Autonomic neuropathy predisposing to arrhythmias in hemodialysis patients.

Arrhythmias are frequent among the dialysis population and can cause symptoms of palpitations or dizziness. Since autonomic disturbances are known to cause an increased arrhythmogenic stimulus, we questioned whether the presence of central autonomic neuropathy increased the frequency of arrhythmias as identified by 24-hour electrocardiographic monitoring in dialysis patients. Seventy-one patients were randomly chosen from patients established on dialysis in two centers. The mean age of the patients was 71.3 years (median age, 67 years) and median duration on dialysis was 17.0 months (range, 1 to 175 months). Four patients had diabetes. Each patient was tested for autonomic control of blood pressure and heart rate, and underwent Holter electrocardiographic monitoring, commencing 30 minutes before dialysis, for a 24-hour period. The tapes were then analyzed for ventricular and atrial rhythm changes. There was a significantly increased incidence of arrhythmias in individuals with abnormal blood pressure responses (P = 0.005), heart rate responses (P = 0.01), and combined blood pressure and heart rate responses (P = 0.004). We conclude that patients with autonomic dysfunction had an increased frequency of arrhythmias during dialysis.

The use of a microcomputer to automate measurement of action potential duration for both transmembrane and monophasic action potentials.

Measurement of action potential duration is made more valuable if it can be made simultaneously with other variables, to which it may be related. We have developed a microcomputer-based system which allows measurement of action potential duration, both for transmembrane action potentials and for monophasic action potentials. The system allows simultaneous recording and analysis of action potentials and intraventricular pressures. Both end-diastolic and maximum systolic pressures have been analysed. Action potential duration was assessed at four different levels of the repolarization curve. We have analysed the consistency of measurements made by the computer, and compared them to measurements made manually, using results from six dog experiments. For action potential duration, there was no systematic difference between the manual and the computer methods, but the computer was significantly more consistent. In the case of the pressure measurements, the two methods were approximately the same in their consistency, and again there was no systematic difference. We have demonstrated that potential errors in determination of the average diastolic potential did not significantly affect the results obtained by our method. The variances of action potential duration measurements made at different levels of repolarization were equal. We demonstrated that there was no effect of amplitude on the action potential duration of potentials recorded under steady-state conditions.