Key result
Maximal bicycle exercise increases LVAD minimum flow and flow pulsatility in ~70% of tests.
Why the study?
LVADs do not currently respond to exercise demands, prompting exploration of hemodynamic responses during maximal exercise to infer patient status and advance physiologically adaptive controllers.
How do LVAD flow waveforms change during maximal exercise in patients with continuous-flow LVADs?
Observational (n=14)
No
How do LVAD flow waveforms change during maximal exercise in patients with continuous-flow LVADs?
LVAD flow waveforms during exercise reveal distinct hemodynamic 'fingerprints' driven largely by left ventricular contractility, which could inform the development of physiologically adaptive LVAD controllers.
Heterogeneous LVAD flow responses to exercise warrant caution against uniform assumptions; hypothesis-generating for contractility-informed adaptive controllers.
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 (QMIN), mean (QMEAN), maximum flow (QMAX) and flow pulsatility (QP2P). 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 ΔQMIN↑ and ΔQP2P↑ from rest to exercise (70% of exercise tests). Two responses, which were never reported in patients so far, were distinguished by QMIN↑ and QP2P↓ (observed in 17%) and by QMIN↓ and QP2P↑ (observed in 13%). The simulations indicated that the QP2P↓ can result from a reduced left ventricular contractility and that the QMIN↓ 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.
No takes yet. Share an insight, caveat, or question.
Gross et al. (2020) conducted an observational in End-stage heart failure with left ventricular assist device (LVAD) (n=14). Maximal bicycle exercise vs. Rest (baseline) was evaluated on Hemodynamic LVAD flow waveform responses (changes in minimum flow and flow pulsatility) from rest to peak exercise. Maximal bicycle exercise in LVAD patients elicited distinct hemodynamic flow waveform responses, with 70% of tests showing an increase in both minimum flow and flow pulsatility.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: