Differential Response to Afterload in Axial and Centrifugal Continuous Flow Left Ventricular Assist Devices (CV-LVAD)

Abstract

Purpose CF-LVADs generate a specific flow for a given pressure differential across the pump. Implications of difference between afterload sensitivity of axial and centrifugal pumps has not been previously described. Methods and Materials All CF LVAD at a single center from 5/06 to 10/11, supported >30 days and managed with a standardized blood pressure (BP) protocol with target mean ≤ 80 mmHg. Mean number of data points per patient was 318. Contour mapping compared speed, pressure, and power. Results There were 96 CF-LVADs with mean support of 262 days. Patient demographics: age 55 years, male 80%, white 79%, ischemic 50%, BTT 55%, 61 axial & 35 centrifugal LVAD. Mean BP was near goal and not different between axial and centrifugal devices ( Figure 1a ). No BP meds at end of follow-up: 25 patients, 14 of whom died on device. Of patients on therapy, 38 were managed on 1 medication and 33 on 2+ medications. As expected, for each pump type at the same BP (afterload), power consumption and thus flow, increased with increasing pump speed. However, pump types differed somewhat in their response to increased afterload ( Figure 1b ). For axial pumps, at a given pump speed there was little change in pump power over clinically relevant ranges of afterload. In contrast, centrifugal pumps had more afterload dependence with a decrease in pump power with increasing afterload. Conclusions In the setting of aggressive BP control, axial and centrifugal pumps demonstrated a differential response to increasing afterload, with centrifugal pumps having greater afterload dependence. BP control is important in all patients with CF-LVADs, but poorly controlled BP may impair pump flow to a greater degree in patients with centrifugal devices.