The Paradox of Stenting
Stents are not magic
I don’t think we doctors are guilty of misleading people on the issue of stenting—in fact, I think we try to clarify whenever we can. The fact is, despite our efforts, many patients have an erroneous understanding of what sort of benefit they can expect when we place a stent in the coronary artery of someone not having a heart attack or significant heart-related symptoms.
Let’s say a middle-aged patient sees his primary doctor for a routine check-up. The patient is rather sedentary, a little overweight, but is having no chest pain or unusual shortness of breath. As part of a screening physical the doctor requests a stress test. The patient does well on the test but the scan suggests mild coronary disease. A heart catheterization follows, which shows an 80% stenosis (blockage) of one of the branch vessels and he undergoes balloon angioplasty and stenting to that artery.
Now it’s quiz time. What does fixing this blockage do for this patient’s risk of having a heart attack?
- Eliminates it
- Decreases it
- Does nothing to it
- Increases it
Although I have no empiric data to support this, I would venture from my anecdotal experience that most patients and their families would pick either answer A or B. It stands to reason, you might say, that opening a narrowed coronary artery would diminish the risk of heart attack.
Well, we cardiologists know better. Despite our fervent desires to the contrary we know that intervening on a coronary blockage in an individual with little or no symptoms does nothing to decrease the future risk of heart attack. We have numerous trials and procedure registries that attest to this. Why is this? The answer lies in an understanding of the origin of an acute coronary event.
Heart attacks occur because a cholesterol-rich “plaque” in the wall of the artery becomes unstable, ruptures, and the body tries to seal the damage with proteins and cells that form a clot. The clot occludes the flow in the vessel and all downstream muscle is starved for oxygen. We’ve known for several years that the physical dimensions of a stenosis (ie. how narrow the blockage) don’t determine its risk of plaque rupture and complete vessel closure—a 50% blockage may be just as likely to result in a heart attack as a 90% blockage.
So we return to our hypothetical patient. If this patient, who has an 80% stenosis in a coronary vessel, has no symptoms it is likely the 20% open area provides enough flow for adequate (perhaps not optimal—the stress test was able to detect the abnormality) cardiac function. The thing we don’t know by simply looking at the appearance of the blockage is whether this stenosis is the “stable” type that will go years without worsening, or the “unstable” variety that is prone to rupture with clot formation and heart attack. At present there is no good test that can determine this. Simply putting a stent in the offending narrowing does nothing to change the stability of this blockage or prevent worsening of blockages elsewhere in the circulation.
For this reason many doctors (and professional societies such as the American College of Cardiology) advocate against routine stress testing in asymptomatic individuals—too many times stress testing leads to unnecessary angiography which leads to unnecessary (and potentially risky) coronary repair procedures.
Risk factor modification can do more than medical interventions
The real treatment for this patient, and others with risk factors for coronary disease, is simply risk factor modification, such as smoking cessation, diet, exercise, and tight blood pressure and cholesterol control. One interesting study a few years ago illustrated this point quite nicely. The researchers took several hundred patients who had high-grade single-vessel coronary stenosis and randomly assigned half to angioplasty and half to high-dose cholesterol medication (a statin) with no angioplasty. Within a short 18 months the difference was striking: treating with a statin drug did a better job of decreasing heart attack and stroke than did opening the blockage in the cath lab.
I would love to hear our readers’ comments as I know from experience this is a topic that generates debate.