TPM1 and cardiac arrhythmia: The previous study showed that programmed ventricular stimulations (PVS) induced SVT or VF in 33% (7/21) of HCM patients carrying the TPM1-Asp175Asn mutation, although 57% (4/7) of those vulnerable HCM patients were under β-blocker therapy (Hedman et al., 2004), indicating that β-blocker treatment is suboptimal in arrhythmia prevention in HCM.