Jan 29, 2019
Jonathan Haft, MD discusses PTE (pulmonary
thromboendarterectomy) surgery, which is the potentially curative
operation offered for some patients with chronic thromboembolic
pulmonary hypertension (CTEPH). Dr. Haft has been the director
of Michigan’s internationally recognized ECMO program since 2005.
He is also the Associate Director of the Cardiovascular Intensive
Care unit, and is the Chief of Cardiothoracic Surgery at the Ann
Arbor VA Hospital.
My name is Jonathan Haft. I am a physician and cardiothoracic surgeon. I practice at the University of Michigan in Ann Arbor. I've been in practice since 2005.
What I'd like to talk about today is pulmonary thromboendarterectomy, which is the potentially curative operation offered for some patients with chronic thromboembolic pulmonary hypertension. I'd like to talk to you a little bit about the indications for surgery, the operation itself, and then the typical recovery period.
Patients that have chronic thromboembolic pulmonary hypertension have symptoms of breathlessness, exertional intolerance, and often times this leads to an echocardiogram. An echocardiogram or an ultrasound of the heart will identify that the patient has pulmonary hypertension.
The next step is typically a V/Q scan or a ventilation–perfusion scan, which will identify that there are areas of the lung that are under perfused, that there is relative obstruction to blood flow within the lungs. Once we have established that the patient has pulmonary hypertension and that the patient has an abnormal V/Q scan, the next step in testing would be a pulmonary angiogram; where a catheter is inserted through a vein, often a vein in the neck or a vein from the lower extremities, and advanced into the arteries of the lungs, the pulmonary arteries and dye or contrast will be injected to create a roadmap of the blood vessels into the lungs. This test, number one, will tell you if the patient has evidence of CTEPH and most importantly, will identify if the patient is potentially a candidate for surgical removal of these obstructing clots.
When I evaluate a patient in my office, there's a number of factors about the patient that we consider whether or not they could benefit from a pulmonary thromboendarterectomy [PTE]. The first is that the patient actually has physical limitations from the disease. The operation itself is invasive and carries risks of complications, and we want to be certain that the operation is being performed with the intent of improving the quality of their life. So, we want to be sure that the patients actually does have some physical limitations; they've noticed that their physical capacity has declined, and therefore the patients quality of life has declined, and they're interested in pursuing with an aggressive strategy to improve their life. We want to be sure that there is substantial burden of obstructing clot that would be surgically accessible.
If we think about the circulation to the lungs, there is the main pulmonary artery, that's the artery that exits the heart that is delivering blood to both lungs. Then there are the branch pulmonary arteries, one for the right, and one for the left. Then there are the lobar branches heading to the upper lobe, the middle lobe, and the lower lobe. There are the segmental branches, heading to the 10 segments that are present in each lung. Then there are a multitude of subsegmental branches beyond the segments.
For the most part, when patients have substantial obstruction that originates at the level of the segments, the segmental level, an experienced surgeon should be able to access that obstructing material and therefore the patient would be a reasonable candidate to proceed with pulmonary endarterectomy. But again, it really depends upon the imaging, and being able to identify the extent and location of the obstructing thrombus, as well as the experience of the surgeon.
The last factor when we evaluate a patient is the patient themselves. Is the patient going to be physically able to withstand an extensive open heart operation? If the patient is too old, or has too many other medical problems, then they may be more at risk of suffering complication.
Let me walk you through the operation, how it's performed, and then we can talk about the postoperative recovery.
The operation is open heart surgery, so again we expose the heart and the blood vessels of the lungs through an incision in the breast bone, we call it a median sternotomy. It's a vertical incision through the breast bone. Obviously, the patient is under full anesthesia and is unaware what's happening during the operation. Then what we do is place the patient on the heart-lung bypass machine, or cardiopulmonary bypass, by placing catheters into the superior and inferior vena cava. Those are the big veins that drain all the blood from the upper and the lower half of the body. We also place a catheter into the aorta, and that's to infuse the blood. Therefore, bypassing all the blood that would normally travel through the heart.
Now the patient is on the heart-lung bypass machine, we can then deliver what we call cardioplegia. It's a cold preservative solution that goes directly into the heart and it induces cardiac quiescence, so the heart is not moving. Under those circumstances, we can now open up the arteries that are traveling to the right and to the left lung, to see where the obstructing clot might be.
