PV-LA Junction Research Articles

Intracardiac Echo‐Guided Image Integration: Optimizing Strategies for Registration

Image integration is being used in ablation procedures. However, the success of this approach is dependent on the accuracy of the image integration process. This study aims to evaluate the in vivo accuracy and reliability of the integrated image. One hundred twenty-four patients undergoing radiofrequency (RF) ablation catheter ablation for atrial fibrillation (AF) were recruited for this study from three different centers. Cardiac computerized tomography (CT) was performed in all patients and a 3D image of the left atrium (LA) and pulmonary veins (PVs) was extracted for registration after segmentation using a software program (CartoMerge, Biosense Webster, Inc.). Different landmarks were selected for registration and compared. Surface registration was then done and the impact on integration and the landmarks was evaluated. The best landmark registration was achieved when the posterior points on the pulmonary veins were selected (5.6 +/- 3.2). Landmarks taken on the anterior wall, left atrial appendage (LAA) or the coronary sinus (CS) resulted in a larger registration error (9.1 +/- 2.5). The mean error for surface registration was 2.17 +/- 1.65. However, surface registration resulted in shifting of the initially registered landmark points leading to a larger error (from 5.6 +/- 3.2 to 9.2 +/- 2.1; 95% CI 4.2-3.05). Posterior wall landmarks at the PV-LA junction are the most accurate landmarks for image integration in respect to the target ablation area. The concurrent use of the present surface registration algorithm may result in shifting of the initial landmarks with loss of their initial correlation with the area of interest.

Patterns of activation in human atrial fibrillation

The electrophysiological properties within the pulmonary vein (PV) and PV-left atrial (LA) junction were evaluated using a basket catheter in patients with paroxysmal atrial fibrillation. The effective refractory period of the distal PV was significantly shorter than that of the PV-LA junction. The conduction delay from the distal to proximal PV was significantly longer than that from the proximal to distal PV. During initiation of AF, a reentry involving exit and entrance breakthrough points at the PV-LA junction was observed. The presence of anisotropic conduction properties at the PV-LA junction may be critical to promote reentry formation.

High‐Density Mapping of Spontaneous Pulmonary Vein Activity Initiating Atrial Fibrillation in Humans

High-density three-dimensional (3D) mapping of the pulmonary vein (PV)-left atrial (LA) junction was performed to characterize spontaneous PV activity in humans. The activation patterns of ectopic beats and of the initial 2 seconds of atrial fibrillation (AF) from the PVs were analyzed using a 64-poles basket catheter. A focal mechanism was defined as a discrete site of early and centrifugal activation. Continuous activity was considered as an activation covering > or = 80% of the tachycardia beat-to-beat cycle length within the mapping field. In 35 patients, 123 spontaneous focal ectopic beats that did not induce AF and 95 that did induce AF were mapped. The mean coupling interval of ectopic discharges not inducing AF was 281 +/- 70 msec versus 236 +/- 90 msec for ectopies initiating AF (P < or = 0.01). The first ectopic activity of all 218 arrhythmogenic events showed exclusively a focal mechanism. During the 95 episodes of AF initiation, one or two ectopic beats from the PVs initiated AF in the LA in 39%, a stable focal tachycardia was recorded in 14%, continuous activity with important changes in cycle length (35 +/- 15 msec) suggestive of decremental or fibrillatory conduction was found in 18%, and in 29% the activation pattern could not be classified. No stable and sustained reentrant circuit could be identified by our mapping tool in the PV-LA junction. Arrhythmogenic activity from PVs in humans is predominantly due to discrete focal activity.

Electroanatomic Remodeling of the Left Atrium in Patients Undergoing Repeat Pulmonary Vein Ablation: Mechanistic Insights and Implications for Ablation

