Copyright © 1995 by the European Society of Cardiology.
© 1995 The European Society of Cardiology
Changes in spontaneous sinus node rate after ventricular pacing as an estimate of autonomic tone: clinical applications
Cardiology A, CHU of Brabois 54500 Vandoeuvre, France
Received 2 May 1994; revised 3 August 1994; accepted 10 August 1994.
Correspondence: Béatrice Brembilla-Pcrrot, Cardiologic A, Chu Brabois, 54500 Vandocuvre, France.
Abstract
Rapid ventricular pacing (VP) reproduces neurohumoral variations associated with ventricular tachycardia. This study was set up to analyse the mechanisms that cause changes in sinus heart rate after rapid VP and to find the clinical factors that adapt sinus heart rate to VP, and the clinical value of the method.
Rapid VP was performed in 356 patients aged 15 to 86 years, in increments of 10 beats, at progressively faster rates every 10 s up to 200 beats. min –1. Group I comprised 122 patients with no underlying heart disease; group II comprised 234 patients with an underlying heart disease. The sinus heart rate (HR) was initially accelerated (SRI), in comparison with the basal sinus HR, for 2 to 5 s (90.5 beats. min ± 21 vs 71 ± 19 in group I, 89.5 ± 26 vs 76 ± 16 in group II). Five seconds later, there was a decrease in HR (SR2) which was slower than the basal HR (62 beats. min ± 22 in group I, 75 ± 15 in group II).
The variations in HR, defined as SR1-SR2/SR1, were significantly higher in group I than group II: 31 ± 18% vs 19 ± 15%, (P<0. 001). With the injection of 2 mg atropine in 14 group I patients tlie variations in HR were suppressed after ventricular pacing. When oral beta-blockers were administered to 21 group I patients, there were still significant changes in HR The changes in HR were reproducible during electrophysiological study.
The changes in HR observed after VP decreased with age in both groups: the variation was important (>40%) in patients younger than 40 years and was negligible in patients older than 80 years. Diabetes and sick sinus syndrome also prevented the adaptation of HR to VP. In group II, the decrease in the rate adaptation to VP was correlated with the decrease in left ventricular eject ion fraction (EF). A decrease in HR <10% was associated with a bad prognosis: during a mean follow-up of 27 ± 11 months, 17 of 73 patients with a decrease in HR <10% died from sudden cardiac death compared to two of 161 with a 
10% decrease in HR. The loss of sinus HR adaptation to rapid VP was correlated with the loss of HR variability on Holier monitoring.
In conclusion, the recording of sinus HR after rapid VP was a useful, simple and reproducible method for evaluating autonomic tone during an electrophysiological study. Increased vagal tone could be the predominant mechanism explaining the variations in HR after VP. The loss of HR adaptation to VP was a simple method to evaluate the prognosis of patients with advanced heart disease and may be useful when assessing patients with ventricular tachyarrhythmias for implantation of a cardioverter defibrillator.
Key Words: Autonomic tone • heart rate • ventricular pacing • sudden cardiac death