This may seem like an esoteric finding, of interest only to cardiologists, but it is actually a matter of life or death to the hundreds of thousands of Americans with the condition. Hypertrophic cardiomyopathy is the most common genetic heart disease, occurring in one out of every 500 Americans, and there has been a running debate in the cardiology community about the danger of left ventricular obstruction since the condition was first identified in the 1950s.
This study settles that debate, says lead author Dr. Martin S. Maron, a cardiology fellow at the Tufts-New England Hypertrophic Cardiomyopathy Center in Boston. His report appears in the Jan. 23 issue of The New England Journal of Medicine.
"The study clearly shows that obstruction directly impacts progression to heart failure and death," Maron says. "We have shown for the first time that this is true."
Both Maron and Dr. Mark V. Sherrid, director of the hypertrophic cardiomyopathy center at St. Luke's- Roosevelt Hospital Center in New York City, say the study will change the way the condition is treated.
Intervention to reduce the obstruction and increase the flow of blood from the ventricle, which pumps blood to the body, will come sooner in many cases, they explain.
Hypertrophic cardiomyopathy is an abnormal thickening of the heart muscle that occurs irregularly in different parts of the heart. It can occur at any age; many of the sudden deaths of young athletes are caused by it. In a large percentage of cases, the heart becomes distorted enough so that the flow of blood from the left ventricle is obstructed and reduced.
The study, done at a number of medical centers, looked at 1,101 patients, of whom 273 had left ventricular obstruction. It found the risk of heart failure and death in patients with obstruction was more than four times greater than in those without obstruction, with the risk higher in older patients.
For those patients, Sherrid says, the first option for treatment is therapy with drugs such as disopyramide, a medication that controls the heartbeat.
"Of all the medical treatments, disopyramide is the single most effective," he says. Other heart drugs, such as beta blockers and calcium antagonists, may also be used.
If drug treatment doesn't work, there are two alternatives. One is surgery to widen the passage out of the atrium. Another, and more controversial, method is alcohol ablation, in which alcohol is directed to a specific part of the heart. Alcohol kills heart cells, Maron notes, and this is "a limited, controlled heart attack in the area where the thickening is occurring." It was introduced only five years ago, and "most people think surgery is the gold standard," he says.
"You can infer from our study that these patients should be offered these procedures earlier in the course of the disease rather than later," Maron says, but he adds the study leaves some questions unanswered.
Specifically, it does not show that early intervention improves the prognosis for these patients. Another, completely different study must be done to show that, Maron adds.