Atrial versus ventricular pacing in sick sinus syndrome: the role of retrograde ventriculoatrial conduction.

This study compares the acute haemodynamic effect of atrial versus ventricular pacing, and ventricular pacing in the presence versus absence of retrograde ventriculoatrial conduction. Twenty-two patients with symptomatic sick sinus syndrome were tested: 12 with ventriculoatrial conduction (Group 1) and 10 without it (Group 2). Cardiac haemodynamics were measured by thermodilution technique at spontaneous rhythm as baseline and during atrial versus ventricular pacing at two different pacing rates. Atrial pacing offered an average augmentation for 20% in cardiac index from spontaneous rhythm in both groups (P < 0.05). The presence of ventriculoatrial conduction was the crucial determinant of cardiac performance during ventricular pacing. The change in cardiac index from the baseline was towards decrease in Group 1 and towards increase in Group 2. The difference between the groups was significant (P < 0.05). We conclude that atrial pacing is superior to ventricular and should be preferred in symptomatic sick sinus syndrome patients without atrioventricular conduction defects. However, ventricular pacing can be considered for preventing clinical symptoms associated with attacks of severe bradycardia or temporary cardiac arrest in patients without ventriculoatrial conduction.