The correct interpretation includes sinus tachycardia with occasional premature ventricular complexes (PVCs), left atrial enlargement, evidence of a previous inferior MI, and an acute anterior MI. Sinus tachycardia is evidenced by a rate ≥ 100 beats/min and the presence of a P wave for every QRS complex with a constant PR interval. A single PVC is evident (12th beat of the rhythm strips V1, II, and V5).
Left atrial enlargement is evidenced by a large P wave in lead II and a biphasic P wave with the terminal portion larger than the initial portion in lead V1. An old inferior MI is evidenced by the presence of Q waves in leads II, III, and aVF.
An evolving anterior MI is diagnosed by the presence of poor R-wave progression with ST-segment elevations and T-wave inversion in leads V2, V3, and V4. This was subsequently confirmed by clinically significant elevations of serum troponin levels and by cardiac catheterization, which revealed occlusion of the left anterior descending artery distal to the internal mammary artery anastomosis.