Safety of upgrades for patients with PICM
Vijayaraman et al demonstrated that the HBP threshold could remain relatively stable after 2 years of follow-up [8]. A recent publication confirmed this finding in a larger sample and showed over 90% of patients have a capture threshold less than 2.5V @ 1ms after a median follow-up of 3 years [16]. In 2 patients failed with HBP, we were not able to capture the distal His-Purkinje system even at high output. In the prior reported by Vijayaraman et al [9], the successful rate of HBP upgrade was 95% (57/60) in western population with AV block. These finding suggest that the progression of conduction dysfunction was extremely rare even in PICM patients. These results extend the long-term data about the threshold for HBP. According to our results, the threshold for HBP was not significant higher after the more than 12-month follow-up period. Device malfunction, lead perforation and embolization were not found during follow-up. The technical challenges in HBP are highly dependent on the operators’ experience [17-19].
Although the results presented are favorable, there are some limitations in the present study. First, HBP was conducted by experienced implanters, and there were high success rates in our study along with potential patient selection bias. Second, the present study focused on PICM patients with reduced LVEFs. PICM patients with preserved LVEFs may have unique pathological progress and deserve more clinical assessment. Third, long-term pacing performance of the his pacing lead and the potential risks of lead extractions need further careful evaluation.