Evaluation of contractile function and inotropic reserve with tissue velocity, strain and strain rate imaging in streptozotocin-induced diabetes

The aim of the present study was to evaluate left ventricular (LV) function and contractile reserve (CR) with Doppler myocardial imaging (DMI) in a small animal model for type 1 diabetes.

Cardiac function was assessed in anaesthetized Wistar rats 6 and 8 weeks after injection of 60 mg/kg of streptozotocin. At 6 weeks of diabetes, colour DMI echocardiography was performed at rest and during incremental dosages of dobutamine (5, 10, 20 µg/kg/min). Left ventricular fractional shortening was decreased after 8 weeks of follow-up [36 ± 5 (D) vs. 41 ± 4% (C); P = 0.049]. After 6 weeks of diabetes, DMI measurements were reduced in the diabetic rats in the inferolateral wall at rest [systolic velocity: 2.5 ± 0.4 (D) vs. 4.4 ± 0.3 (C) cm/s; P < 0.001; systolic strain rate: 12.2 ± 3.4 (D) vs. 17.4 ± 3.2 (C) 1/s; P = 0.012] and during inotropic stimulation [δ velocity (cm/s): 0.2 ± 0.1 (D) vs. 0.5 ± 0.3 (C)/5 µg dobutamine; P = 0.002; δ strain rate (1/s): 1.4 ± 0.9 (D) vs. 3.3 ± 2.2 (C)/5 µg dobutamine; P = 0.049]. Furthermore, the intraventricular delay in time-to-peak systolic strain was larger in diabetes [20 ± 18 (D) vs. 10 ± 7 (C) ms; P = 0.01]. Systolic mitral annular velocity was also lower in the diabetic rats at rest [2.7 ± 0.4 (D) vs. 3.5 ± 0.4 (C) cm/s; P < 0.001] and in response to dobutamine [δ velocity (cm/s): 0.1 ± 0.1 (D) vs. 0.3 ± 0.2 (C)/5 µg dobutamine; P = 0.013].

In experimental diabetes, a reduction in radial and longitudinal LV function and CR can be detected with DMI before the onset of a reduced global LV function.