system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A person with mitral regurgitation and atrial fibrillation presents with syncope. On examination the person has a hea rate of 55. What is the most probable cause ?
assistant
The correct answer is  ref Harrison 20th Ed pg 1456