Sharadanant, Roopalakshmi

Importance: Up to 10% of patients with acute myocardial infarction (AMI) have right bundle branch block (RBBB), and RBBB has been associated with a higher risk of mortality. We performed a systematic review and meta-analysis to determine the prognostic significance of RBBB for patients with AMI. Acute coronary syndrome (ACS) Data Sources: We have systematically searched Ovid, Scopus and Web of Science through January 2014. Study Selection: Reviewers working independently and in duplicate screened all eligible abstracts, selecting studies that described all-cause mortality or cardiovascular death in patients with RBBB and suspected ACS. We excluded studies that reported unadjusted outcomes. Knowledge synthesis: We pooled risk ratio with hazard ratio in studies reporting those outcomes. When reported, odds ratio was converted into risk ratio using reported event rate in each study’s unexposed -read: non RBBB- group. Main Outcomes: All-cause mortality and cardiovascular mortality (death). Results: Eighteen studies were found that reported eligible data. All were observational studies, involving over 89,000 patients. In short-term follow up (up to 30 days), RBBB on presentation was associated with higher all-cause mortality rate, compared to patients without RBBB (RR 2.23, 95% CI 1.76-2.82). There was a trend for higher mortality at long-term follow up (range: 6 months-16 years) that did not reach statistical significance (RR 1.45, 95% CI 0.93-2.25). Figure-1 demonstrates the forest plot. Risk of bias was assessed with the Newcastle-Ottawa scale and majority of included studied were deemed moderate to high quality. Conclusion and Relevance: RBBB is associated with a more than 2-fold higher risk of all-cause mortality in patients with AMI at 30 days follow up. Patients with AMI and RBBB represent a high risk group for adverse outcomes. A sentence on the differential findings for new vs. old RBBB and association with outcomes could follow here.

Importance: Right bundle branch block (RBBB) is observed in approximately 5-14% of patients with heart failure (HF). Multiple observational studies have reported the association of RBBB with clinical outcomes in patients with HF. We performed a systematic review and meta-analysis to determine the prognostic significance of RBBB for patients with HF. Data Sources: We have systematically searched MEDLINE, EMBASE, Cochrane CENTRAL, Web of Science and Scopus through January 2014. Study Selection: Reviewers working independently and in duplicate screened all eligible abstracts that described all cause or cardiovascular mortality in patients with RBBB and HF. We excluded studies that reported unadjusted outcome, i.e.: unadjusted event rates. Knowledge synthesis: We pooled reported risk ratio and hazard ratio. Main Outcomes: All-cause mortality and cardiovascular mortality (death). Results: We found 12 relevant observational studies enrolling over 38,000 patients. Risk of bias was assessed using the Newcastle-Ottawa Scale. Included studies had at least a moderate quality. Seven of those evaluated prognosis of patients with RBBB and heart failure. After a mean follow up period of 2.5 years (range: 1-5 years), RBBB was associated with a statistically significant increased risk of all-cause mortality compared to patients with heart failure but no BBB, RR 1.27, 95% CI (1.08-1.50), Figure 1. The other 5 studies evaluated CHF patients receiving cardiac resynchronization therapy (CRT), comparing outcomes of patients with RBBB to those with LBBB. After a mean f/u period of 3 years, patients with RBBB were once again found to have an increased risk of all-cause mortality, RR 1.45, 95% CI 1.12-1.89. Conclusion and Relevance: RBBB in patients with HF is associated with higher all-cause mortality in comparison to patients without inter-ventricular conduction defects, as well as LBBB patients in patients undergoing CRT setting.

Objective: Multiple large population based observational studies have evaluated the association of various ECG changes with long term adverse outcomes demonstrating conflicting results regarding the significance of right bundle branch block (RBBB). Therefore, we conducted a systematic review and meta-analysis to determine the prognostic significance of RBBB in healthy population. Methods: This systematic review follows an a priori established protocol and is reported following the PRISMA statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). We systematically searched EMBASE, Web of Science and Scopus through January 2014. We also consulted with content experts to recommend studies for screening. Reviewers working independently and in duplicate screened all eligible abstracts, selecting randomized trials and prospective cohort studies that described all cause mortality or cardiovascular death in patients with RBBB. We excluded studies that reported unadjusted outcome or unadjusted event rates. For statistical analysis, hazard ratios were considered to approximate risk ratios. The main outcomes of the study are all-cause mortality and cardiovascular mortality. Results: Based on the eligibility, four large cohorts, with total patient count > 100,000 were included in the meta-analysis. Risk of bias was assessed using the Newcastle-Ottawa scale and included studies were deemed to be of high quality. As demonstrated in Figure 1, RBBB was not associated increase in all-cause mortality (RR 1.05; 95% CI 0.89-1.25) or cardiovascular mortality (RR 1.09; 95% CI 0.70-1.69). Conclusion: In asymptomatic healthy patients, RBBB is not associated with poor outcome.