The correct interpretation is sinus rhythm with a first-degree atrioventricular (AV) block and possible left atrial enlargement. Criteria for sinus rhythm include a P wave for every QRS complex and a QRS complex for every P wave with a consistent PR interval.
Criteria for a first-degree AV block include a consistent PR interval > 200 ms in all leads. Criteria for left atrial enlargement include a P-wave duration > 120 ms in lead II or a downward deflection of the P wave in lead V1 > 40 ms in length with > 1-mm negative deflection.
The P wave in leads II and V1, along with a murmur, is consistent with mitral regurgitation and a history of palpitations and paroxysmal atrial fibrillation. Left atrial enlargement should be considered. An echocardiogram was ordered and confirmed the diagnosis of left atrial enlargement in this patient.