendon back to the bone.

anterior cruciate ligament

Robbie explained to me this surgery: there is a ligament anterior cruciate ligament (ACL) that connects the thighbone to the shinbone. Sometimes this ligament is torn. In the surgery the doctor replaced the damaged ACL with healthy tissue taken from the patellar tendon of the patient. So, I observed how the surgean opened the knee, go through the skin and took out the ligament. But with endoscopy the access to the tore acl.

Tiny Conclusion

This surgeries were very interested, and I can see how the body works in a same way that a perfect machine, which parts can be broken or damaged and we should to repair them or either change them.

The succes on results that a patient can have, in order to improve not only depend of the success of the surgery but the rehabilitation factor is very important as well.

Summary what I did.

-Shadow doctos in neuropathology center.
-Attending Surgeries.
-Lookin on the internet about possible failures of a hip implant.

3rd week report

Monday, 07/10/06, P710A and M014

•Clinical room(M014): The previous Spanish speaking lady visited again and did the follow up today. She is the 1st patient did EVLT on last friday. Because her vessel to be operated is very close to the nerve, to avoid the nerve burning, Dr K lowered down the output of the laser from 70 mw to 25 mw by decreasing the operation time and something else(I guess the power output). Today's feedback from the clinical check is that there is no pain in her leg, which means the nerve around the vessel is not hurt. Her leg still has some swelling and it's the normal phenomena after the EVLT surgery. Dr K aksed her to check again after 1 week to make sure that the swelling would go down.

There is one small trick for the EVLT surgery. Because the vessel to be operated is very close to the skin, so there is chance that the skin would be burnt. So the doctors of NYPH vascular surgery developed a pre-treatment so that the skin would not be hurt. Before the laser was applied, the saline would be injected into the tissue around the vessel so that the vessel could be seperated from the skin. Then the laser would not hurt the neighbor tissue and skin. The hurt is possible because there is burning smell (not much) after starting the laser, which means the laser is still strong. Nornally the volume of the saline would be around 500 ml and the Duplex Ultrasound would be used to monitor the the injection effect: the distance of skin and vessel. Form the image of ultrasound, I could find that the distance between vessel and skin is greatly increased, form 0.3-0.4 cm to around 1.5 cm. Dr K told me that the injection effect is very good and there would be huge difference if there is no injection applied. The injection process would normally cost the doctor about 20 mins.

Here I want to say something more about the Duplex Ultrasound. It has been widely used by the vascular surgery department. The surgery department has a whole Ultrasound team, several technician and one director. For every first time visiting patient, they have great chance to be requested a ultrasound test after the surgeon's check. The untrsound will confirm the blood clots becasue it could detect the flow of blood. If the blood flow is weak or there are reflux blood flow, it means that the following part of vessel is blocked. The ultrasound detector will work with the existance of some kind of special gels. The tecnichian does not know the composition of the gels.
The following is a picture of Duplex ultrasound machine:
•Office(P710A): Dr K and his secretary, Rachel, worked on the patients' bill, I do not know that’s for one week or half month. It seems that they have to do some simple calculation.
After that, they would mail out the bills via the surgery department.

Tuesday, 07/11/06, M014

•Patient1 is a 80 year old lady. She came to have a check for her leg. It seems that one of her legs has clots inside by feeling the pulsation of the vessel and ultrasound results.

•Patient 2 is a 44 yr lady. She has the vessel very close to the skin, some of them are on the skin surface and she wants to use the laser to remove them. Dr K suggested her to do cosmetic surgery. However, the insurance company will not cover cost.

•Patient 3 is a Russian lady. She had a stent/balloon surgery one week ago. Now she came back to have a chek. Before surgery, her leg is very cold and dark. After surgery, the leg seems a little healthy. Her daughter helped her as the translator. Her leg is severely swelling last night, but now it reduced a lot. Dr K used a marker to draw the red part of the leg so that he could compare it. The lady need to be watched again for 2-3 days.

•Patient 4 is an old man. He is very strong and talktive, however I believe the doctors would not like some of his sharp words. He kept walking 4-6 miles everyday and he has some vessels on the leg surface. Anyway, they are nothing to do with his health.

•Patient 5 is an old man. He has long time smoking history and parkinsen disease. When he walked, he would feel pain quickly. His wife helped him to express the symptom. Dr K checked his leg pressue and feel very weak pressue in his both legs, which means that his legs are blocked by the clots. I guess that he need the stent/balloon surgery.

•Patient 6 is an old man, she has some wound on the leg surface, Dr K and the nurse cleaned it and changed the bandage

•Patient 7 is an old man after amputation. His right leg was cut and left foot was cut too. It seems that he recovered well and he talked with Dr K about Yankee. He said he would come to watch the game in future

•Patient 8 is an old man. His legs are fine, no any bad symptom. Dr K suggested that he should have a back (spine) check according to his medical history

•Patient 9 is a middle age woman. She came to have a check for the leg wound

Some techniques for the diagonose: Using hands to feel the pulse of leg and it normally could find the SFA clots
•Nurse: Jorce

Wednesday,07/12/06, OR10
We watched 2 surgery today and thanks Rachel a lot for taking the picture.

The 1st surgery is for stent implant. A stent was applied to the vessel and a balloon was used to help the stent to expand completely.

The 2nd surgey is for filter removing. The filter was used to colltect the flowing clots in the blood vessel and it could be removed from the vessl by inserting a wire with a small hook at the top. The filter itself also has a hook. When the filter passed the wire, it would be hooked, then the surgeon could take it out. It's a little painful when the filter was removed out of the vessel.

Thursday, 07/13/06, OR10

Besides watching the surgery, we continued to think about the stent fracture detecting problems.

Friday, 07/14/06, M014

Today we watched about 20 patients.
Here I want to discuss something about the difficulty patients.
The most of the patients are fine. However, I think we met two patients who are not very nice. It happened before although the percent of happening rate is 5-10%

For the relationship between patient and doctors, from my observing, most of patients of Dr K are very nice(around 90%). Dr K did his job well and he could deal with most of difficulty cases, he would tell the patient the truth of the disease. He tried his best to relieve the patients and make them happy.
For most of the patients, they would tell the doctor the detail of the disease and follow the suggestions of Dr K. They would ask questions if they are not clear about the answers.

However, some patients would think it's the doctor's fault if the doctor could not treat the disease or make a unfavorable prediction of the disease. For example, a lady around 80, her leg is painful and Dr K told her that there is some chance that she would lost her leg in future. And for the pain, it's not easy to remove it. She visited Dr K for 3 times, today is the 3rd time, every time she spoke sharply and I believe the Dr K felt embrassed/ unhappy in his heart. She likes to compare other doctors with Dr K although she even did not visit some of them.

To be frankly, Dr K did not show any unhappy directly, he did his checking well and he explained to her in details. He kept smile evern facing the rude words. I doubt that whether I could do that like him. I think the long time medical training is helpful.

Also Dr K is a good surgeon, I have no doubt that he would be one of the best in this area. But it does not mean all the other doctors are good enough. There is the chance for mistreat or some doctors do not have good enough personality.

If you have interest of it, you could share your opinion with us .