Clot-busters bring bioelectrical benefits.

Clot-busters bring bioelectrical benefits

A tiny blood clot lodges in a coronary artery, interrupting the flow of oxygenrich blood to the heart. Quick work by emergency physicians armed with clot-busting drugs or other vessel-opening techniques restoresthe crimson flow, salvaging suffocating heart muscle that would otherwise die within minutes. But beyond the obvious advantages of renewed gas exchange and the flushing away of toxic metabolic by-products, rapid restoration of blood flow to heart muscle may provide other benefits.

New research indicates that vessel-opening strategies can also prevent potentially fatal abnormal electrical patterns in cardiac muscle -- patterns common in the weeks and months following a heart attack.

In recent years, researchers have recognized that patients who get vessel-opening drugs such as tissue-plasminogen activator (tPA) seem to have a lower incidence of ventricular tachyarrhythmia -- dangerously rapid and uneven heart rhythms -- and sudden death following a heart attack. But they weren't sure why.

Eli S. Gang, Allan S. Lew, Thomas Peter and their colleagues at the Cedars-Sinai Medical Center in Los Angeles investigated the association using an increasingly popular kind of electrocardiogram machine capable of measuring "ventricular late potentials." Late potentials are abnormal bioelectric bursts that have been associated with ventricular tachyarrhythmia and sudden death. The researchers tracked the electrical fates of 44 heart attack survivors who received tPA and 62 controls who received conventional heart attack treatments that did not include any vessel-opening procedure. None of the patients whose vessels reopened after tPA -- and only 14 percent of the controls whose vessels spontaneously reopened -- showed signs of late potentials.

In comparison, about one-third of the patients whose vessels remained partly blocked showed late potentials on their electrocardiograms. Statistical analysis suggests vessel opening in general, and not tPA per se, may hold the key to restoring organized electrical conductivity in the heart, the researchers report in the Sept. 14 NEW ENGLAND JOURNAL OF MEDICINE.

The precise mechanism by which renewed blood flow enhances proper electrical conductance remains unclear, and the researchers have yet to compile data on the patients' long-term incidence of tachyarrhythmia and sudden death. Nonetheless, they conclude, the improved electrical outlook highlights the importance of rapid vessel opening for many heart attack patients.