Don't Be Tachy!

This week I watched 2 surgeries: an on-pump CABG/Mitral Valve Repair and on-pump CABG. In this post, I am going to focus on the CABG/MVR.

To begin, two sections of the saphenous vein were removed endoscopically from each leg before Dr. Patel opened the chest (simply to make sure they are ready when he reaches the heart). This procedure is sometimes called phlebectomy, or ligation and stripping. A phlebectomy is also a surgical approach to treating varicose veins, enlarged veins in the legs, but in this case it is referring to the removal of the vein for CABG. Ligation is the process of tying off the greater saphenous vein, while stripping is the removal of the vein via a 1 inch incision near the groin area. Removal of a portion of this vein will not negatively effect the function of the leg or circulation. The blood that flowed through the vein will change its course (collateral circulation). The image below shows the endoscopic procedure of harvesting the vein.

Removing SVG endoscopically

This surgery differed from the last mitral valve surgery that I observed and discussed earlier in that it was a repair instead of a replacement. The patient's mitral valve was not diseased or damaged so there was no need to replace it, but the leaflets were not closing completely, causing regurgitation. Thus, the valve was repaired by inserting an annuloplasty ring. This ring brings the walls of the heart around the mitral valve closer together so the valve leaflets can close completely. The image below shows the procedure of finding the right sized ring and inserting it to surround the valve. 

Annuloplasty Ring Insertion

The second surgery I saw this week was a quadruple bypass. I have discussed CABG procedures in previous posts, but in this surgery, a large portion of the saphenous vein was removed and divided to use for three bypasses and the LIMA was used to bypass the LAD. Also, it was an on-pump CABG, meaning the patient was on a heart-lung machine. However, when weaned off the machine, the patient's heart was beating abnormally fast (tachycardia) and was not returning to normal sinus rhythm on its own. Dr. Patel had to shock the heart to control the arrhythmia and a pacemaker was used to ensure a regular heartbeat of at least 80 beats per minute. It was exciting to see the paddles put to use! (Of course, I don't hope for every patient's heart to stop or experience irregular rhythms, because that has bad implications...it was just cool to see it in real life rather than on a tv show)

Please feel free to ask questions regarding the surgeries! It can get pretty tricky to understand sometimes. More to come next week!

Week 3: Cardiopulmonary Bypass Machine

Hey guys! For my first post this week, I want to talk in detail about the cardiopulmonary bypass machine (heart-lung machine or CPB machine). This machine plays a major role in open heart surgery, and I think that by explaining how the machine works, you will have a better understanding of the process.

The CPB machine essentially consists of parts that assume the functions of your heart and lungs, and is meant to keep blood flowing through the patient's body while his/her heart is stopped during surgery. A surgeon may want to stop the heart for certain medical procedures such as a valve replacement to protect the heart from damage and reach a valve without major blood loss. This can be done by administering cardioplegic solution (high concentration of potassium) into the coronary sinus, a venous channel that empties blood from the coronary vein into the right atrium.

CPB Machine

The main parts of the machine are the oxygenator, pumps, and heat-exchanger (controls temperature of the blood). Venous blood can be taken from the body into the machine via a tube inserted into the right atrium, vena cave, or the femoral vein. A reservoir collects the venous blood, and it is passed to the oxygenator via tubing. The oxygenator allows for the exchange of oxygen and carbon dioxide between the blood flowing through it and the surrounding gas. It then travels through the heat exchanger which cools and rewarms blood, giving the surgeon the option to reduce or stop blood flow around the body since hypothermia reduces the body's oxygen requirement. From there, blood is pumped back via tubing into the femoral artery or ascending aorta to travel around the body.

Overview of blood flow through the CPB machine

The oxygenator, pump, and connecting tubes are filled with physiologically compatible fluid to avoid introducing air bubbles into the blood. Also, when blood comes into contact with foreign surfaces, such as those of the CPB machine, it will naturally clot. This can be avoided by administering heparin, the body's own anticoagulant, to the patient before blood enters the machine. Once the patient is taken off the machine, they are given protamine to neutralize the heparin and restore normal blood clotting mechanisms.

