Chronic Lithium‐Induced Cardiotoxicity: A Case Report and Lessons for Clinical Practice

<b>Background:</b> Lithium, commonly used in the treatment of bipolar disorders, is primarily known for causing neurological and renal side effects. However, cardiac side effects are rarely reported. <b>Case Summary:</b> We present a case of chronic lithium toxicity in an 80-year-old woman. The patient was admitted to the emergency room due to loss of consciousness. Initial evaluation revealed severe sinus bradycardia as a presentation of sinus node dysfunction on the electrocardiogram, prompting the insertion of a pacemaker. During her admission to the critical care unit, it was discovered that the patient had been undergoing long-term lithium treatment without medical supervision. The serum lithium level confirmed lithium intoxication. Following the discontinuation of lithium, both neurological and cardiac manifestations of lithium toxicity resolved. After the pacemaker was removed, the patient was discharged in stable condition. <b>Discussion:</b> Lithium has a narrow therapeutic range, which can lead to toxicity in the absence of routine monitoring. Lithium toxicity can cause serious cardiac effects and rhythm disturbances that are often overlooked because these manifestations are rare. Cardiac manifestations include arrhythmias, bradycardia, collapse, hypotension, myocardial infarction, and even death. Additionally, lithium toxicity can present with various electrocardiographic abnormalities such as T-wave inversion, sinoatrial block, PR interval prolongation, QT prolongation/dispersion, and ventricular tachyarrhythmias. Clinicians should be aware of the potential cardiac effects of lithium toxicity and consider it in patients undergoing lithium treatment. A thorough understanding of these manifestations is essential, as the wide range of symptoms can be misleading without adequate knowledge.