Impact of Interatrial Epicardial Connections on the Dominant Frequency of Atrial Fibrillation.

BACKGROUND: An epicardial connection (EC) between the right-sided pulmonary venous (RtPV) carina and right atrium (RA) may preclude PV isolation, but its electrophysiological role during atrial fibrillation (AF) remains unknown.Methods and Results: This prospective observational study included 98 consecutive patients undergoing catheter ablation for AF, subdivided into the EC group (n=17) and non-EC group (n=80) based on observation of RA posterior wall breakthrough during RtPV pacing. Mean left atrial (LA) dominant frequency (mean DFLA) was defined as the averaged DFs at the right and left PVs and LA appendage. The regional DF was higher in the EC group vs. the non-EC group except at the left PV antrum. The DF at the RA appendage (RAA) and mean DFLAwere equivocal (6.5±0.7 vs. 6.6±0.7 Hz) in the EC group, but the mean DFLAwas significantly higher than that at the RAA (5.8±0.6 vs. 6.1±0.5 Hz, P=0.001) in the non-EC group, suggesting an LA-to-RA DF gradient. A significant correlation of DF between the RtPV antrum and RAA was observed in the EC group (P<0.001, r=0.84) but not in the non-EC group. CONCLUSIONS: An electrophysiological link via interatrial ECs might attenuate the hierarchical nature of activation frequencies of AF, leading to advanced electrical remodeling of the atria.

Novel preventive effect of isorhamnetin on electrical and structural remodeling in atrial fibrillation.

Isorhamnetin, a natural flavonoid, has strong antioxidant and antifibrotic effects, and a regulatory effect against Ca2+-handling. Atrial remodeling due to fibrosis and abnormal intracellular Ca2+ activities contributes to initiation and persistence of atrial fibrillation (AF). The present study investigated the effect of isorhamnetin on angiotensin II (AngII)-induced AF in mice. Wild-type male mice (C57BL/6J, 8 weeks old) were assigned to three groups: (1) control group, (2) AngII-treated group, and (3) AngII- and isorhamnetin-treated group. AngII (1000 ng/kg/min) and isorhamnetin (5 mg/kg) were administered continuously via an implantable osmotic pump for two weeks and intraperitoneally one week before initiating AngII administration, respectively. AF induction and electrophysiological studies, Ca2+ imaging with isolated atrial myocytes and HL-1 cells, and action potential duration (APD) measurements using atrial tissue and HL-1 cells were performed. AF-related molecule expression was assessed and histopathological examination was performed. Isorhamnetin decreased AF inducibility compared with the AngII group and restored AngII-induced atrial effective refractory period prolongation. Isorhamnetin eliminated abnormal diastolic intracellular Ca2+ activities induced by AngII. Isorhamnetin also abrogated AngII-induced APD prolongation and abnormal Ca2+ loading in HL-1 cells. Furthermore, isorhamnetin strongly attenuated AngII-induced left atrial enlargement and atrial fibrosis. AngII-induced elevated expression of AF-associated molecules, such as ox-CaMKII, p-RyR2, p-JNK, p-ERK, and TRPC3/6, was improved by isorhamnetin treatment. The findings of the present study suggest that isorhamnetin prevents AngII-induced AF vulnerability and arrhythmogenic atrial remodeling, highlighting its therapeutic potential as an anti-arrhythmogenic pharmaceutical or dietary supplement.

Rotational Activation Pattern During Functional Substrate Mapping: Novel Target for Catheter Ablation of Scar-Related Ventricular Tachycardia.

