Representative ECG rhythm strips from patients with ventricular arrhythmias following acalabrutinib initiation. Representative ECG rhythm strip from a patient (A) with unexplained ventricular tachycardia episodes nearly 6 weeks after acalabrutinib initiation for chronic lymphocytic leukemia, as well as (B) from a patient with symptomatic premature ventricular contractions nearly 20 months after acalabrutinib initiation. Acalabrutinib dose was 100 mg twice daily, and symptoms included fatigue, palpitations, and shortness of breath. ECG, electrocardiogram; HR, heart rate.