Cardiovascular reflexes in short-term diabetics with normal physical working capacity.

The aim of the study was to elucidate whether disturbances of sympathetic and parasympathetic control of cardiac functions appear in short-term diabetics. For this purpose, cardiovascular reflexes [resting heart rate (HR), respiratory sinus arrhythmia, Valsalva manoeuvre, orthostatic test] and physical working capacity were investigated in fifteen maturity-onset diabetics (aged 40-60 years, duration of diabetes 1-9 years) and nineteen healthy volunteers. All diabetics had normal sensory tests, positive Achilles tendon jerks, and no signs of retinopathy or nephropathy. In the diabetics, HR at rest was increased (in the diabetics 80 +/- 12 vs 69 +/- 9 beats/min in the controls, P less than 0.01), the Valsalva ratio was decreased (P less than 0.01) and respiratory sinus arrhythmia decreased (P less than 0.05). In contrast, the physical working capacity was not altered. This study demonstrates impairment of cardiovascular reflexes in short-term diabetics, most likely due to neuropathy of the vagal nerves.