A person with mitral regurgitation and atrial fibrillation presents with syncope. On examination the personhas a hea rate of 55. What is the most probable cause?: (A) Digitalis toxicity, (B) Incomplete hea block, (C) Stroke, (D) Subarachnoid Haemorrhage
Answer is A. Bradycardia (hea rate of 55) with atrial fibrillation suggests the probable diagnosis of a complete hea block. This patient is most likely to be on digitalis for hea failure due to mitral regurgitation. Digitalis intoxication is a common cause of complete hea block. Ref: Harrison's Internal Medicine 16th Edition, Page 1345, 1375, 1394; Essentials of Medical Pharmacology, KD Tripathi, 5th Edition, Chapter 35, Page 462 &463.