Hyperinsulinaemia is associated with development of electrocardiographic abnormalities in diabetics

Twelve-lead electrocardiograms (ECGs) were recorded at diagnosis from 247 initially non-insulin-requiring diabetics. The record was normal in 208 (84%) patients and abnormal in 39 (16%). The latter were older (p = 0.002), with higher blood pressures (diastolic and systolic) and greater cardiothoracic ratios (all p less than 0.02). They also had higher fasting (p less than 0.01) and post-glucose (p less than 0.04) plasma insulin concentrations per body mass index than those with normal ECGs. Five years later 17 patients had died (4 from proven and 6 from suspected cardiac cause), 5 had sustained a proven myocardial infarct and 3 a suspected cardiac event. ECGs were recorded from 138 patients both at diagnosis and 5 yr later. The record was normal on both occasions in 100 (72%), changed from normal to abnormal in 21 (15%), from abnormal to normal in 9 (7%), and was abnormal on both occasions in 8 (6%). Patients who developed ECG abnormalities were older (p = 0.011), and had greater mean fasting cholesterol during the 5 yr (p = 0.05). They also had greater fasting insulin levels per body mass index both before (mean of initial and 1-yr values, p = 0.02) and after the abnormality developed (p = 0.003) than those with persistently normal recordings. Insulin levels post-glucose were greater at 5 yr in those with cardiac abnormality but, as with the higher diastolic blood pressure and fasting glucose concentration then (both p less than 0.05), this difference was not significant initially. (ABSTRACT TRUNCATED AT 250 WORDS)