Rarely seen cardiotoxicity of lithium overdose: complete heart block

Serious cardiac toxicity due to lithium toxicity is uncommon and generally only occurs in individuals with underlying heart disease. Cardiac impairment may result in dysrhythmias, including sinus bradycardia, sinoatrial block, and first-degree atrioventricular block. This paper describes a patient with complete AV block in the course of chronic lithium treatment.

Fifty-seven year-old female was brought into the emergency department (ED) due to altered mental status and malaise by ambulance from hospice. She had hypertension, type-II diabetes mellitus, and depression. The caregivers told that she had been fine yesterday, had taken regular medications (lysinopril, furosemid, acetyl salicylic acid, oral antidiabetic tablets and lithium (300 mg tb/day)). Her vital signs were; blood pressure: 70/45 mmHg, pulse: 37 bpm, respiratory rate: 22 bpm, and oxygen saturation 86%. She was confused and unresponsive to verbal stimulation. Her EKG revealed total atrioventricular block. Initial biochemical results were unremarkable except for a lithium level of 2.2 mmol/l (therapeutic range 0.5-0.8 mmol/l) and an increased creatinine of 2.11 mg/dl. A transvenous pacing electrode was introduced into the right ventricle, which allowed rapid restoration of haemodynamic and neurological status. Her neurologic examination was completely normal in the follow-up period and she was discharged without sequelae.

In conclusion, emergency physicians should bear in mind that complete AV block can ensue in the course of lithium toxicity and it is an entity that should be included in the differential diagnosis.