LVAD Pump Flow Does Not Adequately Increase With Exercise

Gross, Christoph; Marko, Christiane; Mikl, Johann; Altenberger, Johann; Schlöglhofer, Thomas; Schima, Heinrich; Zimpfer, Daniel; Moscato, Francesco

doi:10.1111/aor.13349

Cited by 34 publications

(43 citation statements)

References 34 publications

(62 reference statements)

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“… EmaxL : among all the investigated parameters, EmaxL is one of the most important in assuring a higher TCO at exercise. These results are in line with previous clinical studies evidencing the crucial role of the residual LV function in eliciting a higher TCO and exercise capacity . Noor et al observed that patients with a residual LV contractility are able to better accommodate an increase in TCO, resulting in higher exercise capacities.…”

Section: Discussionsupporting

confidence: 91%

“…The increased HR and LV preload resolved in a higher Q AV (+0.5 L/min) while only a minimal increase in Q LVAD (+0.1 L/min). This rather mild relationship between HR and Q LVAD during exercise is in agreement with previous clinical observations . Regardless of the individual contribution of the LV and the LVAD, simulations evidenced that an increase in HR does translate ultimately in an increase in TCO (+0.7 L/min).…”

Section: Discussionsupporting

confidence: 91%

“…A rough classification is provided below: Concomitant increase in Q AV and Q LVAD : the exercise profile with a better chronotropic response (HR+), better right ventricular contractility (EmaxR+), and a better vasodilation (TPR‐) elicited to both Q AV and Q LVAD increase compared to the BL patient. Reduction in Q AV and increase in Q LVAD : AS and AI reduce Q AV and increase Q LVAD compared to BL, in the first case due to the obstruction the blood flow encounters through the aortic valve (AV), in the second case due to the backflow through the AV in diastole. Reduction in Q LVAD and increase in Q AV : a better inotropic response of the LV (EmaxL+) positively affects Q AV while limiting Q LVAD . This inverse trend is named “competing mechanism” between the LV and the LVAD and has been discussed previously . The competing mechanism occurs with AV opening and results in a reduced sensitivity of Q LVAD to preload compared to full‐support.…”

Section: Discussionmentioning

confidence: 80%

“…Fresiello et al reported that LVAD power increased less at peak exertion in patients with better exercise capacity, indicating a possible increase in TCO mostly at the expenses of the LV. In addition, Gross et al reported the importance of the cardiac response during exercise by observing correlations of peak oxygen consumption with HR and AV status, whereas Q LVAD showed no correlation. EmaxR: substantial changes in LAP MAX (+5 mm Hg) and pulmonary pressure (+5.2 mm Hg) compared to BL were observed for EmaxR+. This rather utterly high LAP MAX indicates an insufficient capacity of the LVAD+LV system in balancing the increased right ventricular output, in agreement with Refs.…”

Section: Discussionmentioning

confidence: 99%

“…Current LVADs work at a constant pump speed and do not embed physiological controllers to adapt the support to body needs at exercise. Therefore, patients mainly rely on their remaining cardiac function to increase TCO by the output through the aortic valve (Q AV ) and achieve higher peak VO 2 levels . Dependencies between low LVAD speed (below baseline value) and reduced exercise capacities were found in the previous clinical studies .…”

Section: Introductionmentioning

confidence: 93%

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LVAD speed increase during exercise, which patients would benefit the most? A simulation study

et al. 2019

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Patients supported with a left ventricular assist device (LVAD) have impaired cardiovascular adaptations during exercise, resulting in reduced total cardiac output and exercise intolerance. The aim of this study is to report associations among these impaired cardiovascular parameters and exercise hemodynamics, and to identify in which conditions an LVAD speed increase can provide substantial benefits to exercise. A cardiorespiratory simulator was used to reproduce the average hemodynamics of LVAD patients at exercise. Then, a sensitivity study was conducted where cardiovascular parameters were changed individually ±20% of their baseline value at exercise (heart rate, left/right ventricular contractility, total peripheral resistance, and valve pathologies). Simulations were performed at a baseline LVAD speed of 2700 rpm and repeated at 3500 rpm to evaluate the benefits of a higher LVAD support on hemodynamics. Total cardiac output (TCO) was mostly impaired by a poor left ventricular contractility or vasodilation at exercise (−0.6 L/min), followed by a poor chronotropic response (−0.3 L/min) and by a poor right ventricular contractility (−0.2 L/min). LVAD speed increase better unloads the left ventricle and improves total cardiac output in all the simulated conditions. The most substantial benefits from LVAD speed increase were observed in case of poor left ventricular contractility (TCO + 1.6 L/min) and vascular dysfunction (TCO + 1.4 L/min) followed by lower heart rate (TCO + 1.3 L/min) and impaired right ventricular contractility (TCO + 1.1 L/min). Despite the presence of the LVAD, exercise hemodynamic is strongly depending on the ability of the cardiovascular system to adapt to exercise. A poor left ventricular inotropic response and a poor vascular function can strongly impair cardiac output at exercise. In these conditions, LVAD speed increase can be an effective strategy to augment total cardiac output and unload the left ventricle. These results evidence the need to design a physiological LVAD speed controller, tailored on specific patient’s needs.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 91%