Haemodynamic response to an isometric exercise test in obese patients: Influence of autonomic dysfunction

OBJECTIVE: To investigate blood pressure (BP) and heart rate (HR) responses to an isometric exercise test in obese non diabetic patients and to correl ate the results with vagal function and plasma insulin concentration. SUBJECTS: 63 obese patients, 36 of whom had abnormal cardiac parasympatheti c control (PS +), and 35 healthy control subjects. METHODS: Analysis of HR variations during three standardized tests: deep-br eathing, lying-to-standing and Valsalva. Isometric contraction (handgrip) f or 5 min. RESULTS: In the PS + obese patients, resting HR and body mass index (BMI) w ere significantly higher than in the PS - subjects and there was a trend to higher plasma insulin concentrations. Age-matched comparison showed that d uring the handgrip test, the increase in HR at the first minute was signifi cantly higher in the PS - obese patients than in the controls. The increase in BP was significantly lower in the PS + obese patients than in age-and-B MI-matched PS - obese patients. CONCLUSION: These data suggest that 1) there is an increase in cardiac vaga l tone in PS - obese patients, since the early increase in HR at 1 min of t he handgrip test, results from the withdrawal of vagal tone; 2) BP response to an isometric contraction is impaired in PS + obese patients due to a lo wer sympathetic activation; 3) high plasma insulin concentrations may also contribute to limiting the BP response; and 4) autonomic disorders may acco unt for alterations in the haemodynamic changes during exercise.