IS IMPAIRED BAROREFLEX SENSITIVITY A PREDICTOR OR CAUSE OF SUDDEN-DEATH IN INSULIN-DEPENDENT DIABETES-MELLITUS

Sudden death at night is known to occur in young patients with insulin -dependent (Type 1) diabetes mellitus (IDDM) but the aetiology is unce rtain. A cardiac arrhythmia has been postulated, but there has been li ttle evidence to support this. We present the case of a 31-year-old ma n with IDDM of 17 years duration, who died suddenly while asleep. Over preceding months, he had had strict glycaemic control (HbA(1) 8.9 %), normal 24 h blood pressure (mean 131 +/- 2.1/76 +/- 2.2 mmHg), no evi dence of microangiopathy or endothelial dysfunction and normal standar d clinical tests of autonomic function. An electrocardiogram was simil arly unremarkable, with a QT(c) interval of 0.414 s, and an echocardio gram had demonstrated normal left ventricular mass index (96.4 g m(-2) ). However, there was no nocturnal dip in heart rate (daytime 74 +/- 2 .7, and nocturnal 68 +/- 1.6 beats min(-1)), and he had grossly impair ed baroreflex sensitivity during Phase 4 of the Valsalva manoeuvre (0. 5 ms mmHg(-1)), with power spectral analysis studies suggesting an abn ormality of parasympathetic function. The coroner's autopsy demonstrat ed no structural abnormalities. We hypothesize that abnormal barorefle x sensitivity could either predict a risk of or account for some of th e unexplained deaths in IDDM, in that relative overactivity of the sym pathetic nervous system could cause ventricular arrhythmias.