Hopefully this explanation was helpful, and you now have a decent understanding of how the CPB machine takes over the function of the lungs and heart. It is crucial in protecting the heart and allowing the surgeon to work in a clear, "bloodless" field during many open heart surgeries. In my next post, I will talk about the procedures that I will be observing in the next few days. Stay tuned!

Citation:
Heart-lung machines. Retrieved from http://www.surgeryencyclopedia.com/Fi-La/Heart-Lung-Machines.html

Figuring it all out

Today, I observed another CABG surgery, similar to the ones mentioned in previous posts. Dr. Patel used the left internal mammary artery to bypass the left anterior descending artery and the saphenous vein graft to bypass the obtuse marginal artery. However, in this case double sternal wires were used to close the patient's sternum after surgery rather than single sternal wires (pictured below). The double wires provide additional support.

Single sternal wires vs. double sternal wires

Each surgery is thrilling to watch from the first cut to the last stitch, and I am extremely grateful to be able to watch these open heart procedures. I am starting to realize what it is really like to be a cardiothoracic surgeon, from the crazy long procedures and work days to the fun conversations in the physicians dining hall and OR. Although it has only been two weeks, I have a much better understanding of the demands of the profession. Thankfully, my experiences with Dr. Patel have made me more excited to jump into the medical field. I am looking forward to the next nine weeks!

Week 2: The Beat Goes On

So far this week, I have observed 2 surgeries: off-pump CABG and a redo Mitral Valve Replacement (MVR).

The off-pump CABG on the 13th was the same procedure that I described in my last post. Dr. Patel exposed the heart and used a stabilizer device to limit the movement of the heart. Again, he used the LIMA to bypass the LAD and the saphenous vein graft (SVG) to bypass the obtuse marginal artery (OM). However, I did learn something new about this procedure this week. In order to bypass the OM, one end of the SVG must connect to the aorta in order for oxygenated blood to flow through. This requires making a hole in the aorta, a high pressure artery, while the heart is beating. See the problem? Dr. Patel used a device called the Aortic Cutter (pictured below) to make a precise hole in the aorta, and covered the hole with his finger immediately to stop blood from flowing out of the artery. He then inserted the seal (also, pictured below) which pulls upwards in the internal wall of the aorta. This creates an opening for the attachment of the saphenous vein without blood escaping from the hole.

Aortic Cutter

Seal

The redo MVR was an extremely complex procedure, and was hard to follow at times. The patient was experiencing severe mitral valve regurgitation, and therefore needed a new mitral valve. Since it was a redo surgery, Dr. Patel spent a considerable amount of time removing and working around scar tissue from the patient's previous surgery. During surgery, the patient was put on a heart-lung machine to protect the heart while replacing the valve. An incision was made in the right atrium and through the septum to expose the mitral valve, and it was replaced with a Pericardial Mitral Bioprosthesis (pictured below).

Pericardial Mitral Bioprosthesis

Week 1: Get Pumped

This was the first week of my internship with Dr. Patel, and let me tell you, it was the most educational and exciting week of the year. I got to watch three surgeries, and spend some time visiting patients and studying angiograms in Dr. Patel's office. But before I get into all of the details, lets go over the general anatomy of the human heart.

Here are labeled diagrams showing the pathway of blood through the heart and the four valves:

Valves in the heart (aerial view)

In short, deoxygenated blood travels through the Right Atrium (RA), into the Right Ventricle (RV), and up the Pulmonary Artery (PA) to the lungs to get oxygenated. It returns via the Pulmonary Veins (PV), and travels through the Left Atrium (LA), into the Left Ventricle (LV), and up the Aorta and circulates throughout the body. In the process, the four valves in the heart keep the blood flowing in the right direction.

However, sometimes the function of these valves can be compromised, causing a backflow of blood in the heart. A problem in the Mitral valve, for example, can increase pressure in the left atrium and consequently in the pulmonary veins. Increased pressure may lead to fluid build-up in the lungs which will then affect the pulmonary artery and the right side of the heart. So you can see how a problem with one component of the heart can affect its functioning as a whole.