There is limited information describing late changes in the electroanatomic characteristics of the left atrium (LA) associated with recurrence after an anatomical circumferential pulmonary vein ablation (CPVA) for atrial fibrillation (AF). Forty-seven patients (57 +/- 8 years) undergoing a repeat ablation after CPVA were included. Using an electroanatomic mapping system, we measured the bipolar voltage by averaging points in the pulmonary vein (PV)-LA junction and four other LA sites. Conduction velocity and AF cycle length (AFCL) were also measured and the results are compared with the first procedure. After an initial decrease observed at the end of the first procedure, voltage and conduction velocity returned to intermediate values in all LA sites, with lower voltage at the LIPV antrum (P = 0.004), and lower conduction velocity across the LIPV and RSPV (P < 0.001). Conduction gaps were more prevalent at the septal aspect of the right PV encircling lines (85%), between the left atrial appendage (LAA) and the LSPV (70%) and lines at the posterior wall (71%). There was a nonsignificant increase in AFCL, with a more widespread distribution of organized electrograms (32.4% vs 46.6%). Recurrence after CPVA is associated with a reverse process of voltage and conduction velocity increase across ablated areas, especially the PV-LA junction, and is related to the presence of conduction gaps, which are distributed mostly at the septal aspect of the lines encircling the right PVs and at the LAA-LSPV area. Organization of atrial electrograms seen during AF ablation is maintained at a repeat procedure.

Autonomic Innervation and Segmental Muscular Disconnections at the Human Pulmonary Vein-Atrial Junction: Implications for Catheter Ablation of Atrial-Pulmonary Vein Junction

This study sought to examine the muscle connections and autonomic nerve distributions at the human pulmonary vein (PV)-left atrium (LA) junction. One approach to catheter ablation of atrial fibrillation (AF) is to isolate PV muscle sleeves from the LA. Elimination of vagal response further improves success rates. We performed immunohistochemical staining on 192 circumferential venoatrial segments (32 veins) harvested from 8 autopsied human hearts using antibodies to tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT). Muscular discontinuities of widths 0.1 to 5.5 mm (1.1 +/- 1.0 mm) and abrupt 90 degrees changes in fiber orientation were found in 70 of 192 (36%) and 36 of 192 (19%) of PV-LA junctions, respectively. Although these anisotropic features were more common in the anterosuperior junction (p < 0.01), they were also present around the entire PV-LA junction. Autonomic nerve density was highest in the anterosuperior segments of both superior veins (p < 0.05 versus posteroinferior) and inferior segments of both inferior veins (p < 0.05 vs. superior), highest in the LA within 5 mm of the PV-LA junction (p < 0.01), and higher in the epicardium than endocardium (p < 0.01). Adrenergic and cholinergic nerves were highly co-located at tissue and cellular levels. A significant proportion (30%) of ganglion cells expressed dual adrenocholinergic phenotypes. Muscular discontinuities and abrupt fiber orientation changes are present in >50% of PV-LA segments, creating significant substrates for re-entry. Adrenergic and cholinergic nerves have highest densities within 5 mm of the PV-LA junction, but are highly co-located, indicating that it is impossible to selectively target either vagal or sympathetic nerves during ablation procedures.

Electroanatomic Characteristics of Atrial Premature Beats Triggering Atrial Fibrillation in Patients with Persistent Versus Paroxysmal Atrial Fibrillation

APBs in Persistent Versus Paroxysmal AF. Although the electrical disconnection between the left atrium (LA) and pulmonary veins (PVs) by radiofrequency catheter ablation has been proven to be effective in controlling atrial fibrillation (AF), the recurrence rate is higher in patients with persistent AF (PeAF) than with paroxysmal AF (PAF). We hypothesized that the origin of the atrial premature beats (APBs) that trigger AF and the pattern of their breakthrough into the LA differ between PAF and PeAF. We mapped 75 APBs (53 APBs triggering AF, 22 isolated APBs) from the LA and PVs in 26 patients with AF (age: 49.5 +/- 9.6, males: 23, PAF = 17, PeAF = 9), using a noncontact endocardial mapping (NCM) system. The location of the preferential conduction (PC) sites and their conduction velocity (CV) were compared. In patients with PeAF, the earliest activation (EA) site and exit of the PC were more frequently located on the LA side of the LA-PV junction as compared with PAF (P < 0.001). Eighty-one percent of the PCs were located in the area between the left and right superior PVs. The incidence of PCs was similar between the PeAF and PAF patients (P = NS). PCs were more commonly found with APBs inducing AF (63.3%) than with those not inducing AF (35.2%, P = 0.01). The CV of the PC was slower for PeAF than PAF (P < 0.001). The CV in the LA during sinus rhythm was also slower for PeAF than PAF (P < 0.01). PeAF was more frequently triggered by APBs from the LA side of the LA-PV junction than PAF and resulted in slower conduction than did PAF. These findings may help explain the higher potential for recurrence after electrical PV isolation in patients with PeAF.

