Severe bradycardia from severe hyperkalemia: Patient characteristics, outcomes and factors associated with hemodynamic support

Objective: Bradycardia is an under-studied manifestation of hyperkalemia potentially associated with adverse outcomes. We sought to systematically describe emergency department (ED) patients that present with severe bradycardia (heart rate < 50) associated with severe hyperkalemia (potassium ≥6.0 mEQ/L) and identify factors associated with the receipt of hemodynamic support. Methods: Retrospective, single-center, case series performed at an urban, tertiary-care hospital from 1/1/2014 to 6/30/2020. We included consecutive adult ED patients presenting simultaneously with severe bradycardia and severe hyperkalemia. Patients with prehospital cardiac arrest, hemolyzed potassium specimens, or only point-of-care lab results were excluded. Detailed information, including chronic medications, electrocardiogram (ECG) features, and potassium/heart rate-directed treatments, was abstracted from the ED medical record. Intensive care utilization and in-hospital outcomes were also recorded. Factors associated with receipt of bradycardia-targeted treatment in the ED were determined with univariate comparisons. Results: We screened 319 records and included 87 patients [mean age 72.5 (95% CI 53–92), 55% female, median heart rate 43 (38–47) beats/min, mean potassium 7.1 (95% CI 5.6–8.7) mEQ/L]. Cardiovascular (hypertension 82%, congestive heart failure 28%) and renal (dialysis dependence 30%) comorbidities were common. Many patients were prescribed negative chronotropic agents (84%) or potassium-retaining (52%) chronic medications. Common presenting scenarios were missed hemodialysis, isolated acute renal failure, or acute renal failure in the setting of concomitant critical illness. ECG revealed: junctional rhythm (39%), peaked T waves (27%), and QRS prolongation (30%). Twenty-eight (32%) patients exhibited hypotension and 34 (40%) altered mentation. Thirty-three (38%) patients received hemodynamic support, including 12 (14%) requiring temporary cardiac pacing. Forty-two (48%) patients received emergent renal replacement therapy and 57 (66%) were admitted to the intensive care unit. Hospital mortality was 10%. Factors associated with receipt of hemodynamic-targeted treatment included a lack of dialysis dependence, junctional rhythm, and concomitant presentation with hypothermia, acidemia, or sepsis. Conclusions: Patients presenting with severe bradycardia represent a unique phenotype of ED patients with hyperkalemia that may require significant resuscitation and critical care resources. Further research on the treatment of this uncommon, but potentially life-threatening condition is needed.