Monday, October 12, 2015

Decisions, decisions ...

Almost three years ago, I accidentally discovered that I have severe aortic heart valve regurgitation (leaking). The only treatment for this problem is surgery, the timing of which is somewhat controversial because we lack the highest quality evidence - multiple randomized controlled rials - addressing that question. Nevertheless, there is reasonable evidence suggesting that the time to operate was not then, and I have been grateful for the three pretty normal years that followed. Unfortunately, it appears that that time has come now.

My left ventricle has shown subtle signs of ongoing dilatation on serial cardiac MRI examinations and that volumetric increase was quite clear on my most recent images. Delaying operation has some benefits that seem largely static with the passage of time while the risk of adverse outcomes increases. The recent dilatation in my ventricle suggests that I'm probably at or near the inflection point of the curve relating the risks and benefits of waiting. It's impossible to know for sure, but I've always wanted to err on the side of operating little bit sooner rather than later if an error had to occur. Accordingly, I am going to wait no longer; my surgery is being planned for early in the new year. But no sooner is that question answered to a satisfactory degree that another question arises: what operation should I have?

The Options

Mechanical valve replacement
This option refers to surgically replacing my aortic valve with one made out of pyrolytic carbon discs that tilt open and closed. The advantage of mechanical valves is that they are very durable. There is probably an 80-90% chance that a mechanical valve will last me the rest of my life. The disadvantage of mechanical valves is that they are foreign material, and the body tends to form blood clots on foreign material exposed to the blood stream. If a blood clot formed on the tilting discs, it could prevent the discs from opening or closing properly. The valve could become severely blocked, impairing the flow of blood out of my heart, and causing a life threatening situation. Alternatively, the clot could break free and travel through just the right blood vessels leading to my brain, causing a stroke. To minimize these clot-related risks, an anticoagulant medication called warfarin is indefinitely required. Because warfarin interacts with changes in diet, liver function, and many medications, regular blood testing to determine the adequacy of anticoagulation are indefinitely required. Thankfully, I could perform these tests at home, about once a week, for the rest of my life. Despite good control of my use of warfarin, I'd probably be facing a 25% life time risk of life-threatening bleeding in the worst case scenario, or enough bleeding to require a blood transfusion in the best. So while there's probably a 75% chance of not having a major bleed, mundane human experiences like a bonk on the head, a car accident, or a bleeding ulcer could all pose serious risks to my well-being.

There are a couple of other considerations regarding mechanical valves. Firstly, they make an audible clicking sound when they close. Sometimes it's loud enough to hear in a quiet room when standing next to someone with a mechanical valve. You can check out what the click sounds like here. Some people are bothered by a sound that they can never get away from, while others get used to it and still others find it soothing or comforting. I'm not sure how I would handle the perpetual click, but I do know that if I can hear my watch ticking on my night table, I can't sleep until I put it away. Secondly, ultrasound examinations of the blood vessels of people with mechanical valves often reveal little specks flying around in the blood stream. These are thought to represent very small blood clots or bubbles, and since they are flying around all over the place, some go to the brain. There is some evidence that patients with relatively high numbers of these tiny emboli have deficits on detailed neurocognitive testing (such as memory defecits). It is unpleasant to speculate that a mechanical valve could lead to early onset dementia. Some biological valves (see below) are associated with these micro emboli, too, though they seem more common among people with mechanical valves.

Biological valve replacement
This option refers to surgically replacing my aortic valve with a new one made out of biologic material from a cow or pig heart. The tissue is treated so as to not invoke an immune rejection response. The advantage of biological valves is that they do not require anticoagulants after the first 3-6 months post-op. The major bleeding risk is therefore about half of that observed with mechanical valves. The downside of biological valves is that they wear down over time and that rate of structural deterioration is fastest in younger patients. A biological valve would be expected to last 10-15 years before requiring replacement surgery, so there is a very high chance that I'd have to have a second open heart operation to replace a biological valve in my lifetime, perhaps, even a third. While the risk of bleeding is lower over those years, the risk of the second surgery is probably double the risk of the initial surgery (though we're still talking about relatively low risks), and if a third operation is required, the risk seems to really increase significantly. Plus, each operation also carries a risk of neurocognitive decline just from being on cardiopulmonary bypass for a few hours. Open heart surgery is basically the mother of all operations, taking 8-12 weeks from which to recover. Nobody wants to have to undergo it more than once if they don't have to...

