Search

BACKGROUND: Medical treatment of inappropriate sinus tachycardia (IST) remains suboptimal. Radiofrequency sinus node (RF-SN) ablation has poor success and higher complication rates. OBJECTIVE: We aimed to compare clinical outcomes of the novel SN sparing hybrid ablation technique with those of RF-SN modification for IST management. METHODS: This is a multicenter prospective registry comparing the SN sparing hybrid ablation strategy with RF-SN modification. The hybrid procedure was performed using an RF bipolar clamp, isolating superior vena cava/inferior vena cava with the creation of a lateral line across the crista terminalis while sparing the SN region (identified by endocardial 3-dimensional mapping). RF-SN modification was performed by endocardial and/or epicardial mapping and ablation at the site of earliest atrial activation. RESULTS: Of the 100 patients (hybrid ablation group, n = 50; RF-SN group, n = 50), 82% were women, and the mean age was 22.8 years. Normal sinus rhythm and rate were restored in all patients in the hybrid group (vs 84% in the RF-SN group; P = .006). Hybrid ablation was associated with significantly better improvement in mean daily heart rate and peak 6-minute walk heart rate compared with RF-SN ablation. The RF-SN group had a significantly higher rate of redo procedures (100% vs 8%; P < .001), phrenic nerve injury (14% vs 0%; P = .012), lower acute pericarditis (48% vs 92%; P < .0001), permanent pacemaker implantation (50% vs 4%; P < .0001) than did the hybrid ablation group. CONCLUSION: The novel sinus node sparing hybrid ablation procedure appears to be more efficacious and safer in patients with symptomatic drug-resistant IST with long-term durability than RF-SN ablation.

Background The number of lead extractions is growing because of the greater population and increasing age of individuals with a cardiac implantable electronic device. Lead extraction procedures can be complex undertakings with risk of significant mortality, and vascular tears in the superior vena cava are of greatest concern. Objective The purpose of this study was to study whether a novel algorithm that analyzes pre-extraction computed tomographic (CT) images can determine the likelihood and location of lead–lead interactions and lead–vessel attachment within patients' venous vasculatures. This information can be used to identify potential case challenges in the planning stages. Methods We developed an algorithm to estimate the presence and position of lead–lead interactions and lead–vessel adherences by tracking distance between the leads and distance between the lead and superior vena cava in a sample of 12 patients referred to the United Heart and Vascular Clinic for lead extractions due to infection (n = 5), lead failure (n = 5), and tricuspid regurgitation (n = 2). Results Preliminary results indicate that the developed algorithm successfully identified lead–lead and lead–vascular attachments compared to review of CT images by medical experts. Conclusion With future validation and clinical implementation, this algorithm could aid physician preparedness by minimizing intraprocedural emergencies and may improve patient outcomes.

Background Little is known about the manner in which the superior vena cava (SVC) is activated during sinus rhythm. Objective The purpose of this study was to assess the manner of caval activation with an ultra-high-density mapping system (Rhythmia, Boston Scientific, Marlborough, MA) and its utility for SVC isolation. Methods Forty patients with atrial fibrillation (mean age 55 ± 12 years; paroxysmal atrial fibrillation in 23[58%]) who underwent SVC mapping with Rhythmia were studied. The location of the sinus node (SN), phrenic nerve (PN), and the manner of caval activation during sinus rhythm were analyzed. The SVC was isolated by radiofrequency applications at electrical connections, shown as breakthroughs on the Rhythmia map. Results The SN location varied widely (lateral/posterior/anterior 60%/8%/32%), while the PN was mostly located in the lateral segment (lateral/anterior 82%/18%). In 36 patients who underwent SVC isolation, the mean number of breakthroughs was 2.5 ± 0.8. The first breakthrough predominantly located in the anterior aspect (anterior/septal/posterior/lateral 78%/14%/5%/3%), and atrial activation was conducted superiorly and clockwise from the SN (referred to as spiral activation ) in 32 patients (89%). The mean rotation angle from the SN to the first breakthrough was 79° ± 41°. In addition, 10 patients (25%) showed the SN within the SVC. Although radiofrequency applications were needed at the PN capture site in 11 patients (31%) the SVC was successfully isolated without any complications in all patients. Conclusion The SN location showed great heterogeneity; however, atrial activation predominantly showed a clockwise spiral form. This is the first report to use ultra-high-resolution mapping to demonstrate the manner of spiral activation, which is useful for the safe and efficient isolation of the SVC.

Background Transvenous lead extraction (TLE) carries a significant risk of intraprocedural complications. Phased-array intracardiac echocardiography (ICE) is widely used during cardiac procedures; however, its utility during TLE has not been well described. Objective We sought to define the utility of ICE imaging during TLE. Methods Fifty patients referred for TLE were included. Patients underwent ICE imaging before and throughout TLE. Clinical characteristics of the patients, ICE findings, and procedural outcomes were collected and analyzed. Results Of the 50 patients, 18 (36%) were found to have visible binding sites in the ICE field of view; 13 (26%) had intracardiac binding sites only, and 5 (10%) had both superior vena cava (SVC) and intracardiac binding sites. Lead-adherent echodensities (LAEs) were found in 36 patients (72%), of whom 7 (14%) had bacteremia. Patients with SVC and/or intracardiac binding sites were more likely to have a complex extraction, defined as that requiring the use of internal jugular or femoral venous access, advancement of extraction apparatus beyond the SVC, disruption of lead structure during the procedure, or resulting in major complications (56% vs 0%; P ≤ .0001). Conclusion ICE imaging during TLE can be used to assess the presence of lead binding sites, LAEs, and procedural complications. LAEs were found in the majority of patients, mostly in the absence of bacteremia. The presence of ICE-detected lead binding sites is predictive of a more complex extraction procedure.

