Cw. Barlow et al., EFFECT OF PHYSICAL-TRAINING ON EXERCISE-INDUCED HYPERKALEMIA IN CHRONIC HEART-FAILURE - RELATION WITH VENTILATION AND CATECHOLAMINES, Circulation, 89(3), 1994, pp. 1144-1152
Background The exercise-induced rise in arterial potassium concentrati
on ([K+](a)) may contribute to exercise hyperpnea and could play a rol
e in exertional fatigue. This study was designed to determine whether
the exercise-induced rise in [K+](a) is altered in patients with chron
ic heart failure (CHF) and whether physical training affects K+ homeos
tasis. Methods and Results We evaluated 10 subjects with CHF (ejection
fraction, 23+/-3.9%) and 10 subjects with normal left ventricular fun
ction (NLVF) who had undergone previous coronary artery graft surgery
(ejection fraction, 63+/-8.6%). Subjects performed an incremental cycl
e ergometer exercise test before and after a physical training or detr
aining program. Changes in [K+](a) and ventilation (V-E) during exerci
se were closely related in both groups. Subjects with CHF did less abs
olute work and had reduced maximal oxygen consumption (Vo(2)max) compa
red with subjects with NLVF (P<.01). Exercise-induced rises in [K+](a)
, V-E, norepinephrine, lactate, and heart rate were greater at matched
absolute work rates in subjects with CHF than in subjects with NLVF (
P<.01). However, when the rise in [K+](a) was plotted against percenta
ge of Vo(2)max to match for relative submaximal effort, there were no
differences between the two groups. Physical training resulted in redu
ced exercise-induced hyperkalemia at matched submaximal work rates in
both groups (P<.01) despite no associated change in the concentration
of arterial catecholamines. At maximal exercise when trained, peak inc
reases in [K+](a) were unaltered, but peak concentrations of catechola
mines were raised (P<.05). The decrease in V-E at submaximal work rate
s after training was not significant with this incremental exercise pr
otocol, but both groups had an increased peak V-E when trained (P<.01)
. Conclusions Exercise-induced; rises in [K+](a), catecholamines, and
V-E, are greater at submaximal work rates in subjects with CHF than in
subjects with NLVF, Physical training reduces the exercise-induced ri
se in [K+](a) but does not significantly decrease V-E during submaxima
l exercise with this incremental cycle ergometry protocol. The reducti
on in exercise-induced hyperkalemia after training is not the result o
f altered concentrations of aterial catecholamines. The pathophysiolog
ical significance of the increased exercise-induced hyperkalemia in CH
F and the mechanisms of improved K+ homeostasis with training have yet
to be established.