Heart rate and heart rate variability changes induced by right atrial pacing

This research was conducted to determine (1) whether heart rate and R-R interval variability are modified by atrial pacing, and (2) whether these changes (if they do occur) are related to the inducibility of tachyarrhythmias during electrophysiological studies. We studied 42 patients who were referred for electrophysiological evaluation of supraventricular (n = 16) or ventricular arrhythmias (n = 26). The patients studied for the evaluation of ventricular arrhythmias had structural and functional cardiac damage. The patients evaluated because of supraventricular arrhythmias had normal ejection fraction and no structural cardiac damage. In these patients a significant decrease in R-R interval (P = 0.0002) and in its standard deviation (P < 0.005) was observed following atrial pacing. No significant heart rate or R-R interval standard deviation change was observed after pacing in the patients with structural heart disease. The heart rate or R-R interval variability changes did not allow us to discriminate the patients with inducible ventricular arrhythmias from those without such arrhythmias. We conclude that right atrial pacing induces a heart rate increase and R-R variability decrease in patients without heart disease. In patients with cardiac damage the responses are blunted, and do not permit the identification of patients who have ventricular arrhythmias inducible by means of electrophysiological studies.