P3-72: Intra-esophageal temperature monitoring during balloon cryoablation of the PV-la junction

Cryoablation for AF is thought to carry a decreased risk of PV stenosis and thromboembolism. However, it is unknown what the transmural effects are on the esophagus during delivery of cryoenergy to the PV ostia. The purpose of this study was to assess the changes in intraesophageal temperature during balloon cryoablation.

Diverse Myocardial Extension and Autonomic Innervation on Ligament of Marshall in Humans

The ligament of Marshall (LOM) or the oblique vein of Marshall (VOM) in the left atrium (LA) is one of the origins of nonpulmonary vein ectopies causing atrial fibrillation. The distributions of myocardial bundles (Marshall bundles; MBs) and autonomic nerves adjacent to the LOM have not been completely elucidated. Twenty-eight human hearts were examined postmortem. The inferolateral LA myocardium was dissected en block and cut perpendicularly to the atrioventricular ring. The specimens were sectioned at 1-mm intervals and stained with hematoxylin and eosin, and Azan-Mallory. In addition, S-100 and tyrosine hydroxylase (TH) were employed for the immunohistochemical analysis of the sympathetic and parasympathetic fibers. In 25 cases, MBs were observed. Although the MBs surrounded the VOM at the coronary sinus (CS) juncture, they gradually diminished in density toward the distal venous branch. The connections of the MBs and LA myocardium were frequently observed in the CS juncture and anterior wall of the left pulmonary vein (PV)-LA junctions. TH-stained sympathetic nerve fibers were densely distributed around the PV-LA junctions. On the other hand, non-TH-stained parasympathetic ganglions were mainly observed at the CS juncture. MB-LA connections were mainly observed at the CS juncture and PV-LA junctions. The association between sympathetic nerve fibers and MBs was distinct at the PV-LA junctions. At the CS juncture, the regression of the sympathetic nerve fibers and the increase of parasympathetic ganglions were observed. The diverse arrangement and autonomic innervation of MBs seem to characterize the LOM region in humans.

Endoscopic fiberoptic assessment of balloon occlusion of the pulmonary vein ostium in humans: Comparison with phased-array intracardiac echocardiography

Anatomic pulmonary vein (PV) variants may affect the ability to position balloon catheter systems at the left atrium (LA)-PV junction with complete circumferential contact, resulting in ineffective PV isolation. This feasibility study was performed to assess the use of the fiberoptic endoscopic light ring balloon catheter (ELRBC) in accessing the PVs and achieving adequate contact at the LA-PV junction, as visualized by phased-array intracardiac echocardiography (ICE). We enrolled five men (mean age 59 +/- 8 years) with drug-refractory atrial fibrillation. The ELRBC consisted of a 25-mm balloon catheter with an integral endoscope contained within the balloon and a custom deflectable sheath. At the end of conventional PV isolation, the ELRBC was inserted into the LA in an attempt to position the balloon at each PV ostium. The real position of the ELRBC at this level was assessed by ICE in all patients. All but two PVs (right inferior PVs) (89%) were accessed with the ELRBC in a mean time of 17 +/- 3 minutes, and complete circumferential contact was visualized with the fiberoptic endoscopic component in 15 of 16 PVs accessed (94%). Contact was also confirmed by the absence of color Doppler flow through the balloon-occluded PV, as seen on ICE. On two occasions a gap was seen with the fiberoptic endoscope and visualized by the ICE only after optimization of the echo window. No complications were observed. The ELRBC is able to access the PV without complications. The endoscope and ICE were complementary for positioning of the balloon at the LA-PV junction and for the definition of circumferential contact.

Pulmonary vein isolation under direct visual identification of the left atrium—pulmonary vein junction using intra-cardiac echography

Intra-cardiac echocardiography (ICE) which has some benefits, can be used to obtain detailed anatomy of the heart chambers or large vessels, and the catheter positions, and it has been considered useful for improving the outcome of the ablation. In the present study, we performed pulmonary vein isolation (PVI) under real time monitoring of ICE imaging utilizing an ICE catheter placed at the junction of the left atrium (LA) and PVs (LA-PV junction). PVI for atrial fibrillation (AF) was performed in 30 cases with drug-resistant AF (mean age: 66-years-old; including 22 males). An ICE catheter utilizing a 9 MHz frequency was inserted into the LA via the atrial septum, and placed at the LA-PV junction. Circumferential ablation was performed in the LA outside of the PV ostium, encircling both the superior and inferior ostia together under ICE imaging. The anatomy of the LA to the PVs and catheter sites were clearly identified by the ICE during the procedure, which enabled a precise and safe catheter manipulation with minimal fluoroscopy. Further, the wall thickness of the PV and LA, and position of the esophagus could be obtained by ICE, facilitating care in adjusting the power and/or duration of the current delivery. ICE imaging of the LA-PV junction permitted real time monitoring of the target sites for PVI during the ablation procedure, and was considered a useful technique for performing PVI.