BACKGROUND: Recent advancements in a 3-dimensional mapping system allow for the assessment of detailed conduction properties during sinus rhythm and thus the establishment of a strategy targeting functionally abnormal regions in scar-related ventricular tachycardia (VT). We hypothesized that a rotational activation pattern (RAP) observed in maps during baseline rhythm was associated with the critical location of VT. METHODS: We retrospectively examined the pattern of wavefront propagation during sinus rhythm in patients with scar-related VT. The prevalence and features of the RAP on critical VT circuits were analyzed. RAP was defined as >90° of inward curvature directly above or at the edge of the slow conductive areas. RESULTS: Forty-five VTs in 37 patients (66±15 years old, 89% male, 27% ischemic heart disease) were evaluated. High-density substrate mapping during sinus rhythm (median, 2524 points) was performed using the CARTO3 system before VT induction. Critical sites for reentry were identified by direct termination by radiofrequency catheter ablation in 21 VTs or by pace mapping in 12 VTs. Among them, RAP was present in 70% of the 33 VTs. Four VTs had no RAP at the critical sites during sinus rhythm, but it became visible in the mappings with different wavefront directions. Six VTs, in which intramural or epicardial isthmus was suspected, were rendered noninducible by radiofrequency catheter ablation to the endocardial surface without RAP. RAP had a sensitivity and specificity of 70% and 89%, respectively, for predicting the elements in the critical zone for VT. CONCLUSIONS: The critical zone of VT appears to correspond to an area characterized by the RAP with slow conduction during sinus rhythm, which facilitates targeting areas specific for reentry. However, this may not be applicable to intramural VT substrates and might be affected by the direction of wavefront propagation to the scar during mapping. Graphic Abstract: A graphic abstract is available for this article.

Stellate Ganglion Phototherapy Using Low-Level Laser: A Novel Rescue Therapy for Patients With Refractory Ventricular Arrhythmias.

OBJECTIVES: This study investigates the effect of stellate ganglion (SG) phototherapy in healthy participants and assesses its efficacy in suppressing electrical storm (ES) refractory to antiarrhythmic drugs and catheter ablation. BACKGROUND: Modulation of the autonomic nervous system has been shown to be an effective adjunctive therapy for ES. METHODS: Ten-minute SG phototherapy was performed twice weekly for 4 weeks in 20 healthy volunteers. To evaluate the acute and chronic effects of SG phototherapy, heart rate variability and serum concentrations of adrenaline, noradrenaline, and dopamine were obtained before phototherapy, immediately after the first phototherapy session, after 8 sessions of phototherapy, and 3 months after the first phototherapy session. In addition, the efficacy of SG phototherapy was evaluated in 11 patients with ES refractory to medication, sedation, and catheter ablation. RESULTS: In healthy participants, serum adrenaline concentration significantly decreased after phototherapy, whereas low-frequency power/high-frequency power significantly decreased during phototherapy. Moreover, the effect on heart rate variability did not last beyond 3 months. In the clinical pilot study, 7 patients had a suppression of ES after SG phototherapy; however, without maintenance therapy, 2 patients had a recurrence of ventricular arrhythmias. Furthermore, it did not control ES in 4 patients. CONCLUSIONS: SG phototherapy reduced sympathetic activity and may be a safe and effective adjunctive therapy to control ES in some patients, but its long-term efficacy remains unknown. Chronic phototherapy might help reduce ES recurrence.

Mapping and Ablation of Ventricular Fibrillation Associated With Early Repolarization Syndrome.

BACKGROUND: We conducted a multicenter study to evaluate mapping and ablation of ventricular fibrillation (VF) substrates or VF triggers in early repolarization syndromes (ERS) or J-wave syndrome (JWS). METHODS: We studied 52 patients with ERS (4 women; median age, 35 years) with recurrent VF episodes. Body surface electrocardiographic imaging and endocardial and epicardial electroanatomical mapping of both ventricles were performed during sinus rhythm and VF for localization of triggers, substrates, and drivers. Ablations were performed on VF substrates, defined as areas that had late depolarization abnormalities characterized by low-voltage fractionated late potentials, and VF triggers. RESULTS: Fifty-one of the 52 patients had detailed mapping that revealed 2 phenotypes: group 1 had late depolarization abnormalities predominantly at the right ventricular (RV) epicardium (n=40), and group 2 had no depolarization abnormalities (n=11). Group 1 can be subcategorized into 2 groups: Group 1A included 33 patients with ERS with Brugada electrocardiographic pattern, and group 1B included 7 patients with ERS without Brugada electrocardiographic pattern. Late depolarization areas colocalize with VF driver areas. The anterior RV outflow tract/RV epicardium and the RV inferior epicardium are the major substrate sites for group 1. The Purkinje network is the leading underlying VF trigger in group 2 that had no substrates. Ablations were performed in 43 patients: 31 and 5 group 1 patients had only VF substrate ablation and VF substrates plus VF trigger, respectively (mean, 1.4±0.6 sessions); 6 group 2 patients and 1 patient without group classification had only Purkinje VF trigger ablation (mean, 1.2±0.4 sessions). Ablations were successful in reducing VF recurrences (P<0.0001). After follow-up of 31±26 months, 39 (91%) had no VF recurrences. CONCLUSIONS: There are 2 phenotypes of ERS/J-wave syndrome: one with late depolarization abnormality as the underlying mechanism of high-amplitude J-wave elevation that predominantly resides in the RV outflow tract and RV inferolateral epicardium, serving as an excellent target for ablation, and the other with pure ERS devoid of VF substrates but with VF triggers that are associated with Purkinje sites. Ablation is effective in treating symptomatic patients with ERS/J-wave syndrome with frequent VF episodes.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias.

