We thank the authors for their comments and share their opinion on the limited role of atrioventricular sequential pacing (AVSP) in clinical practice guidelines, given that these recommendations are primarily based on 3 small placebo-controlled trials that are not without limitations.1 The superiority of septal reduction techniques over AVSP has also only been shown in highly specialized centers. The shortage of such centers in Spain and the undesirably high morbidity and mortality associated with septal reduction techniques (15% in myectomy and 40% in septal ablation) make AVSP an appealing strategy in suitably selected patients.
In addition, AVSP has shown greater clinical benefit in elderly patients with more pronounced baseline functional impairment.1 Thus, the notable improvement in the subjective functional class described in our study could be related to the high average age of the patients in our sample (66 years) and the high percentage of them in an advanced functional class (93% in New York Heart Association [NYHA] class III-IV). Although the average patient age in the study by Sandín et al2 was similar to that of our cohort, their study did not include patients in functional class IV and only 62.9% were in class III, possibly explaining the differences in functional improvement. Despite the large sample size and long-term follow-up, we recognize that one of the main limitations of our study is the absence of an objective evaluation of the functional class. Although subjective evaluation of the functional class via the NYHA classification continues to play a large role in determining changes in clinical practice, it would undoubtedly be usefulto design studies objectively analyzing the effects of AVSP through not only conventionalexercise testing (requiring indirect inference of the functional class), but also oxygen consumption studies.