Why Aren't Cardiologists Doing Their Homework?

Here's an interesting study this week from the Journal of the American Medical Association that looks at how often patients underwent a stress test prior to getting angioplasty. In turns out that less than 50% of the time! And so why is this a big deal?

Angioplasty is where a small balloon is used to open up a coronary artery to relieve a blockage, followed sometimes by the placement of a stent to keep the vessel open. It is much less riskier and invasive than open heart surgery and is well known to save lives in people having heart attacks and in those with unstable coronary disease. However, we know that in people with stable coronary disease angioplasty has no more benefit over medical therapy (nitro, blood pressure, and cholesterol meds). The difference between stable and unstable CAD is basically how and when you get symptoms of reduced blood flow to the heart (chest pain, shortness of breath, and so on). In stable CAD you only get these symptoms when your heart is stressed, say when you are climbing the bleachers at the football game, arguing with your spouse, or watching our fine President make an ass of himself on television. So according to our best medical evidence, if you fall into that category you're most likely to be best off with just taking your medicines following your doctor's good advice to exercise and eat your veggies, and staying the hell away from the cardiologist.

Naturally, it is never easy in medicine to separate people nicely into one group or the other. Several professional societies such as the American Heart Association have published guidelines stating that for any non-emergent (elective) angioplasty a patient should have a stress test first to demonstrate myocardial ischemia, that is, insufficient blood flow to your heart muscle. There are lots of types of stress tests, but the principles are the same: make the heart work harder (running on a treadmill) and measure function of the muscle (EKG, echocardiography, nuclear perfusion scans). The tests help sort out if there is ischemia (not all patients with poor blood flow will have symptoms, typically women) and if there is chest pain if it is due to an angry, blood-starved heart or not.

It seems intuitive that just ballooning open vessels with plaques is a good idea. Strangely, we know the probability of having a heart attack is not easy to predict from the degree of vessel narrowing alone. What determines your heart attack risk are based on several factors, and many people with narrowed coronaries or stable CAD never have a heart attack. So its seems it is not simply a structural problem. Hence, the need for the stress test, which allows the doctors to identify the functional nature of the vessel. Incidentally there is trendy new use of CT scans (CT angiography) that takes thin slice, high-resolution images of just your coronaries and is able to actually image individual plaques. The 3-D reconstructions are pretty amazing to say the least. But, the utility of the scans are controversial because they don't tell you which plaques are likely to be trouble makers, which is what we really want to know. Nevertheless, lots of doctors are totally into the scans and convince their patients they need to have them, and so in some places every middle aged man with a history of chest discomfort is getting this expensive trip to the CT scanner. This is a great example of how our medical system readily embraces new technology that seems promising before evaluating the evidence behind its efficacy.

Okay, back to angioplasty. So why the hell are so many people - more than 50% - getting ballooned and stented before verifying that they have a functional vessel problem? That's the question this study raises. A generous explanation is that doctors either intentionally or unintentionally ignore the guideline recommendations, relying instead on personal experience and local practice standards. Call me a pinko Francophilic Obama-loving Terrorist, but my own opinion is that this is just another example of how the fee-for-service system incentivizes doctors and hospitals to provide care that may not actually benefit patient. But to be fair there are other non-financial aspects of medicine that muddy the waters: our professional ethics urge us to provide the best care regardless of cost and over-treatment serves as a bet-hedging maneuver in the paranoia of malpractice claims.