Background: It has been suggested that the cardiac cycle becomes synchronized with the LVAD. Synchronization between the left ventricle and the LVAD may be important for ventricular unloading and coronary flow. In this study, we assessed the synchrony between the cardiac and LVAD cycles.
Methods: We studied 24 patients with HeartMate LVAD support. Native heart rate from an electrocardiogram and LVAD rate were measured at rest and peak exercise. Three patients underwent simultaneous invasive pressure measurement from the left ventricle and the aorta, and 3 patients underwent simultaneous recording of electrocardiogram and LVAD electrical signal.
Results: Resting heart rate was significantly higher than LVAD rate (96 +/- 17 vs 66 +/- 15 beats [b]/min, p < 0.0001), with no correlation between the 2 (r = 0.25). Peak heart rate was significantly higher than LVAD rate (142 +/- 16 vs 102 +/- 14 b/min, p < 0.0001), with no correlation observed (r = 0.31). Electrical signal recording confirmed the absence of cardiac-LVAD synchrony. Pressure measurements revealed a cyclical intraventricular pressure variation, determined by the relationship between the cardiac and LVAD cycles. Intraventricular pressure was lowest when left ventricular systole occurred during pump filling and highest when left ventricular systole occurred during pump ejection.
Conclusions: The cardiac and LVAD cycles are not in synchrony at rest or at peak exercise. However, a cyclical variation in left ventricular pressure exists, dependent upon the phasic relationship of the cardiac-LVAD cycles, which significantly effects ventricular loading. Better understanding of this relationship may be important in developing assist devices for optimal left ventricular unloading and improvement of myocardial recovery.