Real-time myocardial contrast echocardiography for assessing perfusion and function in healthy and infarcted Wistar rats

Abstract

Real-time myocardial contrast echocardiography (MCE) is a noninvasive perfusion imaging method, whereas technical and resolution problems impair its application in small animals. Hence, we investigated the feasibility of NICE in experimental cardiovascular set-ups involving healthy and infarcted myocardium in rats. Twenty-five male Wistar rats were examined under volatile anesthesia (2.5% isoflurane) with high-resolution conventional 2-D echocardiography (2DE) and real-time MICE (Sonos 7500 with 15MHz-transducer, Philips Medical Systems, Andover, MA, USA) in short-axis view. Contrast agent (SonoVue, Bracco, Milan, Italy) was infused as a bolus into a sublingual vein. Background-subtracted contrast signal intensity (SI) was measured off-line in six end-systolic segments and fitted to an exponential curve (gamma variate). Derived peak SI was subsequently calculated and compared with wall motion and common functional measured quantities (left ventricular end-diastolic diameter [LVEDD], area shortening [AS]). Recordings were performed before and 14 days after left anterior descending (LAD) ligature. Infarction induced anterior wall motion abnormalities (WMA) in all animals (16 akinetic, 9 hypokinetic), increased LVEDD (9.1 +/- 0.6 vs. 7.9 +/- 0.6 mm, p < 0.001), reduced AS (36.1 +/- 10.0 vs. 59.5 +/- 4.1%, p < 0.001) and reduced anterior segmental SI (0.4 +/- 0.4 dB akinetic / 1.7 +/- 1.7 dB hypokinetic vs. 15.8 +/- 10.9 dB preinfarct, p < 0.001 / p < 0.001). Segmental SI in normokinetic segments remained unchanged. Area at risk (perfusion defect) correlated well with WMA (r = 0.838). These data confirmed high-resolution real-time NICE as a rational tool for assessing myocardial perfusion of Wistar rats. It may therefore be a useful diagnostic tool for ill-vivo cardiovascular research in small animals.