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Iatrogenic aortic regurgitation after radiofrequency ablation of idiopathic ventricular arrhythmias originating from the aortic valvular region.

BACKGROUND: Radiofrequency ablation at the aortic root has the potential risk of aortic regurgitation (AR). OBJECTIVE: This study investigated the incidence and clinical features of iatrogenic AR after catheter ablation of idiopathic ventricular arrhythmias originating from the aortic root. METHODS: We studied 45 consecutive patients with idiopathic ventricular arrhythmias originating from the aortic cusps (ACs; AC group; n = 32 [71%]) and papillary muscles (control group; n = 13 [29%]) who underwent ablation via a retrograde aortic approach and serial echocardiography before and within 24 hours after the ablation procedure. No patients had preexisting AR. RESULTS: After ablation, mild AR occurred in 5 AC group patients and 1 control group patient. Regurgitant flow was observed at the center of the aortic leaflets in 3 patients, the left coronary cusp-noncoronary cusp commissure in 2 patients, and both in 1 patient. No patients undergoing ablation only above the aortic valve developed AR. In AC group patients, the occurrence of AR was associated with a longer ablation time (24 ± 14 minutes vs 10 ± 5 minutes; P < .01) and higher average output (36.6 ± 4.2 W vs 32.0 ± 3.2 W; P = .01). The same severity of AR still existed after 16.2 ± 3.6 months of follow-up. No patients required any additional medical management or surgical intervention. CONCLUSION: Iatrogenic mild AR after ablation in the aortic root occurred with a noticeable prevalence, which was associated with extensive ablation both above and below the ACs as well as catheter-related mechanical factors. Although it did not appear to aggravate the hemodynamic status during the mid-term follow-up, careful monitoring of AR progression should be considered.

Epicardial connection between the right-sided pulmonary venous carina and the right atrium in patients with atrial fibrillation: A possible mechanism for preclusion of pulmonary vein isolation without carina ablation.

BACKGROUND: Ablation of the pulmonary venous carina is occasionally required for pulmonary vein isolation (PVI) despite its nonessential role in ipsilateral PVI from the anatomical (endocardial) viewpoint. Although the Bachmann bundle (BB) is a common and main interatrial band, local variations in small tongues of muscular fibers were frequently found in autopsy studies. OBJECTIVE: We sought to clarify the effect of the electrical conduction pattern from the right atrium (RA) to the left atrium (LA) during sinus rhythm on the necessity of performing right-sided pulmonary venous carina ablation to achieve PVI. METHODS: Study subjects comprised 37 consecutive patients undergoing initial catheter ablation of lone atrial fibrillation. During sinus rhythm, RA and LA activation maps were acquired using an electroanatomical mapping system. LA breakthroughs were classified into 3 sites: BB, fossa ovalis (FO), and right-sided pulmonary venous carina. Patients were divided into the carina-ABL (ablation) or non-carina-ABL group on the basis of the necessity of pulmonary venous carina ablation to achieve PVI. RESULTS: Patients were classified in the non-carina-ABL group (n = 26 [70%]) and carina-ABL group (n = 8 [22%]) after excluding 3 patients (8%) because of their complex ablation lesion sets. Breakthrough occurred in the BB (n = 21 patients [62%]), FO (n = 7 [21%]), carina (n = 1 [3%]), carina and BB (n = 3 [9%]), and carina and FO (n = 2 [6%]). Carina breakthrough occurred in 6 patients (75%) in the carina-ABL group but in no patients in the non-carina-ABL group (P < .0001). CONCLUSION: PVI was not achievable without carina ablation in one-fifth of patients, probably because of epicardial connections present between the right-sided pulmonary venous carina and the RA.

