In addition to the legion of letters for The Czar, today’s mailbag brings us a letter from Operative Æ, who you may recall wrote that he wrote in about a month ago regarding Dr. J’s first medical update, stating that he was soon to go under the knife. Well he had his surgery and wrote in to let us know how things went:

The Great and Wonderful Dr. J., 

Your post-operative local operative AE reporting back to you from South Carolina following valve replacement surgery. It went fabulously well. Thank you very much for the prayers. Surgery was four days ago, and it is entirely possible that I will be discharged today. Fortunately, my heart has maintained perfect rhythm from the time I was removed from bypass. Unfortunately, the good and great Dr. Surgeon-BD told me he had to chip the old valve out something like tearing down a concrete block wall with a sledgehammer due to the calcification. Also, apparently, I had been living on borrowed time for quite some time. The previous testing had indicated the opening in the valve was 0.64 cm2 rather than the typical of 2.0 cm2 opening I should have had. Upon surgery, the good doctor found the situation much worse and could not find any opening over which the blood passed (of course there was some opening OR I am a member of the Zombie Apocalypse and have yet to be informed. Please remind your readers to continually receive their preventative medical care. I have never been so grateful for the automobile accident which discovered this situation. Been reading Bastiat, Hyack, and Hazlitt over my down time, then it is off to Steyn’s new book. I recommend one and all to your readers also. 

Best, Operative Æ

Operative Æ, thank you for letting us know you are on the mend. Your Get Well Hello Kitty Cookie Bouquet should be arriving anyday, now. I had to pry it away from Puter, who ate all of the chococat cookies. Sorry about that.

It is not unusual to overestimate valve area by echocardiogram. The way aortic valve area is calculated is via the continuity equation. It says that if you know the left ventricular outflow tract (LVOT) area (you measure the diameter), the speed of the blood across the LVOT, and the speed of the blood across the aortic valve, you can calculate the area of the aortic valve.  Area1 * Velocity1 = Area2 * Velocity2, which becomes A1V1/V2=A2.

So, the first way you overestimate the valve area is by overestimating the LVOT diameter. This is pretty easy to do so looking at the raw numbers and V1/V2 ratio are useful in themselves.

The second way is by underestimating the velocity of blood across the aortic valve. You measure the blood velocity by Doppler, so if you are lined up parallel to blood flow, you are measuring the velocity spot on. As your angle deviates from being parallel, the velocity is underestimated as a multiple of the cosine of the angle. (0˚ = 1, 30˚ = 0.87, etc…) but a good sonographer takes care in his or her measurements, and measures in multiple planes/views. There is a third way. There is a phenomenon called pressure recovery. So some folks with aortic stenosis have dilation of their aortic root and the root is also stiffer. So as the blood crosses across the valve, there is a deceleration of blood as energy is dissipated more rapidly into the larger space and walls.

So, Dr. J. is not surprised that the valve area was underestimated. Take solace that once the valve area is < 1cm^2, symptoms are the driver of surgery, so it sounds like you got things taken care of at the right time. Some people require smaller valve areas to have symptoms.

Dr. J. would like to take this opportunity to say that he talked to some of his chums who pop percutaneous aortic valves in. Apparently you can put a valve within a valve it there is an issue. A couple of times tvalves, once they were deployed, had an issue (sitting too low, or at an angle, or a piece of calcium caused sliding of the valve as it is being placed), and placing a percutaneous valve within a percutaneous valve works pretty well and doesn’t appreciably narrow the space the blood has to flow through. This works better with the Sapien valve than the Core Valve as the latter is longer and hourglass shaped.