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Atrioventricular nodal dysfunction secondary to hyperparathyroidism.

The relationship of hyperparathyroid-associated hypercalcemia with clinical significant bradyarrythmias still remains controversial. We present a 66-year-old patient with dizziness, headache and paroxysmal 2:1 atrioventricular block. A 24-hour Holter report revealed symptomatic intermittent 2(nd) degree (2:1) atrioventricular block with a mean heart rate of 46 bpm. A 2D echocardiogramm showed normal ejection fraction and there was no valve dysfunction or calcification. The biochemistry results showed elevated serum calcium level, low phosphate level, elevated serum parathyroid hormone level and normal serum levels of potassium, magnesium and sodium. The urine calcium excretion was 390 mg/24 h. A coronary angiography was performed and revealed no critical lesions. The patient continued to have symptoms despite of the treatment of hypercalcemia and a DDDR pacemaker was implanted. He had a Sestamibi-scan of the neck, that was suggestive of parathyroid adenoma, and parathyroidectomy was performed. The presuming mechanism is the degeneration of AV node due to calcium deposit.