Background Diaphragmatic compound motor action potential (CMAP) amplitude monitoring is a standard technique to anticipate phrenic nerve injury during cryoballoon ablation. Objective The purpose of this study was to evaluate the feasibility of a novel superior vena cava isolation (SVCI) technique using simultaneous pacing and ablation through the tip of a single mapping/ablation catheter. Methods Fifty-four patients with atrial fibrillation were included. Radiofrequency energy was delivered point by point uniformly for 20 seconds with a power of 20 W until achieving SVCI. Diaphragmatic CMAPs were obtained from modified surface electrodes by high-output pacing from the mapping/ablation catheter throughout the procedure (pace-and-ablate group). Applications were interrupted if CMAP amplitudes significantly decreased without fluoroscopy. The data were compared with those of the 54 patients undergoing conventional SVCI (conventional group). Results Successful SVCI procedures were achieved in all with a mean of 10.3 ± 2.9 applications. In total, among 559 ablation sites, CMAPs were recorded at 95 (17.0%) with baseline amplitudes of 0.45 ± 0.23 mV. In 10 patients (18.5%), isolation was achieved without any radiofrequency deliveries at CMAP-recorded sites. Among the 95 applications, 6 (6.3%) were interrupted because of CMAP amplitude reductions. At the remaining 88 sites, 20-second radiofrequency applications were delivered without any amplitude decrease (from 0.45 ± 0.21 to 0.46 ± 0.23 mV; P = .885). Phrenic nerve injury occurred in 1 patient in the pace-and-ablate group, which recovered 3 months later, and in 3 conventional group patients, of whom 1 recovered 1 month later (P = .308). The total procedure time tended to be shorter (14.5 ± 6.3 minutes vs 16.7 ± 9.2 minutes; P = .153) and fluoroscopy time significantly shorter (3.9 ± 3.0 minutes vs 6.7 ± 5.7 minutes, P = .002) in the pace-and-ablate group than in the conventional group. Conclusion A novel and simple pace-and-ablate technique under diaphragmatic electromyography monitoring might be feasible for an electrical SVCI.

Background Diaphragmatic electrogram recording during cryoballoon ablation (CB-A) of atrial fibrillation is commonly used to predict phrenic nerve palsy (PNP). Objective The purpose of this study was to investigate a novel method for predicting PNP at an earlier stage to prevent sustained PNP. Methods A total of 197 patients undergoing CB-A were enrolled. We attempted to detect PNP using fluoroscopic images of diaphragmatic contractions and by monitoring diaphragmatic compound motor action potentials (CMAPs) provoked by superior vena cava (SVC) and left subclavian vein (LCV) pacing during CB-A for bilateral pulmonary veins (PVs). Pacing of the SVC and LCV was performed at 2 outputs, 1 exceeding the pacing threshold by 10% (MIN) and the other at maximum output (MAX). The time from freezing to the initiation of PNP, values of the CMAP amplitude, and severity of PNP were compared for the 2 outputs. Results There was a significant difference in the time from freezing to initiation of PNP between MIN and MAX pacing (25.7 ± 5.7 vs 81.3 ± 7.4 seconds, P Conclusion Pacing the SVC and LCV with lower output detect PNP significantly earlier than maximal output pacing and leads to recovery from PNP on the order of hours postprocedure rather than months.

BACKGROUND: Phrenic nerve injury (PNI) is the most frequently observed complication during pulmonary vein (PV) isolation using the second-generation cryoballoon. OBJECTIVE: The purpose of this study was to analyze anatomic predictors based on preprocedural computed tomographic imaging data. METHODS: Forty-one patients with PNI during the procedure and 123 age-, gender-, and body mass index-matched controls were included. A total of 343 right PVs were evaluated for axial/coronal orientation, ostial diameters with cross-sectional area, ovality index, and branching pattern. External angle between the right superior pulmonary vein (RSPV) and the anterolateral wall of the left atrium (LA) was measured (RSPV-LA angle). Distance from this vertex to the superior vena cava (SVC) was considered the RSPV-SVC distance. RESULTS: For the RSPV, more anterosuperior orientation, larger dimensions, shorter RSPV-SVC distance, and more obtuse RSPV-LA angle (all P

