Regional changes in blood flow, extracellular potassium and conduction during myocardial ischemia and reperfusion

Abstract

Objectives. We postulated that ventricular arrhythmias may arise from the heterogeneous washout of ischemic metabolites. Our objective was to investigate the distribution of extracellular potassium concentration ([K+]0) during myocardial ischemia and reperfusion and to correlate this distribution with regional differences in myocardial blood flow.Background. Our previous study showed that reperfusion after a brief period of ischemia resulted in heterogeneous reflow of the ischemic myocardium.Methods. The changes in regional myocardial blood flow, midmyocardial [K+]0and electrogram duration were quantitated in 14 dogs undergoing 20 min of left anterior descending coronary artery occlusion and 1 min of reperfusion. Regional myocardial blood flow was measured by using 15-μm radioactive microspheres in 1- to 1.5-g full thickness myocardial samples. The [K+]0was measured with intramyocardial K+·sensitive electrodes.Results. During coronary occlusion, the ischemic zone exhibited a reduction in regional blood flow to 0.13 ± 0.06 ml/g per min and increases in [K+]0to 9.3 ± 2.6 mmol/liter and electrogram duration to 131.8 ± 38.6% of control. Heterogeneous reduction in regional blood flow at various sites in the ischemic zone had fair correlations with variable increases in [K+]0(r = −0.70) and electrogram duration (r = − 0.73). During min 1 of reperfusion, regional blood flow ranged from two to more than seven times baseline, resulting in a disorganized spatial distribution of perfusion with islands of high and low blood flows. Associated with the heterogeneous early reperfusion regional myocardial blood flow, [K+]0and electrogram duration changed at different rates toward normal. Whereas correlation between regional blood flow and [K+)0or standardized electrogram duration was fair during ischemia, this correlation was poor during early reperfusion.Conclusions. Spatial heterogeneity in regional myocardial blood flow during myocardial ischemia and early reperfusion is associated with heterogeneity in [K+]0and eleclrophysiologic characteristics, which in turn may play an important role in the genesis of arrhythmias arising from the ischemic and reperfused myocardium.