Widower Experiencing Fatigue

ANSWER
The correct interpretation of this ECG includes marked sinus bradycardia, left atrial enlargement, right bundle branch block, left anterior fascicular block, left ventricular hypertrophy, and an old anteroseptal myocardial infarction.

Marked sinus bradycardia is represented by a heart rate of 46 beats/min. Left atrial enlargement is evident from P waves ≥ 110 ms in lead I (difficult to see in this ECG) and a terminally negative P wave in lead V1 ≥ 1 mm2 (easier to see in this ECG).

Findings of a right bundle branch block include a QRS complex > 120 ms, a terminal broad S wave in lead I, and an RSR’ complex in lead V1. (In this ECG, the RSR’ complex is not obvious.)

A left anterior fascicular block is indicated by S waves > R waves in leads II, III, and aVF with marked left-axis deviation (R axis, –77°). Left ventricular hypertrophy is evident if the sum of the R wave in lead I and the S wave in III ≥ 25 mm or if the sum of the S wave in V1 and the R wave in either V5 or V6 is ≥ 35 mm.

Finally, the diagnosis of an old anteroseptal myocardial infarction is evidenced by Q waves in leads V1 through V3 and a QS pattern in lead V4.

The patient’s bradycardia was responsible for his symptoms of fatigue. Careful questioning revealed that he had inadvertently doubled his dose of atenolol for the preceding two weeks. Upon correction of his dose, his heart rate increased and his symptoms resolved.