Leg blood flow and increased potassium release during exercise in chronic heart failure: effect of physical training.

BACKGROUND: Exercise-induced hyperkalemia, which may contribute to exercise hyperpnea and exertional fatigue, is increased in patients with chronic heart failure (CHF). This study examined whether differences in leg blood flow during exercise could be responsible for alterations in the level of hyperkalaemia, as well as the effect of physical training. METHODS AND RESULTS: We studied 10 subjects with CHF (ejection fraction 23 +/- 3.9%; mean +/- SD) and 10 subjects with normal left ventricular function (NLVF) who had undergone previous coronary bypass graft surgery (ejection fraction 64 +/- 8.0%; mean +/- SD). Subjects performed incremental cycle exercise to exhaustion before and after physical training. The rises in femoral venous potassium concentration ([K+]), heart rate, lactate, and ventilation (VI) with exercise were all greater in the subjects with CHF than in those with NLVF (P < .05). There was no difference between the groups in leg blood flow during submaximal exercise but peak leg flow was greater in the group with NLVF (P < .01). Physical training was well tolerated and both groups increased their peak VO2 (8 +/- 3.2% CHF (P < .05); 11 +/- 2.7% NLVF (P < .01); mean +/- SE). Training resulted in a reduced rise in femoral venous [K+] and VI (P < .05), but did not affect leg blood flow during submaximal exercise in either group. CONCLUSIONS: The rise in the femoral venous [K+] with exercise is increased in patients with CHF and can be reduced by physical training. These changes are not a consequence of different leg blood flows, either between groups or with training. The study also suggests that femoral venous [K+] is not a powerful regulator of leg blood flow during exercise.