U. Premawardhana*, M.R. Adams, D.K. Yue, A. Birrell, S. Heffernan, D.S. Celermajer.

The Department of Cardiology, The Departments of Endocrinology and Renal Medicine Royal Prince Alfred Hospital, and The Department of Medicine, University of Sydney, Australia.

Diabetes mellitus is an important risk factor for both macrovascular and cardiac disease in man. The relative contribution of hyperglycaemia to the development of this process is not clear, as diabetes often coexists with other risk factors for atherosclerosis.  Many of the early structural changes of vascular disease can be detected using ultrasound techniques. The availability of a novel transvenous ultrasound probe allows detailed interrogation of the heart as well as a large proportion of the vasculature during a single examination.

Six male baboons (Papio hamadryas) with insulin dependent diabetes (5-7 years duration) and four control animals were studied. The diabetic baboons had normal serum cholesterol levels, were not exposed to cigarette smoke, and had normal blood pressure, but had documented microvascular disease including neuropathy and renal disease. Vascular structure in all large arteries and cardiac function were studied using transvenous ultrasound. Under general anaesthetic, a single-plane 5.5-10 MHz transducer mounted in a 10F catheter was introduced via the right femoral vein. The catheter was positioned under fluoroscopic control, to obtain 2D images and doppler studies of the iliac, renal, and carotid arteries, the ascending, descending aorta and the aortic arch. The main pulmonary as well as the left and right pulmonary arteries were visualised and detailed cardiac views were obtained. All arteries were examined for presence of atherosclerotic plaque and for presence of increased intima-media thickness (IMT). Left ventricular function was assessed at rest and following infusions of dobutamine and esmolol.

The procedure was performed safely and successfully in all cases. No atherosclerotic plaque was seen in either diabetic or normal baboons. There was no difference in the descending aorta IMT (0.038±0.004 v 0.037±0.005mm normal v diabetic, p=NS), or in doppler flow in the renal or iliac arteries between diabetic and normal baboons. There was no difference in left ventricular wall thickness or systolic velocity between the two groups either at rest (6.9±2.5 v 6.2±1.4cm/sec normal v diabetic p=NS), after peak dobutamine infusion (15.5±2.2 v 12.7±3.9cm/sec normal v diabetic p=NS), or esmolol infusion (4.3±1.0 v 5.6±1.0cm/sec normal v diabetic p=NS).

In a high primate model of diabetes, the presence of hyperglycaemia per se does not produce abnormalities of cardiac function or early structural changes of atherosclerosis.

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