Now [we see] if the clot has undergone a process of organization, where the clot has now turned into scar. By turning into scar, it has now grown into the wall of the blood vessel. It is now incorporated within the blood vessel, so when I open up these arteries it's not just a matter of reaching in there and trying to pluck out that obstructing clot. That's something that might work for a new pulmonary embolism, where it's just clot that's sitting in the obstructing blood vessel. This is clot that has again, has organized and has grown into the wall. The only way for the clot to come out, would be to peel it out. What I explain to patients, it's akin to peeling the rind off an orange. Where you have to get into that right space, and as you peel that rind off, you're always looking to make sure that you're in that right space. So we identify where the obstructing clot is on the inside of the artery, and now we have to very carefully peel it from the wall on the inside of the artery. We have to follow that into all the different branches within the pulmonary artery. Now it is a tedious procedure, and requires a fair amount of meticulous attention to detail. Most importantly, you have to very carefully be able to see, precisely see into all of these branches.
When you're working on the inside of a blood vessel, there tends to be blood on the inside of a blood vessel, and therefore that blood obscures your ability to precisely see those segmental and subsegmental branches. We have to eliminate this blood for better visualization. The way we do that is with a technique called hypothermic circulatory arrest. What this means is that we use the heart-lung machine, or the cardiopulmonary bypass system, to very aggressively cool the blood. By cooling the blood, the entire body, the brain, all the other vital organs, become very, very cold and by making them cold, that reduces the body's metabolism, the metabolic rate. Therefore, the body is consuming very little nutrients and very little oxygen. That allows us, for brief periods of time, to completely stop all circulation. We halt the circulation throughout the body, for brief periods of time, so that we can now visualize on the inside of those blood vessels where the obstructing clot is extending. We then perform our dissection.
We typically limit the period of no circulation to no more than 20 minutes. At 20 minutes we reestablish circulation, reperfuse, or once again deliver blood throughout the body. Once we have completed all of our dissection, then we begin the process of rewarming the patient. Once the patient is warm, and the metabolic rate starts to rise, the heart starts to beat again and then we're able to separate the patient from the heart-lung machine.
Once we finish the operation, and we close the patient up, they are transported directly to an intensive care unit. At our center, specifically unique for this operation, we tend to leave the patient tranquilized and on a ventilator overnight and begin the process the following day to liberate them from the ventilator. That's a process of withholding the sedation, so the patient is now awake and interactive. Once we feel the patient is able to breath on their own, the breathing tube is removed and the patient is now breathing on their own. At our center, we typically do that the following morning after surgery.
It is very important for these patients to fully expand their lungs. These patients have been exposed to obstructive blood flow throughout the lungs, and therefore there's going to be new robust blood flow throughout the lungs. That can cause a phenomenon that we refer to as reperfusion edema. Edema means swelling. So now, you've removed the obstruction and the lung is going to get a tremendous amount of blood flow that it has not seen oftentimes for many years, and the lung may swell because it's unprepared to have all this circulation. So it's very important that we get these patients to take as deep a breath as possible, so we can fill their lungs with as much air, and therefore expanding their lungs and eliminating some of this edema, or extra fluid in the lungs. This is, of course, challenging for patients after surgery, because they have pain from the incision. But mostly we instruct, we educate that is going to be important that they really work on expanding their lungs.
We also initiate these patients on anticoagulation, as soon as we feel it's safe. Though all of these patients were taking some form of anticoagulation before surgery. That anticoagulation is withheld, typically the night before the operation. But the following day, once we're confident there's no evidence of residual bleeding from surgery, we initiate anticoagulation, typically starting with heparin, and then transitioning to an oral agent, most commonly warfarin or Coumadin. At our center, we do tell patients that removing these obstructing clots do not eliminate their needs for anticoagulation. These patients have demonstrated that they have the likelihood to make blood clots, and therefore we recommend that they remain on anticoagulation for the rest of their life.
For this operation, the average length of stay in the hospital is typically around 10 days. Most patients, it takes them about a month until they really feel like they have the wind in their sails again. The vast majority of patients at one to two months have substantial improvement in their baseline symptoms, which continues to improve with postoperative rehabilitation.
Chronic thromboembolic pulmonary hypertension is a mechanical problem, and therefore this condition is potentially curable with an operation. Many of these patients who have a successful operation, are effectively cured of the disease and the symptomatic improvement that they experience is transformative. For me, it is very rewarding to take patients that are suffering from this disease, and then be able to restore really what is normalcy to their life.
This is Dr. Jonathan Haft, and I'm aware that my patients are
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