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Purpose: The available data on the treatment strategy of pulsed field ablation (PFA) for patients with atrial fibrillation (AF) is limited. This study aims to provide a comparative analysis of the efficacy, safety, and procedural efficiency between PFA and cryoballoon ablation (CBA) for AF. Methods: We conducted a comprehensive search of the EMBASE, PubMed, Cochrane Library, and ClinicalTrials.gov databases to identify trials comparing PFA with CBA for AF from their inception until December 2023. The odds ratio (OR) and mean difference (MD), along with a 95% confidence interval (CI), were utilized as measures of treatment effect. Results: The analysis included 15 eligible trials with a total enrollment of 1880 patients. No significant differences were found in recurrent atrial arrhythmia (OR 0.83, 95% CI 0.64, 1.07) or periprocedural complications (OR 0.78, 95% CI 0.46, 1.30) between the two ablation techniques examined in this study. However, the PFA technique demonstrated a significantly shorter procedure time (MD ‐7.17, 95% CI ‐13.60, ‐0.73), but a longer fluoroscopy time (MD 2.53, 95% CI 0.87, 4.19). Similarly, PFA was found to be significantly associated with a decreased incidence of phrenic nerve palsy (OR 0.20, 95% CI 0.07, 0.59), but an increased incidence of cardiac tamponade (OR 4.07, 95% CI 1.15, 14.39). Moreover, there was a significantly higher release of troponin with PFA compared to CBA (MD 470.28, 95% CI 18.89, 921.67), while the increase in S100 protein and heart rate was significantly lower with PFA than with CBA (MD ‐64.41, 95% CI ‐105.46, ‐17.36), (MD ‐8.76, 95% CI ‐15.12, ‐2.40). Conclusion: The utilization of PFA provides a safer, time‐saving, and tissue‐specific procedure compared to CBA, while maintaining comparable success rates. This has the potential to enhance procedural efficiency and optimize resource utilization in clinical practice. These findings underscore the feasibility and promise of PFA as an alternative technique for PVI in patients with AF. [ABSTRACT FROM AUTHOR]

Background: Preprocedural detection of the running course of the right pericardiophrenic bundles (PBs) is considered to be useful in preventing phrenic nerve (PN) injury during catheter ablation for atrial fibrillation (AF). However, previous studies using the arterial phase of contrast‐enhanced computed tomography (CT) reported a relatively low right PBs detection rate. Methods: This study included 63 patients with AF who underwent catheter ablation and preoperative contrast‐enhanced CT imaging of the venous and arterial phases (66.7 ± 10.2 years; 44 male). The venous phase of contrast‐enhanced CT significantly improved the detection rate of PBs compared to the arterial phase (96.8% vs. 60.3%, p <.001), and PBs were detected in the venous phase only in 23 (36.7%) patients. No significant differences were observed between the right PBs detection rate using non‐contrast CT versus the arterial phase of contrast‐enhanced CT (p =.37). Patients without visualization of the right PBs during the arterial phase had a higher frequency of chronic heart failure (p =.0083), lower left ventricular ejection fraction (p =.021), and a higher CHADS2 score (p =.048) than those with visualization. In five patients whose right PBs could only be detected during the venous phase of contrast‐enhanced CT, the reconstructed running course of the right PBs corresponded with the PN generated by electrical high‐output pacing. Conclusion: Contrast‐enhanced CT images of the venous phase, rather than the arterial phase, are useful in detecting the right PBs, especially in patients with heart failure or reduced left ventricular ejection fraction. [ABSTRACT FROM AUTHOR]

Recently, a novel size‐adjustable cryoballoon has been introduced in clinical practice, which can be inflated to two different diameters (28 and 31 mm). The 31 mm cryoballoon is specifically designed to achieve better contact with remodeled pulmonary veins (PVs) that have wider ostia while avoiding deep cannulation, thereby potentially reducing the risk of phrenic nerve injury (PNI) associated with deep balloon cannulation. However, we encountered two cases of PNI during cryoballoon ablation using the novel system among our initial 25 consecutive case series. Herein, we present two cases that exhibited PNI during freezing of the right superior PV with a size‐adjustable balloon. While larger balloons are expected to create a larger area of isolation, the safety of this novel balloon system needs to be evaluated in a large‐scale clinical study. [ABSTRACT FROM AUTHOR]