Arrangement of the Autonomic Nerves Around the Pulmonary Vein-Left Atrial Junctions —Histologic and Immunohistochemical Analyses—

Introduction: Imbalanced autonomic activity in the area of the pulmonary veins (PVs) can result in spontaneous atrial fibrillation (AF). Histologic characteristics of the PV sleeve musculature and associated autonomic nerve are not fully understood. We investigated the arrangement of autonomic nerve fibers around PV-left atrium (LA) junctional musculature. Methods: Thirteen autopsied adult hearts (9 men and 4 women; mean age at death, 66.2 years were studied. The atria were removed from each heart, along with all PV stalks, and cut longitudinally to each PV myocardial sleeve. After treatment with azan-Mallory stain and immunohistochemical staining for S-100 and tyrosine hydroxylase (TH), autonomic nerve distribution was assessed by counting the numbers of TH-positive (adrenergic and -negative (non-adrenergic) fibers within S-100-positive fibers (>50 mm in diameter) in the anterior, posterior, and septal junctions. Results: TH-positive adrenergic fibers, consisting of sympathetic nerves, were most predominant in the anterior and septal junctions. In the anterior junction, these fibers were packed tightly among myocardial sleeve fascicles. In the posterior junction, the numbers of adrenergic and non-adrenergic fibers were fewer. In the septal junction, the number of THnegative non-adrenergic fibers (predominantly parasympathetic nerves) was greater, concomitant diffuse ganglionic nodule distribution in the interatrial fat pad. Conclusions: In each PV-LA junction, autonomic nerves were localized on the anterior and septal walls. Heterogeneous distribution of TH-positive and TH-negative fibers and ganglion nodules around each PV opening appears to represent the major histologic characteristic in these areas.

Pilsicainide for Atrial Fibrillation

Pilsicainide is a class IC antiarrhythmic drug, which has a pure sodium channel blocking action with slow recovery pharmacokinetics. In experimental studies, pilsicainide has a depressant effect on intra-atrial conduction and a prolonging effect on the atrial effective refractory period (ERP). In patients with paroxysmal atrial fibrillation (AF), pilsicainide significantly prolonged the ERP of the distal pulmonary vein (PV), PV-left atrium (LA) junction and LA, and the conduction time from the distal PV to the PV-LA junction. In some patients, PV-LA conduction block has been observed just before pilsicainide-induced termination of AF; this isolation of the PV may provide a new insight into the mechanism of pharmacological conversion of AF. Hybrid therapy with pilsicainide and PV isolation (by radiofrequency catheter ablation) appears to be an effective therapeutic approach for AF. The pharmacological PV isolation by pilsicainide and its suppression of focal discharges from atrial tissue may prevent the development of AF after unsuccessful ablation.

Catheter Ablation of Long‐Lasting Persistent Atrial Fibrillation: Critical Structures for Termination

The relative contributions of different atrial regions to the maintenance of persistent atrial fibrillation (AF) are not known. Sixty patients (53 +/- 9 years) undergoing catheter ablation of persistent AF (17 +/- 27 months) were studied. Ablation was performed in a randomized sequence at different left atrial (LA) regions and comprised isolation of the pulmonary veins (PV), isolation of other thoracic veins, and atrial tissue ablation targeting all regions with rapid or heterogeneous activation or guided by activation mapping. Finally, linear ablation at the roof and mitral isthmus was performed if sinus rhythm was not restored after addressing the above-mentioned areas. The impact of ablation was evaluated by the effect on the fibrillatory cycle length in the coronary sinus and appendages at each step. Activation mapping and entrainment maneuvers were used to define the mechanisms and locations of intermediate focal or macroreentrant atrial tachycardias. AF terminated in 52 patients (87%), directly to sinus rhythm in 7 or via the ablation of 1-6 intermediate atrial tachycardias (total 87) in 45 patients. This conversion was preceded by prolongation of fibrillatory cycle length by 39 +/- 9 msec, with the greatest magnitude occurring during ablation at the anterior LA, coronary sinus and PV-LA junction. Thirty-eight atrial tachycardias were focal (originating dominantly from these same sites), while 49 were macroreentrant (involving the mitral or cavotricuspid isthmus or LA roof). Patients without AF termination displayed shorter fibrillatory cycles at baseline: 130 +/- 14 vs 156 +/- 23 msec; P = 0.002. Termination of persistent AF can be achieved in 87% of patients by catheter ablation. Ablation of the structures annexed to the left atrium-the left atrial appendage, coronary sinus, and PVs-have the greatest impact on the prolongation of AF cycle length, the conversion of AF to atrial tachycardia, and the termination of focal atrial tachycardias.

