Fabritz et al. (2010) showed that chronic propranolol therapy did not suppress the carbachol-mediated ventricular arrhythmias, such as TdPs, in a heterozygous knock-in SCN5A-ΔKPQ LQT3 mice. On the other hand, Calvillo et al. (2014) reported that propranolol pretreatment prevented carbachol-mediated malignant ventricular tachyarrhythmias in the SCN5A-ΔKPQ LQT3 knock-in transgenic mice. The gene discussed is SCN5A; the disease is long QT syndrome 3.