Background Cryoballoon catheter ablation was developed to simplify ablation for atrial fibrillation (AF). Initial enthusiasm for its widespread use has been dampened by phrenic nerve (PN) injury (PNI). Objective The purpose of this study was to assess the effect of cryoballoon inflation at the right superior pulmonary vein (RSPV) orifice on PN location and to elucidate the potential mechanism of PNI. Methods Twenty patients with paroxysmal atrial fibrillation underwent ablation performed with a second-generation 28-mm cryoballoon catheter. Before ablation, the pacing-determined PN course was delineated along the right atrium. PN location and its relation to the RSPV as well as RSPV surface distortions after balloon inflation were established with a NavX mapping system. Results During RSPV ablation, the inflated balloon surface extended anteriorly 6.3 ± 1.8 mm outside the RSPV. This narrowed the distance between the PN capture points in the RSPV vs PN location from 11.4 ± 5.0 mm to 7.5 ± 5.0 mm ( P = .0002) and increased the PN capture area from 1.9 ± 1.3 cm 2 to 3.2 ± 1.8 cm 2 ( P = .0004). Furthermore, the PN capture points shifted toward the orifice within the RSPV and after balloon inflation were located significantly closer to the orifice in the 3 patients with transient PNI than in those without PNI. Conclusion Cryoballoon inflation at the RSPV orifice alters PV/left atrial surface geometry, reducing the distance between the energy delivery source and the PN and increasing PN area, possibly explaining the mechanism of PNI. PN pacing within the RSPV after balloon inflation may be useful for preventing PNI.

Background A percutaneous intravascular cardioverter-defibrillator (PICD) has been developed with a right ventricular (RV) single-coil lead and titanium electrodes in the superior vena cava (SVC)–brachiocephalic vein (BCV) region and the inferior vena cava (IVC). Objective To compare defibrillation thresholds (DFTs) of the PICD with those of a conventional ICD in humans. Methods Ten patients with ischemic cardiomyopathy and ejection fraction ≤35% were randomized to initial testing with either PICD or conventional ICD. A standard dual-coil lead was positioned in the RV apex. If randomized to PICD, the device was placed into the vasculature such that 1 titanium electrode was positioned in the SVC-BCV region and the second in the IVC. For PICD DFTs, the RV coil of the conventional ICD lead was connected to the PICD mandrel [shock vector: RV (+) to SVC-BCV (−) + IVC (−)]. When testing the conventional ICD, a subcutaneous pocket was formed in the left pectoralis region and the ICD was connected to the lead system and positioned in the pocket [shock vector: RV (+) to SVC (−) + active can (−)]. Each device was removed before testing with the other. A step-down binary search protocol determined the DFT, with the initial shock being 9 J. Results The mean PICD DFT was 7.6 ± 3.3 J, and the conventional ICD system demonstrated a mean DFT of 9.5 ± 4.7 J (N = 10; paired t test, P = .28). Conclusion The intravascular defibrillator has DFTs similar to those of commercially available ICDs.

Background The ganglionated plexi (GP) located at the junction of the superior vena cava, aorta, and right pulmonary artery (SVC-Ao GP) was proposed to be the "head station" between the extrinsic and the intrinsic cardiac autonomic nervous system (ECANS and ICANS, respectively). Objective To investigate the chronic effects after interrupting the ECANS-ICANS connections by ablating the SVC-Ao GP. Methods A right thoracotomy in 10 dogs allowed stimulation at the right superior and inferior pulmonary veins (RSPV and RIPV, respectively), right atrial appendage (RAA), and SVC to determine effective refractory period (ERP) and atrial fibrillation (AF) inducibility in the first operation. Group 1 (n = 5) received SVC-Ao GP ablation; group 2 (n = 5) received no ablation. A second operation and the same measurements were made 10 weeks later. A pacemaker with lead implanted at the RSPV recorded atrial fibrillation or tachycardia (AF/AT). Results During the first operation in group 1, ERPs increased significantly in the SVC but not at the RSPV, RIPV, or RAA site immediately after ablation, whereas ERPs decreased significantly in the RSPV, RIPV, and RAA but not the SVC in the second operation performed 10 weeks later (compared to the ERP in the first operation). ERPs decreased and AF/AT burden increased significantly from weeks 4 and 5, respectively, after the first operation in group 1 dogs. The ERP and AF/AT burden in group 2 remained unchanged between operations. Conclusions Ablation of the head station GP between the ECANS and the ICANS prolonged the ERP acutely, but shortened regional ERPs and increased AF/AT burden chronically, suggesting that the ECANS may tonically inhibit the ICANS activity.

Background The majority of patients with recurrence of arrhythmia after the initial atrial fibrillation (AF) ablation procedure have resumption of pulmonary vein (PV) conduction. Adenosine-infusion test after PV isolation identifies acute dormant PV conduction during the index procedure. Objective To evaluate the utility of adenosine-infusion test at a repeat AF ablation procedure. Methods This study included 50 consecutive patients (38 men; mean age 65±9 years) who underwent second ablation procedure for recurrent atrial tachyarrhythmia(s). At the index procedure, which was undertaken for paroxysmal AF, all patients underwent PV isolation and 48 of 50 (96%) underwent superior vena cava (SVC) isolation followed by adenosine infusion. PV and SVC were reisolated—if found reconnected—at the start of the second procedure. Thereafter, adenosine-infusion test was undertaken for all PVs in all patients. Results At the index procedure, adenosine infusion revealed dormant PV conduction in 15 of 50 (30%) patients. At the second procedure, after 10±10 months, PV and SVC reconnections were observed in 46 of 50 (92%) and 33 of 48 (68.8%) patients and they were reisolated. Subsequently, adenosine-infusion test revealed dormant PV conduction in 9 of 50 (18%) patients, including 3 of 50 (6%) who had no PV reconnection at the start of the procedure. In these 3 patients, transient AF resulted after adenosine infusion, and at mean 8.0±3.4 months, they were free from any atrial arrhythmia after the elimination of dormant PV conduction alone. Conclusions Adenosine-infusion test reveals dormant thoracic vein conduction associated with arrhythmia recurrence in the chronic phase after the initial PV isolation.

