Jingtian Li1, Lexin Wang. 1. Department of Cardiology, Hospital of Weifang Medical Collegue, Shandong Province, PR China.
Abstract
BACKGROUND: Our previous study has demonstrated that increased intracoronary perfusion leads to a flow-dependent inversion of T waves on body surface ECG. However, whether increased coronary flow influences ventricular action potential duration measured directly from myocardium is unknown. METHODS: In six pentobarbital-anesthetized sheep, fresh arterial blood was injected into the left circumflex coronary (LCX) artery at a rate of 6 and 10 mL/min, respectively, in the presence of normal coronary flow. Activation-recovery interval (ARI), an estimate of ventricular action potential duration, was measured from epicardial ECGs acquired from the LCX territory. RESULTS: The intracoronary injection prolonged ARI by an average of 21 +/- 9 and 33 +/- 14 msec, respectively. After pre-treatment with nitro-l-arginine, a nitric oxide synthase inhibitor, intracoronary injection at the rate of 6 and 10 mL/min lead to an ARI increase of 3 +/- 2 msec (p >0.05) and 11 +/- 6 msec (p <0.05) respectively. CONCLUSIONS: An increase in coronary flow prolongs ventricular action potential duration in the intact sheep heart. Nitric oxide mediates the injection-induced increase in action potential duration.
BACKGROUND: Our previous study has demonstrated that increased intracoronary perfusion leads to a flow-dependent inversion of T waves on body surface ECG. However, whether increased coronary flow influences ventricular action potential duration measured directly from myocardium is unknown. METHODS: In six pentobarbital-anesthetized sheep, fresh arterial blood was injected into the left circumflex coronary (LCX) artery at a rate of 6 and 10 mL/min, respectively, in the presence of normal coronary flow. Activation-recovery interval (ARI), an estimate of ventricular action potential duration, was measured from epicardial ECGs acquired from the LCX territory. RESULTS: The intracoronary injection prolonged ARI by an average of 21 +/- 9 and 33 +/- 14 msec, respectively. After pre-treatment with nitro-l-arginine, a nitric oxide synthase inhibitor, intracoronary injection at the rate of 6 and 10 mL/min lead to an ARI increase of 3 +/- 2 msec (p >0.05) and 11 +/- 6 msec (p <0.05) respectively. CONCLUSIONS: An increase in coronary flow prolongs ventricular action potential duration in the intact sheep heart. Nitric oxide mediates the injection-induced increase in action potential duration.