A 67-year-old man presents to the emergency room complaining of multiple episodes of fainting since he woke up today. His fainting mainly occurs when he stands up. He has a history of coronary artery disease, diabetes, high cholesterol and hypertension. He takes atenolol, metformin, lovastatin and lisinopril. On physical examination, his blood pressure is 120/75, pulse is 55/min. and irregular, heart sounds are normal and lungs are clear on auscultation. ECG shows dropped beat after progressive lengthening of the PR interval.
What is the most likely initial diagnosis?
A- Atrial flutter
B-Atrial fibrillation
C-Mobitz type I (Wenckebach) second degree AV block
D- Mobitz type II second degree AV block
E- Third degree atrioventricular block