Data on ‘Silent’ Heart Attacks Stirs Questions on Treatment, Effects

New data showing that heart attacks often are painless and sometimes not recognized suggest heart disease may be even more prevalent than believed, an expert warns.

“The concept that a patient may suffer myocardial ischemia--or inadequate blood supply to certain areas of the heart--without chest pain is very poorly understood by physicians,” Dr. William Parmley, president of the American College of Cardiology, said in an interview.

“Data indicates 75% of ischemia cases are painless. And a recent long-term study shows one of five heart attacks was unrecognized by the patient. The more we learn, the more we wonder about whether heart disease, the No. 1 killer in America, is even more widespread than we think.”

Millions Afflicted

The American Heart Assn. reports 43.5 million Americans suffer from one or more forms of heart or blood vessel disease; 1.9 million are victims of strokes; 1.5 million have a heart attack each year, and 500,000 of them die.

High blood pressure afflicts 38 million Americans, and rheumatic heart disease another 2 million.

The economic cost of cardiovascular disease will amount to an estimated $72.1 billion this year, heart association officials said.

Physicians just recently have become aware that myocardial ischemia and heart attacks can be “silent,” said Parmley, professor of medicine and chief of the cardiovascular division of Moffitt Hospital at the University of California, San Francisco.

These findings are all the more significant because many cardiac specialists believe ischemia is a high-risk factor for heart attacks, sudden death, arrhythmias and other cardiac events, he said. A heart attack occurs when blood flow is cut off to part of the heart muscle.

Question of Danger

“The major questions arising from the new data are how common is silent heart disease and how dangerous,” Parmley said.

Some 4.5 million Americans have a history of angina or chest pain, associated with ischemia or heart attack, Parmley said, but it is not known how many more suffer the silent forms of the disorders.

“If this is just the tip of the iceberg, it could have tremendous implications for heart disease,” he said. “Should we be seeking these patients out and treating them and, if we did so, could we reduce the incidence of heart disease?”

Doctors do not know how many heart attack victims die without feeling pain or whether silent ischemia is always asymptomatic or may produce symptoms that people dismiss as indicating other illnesses, such as a chest cold or virus.

“We need further data on silent myocardial ischemia, which I am convinced will become one of the most important areas of cardiology in the next few years,” Parmley said.

Pinpointing the Risk

“Exactly how serious is it? Is painful ischemia more severe than the painless form? Who is at high risk?”

Although most heart patients who die suddenly suffer from severe coronary artery disease, he said, there are those “who just drop on the sidewalk with no visible explanation.”

Perhaps these deaths could be prevented or delayed with earlier treatment of ischemia with such drugs commonly used in heart disease as nitrates, calcium entry blockers and beta blockers, he said.

Myocardial ischemia, with or without pain, may be induced by exercise when a portion of the heart muscle fails to receive sufficient amounts of blood because of a narrowing in the blood vessel supplying that part.

“The narrowing may not allow passage of enough blood to meet the heart’s increased oxygen demand during exercise, so that portion of the muscle then stops moving,” Parmley said.

Long-Term Effects Unknown

“This is usually temporary, and once the person stops exercising, everything returns to normal. But we don’t know the long-term effects. If a person has 100 such episodes, what does that mean?”

New data shows ischemia also may be caused by vasoconstriction, or tightening of the blood vessel.

“This is extremely difficult to monitor because in this case ischemia occurs without an increase in blood pressure or heart rate--the two major indicators of ischemia,” Parmley said.

In another study, doctors analyzed two groups of patients suffering from coronary disease and ischemia, one group with pain, the other painless. Preliminary results showed those without pain lived longer.

“This may indicate that ischemia without pain may be less severe than ischemia with pain, but it’s far too early to draw any conclusions,” said Parmley, who chaired a recent symposium on silent myocardial ischemia.