Depolarization versus repolarization abnormality underlying inferolateral J-wave syndromes: New concepts in sudden cardiac death with apparently normal hearts.

Early repolarization indicates a distinct electrocardiographic phenotype affecting the junction between the QRS complex and the ST segment in inferolateral leads (inferolateral J-wave syndromes). It has been considered a benign electrocardiographic variant for decades, but recent clinical studies have demonstrated its arrhythmogenicity in a small subset, supported by experimental studies showing transmural dispersion of repolarization. Here we review the current knowledge and the issues of risk stratification that limit clinical management. In addition, we report on new mapping data of patients refractory to pharmacologic treatment using high-density electrogram mapping at the time of inscription of J wave. These data demonstrate that distinct substrates, delayed depolarization, and abnormal early repolarization underlie inferolateral J-wave syndromes, with significant implications. Finally, based on these data, we propose a new simplified mechanistic classification of sudden cardiac deaths without apparent structural heart disease.

Efficacy of Endocardial Ablation of Drug-Resistant Ventricular Fibrillation in Brugada Syndrome: Long-Term Outcome.

Background Both endocardial trigger elimination and epicardial substrate modification are effective in treating ventricular fibrillation (VF) in Brugada syndrome. However, the primary approach and the characteristics of patients who respond to endocardial ablation remain unknown. Methods Among 123 symptomatic Brugada syndrome patients (VF, 63%; syncope, 37%), ablation was performed in 21 VF/electrical storm patients, the majority of whom were resistant to antiarrhythmic drugs. Results Careful endocardial mapping revealed that 81% of the patients had no specific findings, whereas 19% of the patients, who experienced the most frequent VF episodes with notching of the QRS in lead V1, had delayed low-voltage fractionated endocardial electrograms. Ablation of VF triggers followed by endocardial substrate modification was performed in the right ventricular outflow tract in 85% of the cases and in the right ventricle in 15%. VF triggers could not be completely eliminated in 1 patient and VF became noninducible in 14 (88%) patients among 16 patients who underwent VF induction with normalization of Brugada-type ECG in 3. During follow-up (56.14±36.95 months), VF recurrence was observed in 7 patients. Importantly, all patients who had nothing of QRS in lead V1 did not respond to endocardial ablation despite presence of VF-triggering ectopic beats during ablation. Conclusions With careful documentation of VF-triggering ectopic beats and detailed endocardial mapping, endocardial VF trigger elimination followed by endocardial substrate modification has an excellent long-term outcome, whereas presence of QRS notching in lead V1 was associated with high VF recurrence suggesting epicardial substrate ablation as effective initial approach.

Radiofrequency Catheter Ablation of Ventricular Tachycardia in Patients With Hypertrophic Cardiomyopathy and Apical Aneurysm.

OBJECTIVES: This study evaluated the characteristics and results of radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in patients with hypertrophic cardiomyopathy (HCM) and left ventricular apical aneurysm (AA). BACKGROUND: Monomorphic VT in patients with HCM and left ventricular AA has been reported. However, outcome data of RFCA are insufficient. METHODS: Fifteen patients with HCM and AA who underwent RFCA for VT at 5 different institutions were included in this study. The data were evaluated retrospectively. RESULTS: Endocardial voltage mapping showed a low-voltage area (LVA), and late potential in the AA was recorded in 12 patients (80%). Although epicardial or intramural origin of VT was suspected in 7 patients, endocardial RFCA successfully suppressed the VT at the LVA border (n = 10) or within the LVA (n = 2). In 2 of 3 patients without LVA at the endocardial site, linear RFCA at the anterior wall of the aneurysmal neck side was successful. In the remaining patient, endocardial RFCA of AA was not effective, and epicardial RFCA site was needed. In all patients, clinical VT became noninducible after RFCA. VT recurrence was observed in 2 patients (13.3%) during the 12-month follow-up period. One patient underwent a second endocardial RFCA, and no VT recurrence was noted. In the other patient, VT recurred 3 months after RFCA and was successfully terminated by antitachycardia pacing of the implantable cardioverter-defibrillator. CONCLUSIONS: In patients with HCM and AA, endocardial RFCA of AA effectively suppressed monomorphic VT which was related to AA and resulted in satisfactory outcomes.