Item does not contain fulltext BACKGROUND: Phrenic nerve palsy (PNP) is the most frequently observed complication during cryoballoon ablation (CB; Arctic Front, Medtronic, MN) occurring in roughly 7%-9% of the cases. The new second-generation cryoballoon ablation Arctic Front Advance (CB-A) (Arctic Front) has recently been launched in the market. OBJECTIVE: To evaluate the incidence of right PNP with the new CB-A in comparison with the first-generation balloon in a series of consecutive patients that underwent pulmonary vein isolation with this modality. METHODS: The study was designed as an observational study with a prospective follow-up. In total, 121 consecutive patients were included: 80 patients with the CB (group 1) and 41 with the CB-A (group 2). RESULTS: Mean procedural times, fluoroscopic times, and time to pulmonary vein isolation documented by real-time recordings were significantly lower in group 2 (P

The end point of current catheter-based ablation approaches for the treatment of atrial fibrillation (AF) is the elimination of all the possible triggers with the least amount of ablation necessary. Once all the triggers have been eliminated, the incremental value of any additional lesion sets remains to be proven. Pulmonary vein (PV) isolation is the cornerstone of catheter ablation approaches for eliminating AF triggers. However, up to 11% of patients demonstrate reproducible sustained AF initiation from non-PV foci. In these patients, triggers can typically be elicited using standardized induction protocols, which include cardioversion of spontaneous and/or induced AF and infusion of high-dose isoproterenol. Non-PV triggers typically arise from discrete anatomical structures that include the mitral and tricuspid periannular regions, the crista terminalis and Eustachian ridge, the interatrial septum, the left atrial (LA) posterior wall, the left atrial appendage (LAA), and other thoracic veins such as the superior vena cava, the coronary sinus, and the ligament of Marshall. Localization of non-PV foci involves a detailed analysis of specific intra-atrial activation sequences using multipolar catheters in standard atrial locations coupled with information from the surface electrocardiogram P wave when possible. Multipolar catheters positioned along the coronary sinus and crista terminalis/superior vena cava region together with direct recordings from the right and left PVs allow a quick localization of non-PV foci. Elimination of non-PV triggers by means of focal ablation at the site of origin or isolation of arrhythmogenic structures (eg, LA posterior wall or superior vena cava) has been associated with improved arrhythmia-free survival.

Background Superior vena cava (SVC) perforation is a rare but potentially fatal complication of transvenous lead removal. Objective The aim of this study was to evaluate the feasibility of hemodynamic stabilization using an occlusion balloon during SVC tear in a porcine model. Methods A surgically induced SVC perforation was created in Yorkshire cross swine (n = 7). Three animals were used to develop and test surgical repair methods. Four animals were used to evaluate hemodynamic, behavioral, and neurological effects up to 5 days after SVC tear and repair. An occlusion balloon (Bridge Occlusion Balloon, Spectranetics Corporation, Colorado Springs, CO) was percutaneously delivered through the femoral vein to the location of the injury and inflated. Once hemodynamic control was achieved, the perforation was surgically repaired. Results After SVC perforation and clamp release, the rate of blood loss was 7.0 ± 0.8 mL/s. Mean time from SVC tear to occlusion balloon deployment was 55 ± 12 seconds, during which mean arterial pressure decreased from 56 ± 2 to 25 ± 3 mm Hg and heart rate decreased from 76 ± 7 to 62 ± 7 beats/min. After the deployment of the occlusion balloon, the rate of blood loss decreased by 90%, to 0.7 ± 0.2 mL/s. The mean time of balloon occlusion of the SVC was 16 ± 4 minutes and hemodynamic measures returned to baseline levels during this time. Study animals experienced no major complications, demonstrated stable recovery, and exhibited normal neurological function at each postoperative assessment. Conclusion Endovascular temporary balloon occlusion may be a feasible option to reduce blood loss, maintain hemodynamic control, and provide a bridge to surgery after SVC injury.

Background Complete electrical isolation of pulmonary veins (PVs) remains the cornerstone of ablation therapy for atrial fibrillation. Entrance block without exit block has been reported to occur in 40% of the patients. Far-field capture (FFC) can occur during pacing from the superior PVs to assess exit block, and this may appear as persistent conduction from PV to left atrium (LA). Objective To facilitate accurate assessment of exit block. Methods Twenty consecutive patients with symptomatic atrial fibrillation referred for ablation were included in the study. Once PV isolation (entrance block) was confirmed, pacing from all the bipoles on the Lasso catheter was used to assess exit block by using a pacing stimulus of 10 mA at 2 ms. Evidence for PV capture without conduction to LA was necessary to prove exit block. If conduction to LA was noticed, pacing output was decreased until there was PV capture without conduction to LA or no PV capture was noted to assess for far-field capture in both the upper PVs. Results All 20 patients underwent successful isolation (entrance block) of all 76 (4 left common PV) veins: mean age 58 ± 9 years; paroxysmal atrial fibrillation 40%; hypertension 70%, diabetes mellitus 30%, coronary artery disease 15%; left ventricular ejection fraction 55% ± 10%; LA size 42 ± 11 mm. Despite entrance block, exit block was absent in only 16% of the PVs, suggesting persistent PV to LA conduction. FFC of LA appendage was noted in 38% of the left superior PVs. FFC of the superior vena cava was noted in 30% of the right superior PVs. The mean pacing threshold for FFC was 7 ± 4 mA. Decreasing pacing output until only PV capture (loss of FFC) is noted was essential to confirm true exit block. Conclusions FFC of LA appendage or superior vena cava can masquerade as persistent PV to LA conduction. A careful assessment for PV capture at decreasing pacing output is essential to exclude FFC.

