New-onset right bundle branch block and other variables associated with primary and secondary ventricular fibrillation in acute myocardial infarction with ST elevation

Ventricular fibrillation (VF) is the main cause of sudden death in acute ST elevation myocardial infarction (STEMI). The objective has been to evaluate which variables are independently associated with each of the forms of VF, taking into account a classic criterion for their characterization in patients with STEMI.

Between 1998 and 2014, 5,301 patients with STEMI were admitted to 2 university hospitals. The incidence of VF and new-onset right bundle branch block (RBBB) was collected, among other variables. Primary FV (PVF) was considered when it occurred early (first 24 hours after the onset of symptoms) and in the absence of heart failure; and Secondary VF (SVF) when it occurred late (24 hours after the onset of symptoms) or in the presence of heart failure. The association between primary FV, secondary VF and the variables considered was analyzed using multinomial logistic regression.

VF was documented in 339 (6.4%) patients: 201 PVF, 201 and 138 SVF. Compared to patients with PVF, those with SVF were characterized by being older, having greater comorbidity, more frequent heart failure on admission, larger infarcts, and a higher proportion of mutivessel disease. PVF was independently associated with new transient RBBB (OR 2.09), male sex (OR 1.71), early admission, magnitude of ST elevation, and lower LVEF. Diabetes emerged as protective (OR 0.66). SVF was independently associated with both forms of RBBB, transient (OR 3.02) and permanent (OR 2.66), younger age, history of AF (OR 2.84), early admission, advanced Killip class, and indicators of infarct size such as peak CK-MB and lower LVEF. Patients with VF had a similar 30-day and 1-year prognosis to patients without VF. Patients with SVF had a worse prognosis at 30 days and one year, at the expense of higher early mortality. In the Cox regression predictive model, both FVP and SVF emerged as predictors of mortality in the short term, but not in the long term.

Among the variables associated with each of the forms of VF, new-onset RBBB stands out, showing particularities based on its transitory or permanent nature. The characterization of primary or secondary ventricular fibrillation based on the time of onset and the presence of heart failure seems relevant since it allows identifying groups of patients with different characteristics and prognoses.