New Substrate-Guided Method of Predicting Slow Conducting Isthmuses of Ventricular Tachycardia: Preliminary Analysis to the Combined Use of Voltage Limit Adjustment and Fast-Fourier Transform Analysis.

BACKGROUND: Several conducting channels of ventricular tachycardia (VT) can be identified using voltage limit adjustment (VLA) of substrate mapping. However, the sensitivity or specificity to predict a VT isthmus is not high by using VLA alone. This study aimed to evaluate the efficacy of the combined use of VLA and fast-Fourier transform analysis to predict VT isthmuses. METHODS AND RESULTS: VLA and fast-Fourier transform analyses of local ventricular bipolar electrograms during sinus rhythm were performed in 9 postinfarction patients who underwent catheter ablation for a total of 13 monomorphic VTs. Relatively higher voltage areas on an electroanatomical map were defined as high voltage channels (HVCs), and relatively higher fast-Fourier transform areas were defined as high-frequency channels (HFCs). HVCs were classified into full or partial HVCs (the entire or >30% of HVC can be detectable, respectively). Twelve full HVCs were identified in 7 of 9 patients. HFCs were located on 7 of 12 full HVCs. Five VT isthmuses (71%) were included in the 7 full HVC+/HFC+ sites, whereas no VT isthmus was found in the 5 full HVC+/HFC- sites. HFCs were identical to 9 of 16 partial HVCs. Eight VT isthmuses (89%) were included in the 9 partial HVC+/HFC+ sites, whereas no VT isthmus was found in the 7 partial HVC+/HFC- sites. All HVC+/HFC+ sites predicted VT isthmus with a sensitivity of 100% and a specificity of 80%. CONCLUSIONS: Combined use of VLA and fast-Fourier transform analysis may be a useful method to detect VT isthmuses.

Temporally stable frequency mapping using continuous wavelet transform analysis in patients with persistent atrial fibrillation.

INTRODUCTION: Dominant frequency (DF) derived from fast Fourier transform (FFT) analysis has failed to guide atrial fibrillation (AF) ablation since it cannot guarantee temporal stability. Continuous wavelet transform (CWT) analysis is another frequency analysis that can show the temporal stability of a frequency. METHODS AND RESULTS: Forty-four consecutive patients with persistent AF (PeAF) underwent pulmonary vein (PV) isolation (PVI) as the first-time catheter ablation. The PVs and left atrium were mapped and electrograms (EGMs) were recorded for 30 seconds at each site. Pseudo-frequency (PF) and coefficient of variation (CV) were calculated by CWT analysis. A PF with CV ≤ 10 was defined as a temporally stable PF (sPF). DF was also calculated by traditional FFT analysis from the first 5 seconds of the recorded EGMs. The highest sPF was shown inside the PVs in 20 patients (PV group), and at the non-PV sites in 24 patients (non-PV group). During the follow-up period of 15.3 ± 4.4 months, the ablation success rate in the PV group was significantly higher than that in the non-PV group (90% vs. 62%, P = 0.023). The location of the highest DF did not have a significant effect on ablation success rate between inside the PVs and at the non-PV sites. CONCLUSION: PVI results for PeAF were significantly worse for patients with highest sPF at the non-PV sites compared to patients with highest sPF sites inside the PVs. CWT analysis during AF could be used to verify whether PVI alone is sufficient for the first-time catheter ablation in patients with PeAF.

Non-Reentrant Fascicular Tachycardia: Clinical and Electrophysiological Characteristics of a Distinct Type of Idiopathic Ventricular Tachycardia.