Background The biatrial substrate properties in patients with paroxysmal atrial fibrillation (AF) originating from the pulmonary veins (PVs) and superior vena cava (SVC) are not available. Objective The purpose of this study is to characterize the differences of biatrial substrate properties in patients with different types of AF. Methods A total of 36 patients with paroxysmal AF originating from the PV (PV-AF) and 9 patients with paroxysmal AF initiating from the SVC (SVC-AF) were included. Regional electrogram voltage, conduction velocity (CV), and spectral analysis to identify the AF nest were performed to characterize the biatrial, PVs, and SVC substrate. Results In the left atrial (LA) body, the bipolar voltage, total activation time, CV, and dominant frequency (DF) were similar between the PV-AF and SVC-AF. However, in the PV regions, the electrogram voltage, CV, and DF were decreased in the PV-AF. The proportions of AF nest in the LA body (72.2% vs. 22.2%, P = .008) and PV regions (100% vs. 22.2%, P .001) were higher in PV-AF compared with SVC-AF, respectively. On the other hand, lower bipolar voltage, longer total activation time, and slower CV of RA body were recognized in the SVC-AF as compared with the PV-AF. In the SVC, lower bipolar voltage, slower CV, higher DF, and higher proportions of AF nest in SVC (16.7% vs. 66.7%, P = .002) were identified in SVC-AF. Conclusion These most-remodeled substrates in different types of paroxysmal AF indicated the importance of the atrial substrate in the vicinity of the arrhythmogenic thoracic veins.

Background Physicians will increasingly encounter patients who require rhythm management devices but have venous obstructions that prevent conventional access. Alternate access options, such as thoracotomy or transiliac approaches, exist but are associated with greater cost and morbidity. Objective The purpose of this study is to describe a novel method of vascular access that allows prepectoral placement of conventional pacing and defibrillation leads in patients with complex central venous occlusions. Methods Eight patients with central venous occlusions were referred for device implantation. Inside-out central venous access (IOCVA) was obtained via a percutaneous femoral approach. A catheter-dilator system was advanced via the right atrium to the most central point of venous occlusion. The occluded vein segment was punctured with a directionally guided needle, which was advanced along intravascular or extravascular tissue planes to the subclavian region. A solid wire needle was oriented toward the skin surface and advanced through the soft tissues until it exists from the body. The wire was used to pull rigid dilators through the occluded segment. Standard transvenous leads were implanted though the newly created channel. Results All patients with total central venous occlusions (4 superior vena cava, 4 brachiocephalic and bilateral subclavian) had successful, prepectoral device implants (4 left-sided, 1 single-chamber, 4 dual-chamber, 3 biventricular). No procedure-related complications occurred. All patients had normal device function at follow-up of 485 ± 542 days. Conclusion IOCVA is an effective method of pacemaker and defibrillator implantation for patients with central venous occlusions. Further clinical evaluation of this novel method is needed.

Background An intravascular, percutaneously placed implantable defibrillator (InnerPulse percutaneous intravascular cardioverter-defibrillator [PICD]) with a right ventricular (RV) single-coil lead and titanium electrodes in the superior vena cava (SVC) and the inferior vena cava (IVC) has been developed. Objective The purpose of this study was to compare defibrillation thresholds (DFTs) of the PICD to those of a conventional implantable cardioverter-defibrillator (ICD) in canines. Methods Eight Bluetick hounds were randomized to initial placement of either a PICD or a conventional ICD. For PICD DFTs, a single-coil RV defibrillator lead was placed in the RV apex, and the device was positioned in the venous vasculature with electrodes in the SVC and IVC. With the conventional ICD, an RV lead was placed in the RV apex and an SVC coil was appropriately positioned. The ICD active can (AC) was implanted in a subcutaneous pocket formed in the left anterior chest wall and connected to the lead system. DFT was determined by a three-reversal, step up-down method to estimate the 80% success level. Two configurations were tested for the conventional ICD (#1: RV to SVC+AC; #2: RV to AC). A single configuration (RV to SVC+IVC) was evaluated for the PICD. Results Mean PICD DFT was 14.8 ± 1.53 (SE) J. Conventional #1 configuration demonstrated mean DFT of 20.2 ± 2.45 J and #2 of 27.5 ± 1.95 J. The PICD had a significantly lower DFT than the better conventional ICD configuration (#1; mean difference 5.4 ± 2.1 J, P Conclusion The new intravascular defibrillator had a significantly lower DFT than the conventional ICD in this canine model.

