Resting muscle sympathetic nerve activity does not predict duration of symptom-limited submaximal exercise in young patients with dilated cardiomyopathy

Abstract

Objective: To determine whether increased sympathetic vasoconstrictor drive to the calf in heart failure is associated with reduced symptom-limited submaximal exercise performance.

Design: 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.

Patients: 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.