Atrioventricular block, supraventricular tachycardia and grossly ischemic ST-T wave changes; what is the culprit?

Background

Hypokalemia is a common problem encountered in the emergency department. Severe cases of hypokalemia are associated with increased morbidity and mortality. ECG is an immediately-available test that can clinch the diagnosis, leading to immediate intervention. The trick is to differentiate ECG changes of severe hypokalemia from severe ischemia.

Case report

We here present a case of a middle-aged woman whose ECG showed sinus tachycardia with atrioventricular block, then supraventricular tachycardia with marked ischemic changes due to severe hypokalemia. Potassium level was 1.1 mEq/L. The ECG could have been mistaken for a high-risk, acute myocardial infarction due to severe left main and/or multi-vessel coronary artery disease. After initial potassium replenishment, classic text-book findings of hypokalemia became apparent. Troponin was mildly positive, however clinical presentation, the absence of chest pain, and confirmatory laboratory results led to the accurate decision not to activate a “Code STEMI” An echocardiogram done later showed no wall motion abnormalities. Supraventricular tachycardia terminated spontaneously. An ECG done after correction of hypokalemia was normal. No Q waves were noted.

Why should an emergency physician be aware of this?

Emergency department physicians, cardiologists, and internists, among other physicians should be aware of the recently-described pattern of diffuse ST segment depression and ST segment elevation due to severe hypokalemia. This will lead to accurate measuring decisions by treating hypokalemia and avoiding activating the catheterization laboratory, performing an unnecessary intervention.