TEMPORAL EVALUATION OF LEFT-VENTRICULAR REMODELING AND FUNCTION IN RATS WITH CHRONIC VOLUME OVERLOAD

The left ventricle (LV) significantly dilates and hypertrophies in res ponse to chronic volume overload. However, the temporal responses in L V mass, volume, and systolic/diastolic function secondary to chronic v olume overload induced by an infrarenal arteriovenous (A-V) fistula in rats have not been well characterized. To this end, LV end-diastolic pressure, size, and function (i.e., isovolumetric pressure-volume rela tionships in the blood-perfused isolated heart) were assessed at 1, 2, 3, 5, and 8 wk post-A-V fistula and compared with age-matched control animals. Progressive hypertrophy (192% at 8 wk), ventricular dilatati on (172% at 8 wk), and a decrease in ventricular stiffness (257% at 8 wk) occurred in the fistula groups. LV end-diastolic pressure increase d from a control value of 4.2 +/- 3.1 mmHg to a peak value of 15.7 +/- 3.6 mmHg after 3 wk of volume overload. A subsequent decline in LVEDP to 11.0 +/- 6.0 mmHg together with further LV dilatation (169%) corre sponded to a significant decrease in LV stiffness (222%) at 5 wk post- A-V fistula. Myocardial contractility, as assessed by the isovolumetri c pressure-volume relationship, was significantly reduced in all A-V f istula groups; however, the compensatory remodeling induced by 8 wk of chronic biventricular volume overload tended to preserve systolic fun ction.