P90 Kinetic Energy and Energy Loss in the Middle Cerebral Artery (MCA) of Heartmate II Patients

Abstract

Background

In heart failure patients with continuous-flow left ventricular assist devices (CF-LVAD), arterial pulsatility in the brain is reduced and diastolic blood velocities (Vmin) are maintained. The effects of such altered hemodynamics on kinetic energy and, importantly, energy loss in the cerebral circulation have never been studied.

Methods

Angle-corrected Doppler ultrasound movies of the middle cerebral artery (MCA) were recorded in 11 healthy volunteers, 5 patients with severe heart failure, and 4 patients with HM II. Data were analyzed offline using validated Vector Flow Mapping software (Cardio Flow Design, Tokyo, Japan). Vmin, pulsatility index (PI), total Energy Loss (ELAUC) and total Kinetic Energy (KEAUC) and both variables normalized for different heart rates (ELAUC/time & KEAUC/time) were calculated (Figure 1). Correlations between these energetic parameters and PI were determined.

Results

PI, KEAUC and ELAUC were significantly lower in HM II (P < 0.0001 and P < 0.05) while Vmin was similar (Fig 1). Normalization of data for different heart rates (ELAUC/time & KEAUC/time) revealed the same results. PI correlated with KEAUC (logr2 = 0.33, P = 0.008) but not ELAUC (logr2 = 0.154, P = 0.087).

Conclusions

ELAUC and KEAUC were significantly lower in HM II. The correlation between KEAUC and PI suggests that pulsatility may have an important impact not only on the stretch of arteries but also on the energetics of blood flow. Future studies should evaluate the clinical meaning of these observations.