Gender differences in idiopathic ventricular arrhythmias.

ustained monomorphic ventricular tachycardia (VT) is most often related to myocardial structural heart disease, including a healed myocardial infarction, and cardiomyopathies. However, no apparent structural abnormalities are identified in approximately 10% of all cases of sustained monomorphic VT in the United States1 and in 20% of those in Japan.2 These cases of VT are referred to as “idiopathic”. Idiopathic VTs usually occur in specific locations of the heart and have specific QRS morphologies, whereas VTs associated with structural heart disease have a QRS morphology that tends to indicate the location of the scar. Idiopathic VT comprises multiple, discrete subtypes that are best differentiated by their mechanism, QRS morphology, and site of origin. The predominant site of origin for idiopathic right VT is the right ventricular outflow tract (RVOT), and the tricuspid annulus VT is the second most common idiopathic right-sided VT. In idiopathic left-sided VTs, there are Purkinje-related VTs, mitral annular VTs, and left ventricular outflow tract (LVOT) VTs. According to the mechanism, idiopathic VT has been classified into 3 subgroups: a verapamil-sensitive type (reentry), adenosine-sensitive type (triggered activity), and propranolol-sensitive type (automaticity).1 Although the mechanism of RVOT-VT is mainly triggered activity and that of verapamil-sensitive left fascicular VT is reentry, the mechanisms of the other idiopathic VTs are not homogeneous.