Left Ventricular Outflow Tract Tachycardia With Preferential Conduction and Multiple Exits

Abstract

A 50-year-old man with idiopathic premature ventricular contractions (PVCs; PVC 1, Figure 1A) and ventricular tachycardias (VTs) was referred for catheter ablation. Activation and pace mapping were performed at multiple sites in the right and left ventricular outflow tracts (RVOT and LVOT) (Figure 1). Nonirrigated radiofrequency (RF) applications delivered in the left coronary cusp where pacing reproduced a perfect pace map failed to suppress PVCs but gave a slight change in the QRS morphology of the PVCs characterized by S waves in lead V6 (PVC 2, Figure 1B). VT with this altered QRS morphology was induced by programmed stimulation (VT 1, Figure 1B). Pacing in the distal great cardiac vein (GCV) reproduced a different QRS morphology ( Figure 1D). During PVC 2, the earliest ventricular activation was observed at the aorto-mitral continuity (AMC) where pacing reproduced a perfect pace map ( Figure 1B). However, nonirrigated RF applications at this site did not prevent the induction of multiple morphologies of VT with programmed stimulation (Figure 1). Those VT morphologies exhibited a fair match to the pace maps from the RVOT, GCV, and right coronary cusp (RCC) (VT 2, Figure 1C; VT 3, Figure 1D; and VT 4, Figure 1E, respectively). Gradual transition between 2 of those VT morphologies (VT 3 and VT 4) was observed, and the local ventricular activation in the GCV preceded the QRS onset during both of those VTs (Figure 2). The local ventricular activation in the GCV relative to that in the His bundle region was 35 ms earlier during VT 3 than VT 4 (Figure 2). Because RF applications in the GCV were limited by high impedance, epicardial mapping via a subxiphoid access was performed. However, no epicardial ventricular activation as early as in the GCV could be recorded. Very detailed endocardial and epicardial activation mapping of both the RVOT and LVOT during the multiple morphologies of VT revealed a consistently early activation in the AMC but variable activation times at remote sites. Finally, RF applications delivered to the medial AMC with an irrigated ablation catheter eliminated all the ventricular arrhythmias (VAs) (Figure 3).In this case, a single intramural origin with a preferential conduction 1 to multiple exit sites all over the RVOT and Figure 1. Twelve-lead electrocardiograms of VTs, PVCs, and pace maps (PMs), and a 3-dimensional computed tomography image showing the presumed ventricular arrhythmia origin (star), preferential conduction (dotted arrows), and exits identified by pace mapping. Ao indicates aorta; GCV, great cardiac vein; LA, left atrium; LCC, left coronary cusp; LV, left ventricle; RCC, right coronary cusp; and RVOT, right ventricular outflow tract.

Preferential Pathway Pacing within the Aortic Sinus of Valsalva: Strong Evidence for the Existence of Preferential Conduction with Different Exit Sites Traversing the Ventricular Septum

“…6 When the RF applications at the exit sites were not effective, detailed mapping for finding discrete prepotentials and applying the RF energy at the more proximal site of the preferential pathway would be highly effective.…”

The Left Ventricular Ostium

“…16,23 Preferential conduction in the LVOT often leads to a discrepancy between the best pace mapping site and successful ablation site. As a result, the ablation is more accurately guided by recording the earliest site of ventricular activation during the VAs than pace mapping, which may identify the preferential breakout site but not the origin.…”

“…However, multiple myocardial fibers traveling from the LVOT to the RVOT or other LVOT sites and the endocardial or epicardial surfaces may occur with preferential conduction. 16,23,24 Because in our experience multiple breakout sites can often be recorded and the breakout site(s) may be wide, catheter ablation is most reliably accomplished by targeting the origin itself. 16,23,24…”

Ablation of ventricular arrhythmias above semilunar valves.

“…Bitan koncept za objaπnjenje ovog entiteta je i razumijevanje povezanosti ovih vlakana s miokardom. Ako se promotre intimni anatomski odnosi LVOT, RVOT te koronarnih kuspisa postaje jasno zaπto naprimjer fokus iz lijevog koronarnog kuspisa moaee imati viπestruke regije izlaza impulsa, najËeπÊe prema LVOT, ali i prema septalnom RVOT πto onemoguÊa-va koriπtenje elektrokardiografskih kriterija za lokalizaciju ishodiπta aritmije 4 (Slika 1). Razumijevanje ovog fenomena, tzv.…”