Initiation of ventricular extrasystoles by myocardial stretch in chronically dilated and failing canine left ventricle.

BACKGROUNDStretch-induced arrhythmias (SIAs) can be elicited in normal canine left ventricles by transient diastolic dilatation. Since clinically important ventricular arrhythmias arise most commonly in failing and dilated ventricles, we hypothesized that the arrhythmogenic effect of transient diastolic stretch would be enhanced in chronically dilated failing canine hearts.METHODS AND RESULTSHeart failure was induced in seven dogs by right ventricular pacing at 250 min-1 for 20.2 +/- 1.6 days. Left ventricular (LV) mechanical properties were measured in vivo with serial echocardiograms in these seven dogs with the dogs awake and tranquilized to confirm the development of LV dilation and failure. By the third week of pacing, average short-axis area ejection fraction decreased by 64.3% (P < .001) as end-diastolic and end-systolic diameters increased by 25.9% and 50.7%, respectively (P < .001). After heart failure was established, the hearts were harvested and in vitro data were obtained as an isolated, bloo...