On Wednesday, I got to observe my first cardiothoracic surgery in the OR! It was an Aortic Valve Replacement (AVR). In this case, the aortic valve failed to close completely after the passage of oxygenated blood, and some of the blood was flowing back into the LV, causing damage. This is called aortic valve regurgitation. In surgery, Dr. Patel performed a median sternotomy (cut through the sternum) to expose the heart, and once the pericardium was open, he put the patient on a cardiopulmonary bypass machine (heart-lung machine) and infused a potassium solution to stop the heart. This machine essentially acts as a heart and lungs, oxygenating and circulating the blood outside the body, while the surgeon replaces the valve. Dr. Patel removed the aortic valve and replaced it with a Pericardial Aortic Bioprosthesis. With the valve in place and the aorta closed, the patient was taken off the heart-lung machine and Dr. Patel closed with steel sutures in the sternum and Braided Vicryl in the skin.

Pericardial Aortic Bioprosthesis

On Thursday, I spent some time in Dr. Patel's office, learning how to identify calcified and blocked arteries on angiograms and meeting patients. It was very interesting to see how Dr. Patel diagnoses his patients and discusses treatment options with them.

Today, I observed two surgeries, a Thoracotomy and an Off-Pump Coronary Artery Bypass Grafting (CABG). In the Thoracotomy, Dr. Patel removed tissues from the lungs for biopsy. It was a very short procedure, lasting only 45 minutes. The Off-Pump CABG, however was much more complex and lengthy. Dr. Patel performed a median sternotomy to expose the heart and visualize the blocked portion of the coronary artery. He used the left internal mammary artery (LIMA) to bypass the left anterior descending artery (LAD). The LAD is the most important of the three main coronary arteries because it supplies over half the heart muscle with blood, so any blockage must be cleared immediately. He also harvested a portion of the saphenous vein from the calf to bypass the obtuse marginal artery, a smaller branch of the left circumflex artery. The open ends of the LIMA and saphenous vein are sewn to the openings in the coronary arteries to create an alternate pathway for blood to nourish the heart. The term "off-pump" means that the patient was not on a heart-lung machine and the heart was beating through surgery. As a result, Dr. Patel used a stabilizer device, as shown below, to limit the motion of the heart as he operated and was very careful when suturing.

Stabilizing device

Coronary arteries

The environment in the OR is very different from what I expected, but not too different from ORs in TV shows such as Grey's Anatomy (except, without the drama and spewing blood). There is always music playing in the background, and the doctors and nurses constantly talk about the craziness of their daily lives and make funny comments while operating. For example, on Wednesday, we talked for almost twenty minutes about bacon. Random, but hilarious. 

Although it has only been one week, I learned so much already! I am looking forward to the next ten weeks with Dr. Patel in and out of the OR.

Shreya

Introduction

Hi all and welcome to my blog!

My name is Shreya Patel and I am a senior at BASIS Phoenix. Since I have satisfied my graduation requirements, I decided to pursue a research project in my third trimester in order to graduate with high honors and explore what interests me. 

The medical profession is exhilarating, and I am excited to say that for the next few months, I will be observing cardiothoracic surgeries at my project sites: Banner Thunderbird Medical Center and Abrazo West Campus. I will also conduct my own experiment, evaluating the infection rates of Monofilament Polypropylene sutures, Monofilament Nylon sutures, and Braided Polyester sutures when sewn into chicken feet. The chicken feet, with their incorporated sutures, will be put under similar conditions of patients with delayed sternal closure after cardiac surgery. 

By the end of this project, I hope to gain a better understanding of what I would like to pursue in college and as a career. I am confident that my internship will expose me to the intense and gratifying world of surgery, and persuade me to strongly consider a medical profession. 

I would like to thank Dr. Patel for volunteering his time to teach me about what he does every day in the OR. With his help, along with that of my advisor at school, Mrs. Anderson, I know I can get the most out of this internship and the knowledge it has to offer. 

I will blog about my findings and what I have learned from each surgery twice a week. Stay tuned!

Shreya