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. 2022 Jul;46(7):1334-1345.
doi: 10.1111/aor.14207. Epub 2022 Mar 3.

Factors influencing the functional status of aortic valve in ovine models supported by continuous-flow left ventricular assist device

Xin-Yi Yu  1 , Jian-Wei Shi  1 , Yi-Rui Zang  1 , Jie-Min Zhang  2 , Zhi-Gang Liu  1
Affiliations

Factors influencing the functional status of aortic valve in ovine models supported by continuous-flow left ventricular assist device

Xin-Yi Yu et al. Artif Organs. 2022 Jul.

Abstract

Objectives: An acute animal experiment was performed to observe factors influencing the functional status of the aortic valve functional status after continuous-flow left ventricular assist device (CF-LVAD) implantation in an ovine model, and a physiologic predictive model was established.

Methods: A CF-LVAD model was established in Small Tail Han sheep. The initial heart rate (HR) was set to 60 beats/min, and grouping was performed at an interval of 20 beats/min. In all groups, the pump speed was started from 2000 rpm and was gradually increased by 50-100 rpm. A multi-channel physiological recorder recorded the HR, aortic pressure, central venous pressure, and left ventricular systolic pressure (LVSP). A double-channel ultrasonic flowmeter was used to obtain real-time artificial vascular blood flow (ABF). A color Doppler ultrasound device was applied to assess the aortic valve functional status. Multivariate dichotomous logistic regression was used to screen significant variables for predicting the functional status of the aortic valve.

Results: Observational studies showed that ABF and the risk of aortic valve closure (AVC) were positively correlated with pump speed at the same HR. Meanwhile, the mean arterial pressure (MAP) was unaltered or slightly increased with increased pump speed. When the pump speed was constant, an increase in HR was associated with a decrease in the size of the aortic valve opening. This phenomenon was accompanied by an initial transient increase in the ABF and MAP, which subsequently decreased. Statistical analysis showed that the AVC was associated with increased pump speed (OR = 1.02, 95% CI = 1.01-1.04, p = 0.001), decreased LVSP (OR = 0.95, 95% CI = 0.91-0.98, p = 0.003), and decreased pulse pressure (OR = 0.82, 95% CI = 0.68-0.96, p = 0.026). ABF or MAP was negatively associated with the risk of AVC (OR < 1). The prediction model of AVC after CF-LVAD implantation exhibited good differentiation (AUC = 0.973, 95% CI = 0.978-0.995) and calibration performance (Hosmer-Lemeshow χ2 = 9.834, p = 0.277 > 0.05).

Conclusions: The pump speed, LVSP, ABF, MAP, and pulse pressure are significant predictors of the risk of AVC. Predictive models built from these predictors yielded good performance in differentiating aortic valve opening and closure after CF-LVAD implantation.

Keywords: LVAD; aortic valve; influencing factors; nomogram; predictive model.

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Conflict of interest statement

All authors had no conflicts of interest to disclose.

Figures

FIGURE 1
FIGURE 1
HeartCon implantable magnetic and hydrodynamic levitation blood pump and attachments. (A) blood pump; (B) artificial vascular protective stent; (C) sewing ring
FIGURE 2
FIGURE 2
The efficiency curve of HeartCon
FIGURE 3
FIGURE 3
The flux characteristic curve of HeartCon. Pressure difference = Outlet pressure − Inlet pressure
FIGURE 4
FIGURE 4
The functional status of the aortic valve with changing pump speed at a constant HR of 70 beats/min. (A) 2100 rpm pump speed, AVO; (B) 2300 rpm pump speed, AVO; (C) 2350 rpm pump speed, AVO; (D) 2400 rpm pump speed, AVC. ABF, artificial vascular blood flow; AOP, aortic pressure; AVC, aortic valve closure; AVO, aortic valve opening; HR, heart rate; PD, pressure difference
FIGURE 5
FIGURE 5
M‐mode echocardiography of the functional status of the aortic valve at a constant HR of 70 beats/min. All ultrasound examinations showed no signs of aortic regurgitation. Aortic valve leaflets open/close 1:1 in A–C. complete closure of the aortic valve leaflets in D. (A) 2100 rpm pump speed, AVO; (B) 2300 rpm pump speed, AVO; (C) 2350 rpm pump speed, AVO; (D) 2400 rpm pump speed, AVC
FIGURE 6
FIGURE 6
The functional status of aortic valve with changing HR at a constant pump speed of 2400 rpm. (A) 61 beats/min HR, AVO; (B) 90 beats/min HR, AVO; (C) 104 beats/min HR, AVO; (D) 120 beats/min HR, AVC. ABF, artificial vascular blood flow; AOP, aortic pressure; AVC, aortic valve closure; AVO, aortic valve opening; HR, heart rate; PD, pressure difference
FIGURE 7
FIGURE 7
Nomogram. ABF, artificial vascular blood flow; LVSP, left ventricular systolic pressure; MAP, mean arterial pressure; PP, pulse pressure; PRS, pump rotate speed
FIGURE 8
FIGURE 8
ROC curve analysis
FIGURE 9
FIGURE 9
Hemodynamics in the normal heart after CF‐LVAD implantation. (A) Normal heart: The left ventricle contracts, blood enters the aorta through the aortic valve; (B) the aortic valve is completely closed, the natural left ventricle and CF‐LVAD work in series model, and blood enters the aorta via CF‐LVAD; (C) aortic valve opening or intermittent opening, natural left ventricle, and CF‐LVAD work in “parallel”, part of the blood enters the aorta through the aortic valve)
FIGURE 10
FIGURE 10
The example of nomogram. ABF, artificial vascular blood flow; LVSP, left ventricular systolic pressure; MAP, mean arterial pressure; PP, pulse pressure; PRS, pump rotate speed
See this image and copyright information in PMC

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