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Effects of left ventricular assist devices on heart rate and Vo2 recovery trends following peak exercise: optimal vs reduced unloading speed

Lookup NU author(s): Dr Djordje Jakovljevic

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Abstract

Purpose: This study assessed heart rate and Vo2 recovery trends following peak exercise in patients recently implanted with a left ventricular assist device (LVAD). Methods: Fourteen non-paced patients (2 females) age 35±8 yrs implanted with continuous-flow LVADs (mean duration of support 45±8.5 days), undertook two modified Bruce continuous progressive exercise tests during the same day. The first test took place with the LVAD on optimal unloading speed, “pump-on”, and the second at a reduced speed where there was minimal contribution from the device into the circulation, “pump-down”. There were at least four hours rest between the two testing conditions. Heart rate and metabolic measurements were continuously recorded. Repeated measures ANOVA and paired t-tests were used to assess individual and group change scores at rest, peak exercise and throughout five minutes of a seated recovery. Delayed heart rate recovery, post peak exercise, was defined as < 18 by minute one, for this recovery position. Results: There was a significant reduction in total exercise time for the pump-down test, 683±131 vs. 617±151 seconds (p = 0.03), although three patients exercised for longer during the pump-down test. Change scores in heart rate, Vo2, RER, and perceived exertion were similar between tests at rest, during peak exercise, and during the recovery period. Four patients (29%, males) demonstrated a reduced heart rate recovery during the first two minutes (mean 15±1.1 by minute one; 22±1.3 by minute two), in both pump-on and pump-down tests. A further two patients demonstrated a delayed recovery (< 15 b min-1 by minute one) in the pump-down test. A post-exercise rise in Vo2 (3.6±0.7 ml kg-1 min-1) during minute one in the pump-down test was observed in four patients (29%, one female). In two of these patients, a smaller increase was also observed in the pump-on test. Interestingly, three of the patients (21%, males) showed a trend towards delayed heart rate and Vo2 recovery in both tests. Conclusion: This study shows that trends in heart rate and Vo2 recovery appear to be similar, despite an acute reduction in LVAD speed. However, within-individual data suggest that further investigation is warranted in order to assess whether continued LVAD support improves post-exercise heart rate and Vo2 responses in those patients demonstrating a delayed recovery pattern.


Publication metadata

Author(s): Donovan G, George R, Jakovljevic DG, Nunan D, Bougard R, Yacoub M, Birks E, Brodie DA

Publication type: Article

Publication status: Published

Journal: European Heart Journal Supplements

Year: 2009

Volume: 30

Pages: 388

Print publication date: 01/01/2009

ISSN (print): 1520-765X

ISSN (electronic): 0195-668X

Publisher: Oxford University Press


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