Background: Diabetic cardiomyopathy (DMCMP) is characterized by myocardial dysfunction regardless of coronary artery disease in diabetic patients. The features of LV dysfunction in rat model of type 1 DM induced by streptozocin, are variable and controversial. Thus, we tested the usefulness of tissue Doppler imaging in the early detection of ventricular dysfunction in a rat model of DMCMP.
Methods: Diabetes was induced by intra-peritoneal injection of streptozocin (70 mg/kg) in 8 weeks of Sprague-Dawley rat. Diagnosis of diabetes was defined as venous glucose level over 350 mg/dL 48 hrs after streptozocin injection. Echocardiography was done at baseline and 10 weeks after diabetes induction both in diabetes group (n=15) and normal control (n=10). After echocardiography at 10 weeks, invasive hemodynamic measurement using miniaturized conductance catheter was done in both groups.
Results: Ten weeks after diabetes induction, heart and lung mass indexes of diabetes were larger than those of normal control (3.2+/-0.3 vs. 2.4+/-0.2 mg/g, p<0.001, 5.5+/-1.1 vs. 3.6+/-0.6 mg/g, p<0.001, respectively). In echocardiographic data, s' (2.4+/-0.4 vs. 3.1+/-0.5 cm/s, p<0.001), e' velocity of mitral annulus (2.9+/-0.6 vs. 3.8+/-1.1 cm/s, p<0.001), and E/e' ratio (27.1+/-5.6 vs. 19.7+/-2.6, p<0.001) were impaired in diabetes group. In hemodynamic measurement, there were no differences in ejection fraction, peak dP/dt between the diabetic group and normal control. However, load independent indexes of contractility, the slope of the end-systolic pressure volume relation (0.18+/-0.07 vs. 0.62+/-0.18 mmHg/microL, p<0.001) and preload recruitable stroke work (51.8+/-22.0 vs. 90.9+/-22.5 mmHg, p<0.001) were impaired in diabetic group compared to normal control.
Conclusion: In a rat model of diabetic cardiomyopathy, tissue Doppler imaging of mitral annulus can be a good modality for early detection of myocardial dysfunction.
Keywords: Diabetic cardiomyopathy; Pressure-volume loop; Tissue Doppler imaging.