[Impairment of cardiac autonomic nervous system and incidence of arrhythmias in severe hyperglycemia].

Abstract

Background and purpose: Deterioration of cardiac autonomic nervous system in diabetics is associated with increased cardiac and arrhythmogenic mortality. Therefore, the present study engaged in the question how heart rate variability is acutely changed in diabetic ketoacidosis or hyperglycemic hyperosmolar syndrome. Moreover was evaluated how blood pressure, heart rate and incidence of arrhythmias can be explained by figures of heart rate variability.

Patients and methods: In a prospective observation of time course we investigated in 4 years consecutively 12 intensive care patients with DKA and 2 with HHS (10 male, 4 female, 19-62 years, initial plasma glucose 404-1192 mg/dl). All patients received a standardized treatment to international current guidelines. In addition to hemodynamic and clinical-chemical monitoring HRV analysis was performed continuously for at least 48 hours. Simultaneously, we determined supraventricular and ventricular arrhythmic episodes.

Results: HRV was diminished over the whole spectrum in dependence on blood glucose concentration. Thus, sympathovagal balance (LF/HF ratio) was initially sympathetic predominated in blood glucose levels < 600 mg/dl (relatively prevailing LF power) and vagal predominated in blood glucose levels > 600 mg/dl (relatively prevailing HF power). In correlation analysis of HRV parameters with blood glucose rS-coefficients from -0.934 to -0.821 were achieved (p < 0.001). Further, the initial mean blood pressure correlated with the LF/HF ratio in HRV minimum (rS = 0.711, p = 0.004). The initial heart rate in relation to assumed intrinsic frequency correlated with minimal found Total Power (rS = -0.656, p = 0.011). In the period of whole 48 hours, more arrhythmic events occurred in consequence to initial glucose levels (rS = 0.693, p = 0.006). But the maximum of arrhythmic episodes was usually later ascertained than the minimum of HRV (p < 0.001). At the time of each arrhythmic maximum the sympathovagal balance (LF/HF) showed no uniform figures. Only similar in all cases was that the LF/HF ratio was found either > 4 or < 1.

Conclusion: Clinical complications in high glucose levels must be seen in the context of a nearly complete blockade of sympathetic and parasympathetic activity. Basically to extreme autonomic restriction, sympathetic and vagal predominance can change rapidly into each other. This retarded vulnerable predisposition may declare the arrhythmic potential. An important progress in the monitoring of patients could be achieved by implementation of a continuous HRV measurement because hereby the actual risk potential can be ascertained timely and reliably.