In a patient with chronic atrial fibrillation with a regular beat of 60/min, the most probable cause 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."
Sleep
Digitalis toxicity
Sino nodal block
Hypothyroidism