Dissociation of effects of nitroglycerin on regional refractoriness and regional myocardial blood flow following acute coronary occlusion.

Nitroglycerin is known to affect the electrophysiological properties of the ischaemic ventricle, possibly by altering regional myocardial blood flow. This study correlated the effects of nitroglycerin, given after acute coronary occlusion, on regional ventricular refractoriness and regional myocardial blood flow. Nitroglycerin returned ventricular refractory periods to their pre-occlusion values in spite of no significant effect on regional myocardial blood flow. Although the beneficial electrophysiological effects of nitroglycerin were not explained by increased regional flow to the ischaemic myocardium, an improved myocardial oxygen supply-demand balance may have produced these favourable effects. This study emphasises the need for electrophysiological evaluation of the effects of interventions intended to limit infarct size.