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 uncertain. A cardiac arrhythmia has been postulated, but there has been little evidence to support this. We present the case of a 31-year-old man with IDDM of 17 years duration, who died suddenly while asleep. Over preceding months, he had had strict glycaemic control (HbA1 8.9%), normal 24 h blood pressure (mean 131 +/- 2.1/76 +/- 2.2 mmHg), no evidence of microangiopathy or endothelial dysfunction and normal standard clinical tests of autonomic function. An electrocardiogram was similarly unremarkable, with a QTc interval of 0.414 s, and an echocardiogram 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 impaired baroreflex sensitivity during Phase 4 of the valsalva manoeuvre (0.5 ms mmHg-1), with power spectral analysis studies suggesting an abnormality of parasympathetic function. The coroner's autopsy demonstrated no structural abnormalities. We hypothesize that abnormal baroreflex sensitivity could either predict a risk of or account for some of the unexplained deaths in IDDM, in that relative overactivity of the sympathetic nervous system could cause ventricular arrhythmias.
Lawrence
I G
IG
Department of Medicine and Therapeutics, University of Leicester, Leicester Royal Infirmary, UK.
Weston
P J
PJ
Bennett
M A
MA
McNally
P G
PG
Burden
A C
AC
Thurston
H
H
D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D003645:Death, Sudden / Q000209:etiology*; D003922:Diabetes Mellitus, Type 1 / Q000401:mortality* / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male