P4600Intraventricular conduction disturbance and ventricular paced rhythms in patients with acute coronary syndromes
Authors: Azevedo P M , Mota T , Bispo J , Guedes J , Carvalho D , Marques N , Santos W , Mimoso J , Jesus I 
Published: October 2019

Abstract

Introduction
Left or right bundle branch block (LBBB or RBBB) and ventricular paced rhythms (PM) difficult the diagnosis and often delay adequate treatment in patients with acute coronary syndromes (ACS). In the past few years, guidelines have placed a greater emphasis on the need for considering urgent revascularization in these patients.

Purpose
Evaluate initial revascularization strategy and short-term prognostic impact of LBBB, RBBB and PM in patients with ACS.

Methods
Multicentric observational study of consecutive patients with ACS recorded in the Portuguese Registry of Acute Coronary Syndromes (ProACS) between October 2010 and January 2019. Patients were categorized according to the ECG at admission: LBBB, RBBB, PM and normal QRS morphology. Patients with missing data on the ECG or the primary outcome were excluded. Demographic, clinical data and in-hospital outcomes were analyzed. The association between LBBB, RBBB, PM and in-hospital adverse outcomes was assessed using a logistic regression model. The primary and secondary outcomes were in-hospital mortality and a composite of in-hospital adverse events (heart failure, re-infarction or cardiac arrest), respectively.

Results
Of the original cohort, 18314 (94.3%) patients were included (mean age 66±13 years, 73.2% male): 243 (1.3%) had PM, 846 (4.6%) had LBBB, 1195 (6.5%) had RBBB and 16030 (87.5%) had normal QRS. Patients with abnormal QRS were significantly older, had more comorbidities, were less frequently diagnosed as ST-elevation MI (LBBB 18%; RBBB 35.1%; PM 7.8%; Normal 44.2%, p<0.001) and considered for urgent reperfusion (LBBB 13%; RBBB 33.6%; PM 5.8%; Normal 41.6%, p<0.001). Among patients who underwent non-urgent coronary angiography, the finding of an occluded culprit coronary artery was not higher compared to patients with normal QRS (Normal 15.2% vs LBBB 14.3%; RBBB 17.4%; PM 11.4%, p>0.05 for difference).
Overall in-hospital mortality was 3.4% (LBBB 6.6%; RBBB 8.1%; PM 5.3%; Normal 3.4%; p<0.001) and the composite endpoint of in-hospital adverse events was 17.4% (LBBB 35.6%; RBBB 27.3%; PM 23.5%; Normal 15.6%, p<0.001). After adjusting for cofounding variables, and using normal QRS as reference, only RBBB was shown to be significantly associated with increased in-hospital mortality (OR 1.94; 95% CI 1.43–2.66), p<0.001); and both RBBB (OR 1.75; 95% CI 1.5–2, p<0.001) and LBBB (OR 1.8; 95% CI 1.4–2.3, p<0.001), but not PM, were significantly associated with the composite endpoint of heart failure, re-infarction or cardiac arrest.

Conclusion
Compared to patients with normal QRS, those with LBBB, RBBB or PM less often undergo urgent revascularization and have higher rates of in-hospital adverse outcomes. In multivariate analysis, RBBB patients are almost two times more likely to die compared to those with normal QRS. LBBB and RBBB were independently associated with increased rates of in-hospital adverse events. PM was not associated with worse in-hospital outcomes.