A Study of Inferior Wall STEMI with and without Conduction defects and their outcomes in a Tertiary Care Centre

Abstract

Background: Conduction abnormalities are important complications of acute inferior wall myocardial infarction (IWMI) and may be associated with hemodynamic instability, arrhythmias, and adverse clinical outcomes. This study was undertaken to evaluate the clinical characteristics, left ventricular function, angiographic profile, complications, treatment patterns, and outcomes of patients with IWMI with and without conduction blocks. Methods: This single-centre prospective observational cross-sectional study was conducted on 145 patients diagnosed with IWMI based on electrocardiography. Patients were categorised into two groups according to the presence or absence of conduction blocks. Clinical characteristics, cardiovascular risk factors, left ventricular systolic function, thrombolysis status, angiographic findings, complications, treatment modalities, and in-hospital outcomes were compared between the groups. Results: Among the 145 patients with IWMI, 67 (46.2%) developed conduction blocks and 78 (53.8%) did not. The mean age of the study population was 56.77 years, with most patients belonging to the 45–65-year age group. Males constituted 63.4% (92/145) of the study population. Smoking was significantly more frequent among patients with conduction blocks than among those without conduction blocks (59.5% vs. 40.7%, respectively; P=0.040) and was the only cardiovascular risk factor significantly associated with conduction blocks. Left ventricular systolic dysfunction was significantly more frequent among patients with conduction blocks (P=0.035). Among patients with conduction blocks, 28 (41.8%) had mild, 20 (29.9%) had moderate, and 1 (1.5%) had severe LV dysfunction, whereas 18 (26.9%) had preserved LV systolic function. Thrombolysis was performed in 99 (68.3%) patients; conduction blocks occurred in 48 (48.8%) thrombolysed patients compared with 19 (41.3%) non-thrombolysed patients. The angiographic profile did not differ significantly between the two groups. The right coronary artery was the predominant vessel involved in both groups, being affected in 85.0% of patients with conduction blocks and 66.6% of those without conduction blocks. Cardiogenic shock occurred in 33 (22.8%) patients, of whom 21 (63.6%) had conduction blocks (P=0.022). Ventricular tachycardia/ventricular fibrillation occurred in 11 (7.6%) patients, with 9 (81.8%) belonging to the conduction-block group (P=0.014). Atrial fibrillation occurred in 8 patients, of whom 7 (87.5%) had conduction blocks (P=0.016). Treatment modalities were comparable between the groups. CABG, PTCA, and conservative management were performed in 17.9%, 70.1%, and 11.9% of patients with conduction blocks, respectively, compared with 19.2%, 69.2%, and 11.5% among patients without conduction blocks.  In-hospital mortality was higher among patients with conduction blocks than among those without conduction blocks (4.2% vs. 1.3%); however, this difference was not statistically significant (P=0.249). Among thrombolysed patients, significant differences were observed with respect to dyslipidemia, right ventricular myocardial infarction (RVMI), ventricular septal rupture, overall outcome, and mortality. Patients with RVMI had significantly higher rates of LV dysfunction (P=0.002), ventricular tachycardia/ventricular fibrillation (P=0.050), and mortality (P=0.002). Conclusion: Conduction blocks were common among patients with IWMI and were significantly associated with smoking and LV systolic dysfunction. Patients with conduction abnormalities had a significantly higher incidence of cardiogenic shock, ventricular tachyarrhythmias, and atrial fibrillation, indicating a more complicated clinical course. Although mortality was numerically higher in patients with conduction blocks, the difference was not statistically significant. The angiographic profile was broadly comparable between patients with and without conduction blocks, with predominant right coronary artery involvement in both groups. RVMI was additionally associated with LV dysfunction, ventricular arrhythmias, and increased mortality. Early recognition and close monitoring of IWMI patients with conduction abnormalities and/or RVMI may therefore be warranted. Keywords: Inferior wall myocardial infarction; conduction block; atrioventricular block; left ventricular dysfunction; ventricular arrhythmia; right ventricular myocardial infarction