Subsequently more detailed mapping was performed to

Subsequently, more detailed mapping was performed to identify the Purkinje potential preceding the QRS onset of the PVCs in their region of origin (Fig. 2B). Radiofrequency ablation was performed at the site of the earliest Purkinje potential preceding the local ventricular potential (Fig. 2C and D). When an acceleration or reduction of ventricular tachycardia (VT) or PVCs was observed at the beginning of the application, radiofrequency delivery was continued for an additional 60s. Ultimately, the PVCs were eliminated within the vicinity of the earliest activation site. Thereafter, no ventricular arrhythmias could be induced, even after programmed electrical stimulation. The second radiofrequency procedure was undertaken because of PVC recurrence 2months after the first procedure. These PVCs had the same morphology as those targeted during the first procedure. Three-dimensional geometries of the papillary muscles and right ventricular chamber were reconstructed using CARTOSOUND™ during the PVCs (Fig. 3), and the SOUNDSTAR was positioned in the right ventricle for acquiring electrocardiogram-gated two-dimensional images. An ablation catheter (NAVISTAR THERMOCOOL, Biosense Webster) was then introduced to the right ventricle under the same heparin protocol as in the first procedure. Activation mapping in the right ventricle was performed during the PVCs using a catheter whose tip position was verified using ICE in real time. The activation map clearly indicated that the earliest ventricular activation site was the same as in the first procedure. At the activation site, ICE showed the anterior papillary muscle (Fig. 4A). Although pace mapping was performed from both the septal and free wall sides of the right ventricular papillary muscle, neither recorded perfect pace matching (Fig. 4B). Therefore, ablation of the papillary muscle was performed under electroanatomic map guidance combined with the real-time ICE. The current was delivered in the power control mode, starting at 25W with an irrigation flow rate of 17mL/min. Radiofrequency purchase Digoxigenin-11-ddUTP was applied at a power of 35W and a maximal temperature of 43°C. The PVCs were successfully eliminated, and no ventricular arrhythmias could be induced thereafter, even after programmed electrical stimulation. During follow-up examination, this patient was free of any ventricular arrhythmias.
Discussion In this case, PVCs that recurred 2months after their elimination by a first radiofrequency procedure were successfully treated with the assistance of an echocardiography-guided electroanatomic mapping system. PVCs originating on or beneath the endocardium of the papillary muscles [1] comprise only approximately 5% of all types of PVCs that can be treated using catheter ablation; in particular, these include PVCs originating in the interventricular septum. These types of PVCs are more frequent in men [2]. Although papillary muscles are located within both the right and left ventricles, PVCs originating in the papillary muscles of the right ventricle are extremely rare. Because the papillary muscles are actively involved in the repeated expansion and contraction of the heart, radiofrequency application can be challenging. These contractions occur deep within the endocardium of the papillary muscles, and their recurrence rate is higher than that of other idiopathic PVCs [3,4]. Activation mapping is the most reliable method for identifying the origin of idiopathic PVCs, although pace mapping usually provides helpful clues. In this case, without an excellent pace map, observation of discrete exit sites would have been difficult because the PVCs originated at a deeper location and additional radiofrequency lesions would have been required to eliminate them. This finding suggests that PVCs may originate at a site some way below the surface of the papillary muscles, and that the origin of the PVCs may be located away from the exit site. An additional problem was that the non-irrigated catheter did not allow good contact with the papillary muscles because of the vigorous motion involved in normal papillary muscle contraction. Therefore, an adequate radiofrequency current could not be delivered at the origin of the PVCs. As with arrhythmias originating from the left-sided papillary muscles, good contact between the ablation catheter and muscle is crucial for successful ablation. The lack of good contact may have been the primary cause of PVC recurrence. Although no PVC episode was observed initially following the first conventional radiofrequency ablation, the PVCs recurred 2months after the procedure.