Within patient comparison of His-bundle pacing, right ventricular pacing
and right ventricular pacing avoidance algorithms in patients with PR
prolongation: Acute haemodynamic study
Abstract
Aims: A prolonged PR interval may adversely affect ventricular filling
and therefore cardiac function. AV delay can be corrected using
right-ventricular-pacing (RVP) but this induces ventricular
dyssynchrony, itself harmful. Therefore, in intermittent heart-block,
pacing-avoidance algorithms are often implemented. We tested His-bundle
pacing (HBP) as an alternative. Methods: Out-patients with a long PR
interval(>200ms) and intermittent need for ventricular
pacing were recruited. We measured within patient differences in
high-precision haemodynamics between AV-optimized RVP, and HBP, as well
as a pacing-avoidance algorithm [Managed Ventricular Pacing (MVP)].
Results We recruited 18 patients. Mean left ventricular ejection
fraction was 44.3±9%. Mean intrinsic PR interval was 266±42ms and QRS
duration was 123±29ms. RVP lengthened QRS duration(+54 ms, 95%CI 42 to
67ms, p<0.0001) whilst HBP delivered a shorter QRS duration
than RVP(-56 ms, 95%CI -67 to -46ms, p<0.0001). HBP did not
increase QRS duration(-2ms 95%CI -8 to 13ms, p=0.6). HBP improved acute
systolic blood pressure by mean of 5.0 mmHg(95%CI 2.8 to 7.1mmHg,
p<0.0001) compared to RVP and by 3.5 mmHg(95%CI 1.9 to
5.0mmHg, p=0.0002) compared to the pacing avoidance algorithm. There was
no significant difference in haemodynamics between RVP and ventricular
pacing avoidance (p=0.055). Conclusions HBP provides better acute
cardiac function than pacing avoidance algorithms and RVP, in patients
with prolonged PR intervals. HBP allows normalisation of prolonged AV
delays (unlike pacing avoidance) and does not cause ventricular
dyssynchrony (unlike RVP). Clinical trials may be justified to assess
whether these acute improvements translate into longer term clinical
benefits in patients with bradycardia indications for pacing.