4.4: Middle Cerebral Artery Pulsatility in Heart Failure and Patients with Continuous-Flow Left Ventricular assist Devices

Abstract

Background

High pulsatility index (PI) in the cerebral circulation has been associated with increased prevalence of stroke (1). Interestingly, heart failure (HF) patients implanted with continuous-flow left ventricular assist devices (CF-LVADs) have increased rates of stroke despite presenting with dramatically lower pulse pressures compared with healthy individuals (20 mmHg vs. 30–40 mmHg). Characterising and understanding flow velocity profiles of the middle cerebral artery (MCA) may provide a useful and local marker of pulsatile energy transmitted into the brain of HF and CF-LVAD patients.

Methods

PI and resistance index (RI) were quantified from Duplex ultrasound images (2D and pulsed-wave Doppler) of the MCA obtained in four heart failure patients (HF; 68 ± 7 yrs), eight CF-LVAD patients (59 ± 4 yrs) and 20 healthy controls (51 ± 7 yrs).

Results

Compared with healthy controls, PI of the MCA was actually higher in the HF group (0.72 ± 0.16 vs. 1.32 ± 0.17, P < 0.0001), but markedly lower in patients on CF-LVAD (0.36 ± 0.21, P <0.0001). However, RI was similar between healthy controls and HF patients (P > 0.05), and only lower in CF-LVAD patients (P < 0.0001).

Conclusions

PI in the MCA is significantly higher in HF but markedly lower in CF-LVAD patients, relative to healthy controls. The higher PI in HF does not appear to be associated with an altered RI. Future work should examine the cerebrovascular outcomes associated with varying levels of pulsatility and resistance in both HF and CF-LVAD patients.