Electrical connections between left superior pulmonary vein, left atrium, and ligament of Marshall: implications for mechanisms of atrial fibrillation

The importance of the ligament of Marshall (LOM) to rapid activations within the left superior pulmonary vein (LSPV) during atrial fibrillation (AF) remains poorly understood. We aimed to characterize the importance of electrical coupling between the LSPV with the left atrium (LA) and the LOM in the generation of high-frequency activations within this PV. We performed high-density mapping of the LSPV-LA-LOM junction in eight dogs, using 1,344 electrodes with a 1-mm resolution before and after posterior ostial ablation to diminish PV-LA electrical connections. A LOM potential was recordable up to 6.5 mm (SD 2.2) into the LSPV in all dogs during sinus rhythm (SR) and LA pacing. Functional LOM-LSPV electrical connections bypassing the PV-LA junction were present in five of eight dogs. Direct LOM-LSPV connections contributed to 46.5% (SD 16.0) of LSPV activations during AF, resulting in a greater propensity to develop focal activations (P < 0.05) and a higher activation rate during AF of LSPVs with direct LOM connections compared with those without (P < 0.03). Posterior LSPV ostial ablation without damaging the anterior wall or LOM slowed residual LA-PV conduction (P < 0.001). This diminished PV-LA coupling prevented the reinduction of LSPV focal activations in all dogs. However, persistent LOM focal activations in two dogs continued to activate the LSPV rapidly [cycle length 151.8 ms (SD 4.8)] via direct LOM-LSPV connections. LOM-LSPV connection forms an accessory pathway that contributes to the electrical coupling between LSPV and LA during SR and AF. This pathway may contribute to rapid activations within the LSPV during AF.

High-density mapping of pulmonary veins and left atrium during ibutilide administration in a canine model of sustained atrial fibrillation

Ibutilide can prolong refractory period and terminate reentry. Whether ibutilide has the same effects on pulmonary vein (PV) focal discharge (FD) is unclear. We induced sustained atrial fibrillation (AF) in seven dogs by rapid left atrial (LA) pacing for 74 +/- 46 days. Ibutilide was repeatedly infused until it terminated AF (0.02 +/- 0.01 mg/kg) or when a cumulative dose was reached (0.04 mg/kg). High-resolution computerized epicardial mapping was performed. We found intermittent FD at the PVs and reentry at the PV-LA junction during AF. Ibutilide increased the cycle length of consecutive reentry from 97 +/- 13 to 112 +/- 18 ms and increased FD from 96 +/- 7 to 113 +/- 9 ms. In four dogs with both FD and reentry at the PVs, the incidence of reentry decreased from 3.5 +/- 1.9/s at baseline to 2.2 +/- 1.8/s after ibutilide administration. However, the incidence of FD remained unchanged. The conducted wave fronts between PV and LA were significantly reduced by ibutilide (10.4 +/- 2.0/s vs. 8.0 +/- 1.6/s). The ibutilide dose needed to terminate AF correlated negatively with the baseline effective refractory period of PV and LA. We conclude that ibutilide reduces reentrant wave fronts but not PV FD in a canine model of pacing-induced sustained AF. These findings suggest that the PV FD during AF is due to nonreentrant mechanisms. High doses of ibutilide may completely terminate all reentrant activity, converting AF to PV tachycardia before the resumption of sinus rhythm.

