RESUMO
BACKGROUND: Hyperkalemia and acute coronary syndrome are not only all responsible for syncope related to complete atrioventricular block, but also share parts of electrocardiogram manifestations. Additionally, they influence each other. CASE PRESENTATION: A 32-year-old Chinese man presented with severe hypokalemia (1.63 mmol/l) at midnight in the emergency room. He developed unexpected rebound hyperkalemia (7.76 mmol/l) after 18 hours of oral and intravenous potassium chloride supplementation at a concentration of about 10 g/day and a rate of 10 mmol/hour. Subsequently, the patient complained of chest discomfort and dyspnea, followed by syncope for several minutes, approximately 2 hours after potassium reduction treatment had been started. The instant electrocardiogram showed complete atrioventricular block and elevated ST segment in the inferolateral leads, which resolved 15 minutes later, before hyperkalemia was corrected. Combined with mild coronary stenosis and negative myocardial injury markers, transient complete atrioventricular block induced by coronary vasospasm due to iatrogenic hyperkalemia was diagnosed. Normal urine potassium excretion, acid-base state, and other examinations made the diagnosis of hypokalemic periodic paralysis possible. CONCLUSIONS: Hyperkalemia may provoke acute coronary syndrome, and early coronary angiography is an effective strategy for identifying the direct cause of acute complete atrioventricular block.