The arrhythmia rates in the complete VM KO group were essentially the same as for the whole-heart Casq2–/– model (P = 0.94), whereas the juxta-Purkinje group had significantly fewer ectopic beats and reduced arrhythmia burden compared with the whole-heart Casq2–/– group (P < 0.001). The gene discussed is CASQ2; the disease is Arrhythmia.