Background: Although a right bundle branch block (RBBB) complicates anterior wall ST-segment elevation myocardial infarction (AW-STEMI), its independent prognostic significance remains understudied.
Material and method: This cross-sectional observational study was conducted at the Punjab Institute of Cardiology, Lahore, over a period of 18 months from January 2022 to June 2023. A total of 349 patients presenting with acute AW-STEMI were enrolled. They were stratified into RBBB and non-RBBB groups. Outcomes included mortality, cardiogenic shock, cardiac arrest, arrhythmias, complete heart block (CHB), post-myocardial infarction (MI) angina, and hospital stay duration. The effect of confounding variables on in-hospital mortality was evaluated through stratification among the two groups.
Results: AW-STEMI with RBBB was reported in 50 (14.3%) out of 349 patients. Both groups had a similar mean age (p = 0.276), and comorbidities, including hypertension (p = 0.363), diabetes mellitus (p = 0.872), chronic kidney disease (CKD) (p = 0.299), dyslipidemia (p = 0.486), smoking status, and prior myocardial infarction (p > 0.05), were comparable. Left ventricular ejection fraction (LVEF) was significantly lower in RBBB patients (p < 0.001). Peak troponin-I levels were significantly higher in the RBBB group (p < 0.001, 95% confidence interval (CI): 6.581-11.803). In-hospital mortality was significantly higher in RBBB patients (16% vs. 5.7%, p = 0.009, odds ratio (OR) = 3.160, 95% CI: 1.284-7.777). Cardiogenic shock occurred more frequently in RBBB patients (36% vs. 16.4%, p = 0.003, OR = 2.672, 95% CI: 1.394-5.120). Arrhythmias were significantly higher in the RBBB group (42% vs. 19.7%, p = 0.001, OR = 2.946, 95% CI: 1.569-5.529). Cardiac arrest (16% vs. 11.4%, p = 0.354) and post-MI angina (24% vs. 15.4%, p = 0.170) were more common in RBBB patients but were not statistically significant. CHB was observed in 12% of RBBB patients vs. 8% in non-RBBB (p = 0.345). CKD was strongly associated with increased mortality, with all affected STEMI patients with RBBB experiencing fatal outcomes, whereas those without RBBB had significantly lower mortality. The choice of reperfusion strategy played a crucial role, with primary PCI demonstrating a survival benefit in RBBB patients, while thrombolysis and medical management were linked to markedly higher mortality rates in this group.
Conclusion: Patients with AW-STEMI and RBBB had significantly worse in-hospital outcomes, including higher mortality, increased risk of cardiogenic shock, and a greater prevalence of arrhythmias. Although cardiac arrest, post-MI angina, and CHB were more frequent in RBBB patients, these differences were not statistically significant. Primary PCI was associated with a lower mortality risk in RBBB patients.
Keywords: in-hospital outcome; mortality; post-myocardial infarction; right bundle branch block; st-elevation myocardial infarction (stemi).
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