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

Abstract

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 V₁ <0.3 mV with ST-segment elevation (ST↑) V₇-V₉, Group B: R V₁ <0.3 mV without ST↑ V₇-V₉, Group C: R V₁ ≥0.3 mV with ST↑ V₇-V₉, and Group D: R V₁ ≥0.3 mV without ST↑ V₇-V₉.

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 V₆, indicative of left ventricle (LV) lateral injury, was more higher in Group C than in Group A, while the ∑ST↑ 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 V₁ <0.3 mV with ST↑ V₇-V₉ suggests prolonged ventricular activation and notable myocardial damage. RV infarction's dominance over LV lateral injury might explain these observations.

Keywords: QRS duration; R‐wave amplitude in V1; inferior wall myocardial infarction; risk stratification.

FIGURE 1

Flow chart of patient inclusion (a) and the ECG examples in four groups (b).

FIGURE 2

Comparisons of mean values of serum cTNI, CK‐MB, and NT‐proBNP among four groups. Group A: R V₁ <0.3 mV with ST↑ V₇–V₉, Group B: R V₁ <0.3 mV without ST↑ V₇–V₉, Group C: R V₁ ≥0.3 mV with ST↑ V₇–V₉, Group D: R V₁ ≥0.3 mV without ST↑ V₇–V₉. Compared with Group C, ^a p < .05, compared with Group D, ^b p < .05, compared with Group B, ^c p < .05. CK‐MB, creatine kinase MB isoform; cTNI, cardiac troponin I; NT‐proBNP, N‐terminal pro‐B‐type natriuretic peptide.

FIGURE 3

Comparisons of mean values of QRS duration (QRSd) among four groups. Group A: R V₁ <0.3 mV with ST↑ V₇–V₉, Group B: R V₁ <0.3 mV without ST↑ V₇–V₉, Group C: R V₁ ≥0.3 mV with ST↑ V₇–V₉, Group D: R V₁ ≥0.3 mV without ST↑ V₇–V₉. Compared with Group C, ^a p < .05, compared with Group D, ^b p < .05, compared with Group B, ^c p < .05.

FIGURE 4

Comparisons of percent of SB‐IG, inverted or biphasic T and early Q among four groups. Group A: R V₁ <0.3 mV with ST↑ V₇–V₉, Group B: R V₁ <0.3 mV without ST↑ V₇–V₉, Group C: R V₁ ≥0.3 mV with ST↑ V₇–V₉, Group D: R V₁ ≥0.3 mV without ST↑ V₇–V₉. SB‐IG, Sclarovsky–Birnbaum Ischemia Grading System.