Use of a Miniature Epicardial Accelerometer as a Sensor of Myocardial Function

Previous studies have indicated that endocardial acceleration correlates with myocardial contractility. An implantable epicardial accelerometer has potential as a sensor of myocardial function. We hypothesized that radial epicardial acceleration would correlate with the maximum rate of left ventricular pressure change (LV dP/dtmax), an indicator of myocardial contractility, over a range of myocardial contractile states. Radial epicardial acceleration was defined as the difference in the peak positive to peak negative acceleration of the left ventricular epicardial surface during a cardiac cycle. Measurements of radial epicardial acceleration were made in 4 anesthetized mongrel dogs. A range of myocardial contractile states was realized with intravenous infusion of esmolol and dobutamine. A miniature, uniaxial accelerometer (PCB Piezotronics, Inc.) was fixed on the anterior epicardial surface of the left ventricle midway between the atrioventricular groove and the apex. Left ventricular pressure was measured with a pressure transducer and LV dP/dtmax was calculated. Calculated LV dP/dtmax ranged from 400 to 14,900 mm Hg/sec. Radial epicardial acceleration ranged from 0.3 to 7.8 g (1 g = 9.81 m/sec2). The linear regression coefficient between radial epicardial acceleration and LV dP/dtmax was 0.92 (p < 0.0001). Radial epicardial acceleration correlates well with LV dP/dtmax, a known measure of myocardial contractility. Measurement of left ventricular epicardial acceleration with an implantable accelerometer has potential application as a continuous sensor of myocardial function.