Quentin Fischer (Department of Cardiology, Quebec Heart and Lung Institute, Laval University, Quebec City, Canada) and others report in Circulation: Cardiovascular Interventions that patients with pre-existing left bundle branch block (LBBB) have a significantly increased risk of requiring permanent pacemaker implantation after undergoing transcatheter aortic valve implantation (TAVI) than patients without pre-existing LBBB. However, pre-existing LBBB is not associated with increased mortality at 30 days or at two years.
Fischer et al report that right bundle branch block (RBBB) is seen as the “most important risk factor” for permanent pacemaker implantation after TAVI and that “some studies have shown an increased mortality risk among patients with pre-existing RBBB”. However, they add “no specific data exist on the impact of pre-existing LBBB on TAVI outcomes”. Therefore, with the present study, the authors sought to “evaluate the impact of pre-existing LBBB on clinical outcomes in patients undergoing TAVI”.
Using data for 4,513 patients who underwent TAVI at 18 centres in Canada, Europe and Brazil between February 2005 and October 2017—after excluding patients with pre-existing RBBB, previous pacemaker, or who did not have high-quality ECG data at baseline—the authors identified 3,404 patients for evaluation. Of these, 398 patients had pre-existing LBBB; Fischer et al report that patients with incomplete LBBB were classed as having no pre-existing LBBB (3,006 overall).
At 30 days, permanent pacemaker implantation was significantly higher in patients with pre-existing LBBB: 21.1% vs. 14.8% for patients without pre-existing LBBB (p=0.006). Pacemaker implantation was also higher among those who received a self-expanding valve than those who received a balloon-expandable valve (23.1% vs. 8.7%, respectively; p<0.001). However, there were no significant differences in all-cause mortality at 30 days: 7.3% for patients with pre-existing LBBB vs. 5.5% for those without pre-existing LBBB; p=0.217).
There were also no differences in all-cause mortality or cardiac mortality between LBBB patients and no LBBB patients at a mean follow-up of 22±21 months (p=0.173 and p=0.093 for the respective differences). Fischer et al note that the cumulative rate of permanent pacemaker implantation was higher in the pre-existing LBBB group (22.9% vs. 16.5% for the no LBBB group; p=0.006), but add that this “was because of an increased permanent pacemaker implantation rate early after TAVI and no differences between groups were observed in the permanent pacemaker implantation rate after the first 30 days post-TAVI”. Additionally, according to the authors, patients with pre-existing LBBB “exhibited a lower left ventricular ejection fraction (LVEF) pre-TAVI but experienced a similar degree of increase in LVEF at one-year follow-up compared with those patients with no significant conduction disturbances pre-TAVI”.
Fischer et al note that the risk of permanent pacemaker implantation associated with pre-existing LBBB occurs early “probably secondary to the mechanical compression of the His bundle during valve implantation” given that there was no increased risk of pacemaker implantation, or sudden cardiac death, at two years. “This provides some reassurance about the management of these patients in the absence of advanced conduction disturbances during the hospitalisation period and contrasts with the results observed in the presence of new-onset LBBB post-TAVI [which is associated with an increased risk of permanent pacemaker implantation and sudden cardiac death in the months after the procedure]”, they add.
In terms of the implications of their study, Fischer et al comment that these results “should be taken into account of the preparation of TAVI procedures considering the use the valve type associated with a lower risk of conduction disturbance issues and a high (more aortic) transcatheter valve positioning in those patients with pre-existing LBBB to decrease the permanent pacemaker implantation after TAVI”.
Study investigator Josep Rodés-Cabau (Quebec Heart and Lung Institute, Laval University, Quebec City, Canada) told Cardiovascular News: “Pre-existing LBBB should be included as a risk factor for PPI early post-TAVR. However, pre-existing LBBB in TAVI recipients was not associated with increased mortality or heart failure hospitalisation at two-year follow-up, and there were significant improvements in LVEF in most patients. This suggest that the possible use of specific therapies including cardiac resynchronisation therapy (CRT) should be delayed by several months in order to avoid implementing unnecessary treatment. Future studies should determine the longer term outcomes of such patients.”