Acute Effect in Mechanical Efficiency by Pressure-Volume Loop Analysis after Transcatheter Aortic Valve Implantation

Abstract

Background: This study aimed to evaluate the immediate effect of transcatheter aortic valve implantation (TAVI) on mechanical efficiency.

Methods: A total of 46 patients (25 females) with an average age of 83 ± 6.4 years underwent TAVI using the CoreValve system. During the same hospitalization, we conducted a comprehensive comparison of the patients before and after TAVI without inotropic support using echocardiography. The parameters encompassed left ventricular (LV) geometry, valvular load, global LV afterload and ventricular hemodynamics. The analysis using pressure-volume loops enabled the determination of load-independent contractility (Ees) and afterload, in addition to assessing potential energy, stroke work, and mechanical efficiency.

Results: The immediate effect was an augmented aortic valve area accompanied by a reduction in the transvalvular pressure gradient. We observed reductions in left ventricular end-systolic volume and end-diastolic volume, and also reductions in global afterload and end-systolic meridional wall stress. The Ea index decreased, while the Ees index remained relatively stable. We noted increases in stroke volume and systemic arterial compliance, indicating more efficient blood transfer from the ventricle to aorta. These changes contributed to the normalization of ventricular-arterial coupling. In terms of mechanical work of the chamber, we observed significant decreases in potential energy, stroke work, and pressure-volume area. There was an increase in the mechanical efficiency of the chamber.

Conclusions: The TAVI procedure immediately reduced global afterload and improved diastolic compliance of the chamber, resulting in enhanced ventricular function and mechanical efficiency.

Keywords: Mechanical efficiency; Pressure-volume loop; Ventricular-arerial coupling.

Figure 1

Average left ventricular pressure-volume loop, pre-TAVI (blue lines) and post-TAVI (red lines). Following TAVI, reductions in ESV, EDV, ESP, and Ea were observed, along with decreases in PE, SW, and PVA. Furthermore, the PV loop exhibited leftward shifts. PE represents the triangular area enclosed by the ESPVR, EDPVR, and the left border of the PV loop, while SW represents the overall area of the PV loop. The PV area is calculated as the sum of PE and SW. Ea, arterial elastance; EDPVR, end-diastolic pressure-volume relationship; EDV, end-diastolic volume; Ees, ventricular end-systolic elastance; ESP, end-systolic pressure; ESPVR, end-systolic pressure-volume relationship; ESV, end-systolic volume; PE, potential energy; PVA, pressure-volume area; SW, stroke work; TAVI, transcatheter aortic valve implantation. Modified from Di Bello (7).

Figure 2

Correlation in alterations of hemodynamics and energetics between baseline and post-TAVI with linear regression. The change in ESV is proportional to the changes in PE, as shown in A. But inverse relation with change in mechanical efficiency as depicted in B. The change in EDV is inverse relation with change in mechanical efficiency as shown in C. The change in SV is proportional with change in stroke work in D. The change in ESP is proportional to the changes in stroke work as depicted in E. The change in wall stress is proportional to change in potential energy as shown in F. cJ, centi-Joule; EDV, end-diastolic volume; ESP, end-systolic pressure; ESV, end-systolic volume; LVESP, left ventricular end-systolic pressure; ME, mechanical efficiency; PE, potential energy; SV, stroke volume; SW, stroke work; TAVI, transcatheter aortic valve implantation; WS, wall stress.

Central Illustration

(A) The ventricular function curve relates end-diastolic pressure to cardiac output. The ventricular function curve shifts up and to the left when increased ventricular contractility, decreased afterload, and increased compliance. (B) TAVI reduces LV end-systolic pressure (LV ESP) and LV end-systolic volume (LV ESV), improving afterload and compliance, ultimately resulting in decreased potential energy and stroke work. Ea, arterial elastance; EDPVR, end-diastolic pressure-volume relationship; EDV, LV end-diastolic volume; Ees, LV end-systolic elastance; ESP, LV end-systolic pressure; ESPVR, end-systolic pressure-volume relationship; ESV, end-systolic volume; PE, potential energy; SW, stroke work; TAVI, transcatheter aortic valve. Modified from Walley (17).