Left ventricular function can be continuously monitored with an epicardially attached accelerometer sensor

Abstract

Objectives: Preservation of left ventricular (LV) function is crucial for a beneficial outcome in high-risk patients undergoing cardiac surgery. The present study evaluated a motion sensor (accelerometer) for continuous monitoring of LV performance during changes in global and regional LV function.

Methods: In 11 pigs, an accelerometer was sutured to the epicardium on the anterior apical LV region. Global LV function was modulated by esmolol, epinephrine and fluid loading, whereas regional LV dysfunction was induced by a 3-min occlusion of left anterior descending (LAD) coronary artery. Epicardial acceleration in the circumferential direction was obtained by the accelerometer, and from this signal, epicardial velocity was calculated. Peak systolic velocity was measured and used as an index of LV performance. The accelerometer was compared with left ventricular stroke work (LVSW), ejection fraction and myocardial strain by echocardiography.

Results: Accelerometer peak systolic velocity and LVSW changed significantly during all interventions, affecting global LV function. Systolic velocity by the accelerometer increased during epinephrine and fluid loading from 14.1 [10.2; 17.3] to 25.4 [16.7; 28.5] (P < 0.05) and 14.8 [12.5; 18.5] cm/s (P < 0.05), respectively. Esmolol infusion significantly decreased accelerometer peak systolic velocity to 9.4 [7.3; 10.7] cm/s (P < 0.05). Minor changes were seen in the echocardiographic measurements, with significant changes only observed in myocardial strain during the interventions with esmolol and epinephrine. Regional LV dysfunction was clearly detected by the accelerometer during LAD occlusion, and peak systolic velocity was reduced from 14.1 [10.2; 17.3] to 5.7 [5.0; 6.8] cm/s (P < 0.05). The accelerometer demonstrated higher sensitivity and specificity for the detection of myocardial ischaemia than LVSW and ejection fraction. For all interventions, accelerometer peak systolic velocity correlated strongly with LVSW (r = 0.81, P < 0.01) and myocardial strain (r = 0.80; P < 0.01).

Conclusions: It was possible to obtain accurate information on LV performance by the use of an epicardially attached accelerometer. The method allows continuous monitoring of LV function and may therefore improve perioperative monitoring of cardiac surgery patients.

Keywords: Continuous cardiac monitoring; Contractility; Left ventricular function; Strain echocardiography.