Cardiac ischemia and reperfusion in mice: a comprehensive hemodynamic, electrocardiographic and electrophysiological...

Malignant ventricular arrhythmias (VA) after acute myocardial infarction remain a major threat. Aim of this study was to characterize the electrophysiological and autonomic sequelae of cardiac ischemia and reperfusion (I/R) in mice during the first week post incident. Left ventricular function was serially assessed using transthoracic echocardiography. VA were quantified by telemetric electrocardiogram (ECG) recordings and electrophysiological studies on the 2nd and 7th day after I/R. Cardiac autonomic function was evaluated by heart rate variability (HRV) and heart rate turbulence (HRT). Infarct size was quantified by planimetric measures. I/R caused significant myocardial scarring and diminished left ventricular ejection fraction. The ECG intervals QRS, QT, QT_c, and JT_c were prolonged in I/R mice. Both spontaneous VA scored higher and the inducibility of VA was raised in I/R mice. An analysis of HRV and HRT indicated a relative reduction in parasympathetic activity and disturbed baroreflex sensitivity up to 7 days after I/R. In summary, during the first week after I/R, the murine heart reflects essential features of the human heart after myocardial infarction, including a greater vulnerability for VA and a decreased parasympathetic tone accompanied by decelerated depolarization and repolarization parameters.