Sunday, July 1, 2007

Electrophysiology Lab

At the EP lab, I had the pleasure to shadow Dr. Zacks while he performed ablations on the heart and installed pacemakers.  The first day I met him, he performed an ablation procedure on a mid-20 year old female who had recently discovered that she was prone to fainting due to a congenital heart defect.  Her heart had an accessory pathway (AP) between the right atrium and right ventricle that predisposed her to mild arrhythmias that interfered with her life-style.  Fortunately, the treatment was relatively safe so she agreed to have a few wires inserted into her so that the doctor could ablate the AP using high-energy radio frequencies.  In less than an hour, the procedure was over and post ablation ECG readings suggested that the patient's heart was functioning normally.

In my opinion, she was one of the lucky ones.  Sometimes the ablation procedures don't run so smoothly.  Take for example the case of an elderly patient that was being treated for atrial fibrillation.  In his case, the boundary between the arterial/venous tissue and the atrial myocardium were deemed as sights that promoted electrical conduction anomalies.  To deal with this boundary, the common procedure is to ablate circumferentially around the superior/inferior vena cava and the pulmonary artery and vein.  To my surprise, this procedure was incredibly difficult due to the lack of good engineering tools.  Although the doctor was assisted by a 3D model of the patient's atrium - mapped using an electrode - it seemed like he ablated most of the atrium.  According to an anonymous doctor, this is usually not uncommon because such damage to the endocardium does not compromise the function of the heart.  Nevertheless, one could use an ablation probe that could be adjusted to form a circle or some other shape. (Get at it guys! :)

Patients can obviously have other problems that can cause the electrical propagation down the heart to fail.  For those that have problems with their SA/AV node, the common procedure is to implant an electrical pacemaker.  Frankly, this procedure seemed very simple (this is a good thing).  Two wires with screws at the ends were inserted into the left subclavian artery and were attached inside the right ventricle and right atrium.  Following, the other ends of the wires were attached to a small pacemaker implanted in a sac near the patient's left clavical bone.  This procedure lasted about an hour.  

Catheterization Lab

In the Cath lab, I shadowed Dr. Wong while he performed angiograms and angioplasty.  From what I could gather, it was routine to do an angiogram on a patient to diagnose abnormal growth of the heart's myocardium, occlusions in the coronary arteries or regurgitation in the chambers. Often, while doing the angiograms, if a doctor observes that the vessel is occluded more than 60%, he/she will usually recommend the patient for angioplasty.  Apparently, most doctors prefer not to perform angioplasty on any occlusion since the stent used in the procedure can cause problems in the future.  Mainly, it has been shown that introducing a stent into an artery raises the risk of a clot unless the patient takes a drug such as Plavix for at least a year.  Nevertheless, if the stent is not flush with the arterial wall, the risk of a clot is very high.  As a result, most doctors will use unique high-pressured balloon to insure that the stent is flush with the vessel wall.  A few doctors will even use an interventional ultra sound device (IVUS) to visualize the lumen of the vessel.  

The IVUS seems like a good way to assess the placement of a stent, but it prolongs the procedure.  As a result, most experienced doctors will not use it.  I personally think the IVUS should be built into the lead that carries the balloon.  This would greatly improve the accuracy and long-term success rate of the procedure since the built in IVUS will allow doctors to visualize the lumen of the arteries while they implant the stent. (Get at it guys! :)


No comments: