A 55-year-old man developed sinus arrest and syncope while receiving lithium [lithium carbonate] and ramipril [routes not stated] concomitantly.The man presented with two episodes of dizziness and vomiting followed by syncope. On examination, his HR was 40 beats/min and his BP was 105/65 mmHg. An ECG showed sinus arrest with a junctional escape rhythm of 35-40 beats/min.The man received atropine and temporary pacemaker implantation. Two weeks prior to presentation, he had undergone a percutaneous coronary intervention (PCI) and was started on low-dose ramipril [dosage not stated]. He had a 15-year history of bipolar disorder and was receiving lithium 450mg daily. Tests revealed an elevated serum lithium level, at 2.1mM. He was diagnosed with lithium induced sinus node dysfunction. His lithium and ramipril were discontinued. Sixty hours later, his sinus rhythm returned to normal. His lithium was restarted at a lower dose given the high likelihood of a reccurrence of his bradyarrhythmia and subsequently, he was discharged.Author comment: "Our patient was prescribed ramipril after PCI which precipitated lithium toxicity leading to sinus arrest and syncope." "This case reminds us of an unusual interaction of two commonly used drugs for cardiac disorders (ACE inhibitor) and for bipolar depression (lithium)." ACE inhibitors have been reported to increase serum lithium levels.Gupta MD, et al. Unusual cause of syncope in a patient with ischemic heart disease.