A 38 year old woman presents to you for episodes of paroxysmal palpitations since her childhood. You request an ECG in clinic to assess.

Question: What is the abnormality in this ECG?

Answer: This ECG shows a sinus rhythm with short PR interval, and broad QRS complexes with a slurred upstroke to the QRS complex, also referred to as the delta wave. You can also appreciate tall R waves and inverted T waves in V1-3, which mimic right ventricular hypertrophy, but these changes are due to the presence of a left-sided accessary pathway (dominant R wave in V1), and doesn’t indicate underlying RVH.

Overall this ECG is concerning for a pre-excitation syndrome, specifically Wolff-Parkinson-White syndrome.