Slow bidirectional ventricular tachycardia as a manifestation of immune checkpoint inhibitor myocarditis

A 69-year-old male with a normal baseline electrocardiogram (Panel A) taking pembrolizumab for metastatic prostate cancer presented with cardiogenic shock. Cardiac MRI demonstrated ejection fraction of 17% secondary to immune checkpoint inhibitor (ICI) myocarditis complicated by slow bidirectional ventricular tachycardia (VT) at a rate of 107 b.p.m. (Panel B). With discontinuation of the ICI and the use of plasmapheresis, this patient's myocarditis improved and bidirectional VT resolved. Bidirectional VT is a wide complex ventricular rhythm with beat-to-beat alternation of QRS axis and morphology. It is distinct from ventricular bigeminy as none of the QRS complexes resemble sinus rhythm. Bidirectional VT can be caused by myocarditis, digitalis toxicity, catecholaminergic polymorphic VT, hypokalemic periodic paralysis, ischaemic heart disease, aconitine poisoning, LV noncompaction, cardiac sarcoidosis, and Anderson–Tawil (long QT 7) syndrome. ICIs are an emerging class of oncological medications but are associated with adverse cardiac events including arrhythmias and...