Mechanical and biological valves compared:
Both mechanical and biological prosthetic heart valves carry a similar and, thankfully, very small risk of becoming infected (endocarditis). This is a serious complication, often requiring redo surgery to remove the infected valve and replace it with a new one. At the end of the day, when these valves have been compared in people over 55, the risk over time of stroke is the same, though mechanical valves require anticoagulants for that to be the case. Survival has seemed pretty much the same, too. With a mechanical valve, the risk of bleeding is spread out over time, while with a biological valve, the risk is concentrated at those times when the valve degenerates and re-operation is required. However, there have been no randomized trials comparing mechanical and biological valves in people in their 40's, so the bottom line is that nobody can provide any confident information about how someone like me ought to expect to fare with either. All one can do is make an educated guess based on trials involving older patients and the best guess of some experts is a mechanical valve, while for others, its a biological one. (Hmmm, an interesting and important disagreement.)

Valve Repair: There is a small chance (estimated at 20-30%), that my aortic valve could be surgically repaired. This would mean that the surgeon could, if the tissues are strong and the valve leaflets long enough, artfully put in some carefully places sutures that would re-align the leaflets and make them close well again. Like a biological valve, repair would have the advantage of not requiring anticoagulants, but more importantly, it would not be associated with an increased risk of infection because no foreign material is involved. The coolest thing about a repair is that while prosthetic valves just palliate the problem, a repair could potentially cure it. The downside of a repair is that its longevity would be unknown. It could last my lifetime, but it could also fail within 2 years and require redo surgery that soon. One estimate is a 20% chance of needing a second operation at or before 10 years. The trouble with these estimates is that the cause of my valve leak isn't known; the usual conditions that cause it have been excluded. Maybe I have weak connective tissues and a repair would be destined to fail again just as my original valve did?

What am I going to do?
Well, I've made a choice, but it's not like I feel very confident about it. I remain open to new evidence and other opinions. At this moment in time, I'm planning to have a surgeon who is very experienced with aortic valve repair - and there are not that many in the world - make a judgement call in the OR: if he thinks that there is a good chance for a durable repair, that is my #1 choice. If he feels otherwise, my second choice is a mechanical valve. The On-X aortic valve has recently been shown to be as safe with less aggressive anticoagulation (INR 1.5-2 rather than 2-3) and therefore less bleeding, so I have asked my surgeon to use this valve if it comes to that.

Repair is attractive because of the lower risk of endocarditis, and because it represents a chance to be normal again. I'm willing to risk something for that, but not much. If the surgeon thinks my tissues are not up to the job of providing me with a lasting competent aortic valve, then I would prefer erring on the side of implanting a mechanical prosthesis. Why mechanical? Because while survival of patients with mechanical and biological valves has been similar in trials of older patients, my suspicion is that there will be a survival advantage in younger patients because the risk of bleeding - the major risk of a mechanical valve over biological - is lower in young patients. Plus, I'm choosing a valve that likely requires less intensive anticoagulation than has traditionally been required, and I would monitor my anticoagulation at home. All of these things should help to reduce the risk of bleeding with a mechanical valve during young years when a biological valve would be undergoing relatively rapid structural deterioration. Also, I somehow feel more comfortable taking my chances with anticoagulants, which I can to some extent control, than with watching and waiting for the clock to tick down to a second big operation. (That doesn't seem like a particularly rational consideration, but I'm with David Hume, whom I must quote at every opportunity: "Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them.")

I wish that there was an ongoing randomized controlled trial comparing mechanical and biological valves in 40 year-olds with long term follow up. I would gladly participate in such a trial and let the study make that decision for me. Unfortunately, and for reasons that are really unclear to me, no such study is underway, nor, to my knowledge, even being planned. It would seem to be so easy to do, and it's a question that's important to many thousands of people like me around the world. Too bad.

So that's likely going to be my roll of the dice. I'll probably end up with a mechanical valve and the best case scenario is that it never gets infected (95% chance), that I have no major bleeding while on warfarin (75% chance), that I get used to the click and even come to like it (? chance), and that it lasts me a long life (80-90% chance) without major neurocognitive decline (? chance). Of course, this discovery has forced me to rethink the concept of a long life: my average life expectancy is probably somewhere around 65* while it ought to be well over 70. And while it would be nice to make it to 75, doing so with cognitive dysfunction represents a particularly unattractive scenario to me. Hopefully, safer alternatives to warfarin will become available for use with mechanical valves in my lifetime.

But like I said, I'm open to other perspectives. Please share your thoughts in the comments below. Would you take a chance at valve repair? Would your back-up plan be a biological valve with a high chance of a second operation, or a mechanical valve with the life-long use of warfarin? How would you roll the dice if you were in my shoes?

*Martijn W.A. van Geldorp , W.R. Eric Jamieson , A. Pieter Kappetein , Jian Ye , Guy J. Fradet , Marinus J.C. Eijke... Patient outcome after aortic valve replacement with a mechanical or biological prosthesis: Weighing lifetime anticoagulant- related event risk against reoperation risk. The Journal of Thoracic and Cardiovascular Surgery Volume 137, Issue 4 2009 881 - 886.e5