Five Year Clinical Outcome of a Randomised Comparison between Right Ventricular Apical (RVA) or High Septal Pacing (RVHS) in Patients with High Grade Atrioventricular Block

Introduction:
Chronic RVA pacing may contribute to impaired left ventricular (LV) systolic function in some patients which may be prevented or minimised with septal pacing. The Protect-Pace randomised trial compared RVA to RVHS pacing over a two year follow up period and showed no statistical difference in LV ejection fraction between the two arms. We present the 5 year clinical follow-up data.

Methods:
Patients with preserved LV function, high-grade atrioventricular block (AVB), and sinus rhythm (SR) or permanent atrial fibrillation (AF), were randomised 1:1 to RVA or RVHS pacing. Clinical outcome measures were burden of AT/AF and a composite endpoint of worsening heart failure, stroke or mortality.

Results:
Of 240 patients initially , 18 died in the first 2 yrs and 17 in the subsequent 3 yrs. 122 patients (males n=80) were followed to 5 yrs (RVA n= 60; RVHS n=62). The median follow-up period was 4.9yrs. There were no significant differences in either composite clinical endpoint or the burden of AT/AF between the groups. In those patients with SR at baseline in whom no AF had been diagnosed prior to study inclusion developed AF by five year follow up in whom <10% developed persistent AF, the majority having frequent episodes of paroxysmal AF. Of the 17 later deaths, 11 were non-cardiac (RVA n=6, RVHS =5), 4 cardiac but not sudden (RVA n= 3, RVHS n=1) and 2 sudden cardiac deaths (RVA = 1, RVHS =1)

Conclusion:
In patients with preserved baseline LV systolic function presenting with high grade AVB the burden of atrial arrhythmias or composite clinical end point at 5 years was not statistically different between the two pacing arms. Allowing for the small final patient numbers the result suggests that septal pacing may not confer a long term clinical benefit over apical pacing.