The superior vena cava (SVC) is an important focus of atrial fibrillation (AF) for which SVC isolation is effective. However, SVC isolation may cause serious complications, and indications for SVC isolation combined with pulmonary vein (PV) isolation are unclear.The purpose of this study was to identify structural and electrophysiologic differences that might exist between the SVC of patients with and those without SVC triggering of AF.This study included paroxysmal (n = 46) and persistent (n = 14) AF patients without structural heart disease who underwent circumferential antral PV isolation. Patients with AF of SVC origin were assigned to the SVC group (n = 12); the remaining patients were assigned to the control group (n = 48). The area where SVC potentials were recorded was defined as the SVC sleeve. The length of the SVC sleeve and the maximum amplitude of the SVC potential were measured.SVC group patients had a longer SVC sleeve (34.7 +/- 4.4 mm vs 16.5 +/- 11.4 mm, P.0001) than did control group patients. Maximum amplitude of the SVC potential was greater in SVC group patients than in control group patients (1.50 +/- 0.43 mV vs 0.98 +/- 0.60 mV, P = .03). SVC sleeve length30 mm and maximum amplitude of SVC potential1.0 mV strongly predicted an SVC focus of AF (100% sensitivity, 94% specificity). Fifty of 60 patients became AF-free without antiarrhythmic drugs after undergoing circumferential antral PV isolation and/or SVC isolation.The results of this study suggest that in patients with long SVC sleeve (30 mm) and large SVC potential (1.0 mV), arrhythmogenic triggers of AF reside in the SVC.

Background Typical atrial flutter is characterized by cavotricuspid isthmus dependence and activation sequentially around the tricuspid annulus (TA), usually counterclockwise. However, analysis of the upper portion of the annulus by postpacing interval after entrainment sometimes suggests it is outside the circuit. Details on the true active circuit are limited, particularly in the upper portions. Objective The purpose of this study was to define the full active circuit in atrial flutter. Methods In 26 patients with isthmus-dependent atrial flutter, we created detailed electroanatomic maps of postpacing intervals throughout the entire right atrium. Postpacing intervals within 20 ms of the flutter cycle length were defined as within the circuit. Results Creating postpacing interval maps allowed characterization of the full active circuit in all patients, and revealed significant variations despite similar counterclockwise or clockwise patterns with activation mapping. In 8, the active circuit was solely around the TA. In 14, an oblique course between the anterior and posterior borders was found, with the upper circuit off the annulus, posterior to the right atrial appendage base. Of these, 8 coursed anterior to the SVC, 5 behind the SVC and 1 bifurcated the SVC. In 4 others, bifurcation of the upper circuit was seen around the right atrial appendage (n = 3), or around the combined right atrial appendage–superior vena cava (n = 1). Conclusion Despite similar activation around the TA, creating electroanatomic postpacing interval maps distinguishes the active flutter circuit from passively activated myocardium. Significant variability exists in the active circuit, with only a minority around the TA. Most commonly, the circuit courses not around a single barrier but obliquely between anterior and posterior borders.

Background Mapping and ablation of atrial macroreentrant tachycardia focus on activation mapping with identification of the area of slow conduction. Objective The purpose of this study was to evaluate a new concept for analysis and treatment of macroreentrant tachycardia based on color-coded three-dimensional (3D) entrainment mapping and subsequent placement of strategic lesion lines. Methods Twenty-six patients presented with macroreentrant tachycardia (cycle length 329 ± 70 ms). Using nonfluoroscopic systems (CARTO 12, NavX 14), sequential mapping of the target atrium was performed. On each mapping point, the 3D location was paired with color-coded entrainment information so that the reentrant circuit could be directly visualized. Results Procedural duration, fluoroscopy time, and radiofrequency time measured 181 ± 58, 37 ± 19, and 31 ± 17 minutes, respectively. Thirty-nine macroreentrant tachycardias were ablated: perimitral 9, around pulmonary vein ostium 6, through left atrial roof 5, around left atrial appendage 3, right atrial cavotricuspid isthmus dependent 6, around right atrial scar 2, around superior vena cava 1, within the septum 5, and within the coronary sinus 2. Tachycardia termination and noninducibility of any macroreentrant tachycardia was the procedural end-point. In case of left atrial macroreentrant tachycardia, pulmonary vein isolation was completed. Follow-up with serial 7-day Holter covered 302 ± 82 days. Two (8%) patients experienced recurrences of a pretreated macroreentrant tachycardia. Conclusion In patients with macroreentrant tachycardia, color-coded 3D entrainment mapping is feasible to accurately determine and visualize the 3D location of the reentrant circuit and to plan a strategic ablation line concept. That approach, not targeting the area of slow conduction of the circuit, resulted in excellent procedural success (100%), with long-term freedom from any tachycardia recurrences in 88% of patients.

