ECG Review

The Likely Diagnosis?

By Ken Grauer, MD, Professor, Department of Community Health and Family Medicine, University of Florida. Dr. Grauer is the sole proprietor of KG-EKG Press, and publisher of an ECG pocket brain book.

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Scenario

The ECG shown above was obtained from a 60-year-old man with a history of a dilated cardiomyopathy. Given this information, what clinical concerns might you have if this patient presented to the emergency department in heart failure with the tracing above?

Interpretation

The rhythm in the tracing is atrial fibrillation. Lack of a lead II rhythm strip makes it difficult to assess the ventricular response. The initial part of the tracing shows a heart rate just over 100 beats/minute. There follows two periods of extreme slowing in the ventricular response (in leads aVL and V5). This should raise concern for the "tachy-brady" component of sick sinus syndrome vs excessive rate slowing from medication effect. If the marked bradycardia does not resolve after holding any potential rate-slowing medications — and both hypothyroidism and acute infarction are ruled out — then permanent cardiac pacing may be needed in view of the patient's symptoms.

Other findings of note on this ECG tracing include left ventricular hypertrophy (LVH), evidenced by the marked increase in R wave amplitude in leads V5,V6 in association with "strain-equivalent" relative ST-T wave flattening in these lateral precordial leads; a small q wave with a hint of ST elevation isolated to lead aVL; a suggestion of shallow T wave inversion in leads III and aVF; and T wave peaking (albeit with a broader base to the T wave than is usually seen with hyperkalemia) in leads V2 through V4. The LVH is consistent with this patient's underlying diagnoses of cardiomyopathy and heart failure. We'd guess that the findings described in the infero-lateral leads are not indicative of acute infarction, but serum troponins and serial tracings would be needed for confirmation. Whether the anterior T wave peaking was the result of hyperkalemia, posterior ischemia, or repolarization variant in this patient with probable sick sinus syndrome would be answered by results of serum electrolytes and the ensuing course of events.