R-wave Amplitude Distinguishes Early Repolarization from Subtle Anterior ST-Elevation Myocardial Infarction

Study of:

Objectives:
Anterior STEMI (MI) due to LAD occlusion may be difficult to differentiate from early repolarization (ER). We hypothesized that the ratio of T-wave amplitude (TA) to R-wave amplitude (RA) in leads V2-V4 differentiates MI and ER .

Methods:
We evaluated ECGs in 124 consecutive patients undergoing direct percutaneous coronary intervention (PCI) for MI with documented LAD occlusion and a control group of 70 consecutive non-cardiac chest pain patients with ECGs coded as ER. We excluded those with BBB and obvious MI (STE >5 mm, nonconcave morphology, inferior ST depression, or T inversion, terminal QRS distortion). ST elevation at the J point (STEJ), RA and TA were measured to the nearest 0.5 mm in each of V1-V6. Analysis was by 2-tailed t-test and Chi square. Optimally discriminative cutoff values were manually selected.

Results:
64 patients with MI and 70 with ER remained after exclusions. See Table 1 for mean measurements and Table 2 for cutoffs. Mean RA was a better discriminator than STEJ.

Conclusion:
TA:RA ratio is higher (because RA is lower) in subtle MI than in ER. RA =5 is a better discriminator than any STE cutoff to diagnose subtle anterior STEMI.

Timothy D. Henry, MD, FACC

Scott W. Sharkey, MD, FACC

For more information about this study or other research studies at the Minneapolis Heart Institute and Minneapolis Heart Institute Foundation, please contact Katie Menssen at 612-775-3052.