A 75 y.o. man with IHD (atherosclerotic cardiosclerosis, atrial fibrillation, cardiac insufficiensy stage 2 B; chronic pyelonephritis) was prescribed di-goxin. During the first 6 days the digoxin dose amounted 0,25 mg twice per day that let to abatement of dyspnea, edemata and cyanosis. But on the 7-th day the patient developed nausea and bradycardia. What is the most probable cause of digoxin intoxication?