Multiple Episodes of Presyncope in a Pacemaker Dependent Patient: What is the Diagnosis?

An 85 year old male presents to the emergency room with presyncopal episode associated with nausea and diaphoresis that lasted for 10 minutes. He has past medical history of hypertension and paroxysmal atrial fibrillation on anticoagulation. He also had complete AV block that necessitated the implantation of a dual chamber pacemaker (Medtronic Kappa KDR 701) 6 years prior to current presentation. The lead parameters were within normal limits during regular follow up every six months. A recent echocardiogram suggested dilated left atrium and ventricle with preserved systolic function. His home medications included coumadin 5mg once daily and amlodipine 10mg once daily. The physical examination was unremarkable and orthostatic blood pressure measurements were within normal limits. All laboratory parameters were within normal limits. The electrocardiogram suggested atrial synchronous right ventricular apical pacing.