Effect of diltiazem on ischemic myocardial depolarization and extracellular K+ accumulation.

Diltiazem retards ischemic arrhythmias and reduces cellular depolarization, as inferred from recordings of T-Q segment depression (delta T-Q). To explore this further, we correlated delta T-Q with the extracellular K+ electrode potential (delta EK) during serial ischemic trials. delta T-Q and delta EK were uniform in control trials, but decreased markedly in trials that immediately followed diltiazem infusion (0.5 mg/kg). delta EK at 2 min of ischemia was reduced from 11.8 +/- 1.3 to 7.4 +/- 1.2 mV; while delta T-Q was reduced from 7.2 +/- 0.5 to 4.4 +/- 0.7 mV. The effect of diltiazem on ischemic depolarization is largely, but not entirely explained by reduction of delta EK.