Impact of Abnormal Potassium on Arrhythmia Risk During Pediatric Digoxin Therapy

Background: Digoxin is used in children with heart failure and tachyarrhythmia. Its use in patients with single ventricle anatomy has increased following evidence of improved interstage survival after the Norwood procedure. Digoxin has a narrow therapeutic window and may alter serum potassium balance, inducing arrhythmias. We hypothesized digoxin use in the setting of abnormal serum potassium levels is associated with arrhythmias. Methods: We reviewed all patients ≤18 years who received digoxin while admitted at our institution from 2014-2021. Admissions <2 nights were excluded. We compared patients with a hemodynamically significant arrhythmia to those without. We performed adjusted logistic regression with arrhythmia as the outcome variable and potassium status as the predictor variable; adjusting for weight, route of digoxin administration, digoxin indication, serum creatinine, and number of interacting drugs prescribed. Abnormal potassium was defined as serum levels <3.5 mmol/L or >6.0 mmol/L. Results: There were 272 encounters in 172 patients. Potassium levels were abnormal in 72.9% of patients who experienced an arrhythmia during digoxin administration, compared to 40.3% who did not (p < 0.001). Odds of arrhythmia was 133% higher in patients with abnormal potassium receiving digoxin (AOR=2.33, 95% CI 1.16 – 4.68, p=0.02). Receiving intravenous digoxin was also associated with a 4.46 odds of cardiac arrhythmia (AOR 4.46, p=0.04, 95% CI 1.07 to 18.50). Conclusion: Odds of arrhythmia is increased during digoxin administration when pediatric patients have abnormal potassium levels. Vigilant attention to potassium levels is essential to prevent adverse outcomes during digoxin therapy.