Clinical significance of R-wave amplitude in lead V1 and inferobasal myocardial infarction in patients with inferior wall myocardial infarction

Objective: To assess electrocardiogram (ECG) for risk stratification in inferior ST-elevation myocardial infarction (STEMI) patients within 24 h. Methods: Three hundred thirty-four patients were divided into four ECG-based groups: Group A: R V-1 <0.3 mV with ST-segment elevation (ST up arrow) V-7-V-9, Group B: R V-1 <0.3 mV without ST up arrow V-7-V-9, Group C: R V-1 >= 0.3 mV with ST up arrow V-7-V-9, and Group D: R V-1 >= 0.3 mV without ST up arrow V-7-V-9. Results: Group A demonstrated the longest QRS duration, followed by Groups B, C, and D. ECG signs for right ventricle (RV) infarction were more common in Groups A and B (p < .01). ST elevation in V-6, indicative of left ventricle (LV) lateral injury, was more higher in Group C than in Group A, while the & sum;ST up arrow V3R + V4R + V5R, representing RV infarction, showed the opposite trend (p < .05). The estimated LV infarct size from ECG was similar between Groups A and C, yet Group A had higher creatine kinase MB isoform (CK-MB; p < .05). Cardiac troponin I (cTNI) was higher in Groups A and C than in B and D (p < .05 and p = .16, respectively). NT-proBNP decreased across groups (p = .20), with the highest left ventricular ejection fraction (LVEF) observed in Group D (p < .05). Group A notably demonstrated more cardiac dysfunction within 4 h post-onset. Conclusions: For inferior STEMI patients, concurrent R V-1 <0.3 mV with ST up arrow V-7-V-9 suggests prolonged ventricular activation and notable myocardial damage. RV infarction's dominance over LV lateral injury might explain these observations.