Demonstrating the deceleration zone associated with epicardial conduction using isochronal late activation mapping during right ventricular apex pacing

Figure 1. A: Voltage map of the left ventricle during sinus rhythm (right anterior oblique). A huge low voltage area from the inferior wall to the septal wall was observed. B: Isochronal latest activation mapping (ILAM) during sinus rhythm. The broad wavefront pattern from the basal region to the apex is shown, and there was no deceleration zone (DZ). C: ILAM during right ventricular apex (RVA) pacing. Several DZs became apparent in the area from the inferior wall to the septal wall during RVA pacing (white frame). The pink and blue tags indicate the good pace map sites. Moving from the basal region to the apex, the S-QRS becomes shorter. D: Intracardiac electrocardiogram in the DZ during right ventricular apex pacing and sinus rhythm. S-QRS = stimulus-QRS; SR = sinus rhythm; VT = ventricular tachycardia.

Figure 2. A: Propagation map during ventricular tachycardia (VT). A wavefront breaking out from the left ventricular apical inferior wall area with a conduction delay during right ventricular apex (RVA) pacing circled around the inferior wall with an activation gap in the distal isthmus. The black line indicates conduction block; the white arrow indicates propagating excitation. B: Omnipolar mapping at the activation gap site during VT. On the same D spline, a split potential on the proximal side and long-lasting fractionated presystolic potentials on the distal side were simultaneously recorded across the gap site. C: Isthmus activation during 3-dimensional VT reentry. The mechanism by which the gap occurred on the endocardial side was presumed to be that part of the slow conduction area (central isthmus) that mediated the epicardial conduction. The arrows indicate propagating excitation.

Figure 3. A: Isochronal latest activation mapping (ILAM) during right ventricular apex pacing (RAO). Several deceleration zones (DZs) and lines of conduction block (LOBs) were observed. The white frame indicates the DZ; the black dotted line indicates the LOB. B: Propagation excitation during sinus rhythm. The main wavefront conducted longitudinally along the lateral isthmus boundaries (LIBs), and some wavefronts propagated across the LIB with a conduction delay. The blue arrow indicates propagating excitation. C: Propagation excitation during right ventricle apex pacing. It was estimated that an LOB accompanied by a DZ and functional block was formed because the wavefront moving toward the isthmus during the ventricular tachycardia (VT) traveled in a different direction than that during SR. Black dotted lines indicate LIBs; red lines indicate LOBs. D: VT induction and excitation propagation during right ventricular apex (RVA) stimulation. Stimulation from the RVA caused conduction block within the central isthmus, leading to the induction of a reentrant VT.