Resting muscle sympathetic nerve activity does not predict duration of symptom-limited submaximal exercise in young patients with dilated cardiomyopathy.
OBJECTIVE
To determine whether increased sympathetic vasoconstrictor drive to the calf in heart failure is associated with reduced symptom-limited submaximal exercise performance.


METHODS
Blood pressure, heart rate and peroneal muscle sympathetic nerve activity (MSNA) were recorded during rest and before symptom-limited treadmill exercise at 70% of resting heart rate reserve for up to 45 mins.


METHODS
Thirteen young patients with dilated cardiomyopathy (age 36 +/- 2 years).


RESULTS
MSNA (45 +/- 6 bursts/min) was more than double the level documented in an age-, sex- and weight-matched group of normal subjects studied under identical baseline conditions. Patients with ventricular dysfunction exercised for 30 +/- 3 mins on average, but exercise distance and duration were independent of resting MSNA.


CONCLUSIONS
In young patients with dilated cardiomyopathy, sympathetic nerve traffic to the calf vascular bed, measured at rest, does not predict the distance or duration of symptom-limited submaximal treadmill exercise.
Hara
K
K
Division of Cardiology, Toronto Hospital, Ontario.
Floras
J S
JS
D000328:Adult; D001794:Blood Pressure; D002311:Cardiomyopathy, Dilated / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*; D004452:Echocardiography; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D007866:Leg / Q000294:innervation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation*; D010101:Oxygen Consumption; D010991:Plethysmography; D011237:Predictive Value of Tests; D012146:Rest / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014661:Vasoconstriction / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology