Prediction of the External Work of the Native Heart From the Dynamic H‐Q Curves of the Rotary Blood Pumps During Left Heart Bypass

Abstract

The ventricular performance is dependent on the drainage effect of rotary blood pumps (RBPs) and the performance of RBPs is affected by the ventricular pulsation. In this study, the interaction between the ventricle and RBPs was examined using the pressure-volume (P-V) diagram of the ventricle and dynamic head pressure-bypass flow (H-Q) curves (H, head pressure: arterial pressure minus ventricular pressure vs. Q, bypass flow) of the RBPs. We first investigated the relationships in a mock loop with a passive fill ventricle, followed by validation in ex vivo animal experiments. An apical drainage cannula with a micro-pressure sensor was especially fabricated to obtain ventricular pressure, while three pairs of ultrasonic crystals placed on the heart wall were used to derive ventricular volume. The mock loop-configured ventricular apical-descending aorta bypass revealed that the external work of the ventricle expressed by the area inside the P-V diagrams (EW(Heart) ) correlated strongly with the area inside dynamic H-Q curves (EW(VAD)), with the coefficients of correlation being R² = 0.869 ∼ 0.961. The results in the mock loop were verified in the ex vivo studies using three Shiba goats (10-25 kg in body weight), showing the correlation coefficients of R² = 0.802 ∼ 0.817. The linear regression analysis indicated that the increase in the bypass flow reduced pulsatility in the ventricle expressed in EW(Heart) as well as in EW(VAD) . Experimental results, both mock loop and animal studies, showed that the interaction between cardiac external work and H-Q performance of RBPs can be expressed by the relationships "EW(Heart) versus EW(VAD) ." The pulsatile nature of the native heart can be expressed in the area underneath the H-Q curves of RBPs EW(VAD) during left heart bypass indicating the status of the level of assistance by RBPs and the native heart function.

Simulation of Ventricular, Cavo‐Pulmonary, and Biventricular Ventricular Assist Devices in Failing Fontan

“…The LVAD (Jarvik 2000) pump speed was set at 35 000 rpm, while the RVAD (intravascular axial flow blood pump) pump speed was set at 4000 rpm. The VADs’ power consumption ( EW VAD ) was calculated for each simulation as : …”

Correlation between Myocardial Function and Electric Current Pulsatility of the Sputnik Left Ventricular Assist Device: In-Vitro Study

“…Control issues of the LVAD presented in Figure 2 include: (1) The discrepancy between the parameters that need to be controlled ensuring circulatory support (i.e., P 1 , P 2 , Q 1 , Q 3 ); (2) the parameters generated by the continuous-flow rotary pump (H, Q 2 ); and (3) the parameters that can be tracked and changed in real-time during LVAD support (I, ω). It was previously shown that there are ways to find correlations between different parameters using: (1) A ratio between the maximum flow acceleration and flow pulsatility at baseline pump speed as an alternative to a regression coefficient between the maximum flow acceleration and flow pulsatility at different pump speeds [25]; (2) the external work of the ventricle expressed by the area inside the P-V diagrams which correlates with the area inside dynamic H-Q curves [26]; or (3) energetic characteristics of LV-LVAD interaction [27]. Our hypothesis is that changes in the work (A) of the left ventricle affect the recorded parameter of the electric current (I).…”

Evaluation of Left Ventricular Assist Device Electrical Current as a Predictor of Left Ventricular Recovery

“…2) the external work of the ventricle expressed by the area inside the P-V diagrams correlates with the area inside dynamic H-Q curves [31]; or 3) energetic characteristics of LV-LVAD interaction.…”