Simultaneous antegrade dual AV node conduction initiates AV nodal re-entrant tachycardia [a rare initiation mechanism]

Typical atrioventricular nodal reentrant tachycardia [AVNRT] is the most common paroxysmal supraventricular tachycardia among adults. The concept of dual pathway physiology remains widely accepted, although this physiology likely results from the functional properties of anisotropic tissue within the triangle of Koch, rather than anatomically distinct tracts of conduction. AVNRT is typically induced with anterograde block over the fast pathway and conduction over the slow pathway, with subsequent retrograde conduction over the fast pathway. On rare occasions, anterograde AV node conduction occurs simultaneously through fast and slow pathways resulting in two ventricular beats in response to one atrial beat. We report a case of AVNRT where the tachycardia is always induced by the same mechanism described above. Successful ablation was achieved by slow pathway modification

Coronary sinus diverticulum as a cause of resistant posteroseptal pathway ablation

Coronary sinus [CS] anomalies such as diverticulum, persistent left superior vena cava or CS ostium dilatation are predominantly found in patients with accessory pathway-related tachycardias. Diverticulum of the proximal CS found in 7-11% of patients with postero-septal or left posterior manifests accessory pathways. We reported a 28 year old gentleman with manifested postero-septal accessory pathway, who underwent repeat electrophysiological study [EPS] and radiofrequency ablation for previously failed ablation. Huge CS diverticulum was identified by angiography as a reason for resistant accessory pathway. Successful RF ablation was achieved at the neck of the diverticulum without complications. Other associated anomalies were ruled out by cardiac computerized tomography [CT] and trans-esophageal echocardiography

importance of utilizing 24-h Holter monitoring as a non-invasive method of predicting the mechanism of supraventricular tachycardia

Despite the emergence of advanced invasive technology in identifying the various types of arrhythmia mechanisms, 24-h ambulatory electrocardiogram monitoring as a non-invasive method remains an invaluable informative tool in delineating such mechanisms. Furthermore, one observational study has supported the utilization of 24-h Holter monitoring in exploring AV Node [AVN] characteristics sufficiently in correlation with invasive studies when limited to patients without Wolf Parkinson White syndrome showing a positive predictive value of 98% in their supraventricular tachycardia [SVT] assessment [Fukuda et al., 2005]. We describe in this report suspected tachycardia initiation mechanism in three SVT cases based on 24-h Holter recordings. Premature atrial contraction with subsequent AVN fast pathway conduction block initiated the common type AVN re-entrant tachycardia [AVNRT]. Dual AVN physiology was documented during the electrophysiological studies in all three cases and a definitive therapy was achieved by the AVN slow pathway modification