Polymorphic ventricular tachycardia (PMVT)

• QRS morphology changes from beat to beat
• Etiologies: ischemia; CMP; catecholaminergic torsades de pointes (TdP = “twisting of the points,” PMVT + ↑ QT): ↑ QT acquired (meds, lytes, stroke, see “ECG”) w/ risk ↑ w/ ↓ HR, freq PVCs (pause dependent) or congenital (K/Na channelopathies) w/ resting Tw abnl & TdP triggered by sympathetic stimulation (eg, exercise, emotion, sudden loud noises) (Lancet 2008;372:750) Brugada syndrome (Na channelopathy; JACC 2018;72:1046): ♂ > ♀; pseudo-RBBB w/ STE in V1–V3 (provoked w/ class IA or IC) on resting ECG