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Current Treatments for Heart Attacks

Richard W. Smalling, M.D., Ph.D.
 
Cardiovascular disease continues to be the leading cause of death and disability in Western civilization. In the United States alone, approximately 500,000 people per year succumb to heart attacks. Despite significant reductions in the incidence and mortality from heart disease, it still kills twice as many people as cancer (Table 1).

Table 1.
Deaths in U.S. in 1990 Per 100,000 Population

CAUSE OF DEATH RATE % OF ALL DEATHS
Cardiovascular 355 41
Cancer 203 23
Lung Disease/Pneumonia 67 8
Accidents 37 4
Diabetes 19 2
Suicide 12 1.4
AIDS 10 1.2
Renal Disease 8 1.0

CDC Monthly Vital Statistics Report: 1993;41,7 Supplement 1-12.


What Causes a Heart Attack?
Heart attacks generally occur in people who already have deposits of fat (lipids) attached to the walls of their coronary arteries (vessels supplying blood to the heart muscle). When these deposits (atheromatous plaques) somehow become disrupted and release lipid into the circulation, blood platelets, which are part of the body's clotting system, are activated. Clots form at the site of the disrupted plaque and a blockage of a coronary artery can occur.

Figure 1.
blood flow
Representation of a coronary artery (longitudinal section) showing plaque (in yellow) which has pushed into the arterial lumen, narrowing it and thereby reducing blood flow downstream




If the coronary artery is completely blocked, the heart tissue that receives oxygen and nutrients via the artery ceases to function within seconds after a blockage. Irreversible heart tissue death (what we call a heart attack and what doctors call a myocardial infarction) is, however, delayed for approximately 20-30 minutes. Over the next three to twelve hours, more irreversible damage occurs. The extent of the damage depends on how much blood flow can reach the deprived heart tissue via naturally occurring bypass (collateral) circulation.

Clot Busting Therapy
Much clinical experience has shown the benefits of prompt restoration of coronary artery blood flow in patients with acute myocardial infarction. The I.V. administration of clot destroying medicines (thrombolytics) markedly reduces death in heart attack patients. And the earlier the treatment, the better. Patients treated within 90 minutes after onset of chest pain are one-seventh as likely to die compared to those patients who receive therapy after 90 minutes.

The quality of restored blood flow is also very important. It can't be just a trickle. It has to be sufficient to allow the heart to pump efficiently and effectively. Once a clot has been dissolved and the blockage cleared away, it is important to keep the artery open. Otherwise, mortality worsens, at an accelerated rate, in patients whose arteries close again during the following year.

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