Visualization of the preferential conduction pathway in a case of premature ventricular contractions arising from the pulmonary artery

Abstract

A 50yearold man was referred to our hospital with a previously diagnosed premature ventricular contractions (PVCs) and unsuccessful ablation attempt twice. The QRS complex of his PVCs was left bundle blanch block morphology and inferior axis. Highresolution mapping was performed in the right ventricular outflow tract (RVOT) and pulmonary artery (PA) using a 16equidistant electrodes catheter (HD Grid Mapping Catheter Sensor Enabled, Abbott Technologies, Minneapolis, MN). Figure 1 showed the activation and voltage mapping, the surface electrocardiogram, and intracardiac electrograms during sinus rhythm and PVC. During the mapping into PA, sharp potential and fractionated potentials were recorded before the early phase of the QRS complex during PVCs (Figure 1AD). In addition, sharp potentials after the late phase of the QRS during sinus rhythm were observed (arrow in Figure 1G). The activation mapping revealed that the earliest site of PVCs (arrow in Figure 1A) was in the PA and about 10 mm above the pulmonary valve (dot lines in Figures 1 and 2; confirming the position of pulmonary valve by the catheter’s hookup), where a sharp potential preceded QRS onset of PVCs by 45 ms (arrow in Figure 1A). The activation mapping also showed that the preferential conduction pathway was well delineated. The PVC excitation traveled 10 mm toward the anterior septum (arrow in Figure 1C) and then 10 mm downward (arrow in Figure 1D), propagating to the RVOT just below the pulmonary valve (arrow in Figure 1E). In other words, the length of the preferential conduction pathway was 20 mm. At the exit site of PVCs, the precedence from the QRS complex was 25 ms (arrow in Figure 1E). The ablation catheter was advanced into the septal site of PA just above the pulmonary valve, where was directly above the exit site of PVCs. Then we ablated to cross the preferential pathway (round tags in Figure 2) to avoid injury to the PA and prevent conduction of firing from other parts of this preferential pathway to the ventricular muscle. After the elimination of PVCs, spiky potentials (arrow in Figure 3), representing firings of PA myocardial sleeve, were recorded on the ablation catheter repetitively. This meant the conduction block was formed between the origin in PA and the exit of RVOT, which was on the preferential conduction pathway of PVCs.