Lithium-Induced Bradycardia and Cardiomyopathy in a Patient With Bipolar Disorder and Paranoid Schizophrenia

Lithium is primarily known to cause neurological and gastrointestinal side effects, however, cardiac effects have been rarely reported. We present a unique case of lithium cardiotoxicity causing bradyarrhythmia and cardiomyopathy. A 68-year-old man with a history of paranoid schizophrenia and bipolar disorder presented with altered mental status. On examination, the patient was lethargic, afebrile, with dry oral mucosa, and a regular pulse of 42 bpm. Labs revealed acute kidney injury and elevated lithium levels. Electrocardiogram (ECG) revealed a junctional escape rhythm with a right bundle morphology. Lithium toxicity was strongly suspected in the setting of raised serum lithium levels, decreased oral intake and acute kidney injury. The patient was found to have lithium-induced junctional bradycardia. Transvenous pacing was not indicated as the patient responded to fluids and atropine and had no severe hemodynamic compromise. As his serum lithium levels decreased, the bradycardia gradually improved. His echocardiogram revealed moderate left ventricular systolic dysfunction. Workup of cardiomyopathies was negative: no obstructive coronary artery disease; viral panel, and autoimmune markers were unremarkable. Thus, his cardiomyopathy was attributed to lithium toxicity. Lithium cardiotoxicity may manifest as arrhythmias and/or cardiomyopathy. Clinicians should have a high index of suspicion for lithium cardiotoxicity due to the narrow therapeutic range of lithium.