Clinical Scenario. The ECG shown in the Figure was obtained from a previously healthy 56-year-old man with a history of gradually progressive fatigue. No chest pain. No history of prior infarction. The patient has never smoked. An echocardiogram was diagnostic and distinctly abnormal. Can you guess what the echo might show?
Interpretation. The rhythm is sinus bradycardia at a rate of 50 beats/minute. All intervals are normal. The mean QRS axis is indeterminate (QRS complexes are nearly equiphasic in all six limb leads). There is no ECG evidence of chamber enlargement. In the precordia leads transition occurs early; small q waves are seen in leads I, aVL, and V3 through V6; and there is nonspecific ST segment flattening with shallow T wave inversion in leads V2 to V4.
The overall ECG picture is nonspecific in nature. However, in view of the hints provided in the history (the patient was previously healthy, he does not smoke, and has no history of prior infarction)—the early transition with relatively prominent R waves in anterior precordial leads suggests prominent septal forces. The patient had nonobstructive hypertrophic cardiomyopathy with septal hypertrophy that was disproportionately enlarged compared to left ventricular wall thickness (asymmetric septal hypertrophy or ASH). It is likely that the small narrow q waves in leads V3 through V6 are also the reflection of prominent septal forces. Although the ECG will usually be abnormal in patients with hypertrophic cardiomyopathy, the changes seen are most often nonspecific and nondiagnostic. This would have been the case here had there not been the hints we have given.