Detection of myocardial ischaemia by epicardial accelerometers in the pig

Background. We describe a novel technique for continuous real-time assessment of myocardial ischaemia using a three-axis accelerometer. Methods. In 14 anaesthetized open-chest pigs, two accelerometers were sutured on the left ventricle (LV) surface in the perfusion areas of the left anterior descending ( LAD) and circumflex (CX) arteries. Acceleration was measured in the longitudinal, circumferential, and radial directions, and the corresponding epicardial velocities were calculated. Regional LV dysfunction was induced by LAD occlusion for 60 s. Global LV function was altered by nitroprusside, epinephrine, esmolol, and fluid loading. Epicardial velocities were compared with strain by echocardiography during LAD occlusion and with aortic flow and LV dP/dt(max) during interventions on global LV function. Results. LAD occlusion induced ischaemia, shown by lengthening in systolic strain in the LV apical anterior region (P<0.01) and concurrent changes in LAD accelerometer circumferential velocities during systole (P<0.01) and during the isovolumic relaxation phase (P<0.01). The changes in accelerometer circumferential velocities during LAD occlusion were greater compared with the changes during the interventions on global function ( P, 0.01). For the LAD accelerometer circumferential velocities, sensitivity was 94-100% and specificity was 92-94% in detecting ischaemia. Conclusions. Myocardial ischaemia can be detected with epicardial three-axis accelerometers. The accelerometer had the ability to distinguish ischaemia from interventions altering global myocardial function. This novel technique may be used for continuous real-time monitoring of myocardial ischaemia during and after cardiac surgery.