ASSOCIATION OF SICK SINUS SYNDROME WITH HYPERINSULINEMIA AND INSULIN-RESISTANCE IN PATIENTS WITH NON-INSULIN-DEPENDENT DIABETES-MELLITUS - REPORT OF 4 CASES

We report four non-insulin-dependent diabetic (NIDDM) patients accompa nied by a unique combination of sick sinus syndrome (SSS) and hyperins ulinemia of unknown etiology, SSS of all four cases was due to sinus a rrest in association with paroxysmal atrial fibrillation (Rubenstein-I II). Of special interest is that one patient showed a high prevalence of SSS and NIDDM among her close relatives, Hyperinsulinemia of modera te degree was seen at fasting state or after carbohydrate ingestion in the absence of obesity. The resistance to the action of insulin on gl ucose metabolism which was evaluated in three patients by the euglycem ic hyperinsulinemic clamp study was found to be comparable to the lowe st quartile level for common NIDDM patients, Because insulin is a phys iological regulator of cell-membrane Na+/K+-ATPase, we speculate that malfunction of the sinus node automaticity may be caused by chronic ex posure to hyperinsulinemia secondary to insulin resistance in these NI DDM patients.