Objectives The purpose of this study was to identify clinical predictors of atrial defibrillation thresholds (DFTs) with standard implantable cardioverter-defibrillator (ICD) leads. Background Atrial defibrillation can be achieved with active pectoral, dual-coil transvenous ICD lead systems. If clinical predictors of atrial defibrillation efficacy with these lead systems were identified, they could be used to predict which patients may require more complex lead systems for atrial defibrillation, such as a coronary sinus electrode. Methods This was a prospective study of 135 consecutive patients undergoing initial ICD implant for standard indications. The lead system evaluated was a transvenous defibrillation lead with coils in the superior vena cava (SVC) and right ventricular apex (RV), and a left pectoral pulse generator emulator (CAN). The shocking pathway was RV→SVC+CAN. Atrial DFT was measured using a step-up protocol. Clinical and echocardiographic parameters were evaluated as predictors of atrial DFT and multiple linear regression was performed. Results Mean atrial DFT was 4.6 ± 3.8J. Atrial DFT was ≤3 J in 70 patients (52%) and ≤10 J in 97% of patients. The highest atrial DFT was 20 J (one patient). Left atrial size (r = 0.21, P = .01) and left ventricular end-diastolic diameter (r = 0.19, P = .02) were independent predictors of atrial DFT. However, these two predictors accounted for only 6% of the variability in atrial DFT. Conclusions Clinical parameters are of limited use in predicting atrial DFT with a dual-coil, active pectoral ICD lead system. Because the RV→SVC+CAN shocking pathway provides reliable atrial and ventricular defibrillation, this configuration should be preferred for combined atrial and ventricular ICDs.

Objectives The purposes of this study were to examine the first activations following atrial defibrillation shocks to help understand how and where atrial fibrillation (AF) relapsed following failed shocks and to assess the difference in postshock activation between failed and successful shocks. Background While many studies have investigated the mechanism of ventricular defibrillation, much less is known about the mechanisms of AF. Methods Sustained AF was induced electrically after pericardial infusion of methylcholine in 10 sheep. Biphasic subthreshold shocks were delivered to three configurations: right atrium to distal coronary sinus (RA-CS), sequential shocks with RA-CS as the first pathway followed by proximal CS to superior vena cava as the second pathway (Sequential), and right ventricle to superior vena cava plus can (V-triad). In eight sheep, global atrial mapping was performed with 504 electrodes spaced 3 to 4 mm apart. Results Earliest postshock activations mostly arose from the left atrium for V-triad but arose from either atrium for RA-CS and Sequential. Preshock AF cycle lengths were significantly shorter at the earliest activation sites than at seven of eight other sites globally distributed over both atria. In all type B successful episodes in which one or more rapid activations occurred after the shock and in 50 of the 72 failed episodes analyzed, activation fronts spread away from the earliest site in a focal pattern, and discrete nonfragmented activation complexes were present in the first derivatives of the electrograms. In the other 22 failed episodes, earliest activation fronts spread in a nonfocal pattern, and earliest postshock electrogram derivatives were fractionated. To better interpret the activation pattern in the fragmented regions, a 504 electrode plaque with 1.5-mm electrode spacing was placed on the right atrial appendage in two additional sheep. In 11 of 108 failed episodes, earliest postshock activation appeared inside the plaque and spread in a focal pattern with nonfragmented electrogram derivatives in 10 episodes and in a reentrant pattern with fragmented electrogram derivatives in the other. Conclusions (1) The electrode configuration influenced the location of earliest postshock activation. (2) Earliest postshock activation occurred where the preshock AF cycle length was short. (3) Earliest activations following all type B successful and most failed episodes were not fragmented and spread in a focal pattern. (4) The region of earliest postshock activation in the failed episodes without a focal postshock activation pattern exhibited regions of fragmented electrogram derivatives that may represent conduction block and possibly reentry.

Background Implantation of a left ventricular (LV) lead fails in 5% to 10% of patients in whom cardiac resynchronization therapy (CRT) is attempted. Alternatives for delivery of CRT are surgical epicardial and endocardial transvenous leads. Endocardial transseptal LV lead delivery is challenging because of the absence of dedicated equipment designed for this procedure. Objective The purpose of this study was to describe a new technique for delivery of a transseptal LV lead. Methods This dual approach from the right femoral vein and left subclavian vein involves use of an Endrys transseptal needle and Mullins sheath to deliver a gooseneck snare from the left subclavian vein into the right atrium that can then be used to deliver a deflectable sheath into the left atrium. An active fixation lead is advanced into the LV through the sheath and screwed into the lateral wall. Results The procedure was performed successfully in 12 patients in whom transvenous LV lead implantation had previously failed. The Endrys transseptal needle, ideally suited for this technique, facilitated passage of the gooseneck snare into the left atrium with no difficulty. Median procedure time was 148 minutes (interquartile range [IQR] 113–176 minutes), and median fluoroscopy time was 16 minutes (IQR 10–19 minutes). There was no need for repeat procedures after median follow-up of 97 days (IQR 36–313 days). Conclusion This approach using an Endrys needle and a gooseneck snare provides a reliable and effective alternative technique for delivery of an endocardial LV lead that is delivered easily through a deflectable sheath inserted transseptally into the LV.

