ECG Challenge: A 90-Year-Old Woman with Intermittent Lightheadedness

Differential Diagnosis

• Wolff Parkinson White (WPW)
• Inferior STEMI
• Premature ventricular contractions (PVCs)
• Right bundle branch block (RBBB)
• Left bundle branch block (LBBB)

Diagnosis
The ECG reveals a left bundle branch block, with wide complex QRS complex, a dominant S wave in lead V1, and a broad R wave in the lateral leads.

WPW has a wide QRS, but a short PR interval and a delta wave—which is not present in this ECG. There are no ST elevations in the inferior leads (II, III, aVF) or reciprocal changes, making inferior STEMI unlikely. There are no PVCs and no evidence of RBBB.

Learnings/What to Look for

• In LBBB, the depolarization of the heart is reversed, resulting in prolonged QRS duration
• LBBB may be caused by aortic stenosis, dilated cardiomyopathy, or acute ischemia
• The Sgarbossa criteria can be used in the presence of LBBB to evaluate for ischemia (specific criteria beyond the scope of this presentation)

Pearls for Urgent Care Management and Considerations for Transfer

• Compare to a previous ECG, if available
• If a patient has new-onset LBBB and symptoms concerning for ischemia, they should be emergently transferred to the emergency department
• An incidental finding of LBBB can be further evaluated on an outpatient basis