Survival, Exercise Capacity, and Left Ventricular Remodeling in a Rat Model of Chronic Mitral Regurgitation: Serial Echocardiography and Pressure-Volume Analysis

BACKGROUND AND OBJECTIVES The aims of this study were to establish a reliable model of chronic mitral regurgitation (MR) in rats and verify the pathophysiological features of this model by evaluating cardiac function using serial echocardiography and a pressure-volume analysis. MATERIALS AND METHODS MR was created in 37 Sprague-Dawley rats by making a hole with a 23 gauge needle on the mitral leaflet through the left ventricular (LV) apex under the guidance of transesophageal echocardiography. RESULTS Serial echocardiograms revealed that the LV began to dilate immediately after the MR operation and showed progressive dilation until the 14th week (LV end-systolic dimension at 14 weeks, 4.71±0.25 mm vs. 6.81±0.50 mm for sham vs. MR, p<0.01; LV end-diastolic dimension, 8.32±0.42 mm vs. 11.01±0.47 mm, p<0.01). The LV ejection fraction tended to increase immediately after the MR operation but started to decrease thereafter and showed a significant difference with the sham group from the 14th week (70.0±2.2% vs. 62.1±3.1% for sham vs. MR). In a pressure-volume analysis performed at the 14th week, the LV end-systolic pressure-volume relationship and +dp/dt decreased significantly in the MR group. A serial treadmill test revealed that exercise capacity remained in the normal range until the 14th week when it began to decrease (exercise duration, 406±45 seconds vs. 330±27 seconds, p<0.01). A pathological analysis showed no significance difference in interstitial fibrosis between the two groups. CONCLUSION We established a small animal model of chronic MR and verified its pathophysiological features. This model may provide a useful tool for future research on MR and volume overload heart failure.