Introduction Coumel et al initially reported that activation of the cardiac vagal nerve initiates paroxysmal atrial fibrillation (AF). Swallowing of cold substances is one of the reasons for the situational neurally mediated syncope associated with hypervagotonia. Although this is a rare phenomenon, several reports indicate that the ingestion of cold substances can induce vagally mediated AF. Cold substances can stimulate the cardiac parasympathetic nerve during ingestion, because the esophagus is located adjacent to the left atrial posterior wall. The third fat pad, containing the gate keeper ganglia of the cardiac parasympathetic nerve, is located at the junction of the superior vena cava (SVC), right atrial (RA) septum, and ascending aorta. Here, we report a case of cold water swallowing–induced paroxysmal AF, successfully treated by radiofrequency catheter ablation (RFCA) on the SVC and RA septum. We carefully mapped the initial triggers of AF on the SVC and RA septum by asking our patient to drink cold water and then successfully ablated them.

Background Percutaneous removal of implantable cardioverter-defibrillator (ICD) leads is a difficult procedure because of the consequence of massive fibrous tissue growth along the lead. Objective The purpose of this study was to describe the occurrence and location of fibrous adherences in ICD lead extraction and to identify potential predictors among patient and lead characteristics. Methods We studied 637 consecutive patients who underwent transvenous extraction of 678 ICD leads from 1997 to 2013. Results Procedural success rate was 99%, without major complications. Areas of adherence were found in the subclavian vein (78%), innominate vein (65%), superior vena cava (66%), and heart (73%). Dwell-time, passive fixation, and dual-coil lead design were independently associated with adherences. Dual-coil lead design was associated with adherences in the innominate vein and superior vena cava, whereas coil treatment (eg, expandable polytetrafluoroethylene-coated or medical adhesive back-filled strategies) prevented adherences. Passive fixation mechanism was associated with adherences in the heart. Conclusion ICD leads, after long dwell-time, are affected by fibrous adherences uniformly distributed along the lead course. Lead features represent major predictors of the phenomenon. Careful lead selection is recommended at the time of implantation to prevent adherences. In addition, lead-related risk stratification is mandatory before a transvenous extraction procedure.

Introduction Atrioventricular block (AVB) is a common issue in fetuses from mothers with autoimmune disease, but could also be encountered in healthy pregnancies. The assessment of heart rhythm in fetuses is challenging because transmaternal fetal electrocardiography (ECG) remains unreliable during part of gestation and involves signal averaging, limiting its clinical application. Fetal magnetocardiography, the magnetic analog of the fetal ECG, is at this time the most effective means of assessing fetal rhythms. However, as it requires a very expensive magnetically shielded facility, it is still primarily used for clinical research. The analysis of arrhythmias is therefore mostly based on evaluating the temporal relationship of circulatory markers of both atrial and ventricular contractions. Our technique, the superior vena cava (SVC)/ascending aorta (AA) approach, has been documented previously. Briefly, from a transverse crosssectional image at the level of the atrioventricular (AV) valves with the ultrasound beam directed at the left anterior or right posterior side of the fetus, a 4-chamber view is obtained with the heart in a vertical or slightly oblique position. From this position, 90° rotation shows a sagittal view of the fetus with the inferior vena cava, right atrium, and SVC connecting together (bull horn appearance). On this view, the AA and SVC appear closely related to each other. Slight cranial or caudal angulation allows the ultrasound beam to align with both vessels and to simultaneously record SVC/AA Doppler signals (Figure 1). AV correlation can then be assessed because the retrograde wave, caused by atrial contraction (A wave) in the SVC, and the onset of the aortic ejection wave (V wave, marker of ventricular contraction) are clearly identifiable (Figure 2). In our experience, the SVC/AA approach allows most fetal arrhythmias to be diagnosed. This is the technique of choice to detect and monitor AVB. Moreover, we have already described the appearance of typical type-I, seconddegree AVB (AVB-2) with Wenckebach phenomenon using this approach. We report the identification of an atypical, reversible, Wenckebach type AVB-2. To our knowledge, such an arrhythmia has never been described in prenatal life.

53-year-old Caucasian woman with a medical history of requent, symptomatic paroxysmal atrial fibrillation for 4 ears and hypothyroidism was scheduled to undergo a cirumferential, anatomic pulmonary vein ablation. Prior to the radiofrequency ablation, nine standard surace skin markers (IZI Medical Products, Baltimore, MD, SA) were placed on the chest from the sternum to the right nd left axillary line. As part of the preprocedural magnetic esonance imaging (MRI), continuous ECG-gated, T2eighted fast spin-echo (FSE) images were obtained with a .5T Signa XL GE scanner and a cardiac phased-array (TR in/full, TE 68 ms, echo train length 32, field of view 6 cm, readout bandwidth 62.5 kHz, matrix 512 256, lice thickness 1.5 mm, nexus 2). After the scan, the urface markers were removed and the exact location arked on the skin with permanent marker. When the patient returned 2 days later, the nine skin arkers were placed at their marked location on the paient’s chest. The clinically indicated pulmonary vein isolaion was performed with the standard approach. At the end f the procedure, the T2-weighted MR images of the heart ere transferred to the novel, stereotactic catheter guiding ystem. Image registration, the process that superimposes he catheter mapping space with the MRI, was performed by lacing the ablation catheter at each skin marker and corelating it with the corresponding imaged marker (external egistration; skin marker shown in Figure 1) or using a ombination of external makers and a software-supported best fit” algorithm of a superior vena cava (SVC)/inferior ena cava (IVC) shell (hybrid registration). Registration equired between 10-12 minutes. A reference catheter was