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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
In a patient with chronic atrial fibrillation with a regular beat of 60/min, the most probable cause is :
assistant
The correct answer is  Answer is B (Digitalis toxicity) "If in the presence of atrial fibrillation, the ventricular rhythm becomes regular and slow (30 to 60/m) complete hea block is suggested and if ventricular rhythm is regular and rapid > = 100/ min, a tachycardia arising in AV junction or ventricle should be suspected. Digitalis intoxication is a common cause of both phenomenon" Digitalis toxicity is a common cause of such a presentation and hence has been picked up as the answer of choice. Infact "Non paroxysmal atrial tachycardia with AV block is characteristic of digitalis intoxication."