Association of idiopathic RVOT VT and AVNRT: anything else than chance?

In the current issue of the journal, Kautzner et al .1 report a surprising and to date unrecognized high incidence (15%) of concomitant atrioventricular nodal reentrant tachycardia (AVNRT) in patients referred to the electrophysiology laboratory for catheter ablation of symptomatic right ventricular outflow tract tachycardia (RVOT VT). Although association of these two arrhythmias had not been clinically documented before ablation, they were beyond any doubt sequentially inducible in the same heart. Before concluding that this is mere chance, several potential common factors such as mechanisms, substrates, triggers, or sympathovagal status for initiation, which may contribute to the coexistence of these two different arrhythmias in the same patient, should be analysed. By definition, idiopathic VT refers to ventricular arrhythmias that originate in hearts without structural disease2. Although several magnetic resonance imaging studies have reported absence of structural ventricular defects in these patients, others have shown RVOT abnormalities including focal wall thinning and abnormal regional systolic wall motion. However, the causal relationship between the anatomic abnormalities and the site of tachycardia origin remains controversial3,4. Results of studies of right ventricular biopsy sample are heterogeneous. Pathological findings range from normal myocardium, interstitial fibrosis, myocardial cell hypertrophy to myocarditis5,6. Therefore, the implication of these histologic findings in the pathophysiology of RVOT VT remains unclear. Many studies have implied that the so-called fast and slow pathways involved in the genesis of AVNRT were anatomically distinct structures. However, …