Third-degree AV block from extended-release diltiazem ingestion in a nine-month-old

Calcium channel blocker (CCB) overdose is associated with dysrhythmias and atrioventricular (AV) block, however, experience with infant CCB overdose is limited. A 9-month-old girl was found playing with tablets of extended-release diltiazem 120 mg. The patient had two episodes of emesis, which contained pill fragments, and was brought to the Emergency Department (ED) 4.5 h after being found. Vital signs were: rectal temperature 37.1 degrees C, pulse 87 beats/min, respiratory rate 30-40 breaths/min, blood pressure 72/48 mm Hg, and oxygen saturation (SpO(2)) 99% on room air. Otherwise, the patient was well-appearing, with normal skin color and examination. The electrocardiogram revealed third-degree atrioventricular block with a ventricular rate of 90 beats/min, QRS 68 ms, and QTc 411 ms. Atropine 0.1 mg i.v. was given, which increased the heart rate to 100-110 beats/min. Calcium gluconate 500 mg was also given intravenously. Laboratory evaluation revealed bicarbonate 17 mEq/L, anion gap 16, and glucose 129 mg/dL. On hospital day 1, the patient was noted to have a junctional rhythm with a rate of 90-100, and systolic blood pressure of 80-90 mm Hg. No additional medications were given. Early on day 2, the patient converted spontaneously to a normal sinus rhythm and was discharged approximately 42 h after presentation to the ED. In addition to bradycardia and hypotension, this 9-month-old patient manifested third-degree AV block after ingesting extended-release diltiazem.