Answer:

The EKG demonstrates normal sinus rhythm with probable type 1 sino-atrial exit block with incomplete AV dissociation, frequent capture and intermittent junctional escape complexes. There is right axis deviation. The p-wave morphology is consistent with biatrial abnormalities. There is right bundle branch block and a deep S wave in lead V3. Therefore, biventricular hypertrophy cannot be excluded. The ST segment depression and inverted T waves may be secondary to strain and/or ischemia.

Clinical Correlation:

The patient has a history of congenital pulmonary atresias with incomplete correction. She has undergone a Blalock-Taussig shunt and Glenn procedure and is awaiting a Fontan shunt. She presented with acute onset of shortness of breath and hypoxia.

 Sometimes it is difficult to differentiate sinus arrhythmia from type I SA block in young patients.