Open AccessHemodynamic exercise responses with a continuous-flow left ventricular assist device: Comparison of patients’ response and cardiorespiratory simulations
Author(s) -
Christoph Gross,
Libera Fresiello,
Thomas Schlöglhofer,
Kamen Dimitrov,
Christiane Marko,
Martin Maw,
Bart Meyns,
Dominik Wiedemann,
Daniel Zimpfer,
Heinrich Schima,
Francesco Moscato
Publication year - 2020
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0229688
Subject(s) - cardiology , medicine , hemodynamics , ventricular assist device , cardiorespiratory fitness , heart failure , contractility , inotrope
Background Left ventricular assist devices (LVADs) are an established treatment for end stage heart failure patients. As LVADs do not currently respond to exercise demands, attention is also directed towards improvements in exercise capacity and resulting quality of life. The aim of this study was to explore hemodynamic responses observed during maximal exercise tests to infer underlying patient status and therefore investigate possible diagnostics from LVAD derived data and advance the development of physiologically adaptive LVAD controllers. Methods High resolution continuous LVAD flow waveforms were recorded from 14 LVAD patients and evaluated at rest and during maximum bicycle exercise tests (n = 24). Responses to exercise were analyzed in terms of an increase (↑) or decrease (↓) in minimum (Q MIN ), mean (Q MEAN ), maximum flow (Q MAX ) and flow pulsatility (Q P2P ). To interpret clinical data, a cardiorespiratory numerical simulator was used that reproduced patients’ hemodynamics at rest and exercise. Different cardiovascular scenarios including chronotropic and inotropic responses, peripheral vasodilation, and aortic valve pathologies were simulated systematically and compared to the patients’ responses. Results Different patients’ responses to exercise were observed. The most common response was a positive change of ΔQ MIN ↑ and ΔQ P2P ↑ from rest to exercise (70% of exercise tests). Two responses, which were never reported in patients so far, were distinguished by Q MIN ↑ and Q P2P ↓ (observed in 17%) and by Q MIN ↓ and Q P2P ↑ (observed in 13%). The simulations indicated that the Q P2P ↓ can result from a reduced left ventricular contractility and that the Q MIN ↓ can occur with a better left ventricular contractility and/or aortic insufficiency. Conclusion LVAD flow waveforms determine a patients’ hemodynamic “fingerprint” from rest to exercise. Different waveform responses to exercise, including previously unobserved ones, were reported. The simulations indicated the left ventricular contractility as a major determinant for the different responses, thus improving patient stratification to identify how patient groups would benefit from exercise-responsive LVAD control.