Intracellular Calcium Dynamics and Anisotropic Reentry in Isolated Canine Pulmonary Veins and Left Atrium

Rapid activations due to either focal discharge or reentry are often present during atrial fibrillation (AF) in the pulmonary veins (PVs). The mechanisms of these rapid activations are unclear. We studied 7 isolated, Langendorff-perfused canine left atrial (LA) and PV preparations and used 2 cameras to map membrane potential alone (Vm, n=3) or Vm and intracellular calcium simultaneously (Ca(i), n=4). Rapid atrial pacing induced 26 episodes of focal discharge from the proximal PVs in 5 dogs. The cycle lengths were 223+/-52 ms during ryanodine infusion (n=13) and 133+/-59 ms during ryanodine plus isoproterenol infusion (n=13). The rise of Ca(i) preceded Vm activation at the sites of focal discharge in 6 episodes of 2 preparations, compatible with voltage-independent spontaneous Ca(i) release. Phase singularities during pacing-induced reentry clustered specifically at the PV-LA junction. Periodic acid-Schiff (PAS) stain identified large cells with pale cytoplasm along the endocardium of PV muscle sleeves. There were abrupt changes in myocardial fiber orientation and increased interstitial fibrosis in the PV and at the PV-LA junction. PV muscle sleeves may develop voltage-independent Ca(i) release, resulting in focal discharge. Focal discharge may also be facilitated by the presence of PAS-positive cells that are compatible with node-like cells. During reentry, phase singularities clustered preferentially at sites of increased anisotropy such as the PV-LA junction. These findings suggest that focal discharge caused by spontaneous calcium release and anisotropic reentry both contribute to rapid activations in the PVs during AF.

Electrophysiologic characteristics and catheter ablation in patients with Lewis right atrial fibrillation

Extensive encircling isolation of ipsilateral both pulmonary veins (EEPVI) disconnects linearly the posterior junction between left atrium (LA) and PVs, and segmentally the anterior junction. EEPVI of arrhythmogenic PV (APV) can terminate persitent atrial fibrillation (AF) and prevent AF re-initiation by modifying the electrophysiologic properties of posterior LA-PV junction prior to achievement of PVI. Clinical implication of AF termination during posterior junction ablation of APV in persistent AF (PRAF, defined as not self-terminating) on the outcome of EEPVI was studied. Methods: We performed EEPVI targeting the arrhythmogenic ipsilateral PVs (APV) initially and then remaining couple of PVs at PV-LA junction during ongoing AF in 41 PRAF patients (pts) (mean age: 55 10 years, M / F 32/9), in whom multiple internal cardioversions (CVs) applied to identify APV at the beginning of EEPVI failed in maintaining sinus rhythm (SR) due to immediate recurrence of AF (IRAF). CV was applied again in pts with ongoing AF despite the most parts of posterior junction of APV ablated to disconnect anterior junction in sinus rhythm(late CV). All pts were followed-up without antiarrhythmic medications. Results: During posterior LA-PV junction ablation, AF terminated following organization and slowing of PV and LA electrical activities before APVI achieved in 15 pts (37%), whether repetitive firings from APV remaining or not (group-1). In the remaining 26 pts (63%), AF was terminated by late CV without IRAF before APVI achieved (group-2). In all pts, EEPVI was successfully achieved with sinus rhythm restored. During a mean follow-up of 15 7 months, 14 of 15 group-1 pts were free from AF, while 15 of 26 group-2 pts were free from AF (group-1 vs -2. p 0.015). Conclusions: Termination of ongoing AF during substrate-modification at posterior LA-PV junction appears to be strong predictor of successful outcome of EEPVI for PRAF. This suggests posterior LA-PV junction might be crucial substrates for initiation and perpetuation of AF in some subset of PRAF.

Electrophysiological Characteristics of Arterially-Perfused Canine Pulmonary Veins: Role of the Delayed Afterdepolarization-Induced Triggered Activity

