Lookup NU author(s): Dr Djordje Jakovljevic
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Purpose: The present study assessed the effect of acute reduction of continuous-flow left ventricular assist device (LVAD) support on resting and peak exercise cardiac power output and other haemodynamic and metabolic measurements. Methods: Twelve male patients (age 37±10 yrs) implanted with continuous-flow LVADs, visited the exercise laboratory twice during the same day with at least four hours rest between the two visits. During the first visit, LVAD support was optimal with speeds ranging from 9,000 to 9,600 revolutions per minute. During the second visit the LVAD support was reduced at 6,000 revolutions per minute. Measurements at rest and at the peak exercise of the modified Bruce protocol were undertaken using non-invasive, inert gas, rebreathing haemodynamic and respiratory gas procedures. Cardiac power output, expressed in watts (W), was calculated from cardiac output and mean arterial blood pressure as previously suggested. Results: In response to reduced LVAD support, resting cardiac power output decreased by 21% (from 0.87 to 0.69 W, p=0.068) as was cardiac output by 13% (from 5.3 to 4.6 l min-1, p=0.141) and mean arterial pressure by 9% (from 74.1 to 67.3 mm Hg, p=0.123). Resting stroke volume decreased by 18% (from 71.4 to 58.2 ml.beat-1, p=0.072) while resting heart rate increased by 5% (from 74 to 79 beats min-1, p=0.126). At peak exercise most of the measured haemodynamic and metabolic variables decreased significantly in response to reduced device support. Cardiac power output decreased by 39% (from 2.31 to 1.40 W, p<0.001), cardiac output by 30% (from 12.2 to 8.6 l min-1, p<0.001), mean arterial pressure by 13% (from 85.4 to 74.3 mm Hg, p=0.006), stroke volume by 24% (from 88.4 to 67.5 ml beats-1, p=0.039) and heart rate by 9% (from 138 to 126 beats min-1, p=0.046). Peak oxygen consumption reduced by 23% (from 18.2 to 14.1 ml kg-1 min-1, p=0.004) whereas exercise time decreased by 18% (from 628 to 516 seconds, p=0.032). Conclusion: The present study suggests that cardiac power output is more sensitive to acute reduction of LVAD support than conventionally measured peak oxygen consumption, and therefore should probably be used in the management of LVAD patients.
Author(s): Jakovljevic DG, George R, Donovan G, Nunan D, Bougard R, Birks E, Yacoub M, Brodie DA
Publication type: Article
Publication status: Published
Journal: European Heart Journal Supplements
Print publication date: 01/01/2009
ISSN (print): 1520-765X
ISSN (electronic): 0195-668X
Publisher: Oxford University Press