ABNORMAL BARORECEPTOR-CARDIAC REFLEX SENSITIVITY IS NOT DETECTED BY CONVENTIONAL TESTS OF AUTONOMIC FUNCTION IN PATIENTS WITH INSULIN-DEPENDENT DIABETES-MELLITUS

1. Autonomic neuropathy is a common complication of diabetes mellitus and is a major risk factor for sudden death. 2. A group of 30 patients with insulin-dependent diabetes mellitus and 30 age-, sex- and blood pressure-matched control subjects underwent traditional tests of auton omic function. Resting supine R-R interval and systolic blood pressure variability were assessed using spectral analysis methods. In additio n, we assessed the baroreceptor-cardiac reflex from the linear relatio n of the change in R-R interval to the increasing systolic blood press ure measured noninvasively with the Finapres monitor during phase 4 of the Valsalva manoeuvre and from resting heart rate and systolic blood pressure power spectra. 3. Whereas standard tests of autonomic functi on revealed no differences between patients with insulin-dependent dia betes mellitus and control subjects, there was a significant reduction in power spectral density of heart rate variability around the high-f requency region (125.2+/-112.9 versus 459.3+/-189.8 ms(2), mean+/-SD). Furthermore, reductions in baroreflex sensitivity calculated from the Valsalva manoeuvre were detected in diabetics compared with controls (3.3+/-1.6 versus 9.5+/-2.5 ms/mmHg, mean+/-SD, P<0.00001). There were significant relations between impairment of the baroreflex and durati on of diabetes (P<0.001) and poor diabetic control (P<0.05). 4. In sum mary, autonomic dysfunction occurs much more frequently in diabetic pa tients than conventional tests would suggest. Abnormal baroreceptor-ca rdiac reflex sensitivity in patients with insulin-dependent diabetes m ellitus may in part be explained by abnormal parasympathetic function. This unrecognized abnormality may have a role in the increased incide nce of sudden death seen in young diabetic subjects.