Background and Objectives：The mechanism responsible for the generation of ectopic beats in pulmonary veins (PVs) remains to be well defined. The present study examines the electrophysiological characteristics of the PVs and other regions of the canine left atrium (LA) under low dose (300 μM) caffeine condition. Materials and Methods：Transmembrane action potentials were recorded from the left superior PVs, PV-LA junctions (PLJ, atrium <5 mm from the PV ostium), LA appendage (LAA) or Bachmann’s bundle (BB) in arterially perfused canine LA-PV preparations, using floating glass microelectrodes. Rapid atrial pacing (cycle lengths 140-300 ms, 10 sec) was used to induce delayed afterdepolarizations (DAD) at the baseline and under low dose (300 μM) caffeine conditions. Results：Spontaneous diastolic depolarization or triggered activity (TA) was not observed in any of the recording area under the baseline condition. DAD and TA were induced by caffeine in 4/8 PVs and in 3/8 PLJs, but in no LAA (0/6) or BB (0/5). These TA and DAD were also observed after termination of pacing-induced atrial tachyarrhythmia. DAD was abolished by pretreatment of the atria with verapamil or propranolol (1.0 μM). Conclusion：Spontaneous diastolic depolarization was not present in perfused canine left atria or proximal PV. Pulmonary veins and adjacent areas displayed an increased susceptibility to develop DAD-induced TA under low dose caffeine condition. This distinctive electrophysiological property of the PV and PLJ area may contribute to the arrhythmogenic substrate responsible for the ectopic activity that initiates atrial fibrillation. (Korean Circulation J 2005;35:643-648)

Computerized Three-Dimensional Potential Mapping with a Multielectrode Basket Catheter Can be Useful for Pulmonary Vein Electrical Disconnection

Pulmonary vein (PV) isolation (PVI) has been recently proposed as an effective technique to cure atrial fibrillation (AF). The aim of this study was to investigate the efficacy of a novel technique utilizing a computerized three-dimensional mapping system (QMS2) with a multielectrode basket catheter (MBC) for PVI and to reveal the relation between the style of breakthrough and the network of the PV musculature. Sixty-five consecutive patients with frequent AF attacks underwent PV mapping with a 31-mm MBC, and a three-dimensional color animation of the potential map was constructed by the QMS2. The animation color schema was arranged to minimize the low-amplitude left atrial (LA) potentials and emphasize the high-amplitude PV potentials (PVPs). The longitudinal PVP map enabled us to recognize the true breakthroughs and reveal the network of the PV musculature. A total of 205 PVs (65 left superior PVs, 65 right superior PVs, 57 left inferior PVs and 18 right inferior PVs) were mapped and successful PVI was achieved in all PVs, except one that had no PVPs, with a mean radiofrequency duration of 7 +/- 5 minutes per PV. In about 90% of the PVs, a final radiofrequency application eliminated all the distal PVPs simultaneously because the PVI was performed at the appropriate LA-PV junction. A single segmental breakthrough was detected in 17 PVs, single broad breakthrough in 83 PVs, multiple separate breakthroughs with a distal connection between the PV musculatures extending from each separate breakthrough in 88 PVs and multiple separate breakthroughs without that connection in 16 PVs. During the follow-up period, fifty-one (78%) patients were free of symptomatic AF without any antiarrhythmic drugs after multiple procedures (thirty-three (51%) of those patients after the first procedure) and no PV stenosis was found. Computerized three-dimensional potential mapping can be useful for PVI because it can not only identify the true breakthrough, but can also confirm the elimination of the breakthroughs by the change in the activation sequence through the network of the PV musculature.

Hybrid Therapy With Pilsicainide and Pulmonary Vein Isolation for Atrial Fibrillation

Pulmonary vein (PV) isolation is commonly performed in patients with drug-refractory atrial fibrillation (AF) and in cases of unsuccessful ablation, antiarrhythmic agents that were ineffective before the ablation sometimes become effective afterward. Therefore, the effects and mechanisms of hybrid therapy with pilsicainide and PV isolation for AF were assessed in the present study. Seventy-four patients with paroxysmal AF in whom pilsicainide was ineffective underwent PV isolation. If AF recurred, a second procedure was performed and if AF recurred again, pilsicainide was re-administered. After the first procedure, AF recurred in 42 patients, and a second procedure was performed in 31 patients, of whom 28 had recovery of left atrial (LA)-PV conduction and non-PV foci were identified in 3. After the second session, ablation eliminated AF without drugs in 53 (72%) patients. Pilsicainide suppressed the conduction properties at the LA-PV junction. In 21 patients with recurrence of AF, pilsicainide was re-administered and eliminated AF in 11 patients (success with pilsicainide: 86%). In cases of unsuccessful PV isolation, pilsicainide may prevent AF by modifying the LA-PV conduction properties. Hybrid therapy with pilsicainide and PV isolation may be an effective therapeutic approach for AF.