Rational and design of the Baseline Interatrial block and Transcatheter aortic valve implantation (BIT) registry.

Background: Aortic stenosis (AS) is currently the most frequent heart valve disease. Symptomatic severe AS has a poor prognosis and transcatheter aortic valve implantation (TAVI) is becoming the therapy of choice in these patients. Changes in the conduction tissue after the procedure constitute one of the main limitations of TAVI, with a frequent need for a definitive pacemaker. Interatrial block (IAB) is defined as a prolonged P-wave duration and is related with atrial fibrosis. The presence of IAB could be a marker of conduction tissue abnormalities at other levels. No study has specifically analyzed the role of IAB as a predictor of the need for permanent pacemaker in patients with AS undergoing TAVI.

Methods: The Baseline Interatrial block and Transcatheter aortic valve implantation (BIT) registry will be performed in approximately 3000 patients with severe AS treated with TAVI. A centralized analysis of baseline ECGs will study the presence and type of IAB and other ECG data (rhythm, P-wave duration, PR and QRS intervals/intraventricular conduction disorders). Clinical follow-up will be carried out by local researchers. The primary endpoint will be the requirement of permanent pacemaker during post-TAVI hospitalization. As secondary objectives, the incidence of new onset AF, stroke, or mortality during follow-up will be analyzed. Secondary endpoints will include the incidence of new onset AF, stroke, or mortality during follow-up.

Conclusion: The BIT registry will study, for the first time, the influence of previous IAB in the need of permanent pacemaker after TAVI: This large registry will also provide information regarding the association of this and other ECG parameters with prognosis.