Effect of coronary artery bypass surgery on autonomic nervous function and retinopathy in diabetic patients.

To assess whether coronary artery bypass surgery (CABS) has any adverse effect on diabetic late complications 13 diabetic patients (mean duration of diabetes 11 yr) were studied. Tests of autonomic nervous function were performed before and 6 weeks after CABS. Heart rate response to hyperventilation diminished markedly after operation (from 10.2 +/- 5.7 to 5.7 +/- 4.0 beats/min, p less than 0.01). A similar impairment tended to occur also in the heart rate response to standing up (the 30:15 ratio) (from 1.06 +/- 0.10 to 1.02 +/- 0.05, p = 0.08). Systolic blood pressure decreased more upon standing after CABS (-14 vs -3 mm Hg, p less than 0.05) and asymptomatic postural hypotension evolved in 1 patient. Ophthalmological study including photography of the fundi was carried out in 10 patients 2-3 days before and 7-10 days after CABS. Four patients had diabetic retinal changes and no change in these fundi occurred after CABS. One patient with no pre-existing retinal changes had multiple cotton wool exudates as a sign of arteriolar occlusion in both retinas after CABS. Thus, CABS seems to impair cardiovascular reflexes used in the diagnosis of diabetic autonomic neuropathy. Retinal changes suggesting microembolisation of fundi do also occur after CABS of diabetic subjects.