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↑) V 7 –V 9 , Group B: R V 1 <0.3 mV without ST↑ V 7 –V 9 , Group C: R V 1 ≥0.3 mV with ST↑ V 7 –V 9 , and Group D: R V 1 ≥0.3 mV without ST↑ 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 ∑ST↑ V 3 R + V 4 R + V 5 R, 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↑ V 7 –V 9 suggests prolonged ventricular activation and notable myocardial damage. RV infarction's dominance over LV lateral injury might explain these observations.