Theoretical estimation of cannulation methods for left ventricular assist device support as a bridge to recovery

Abstract

Left ventricular assist device (LVAD) support under cannulation connected from the left atrium to the aorta (LA-AA) is used as a bridge to recovery in heart failure patients because it is non-invasive to ventricular muscle. However, it has serious problems, such as valve stenosis and blood thrombosis due to the low ejection fraction of the ventricle. We theoretically estimated the effect of the in-series cannulation, connected from ascending aorta to descending aorta (AA-DA), on ventricular unloading as an alternative to the LA-AA method. We developed a theoretical model of a LVAD-implanted cardiovascular system that included coronary circulation. Using this model, we compared hemodynamic responses according to various cannulation methods such as LA-AA, AA-DA, and a cannulation connected from the left ventricle to ascending aorta (LV-AA), under continuous and pulsatile LVAD supports. The AA-DA method provided 14% and 18% less left ventricular peak pressure than the LA-AA method under continuous and pulsatile LVAD conditions, respectively. The LA-AA method demonstrated higher coronary flow than AA-DA method. Therefore, the LA-AA method is more advantageous in increasing ventricular unloading whereas the AA-DA method is a better choice to increase coronary perfusion.

Keywords: Bridge to Recovery; Cannulation Methods; Left Ventricular Assist Device (LVAD); Ventricular Unloading.

Fig. 1

Schematic of the LVAD-implanted cardiovascular model. Cardiovascular model (A) and three types of cannulation methods: LV-AA (B), LA-AA (C), and AA-DA (D). R, resistance; C, compliance; LA, left atrium; MV, mitral valve; LV, left ventricle; AA, ascending aorta; BA, brachiocephalic artery; UBA, upper body arteries; UBV, upper body veins; SVC, superior vena cava; RA, right atrium; TV, tricuspid valve; RV, right ventricle; PA, pulmonary arteries; PV, pulmonary veins; LCA, left coronary arteries; LCX, left circumflex; LAD, left anterior descending artery; CV, coronary veins; DA, descending aorta; LBA, lower body arteries; LBV, lower body veins; IVC, inferior vena cava, IMP, intra-myocardial pressure.

Fig. 2

Flow waveforms of pulsatile and continuous LVADs. LVAD flow waveforms during one cycle (T; 860 milliseconds) in continuous and pulsatile LVADs. Solid line, pulsatile LVAD inflow; dashed line, pulsatile LVAD outflow; dotted line, continuous LVAD flow.

Fig. 3

Comparison of cardiovascular characteristics between normal and heart failure patient. Relative value of time-varying elastance of the left ventricle under HF condition compared with normal condition (A) and following hemodynamic responses: pressure and volume curves for normal and HF conditions (B); pressure waveform of the left ventricle, left atrium, and aorta for normal (C) and HF condition (D). HF, heart failure; LV, left ventricle; LA, left atrium; Ao, aorta; T, cycle length (860 milliseconds).

Fig. 4

Cardiovascular pressure waveforms according to LVAD cannulation type. Simulated pressure waveforms in the left ventricle (LV) and atrium (LA) and ascending aorta (AA) according to cannulation locations, from left ventricle to ascending aorta (LV-AA), from left atrium to ascending aorta (LA-AA), and ascending aorta to descending aorta (AA-DA), for the LVAD-implanted HF model operating in continuous flow (A, B, and C) and counter-pulsating flow (D, E, and F) modes. T, cycle length (860 milliseconds).

Fig. 5

Pressure-volume diagram according to LVAD cannulation type. Simulated pressures-volume curves of the left ventricle according to cannulation locations, from left ventricle to ascending aorta (LV-AA), from left atrium to ascending aorta (LA-AA), and ascending aorta to descending aorta (AA-DA), for LVAD-implanted HF model operating in continuous flow (A) and counter-pulsating flow (B) mode.

Fig. 6

Coronary perfusion according to LVAD cannulation type. Simulated coronary perfusion according to cannulation locations, from left ventricle to ascending aorta (LV-AA), from left atrium to ascending aorta (LA-AA), and ascending aorta to descending aorta (AA-DA), for LVAD-implanted HF model operating in continuous flow and counter-pulsating flow mode.