Hydroxychloroquine Cardiotoxicity and Syncope

Cardiac Complications of Hydroxychloroquine

The American College of Cardiology recommends that hydroxychloroquine is not associated with vasovagal syncope, but rather with conduction abnormalities, QT prolongation, cardiomyopathy, and heart failure 1, 2
Conduction disorders are the predominant cardiac complication, affecting 85% of patients with hydroxychloroquine cardiotoxicity, including bundle branch blocks, QRS widening, and atrioventricular blocks 1
QT prolongation and torsades de pointes represent the arrhythmic risk, not vasovagal mechanisms 1, 3

The American Heart Association recommends that when evaluating syncope in patients taking hydroxychloroquine, prioritize cardiovascular assessment over vasovagal mechanisms 4, 5
Obtain 12-lead ECG immediately to assess for QRS widening, bundle branch blocks, AV blocks, or QTc prolongation >500 ms 5, 1, 3
Hospitalize patients with documented or suspected ventricular arrhythmia or syncope likely due to cardiac causes 5
Check electrolytes (potassium, magnesium) as hypokalemia compounds QT prolongation risk and increases torsades de pointes probability 3

The American College of Cardiology recommends ambulatory ECG monitoring (24-48 hour Holter or event recorder) to capture arrhythmias if conduction abnormalities present on baseline ECG 4
Discontinue hydroxychloroquine immediately if any cardiac manifestations are present, as conduction disorders may represent initial manifestations of potentially irreversible toxicity 1, 3
Do not attribute syncope to vasovagal mechanisms in hydroxychloroquine users without excluding cardiac causes through ECG and echocardiography 4, 5
Do not continue hydroxychloroquine if QTc exceeds 500 ms or any conduction abnormalities develop, as this represents unacceptable arrhythmia risk 3