Table 1. Characteristics of LQTS-3 patients reported in this study.

Parameters	Patient NP0012	Patient NP0016
Mutation and location	c.1604GA; p.R535Q in the intracellular linker region between DI and DII	c.718GA; p.V240M in the cytoplasmic loop between S4 and S5 within the DI
Gender	Female	Male
Date of birth	1972	1976
QTc (ms)	540	440
Clinical phenotype	At age of 32, the patient presented with several episodes of syncopes and torsades de pointes tachycardia, and survived one sudden cardiac death event. This patient developed DCM* in the later course of the disease.	This patient presented with frequent syncopes at age of 23 and at age of 30 with recurrent tachycardias. The patient was resuscitated from one sudden cardiac death event.
Therapy	Class IB anti-arrhythmic drug (mexiletine); β1-adrenergic antagonist (metoprolol); K+ and Mg2+ supplementation; ICD implantation. Despite medication the ICD recorded frequent VES and terminated recurrent VT.	Antiarrhythmic drug (phenytoin); β1-adrenergic antagonist (metoprolol); K+ and Mg2+ supplementation; ICD implantation. Despite medication episodes of torsades de pointes VT recurred and were terminated adequately by the ICD.

Abbreviations: QTc – corrected QT interval; DCM – dilated cardiomyopathy; ICD - implantable cardioverter defibrillator; VES - ventricular extrasystoles; VT – ventricular tachycardias.

^* Mutations in typical DCM-causing genes could not be identified in this patient.