We present a case of pacing-induced cardiomyopathy and an occluded left subclavian vein (SCV). The SCV occlusion was delineated in a retrograde manner from femoral venous access and bypassed through direct puncture of a collateral branch. Cardiac resynchronisation therapy was achieved through His bundle pacing, with subsequent normalisation of LV function.

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.