Correspondence Response

Additional data needed for a better understanding of the potential relationship between atrial fibrillation and ibrutinib Atrial fibrillation (AF) is a common cardiac arrhythmia observed in elderly patients who are representative of those who require therapy for chronic lymphocytic leukemia. A higher frequency of AF was noted with ibrutinib in the RESONATE phase 3 trial comparing the covalent Bruton’s tyrosine kinase inhibitor vs ofatumumab.1 In an attempt to address a possible role of ibrutinib in this process, McMullen et al2 used a specific mouse model to evaluate the in-hibition of the related phosphatidylinositol 3-kinase (PI3K) pathway and susceptibility to AF in dilated cardiomyopathy with depressed left ventricular function. Limitations of this study include species-and disease-specific electrophysiologic properties of cardiac cells that can lead to major functional differences between human and nonhuman heart.3,4 To the best of our knowledge, there is n