Measurements of heart motion using accelerometers.
ABSTRACT We have used acceleration sensors to monitor the heart motion during surgery. A three-axis accelerometer was made from two commercially available two-axis sensors, and was used to measure the heart motion in anesthetized pigs. The heart moves due to both respiration and heart beating. The heart beating was isolated from respiration by high-pass filtering at 1.0 Hz, and heart wall velocity and position were calculated by numerically integrating the filtered acceleration traces. The resulting curves reproduced the heart motion in great detail, noise was hardly visible. Events that occurred during the measurements, e.g. arrhythmias and fibrillation, were recognized in the curves, and confirmed by comparison with synchronously recorded ECG data. We conclude that acceleration sensors are able to measure heart motion with good resolution, and that such measurements can reveal patterns that may be an indication of heart circulation failure.
- [show abstract] [hide abstract]
ABSTRACT: We describe a novel technique for continuous real-time assessment of myocardial ischaemia using a three-axis accelerometer. 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. 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. 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.BJA British Journal of Anaesthesia 12/2008; 102(1):29-37. · 4.24 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Myocardial ischemia may be detected with epicardial accelerometers. We developed and tested automated algorithms for real-time detection of myocardial ischemia by accelerometer measurements in both experimental and clinical settings. In 10 pigs, an accelerometer was fixed to the epicardium in the area perfused by left anterior descending coronary artery. Acceleration and electrocardiogram were simultaneously recorded, and the QRS complex was automatically detected for exact timing of systole. Peak circumferential velocity and displacement were automatically calculated from epicardial acceleration signal within 150 milliseconds after peak R on electrocardiography. Global myocardial function was reduced by esmolol infusion, and regional function was altered by temporary left anterior descending occlusion. Automated ischemia detection analyses were tested in 7 patients during off-pump coronary artery bypass grafting. Left anterior descending coronary artery was occluded for 3 minutes before grafting. In both models, echocardiographic myocardial circumferential strain was used to confirm ischemia. Systolic displacement changed most during left anterior descending occlusion. Negative displacement during ischemia was found in pigs (11.5 +/- 2.3 to -1.2 +/- 2.8 mm, P < .01); regional hypokinesia was found in clinical study (12.8 +/- 8.1 to 3.5 +/- 4.4 mm, P < .01). Ischemia was confirmed by echocardiography in both settings. Esmolol infusion induced smaller changes in automated accelerometer measurements than did left anterior descending occlusion (P < .01). Automatic real-time detection of myocardial ischemia with epicardial accelerometer was feasible. Automated ischemia detection analysis may be used for continuous monitoring of myocardial ischemia during cardiac surgery.The Journal of thoracic and cardiovascular surgery 08/2009; 139(4):1026-32. · 3.41 Impact Factor
- Vietnam Journal of Mechanics. 01/2012; 34(4):271-280.