Wenckebach Block due to Hyperkalemia: A Case Report

Hyperkalemia is a commonly encountered electrolyte abnormality that can significantly alter normal cardiac conduction. Potentially lethal dysrhythmias associated with hyperkalemia include complete heart block and Mobitz Type II second-degree AV block. We report a unique case of Mobitz Type 1 second-degree atrioventricular (AV) block, known commonly as Wenckebach, due to hyperkalemia. The patient's symptoms and electrocardiogram (ECG) evidence of Wenckebach block resolved with lowering of serum potassium levels, with subsequent ECG showing first-degree AV block. This paper highlights an infrequently reported dysrhythmia associated with hyperkalemia that emergency physicians should be familiar with. 1. Introduction Hyperkalemia is a common and potentially life-threatening electrolyte abnormality [1]. While the incidence of hyperkalemia in the general population is not known, it is approximated that this electrolyte disturbance occurs in 1–10% of hospitalized patients annually and carries a mortality rate of 1 per 1,000 patients [1]. Hyperkalemia is associated with significant disturbances in cardiac conduction, ranging from QT interval shortening, to PR interval lengthening and QRS widening [2]. Reversible fascicular blocks, as well as bundle branch blocks or intraventricular conduction delay can be seen. Moreover, hyperkalemia is known to cause potentially lethal dysrhythmias including ventricular tachycardia, ventricular fibrillation, idioventricular rhythms, and asystole [1–9]. Despite the range of heart blocks associated with hyperkalemia, Mobitz Type 1 second-degree AV block or Wenckebach is infrequently reported in the medical literature. Hyperkalemia-induced Wenckebach in the setting of a pacemaker, termed pacemaker exit block, has been previously reported [9]. In the absence of a pacemaker, there is only a single reported case of hyperkalemia-induced Wenckebach—however, this case occurred in a patient with significant pre-existing underlying cardiac disease [4]. To our knowledge, there is no report of hyperkalemia-induced Wenckebach in the absence of pre-existing documented cardiac disease, conduction abnormality, or pacemaker. We present a case of symptomatic hyperkalemia presenting as Wenckebach, with resolution of this form of AV block as serum potassium levels were corrected. 2. Case Report A 68-year-old man was brought in by ambulance after his wife called EMS upon finding her husband sitting on the toilet and complaining of head and neck pain. Per the paramedic report, the patient was found seated on the toilet, cool, pale, diaphoretic, and