ABSTRACT: A 59-year-old man presented to our hospital reporting 3 months of exertional dyspnea, ortopnea, paroxysmal nocturnal dyspnea, and lower leg edema. On physical examination, he had jugular venous distention, bibasilar rales, large tender liver, and peripheral edema. On cardiac auscultation, he had a regular heart rate with premature ventricular contractions, systolic ejection grade III/VI cardiac murmur in pulmonic area, and louder P2 than A2. Chest x-ray showed cardiac enlargement, and an ECG (Figure 1) was recorded; because of premature heartbeats on admission, a 24-hour Holter ECG was obtained (Figure 2). On the basis of ECG findings, what is the rhythm of the patient and what is the structural abnormality?