Echocardiographic assessment of flow across continuous-flow ventricular assist devices at low speeds

Testing of native myocardial function in patients with continuous-flow pumps is challenging as reduction/cessation of the pump could result in regurgitation, although the amount and significance of this regurgitation remains unknown. The aim of this study was to determine the optimal speed at which to assess the native left ventricular (LV) function and the physiologic response to speed reduction.

Fifteen male patients with a HeartMate II (HMII) device were studied prospectively on 46 occasions. Measurements were performed serially at three device speed settings: baseline speed; 6,000 rpm; and either 5,000 rpm (Group A) or 4,000 rpm (Group B). The device's forward and reverse velocity (Vmax(f), Vmax(r)), forward and reverse velocity time integral (VTI(f), VTI(r)) and blood volume (BV) were also measured using Doppler with LV echocardiographic parameters and peripheral hemodynamics.

No adverse incidents were reported. Speed reduction to 6,000 rpm resulted in a significant decrease in Vmax(f), VTI(f) and BV. There was no significant difference in either forward or reverse flow with further speed reduction in either group. Speed reduction to <6,000 rpm did not have a significant effect on LV loading.

Speed reduction in patients with the HMII device is safe. There was no difference between 6,000 rpm and lower speeds, suggesting that 6,000 rpm is sufficient to assess native myocardial function. The absence of significant retrograde filling suggests that LV loading is a physiologic response to speed reduction at 6,000 rpm.