The Open Artery: Electrophysiologic Considerations.

Prompt opening of the infarct-related artery reduces mortality and subsequent morbid events. Not all benefit of timely thrombolysis or angioplasty appears to be accounted for by myocardial preservation. A favorable modification of the electrophysiologic postinfarction milieu by a patent infarct-related artery has been proposed to help explain this improved outcome. This review investigates the support for such a hypothesis. Long-term follow-up data from controlled trials is scarce but suggests that episodes of life-threatening ventricular arrhythmias and sudden cardiac death are less frequent after thrombolysis with a patent infarct-related artery. The preponderance of data investigate the modification of postinfarction risk stratification parameters, including the signal-averaged electrocardiogram, assessment of heart-rate variability, response to programmed extrastimuli, and dispersion of refractoriness. Reduction of the incidence of late potentials after thrombolysis has been reported by many, but not all, investigators. Differences in signal-averaging technique and timing may help explain the disparity of findings. A patent infarct-related artery is associated with a reduction in late potential incidence. Heart-rate variability, a measure of autonomic balance, appears to be improved in those high-risk patients who receive thrombolysis. Likewise, most investigators reported an association of improved heart-rate variability with a patent infarct-related artery. QT interval dispersion, a measure of ventricular arrhythmic risk, declines as antegrade infarct-related artery flow improves. High-risk patients undergoing programmed extrastimuli have a lower incidence of inducibility and an improved response to pharmacologic therapy after thrombolysis or with a patent infarct-related artery. The mechanisms of arterial flow's modulation of electrophysiologic substrate remains to be elucidated. Long-term follow-up of large post-infarction populations will be necessary to demonstrate benefit conclusively.