Biomechanical efficiency is impaired in patients with chronic heart failure.
BACKGROUND
Patients with chronic heart failure (CHF) have a lower peak oxygen consumption (pVO2) than normal subjects, and for a given quantity of work, have a lower total oxygen consumption (VO2) than controls. This apparent increase in biomechanical efficiency (BE) might be due to a higher proportion of anaerobic metabolism which, although leading to lower VO2 during steady state exercise, must be compensated for during recovery.


METHODS
13 patients with stable CHF and 12 controls underwent peak cycle exercise testing followed by three separate steady state exercise tests at 15%, 25% and 50% of the peak workload in random order. Oxygen consumption at steady state, deficit (during onset) and debt (during recovery) were calculated. BE was estimated as the total oxygen required to perform a given quantity of work.


RESULTS
Patients had lower pVO2 and peak workload than control subjects. Absolute oxygen deficit and debt as a percentage of total oxygen consumed during the steady state tests was the same in both groups. However, once controlled for workload, VO2 deficit, debt and uptake at steady state were greater in patients than controls for the tests at 15% and 25% of peak. BE was inversely related to peak oxygen consumption in controls and patients.


CONCLUSIONS
Patients with CHF have impaired BE at low work loads when compared with normal subjects.
Witte
Klaus K
KK
Department of Cardiology, Leeds General Infirmary, Great George Street, Leeds, LS1 3EX, UK. klauswitte@hotmail.com
Levy
Wayne C
WC
Lindsay
Kenneth A
KA
Clark
Andrew L
AL
D000368:Aged; D015308:Anaerobic Threshold; D001696:Biomechanical Phenomena; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D010101:Oxygen Consumption