Clinical Significance of R-wave Amplitude in Lead V 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 <0.3 mV with ST-segment elevation (ST↑) V-V, Group B: R V <0.3 mV without ST↑ V-V, Group C: R V ≥0.3 mV with ST↑ V-V, and Group D: R V ≥0.3 mV without ST↑ V-V.

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, indicative of left ventricle (LV) lateral injury, was more higher in Group C than in Group A, while the ∑ST↑ VR + VR + VR, 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 <0.3 mV with ST↑ V-V suggests prolonged ventricular activation and notable myocardial damage. RV infarction's dominance over LV lateral injury might explain these observations.