BACKGROUND: The most common form of idiopathic Purkinje-related ventricular tachycardia (VT) is the reentrant type. We describe the clinical and electrophysiological characteristics of focal non-reentrant fascicular tachycardia. METHODS AND RESULTS: Among 530 idiopathic VT patients who were referred for ablation, we identified 15 (2.8%) with non-reentrant fascicular tachycardia (11 men, 45±21 years). Sinus rhythm ECG showed normal conduction intervals with a His-ventricular interval of 41±4 ms. All patients had monomorphic VT (cycle length: 337±88 ms) with a relatively narrow QRS (123±12 ms), and they did not respond to verapamil during the initial presentation. VT exhibited right bundle-branch block/superior axis configuration in 11 patients (73%) and inferior axis in 3 (20%). In 1 patient (7%), VT exhibited left bundle-branch block/superior axis configuration. During ablation, spontaneous VT occurred in 3 patients (20%) and nonentraintable VT or identical premature ventricular complex was induced in 9 (60%). A high-frequency presystolic Purkinje potential was recorded during VT/premature ventricular complex, preceding the QRS by 25±16 ms. VT recurrence was observed in 4 patients (27%), and among them, 3 underwent pacemap-guided ablation during the first session. A second ablation with activation mapping guidance eliminated the VT during the 88±8-month follow-up. CONCLUSIONS: Among idiopathic VT cases referred for ablation, 2.8% were focal non-reentrant fascicular tachycardia, which had distinct clinical characteristics and usually originated from the left posterior fascicle, and less commonly from the left anterior fascicle and right ventricular Purkinje network. Catheter ablation is effective, whereas pacemap-guided approach is less efficacious.

Noninvasive Localization of Accessory Pathways in Wolff-Parkinson-White Syndrome by Three-Dimensional Speckle Tracking Echocardiography.

BACKGROUND: We have developed a noninvasive isochrone activation imaging (AI) system with 3-dimensional (3D) speckle tracking echocardiography (STE), which allows visualization of the wavefront image of mechanical propagation of the accessory pathway (ACP) in Wolff-Parkinson-White syndrome. METHODS AND RESULTS: Patients with manifest Wolff-Parkinson-White syndrome were imaged in 3D-STE AI mode, which quantified the time from QRS onset to regional endocardial deformation. In 2 patients with left- and right-side ACP, we confirmed that intraoperative contact endocardial electric mapping and the 3D-STE AI system showed comparable images pre- and postablation. In normal heart assessment by 3D-echo AI, the earliest activation sites were found at the attachment of the papillary muscles in the left ventricle and midseptum in the right ventricle, and none showed earliest activation at the peri-atrioventricular valve annuli. An analyzer who was unaware of the clinical information assessed 39 ACP locations in 38 Wolff-Parkinson-White syndrome patients using 3D-STE. All showed abnormal perimitral or tricuspid annular activations, and the location of 34 ACP (87%) showed agreement with the successful ablation sites within a 2-o'clock range. Especially for left free wall ACP, 17/18 (94%) showed consistency with the ablation site within a 2 o'clock range. Among 15 ACP at the ventricular septum, 9 (60%) showed early local activation in both right and left sides of the septum. CONCLUSIONS: Isochrone AI with 3D-STE may be a promising noninvasive imaging tool to assess cardiac synchronized activation in normal hearts and detect abnormal breakthrough of mechanical activation from both atrioventricular annuli in Wolff-Parkinson-White syndrome.

Epicardial catheter ablation of ventricular tachycardia in no entry left ventricle: mechanical aortic and mitral valves.

BACKGROUND: In patients with mechanical aortic and mitral valves and left ventricular tachycardia, catheter ablation may be prevented by limited access to the left ventricle. METHODS AND RESULTS: In our series of 6 patients, 2 patients underwent direct surgical ablation and 4 underwent epicardial catheter ablation via a pericardial window. All patients had abnormal low voltage areas with fractionated or delayed isolated potentials on the apical epicardium. Most of the ventricular tachycardias were targeted by pace mapping. Sites with a good pace match or abnormal electrograms were ablated using an irrigated radiofrequency ablation catheter. A microscopic pathological evaluation of the resected tissue from 2 of the open-heart ablation patients revealed dense fibrosis on the epicardium compared with the endocardium, supporting the feasibility of an epicardial ablation for the ventricular tachycardia. CONCLUSIONS: Epicardial catheter ablation of ventricular tachycardia is a potentially useful therapy in patients who have mechanical aortic and mitral valves.

Left septal atrial tachycardia after open-heart surgery: relevance to surgical approach, anatomical and electrophysiological characteristics associated with catheter ablation, and procedural outcomes.

BACKGROUND: Septal atrial tachycardia (AT) can occur in patients without structural heart disease and in patients with previous catheter ablation of atrial fibrillation. We aimed to assess septal AT that occurs after open-heart surgery. METHODS AND RESULTS: This study comprised 20 consecutive patients undergoing catheter ablation of macroreentrant AT after open-heart surgery. Relevance to surgical approach, mechanisms, anatomic and electrophysiological characteristics, and outcomes were assessed. Septal AT was identified in 7 patients who had all undergone mitral valve surgery. All septal ATs were localized in the left atrial septum, whereas 10 of 13 nonseptal ATs originated from the right atrium. Patients with left septal AT had a thicker fossa ovalis (median, 4.0; 25th-75th percentile, 3.6-4.2 versus 2.3; 1.6-2.6 mm; P=0.006) and broader area of low voltage (<0.3 mV) in the septum than patients with nonseptal AT (82; 76-89 versus 31; 28%-36%; P=0.02). Repeated gradual prolongations of the tachycardia cycle length without change of the septal circuit were observed in all patients with septal AT (70; 63-100 versus 15; 10-40 ms; P=0.0008). Although ablation terminated all ATs, recurrence of targeted ATs was more frequent in patients with left septal AT during 30-month follow-up (71 versus 0%; P=0.001). CONCLUSIONS: Left septal AT after open-heart surgery was characterized by a thicker septum, more scar burden in the septum, and repeated prolongations of the tachycardia cycle length during ablation. Such an arrhythmogenic substrate may interfere with transmural lesion formation by ablation and may account for higher likelihood of recurrence of left septal AT.

Mapping and ablating ventricular premature contractions that trigger ventricular fibrillation: trigger elimination and substrate modification.

Ventricular fibrillation (VF) is a malignant arrhythmia, usually initiated by a ventricular premature contraction (VPC) during the vulnerable period of cardiac repolarization. Ablation therapy for VF has been described and increasingly reported. Targets for VF triggers are VPC preceded Purkinje potentials or the right ventricular outflow tract (RVOT) in structurally normal hearts, and VPC triggers preceded by Purkinje potentials in ischemic cardiomyopathy. The most important issue before the ablation session is the recording of the 12-lead electrocardiogram (ECG) of the triggering event, which can prove invaluable in regionalizing the origin of the triggering VPC for more detailed mapping. In cases where the VPC is not spontaneous or inducible, ablation may be performed by pacemapping. During the session, mapping should be focused on the earliest activation and determining the earliest potential is the key to a successful ablation. However, a modification of the Purkinje network might be applied when the earliest site cannot be determined or is located close to the His-bundle. Furthermore, the electrical isolation of the pulmonary artery (PA) can suppress RVOT type polymorphic ventricular tachycardia in some patients with rapid triggers from the PA. Suppression of VF can be achieved by not only the elimination of triggering VPCs, but also by substrate modification of possible reentry circuits in the Purkinje network, or between the PA and RVOT. Further studies are needed to evaluate the precise mechanisms of this arrhythmia.

Negative participation of the left posterior fascicle in the reentry circuit of verapamil-sensitive idiopathic left ventricular tachycardia.

Left posterior fascicle and idiopathic Left VT. The left posterior fascicle may be a bystander of the circuit of verapamil-sensitive idiopathic left ventricular tachycardia. During ventricular tachycardia (VT), 3 sequences of potentials were seen at the left posterior septum: diastolic Purkinje potentials propagating from base to apex and presystolic left posterior fascicular potentials and systolic left ventricular (LV) myocardial potentials propagating in the reverse direction. Selective capture of the left posterior fascicle by the sinus beat did not affect the VT cycle length. Entrainment pacing revealed that the retrograde limb of the circuit was not the left posterior fascicle, but the LV myocardium.