Background: The implantation procedure of left ventricular (LV) leads and the management of cardiac resynchronization therapy (CRT) patients can be challenging. The IS‐4 standard for CRT offers additional pacing vectors compared to bipolar leads (IS‐1). IS‐4 leads improve procedural outcome and may also result in lower adverse events during follow‐up (FU) and improve clinical outcome in CRT patients. Further long‐term FU data comparing the two lead designs are necessary. Methods: In this retrospective, single‐center study we included adult patients implanted with a CRT‐Defibrillator (CRT‐D) or CRT‐Pacemaker (CRT‐P) with a quadripolar (IS‐4 group) or bipolar (IS‐1 group) LV lead and with available ≥3 years clinical FU. The combined primary endpoint was a combination of predefined, lead‐related adverse events. Secondary endpoints were all single components of the primary endpoint. Results: Overall, 133 patients (IS‐4 n = 66; IS‐1 n = 67) with a mean FU of 4.03 ± 1.93 years were included. Lead‐related adverse events were less frequent in patients with an IS‐4 lead than with an IS‐1 lead (n = 8, 12.1% vs. n = 23, 34.3%; p =.002). The secondary outcomes showed a lower rate of LV lead deactivation/explantation and LV lead dislodgement/dysfunction (4.5% vs. 22.4%; p =.003; 4.5% vs. 17.9%; p =.015, respectively) in the IS‐4 patient group. Less patients suffered from unresolved phrenic nerve stimulation with an IS‐4 lead (3.0% vs. 13.4%; p =.029). LV lead‐related re‐interventions were fewer in case of an IS‐4 lead (6.1% vs. 17.9%; p =.036). Conclusion: In this retrospective analysis, the IS‐4 LV lead is associated with lower lead‐related complication rates than the IS‐1 lead at long‐term FU. [ABSTRACT FROM AUTHOR]

Background: Recently a double 120 s freeze cryoballoon (CB) pulmonary vein isolation (PVI) protocol proved to be non inferior to a double 240 s freeze protocol in terms of atrial fibrillation (AF) recurrences. We hypothesized that this approach could also result in an increased procedure safety. Methods: Eighty consecutive patients treated with a double 120 s freeze protocol (Group CB120) were compared with 80 previous consecutive patients treated with a single 240 s freeze protocol (Group CB240). Procedures were performed with a temperature probe to monitor the luminal esophageal temperature (LET), using a cut off for cryoenergy interruption of 15°C. During ablation at the septal pulmonary veins (PVs), the phrenic nerve (PN) function was monitored by pacing. Results: In CB120 and CB240 the rate of single shot isolation was similar in all PVs. Time to isolation was not different between the two groups. Mean minimal esophageal temperature was lower in LSPV and LIPV of the CB240 group. A total of 4/80 patients (5%) of the CB120 group experienced a PN injury, but no persistent form was recorded; 11/80 patients (14%) of the CB240 group experienced a PN injury, three in a persistent form (p =.10). A LET <15°C was recorded in 3/80 patients (4%) in the CB120 group and in 16/80 patients (20%) in the CB240 group (p <.01). Composite rate of energy‐related safety events (LET <15°C and PN injury) was significantly lower in the CB120 (34% vs. 9%, p <.01). Conclusions: Safety of second generation CB PVI can be increased using a double 120 s freeze protocol. [ABSTRACT FROM AUTHOR]

Background: In the 123‐study, we prospectively assessed, in a randomized fashion, the minimal cryoballoon application time necessary to achieve pulmonary vein (PV) isolation (PVI) in patients with paroxysmal atrial fibrillation (AF) with the aim to reduce complications by shortening the application duration. The first results of this study demonstrated that shortened cryoballoon applications (<2 minutes) resulted in less phrenic nerve injury (PNI) without compromising acute isolation efficacy for the right PVs. We now report the 1‐year follow‐up results regarding safety and efficacy of shorter cryoballoon applications. Methods: A total of 222 patients with AF were randomized to two applications of 1 min "short," 2 min "medium," or 3 min "long" duration, 74 per group. Recurrence of AF and PV reconduction at 1‐year follow‐up were assessed. Results: The overall 1‐year freedom from AF was 79% and did not differ significantly between the short, medium, and long application groups (77%, 74%, and 85% for short, medium, and long application groups, respectively; P = 0.07). In 30 patients, a redo PVI procedure was performed. For all four PVs, there was no significant difference in reconduction between the three groups. Reconduction was most common in the left superior PV (57%). The right superior PV (RSPV) showed significantly less reconduction (17%) compared to the other PVs. Conclusions: Shortening cryoballoon applications of the RSPV to <2 minutes results in less PNI, while acute success and 1‐year freedom from AF are not compromised. Therefore, shorter cryoballoon applications (especially) in the RSPV could be used to reduce PNI. [ABSTRACT FROM AUTHOR]

Background: Atrial fibrillation (AF) ablation is a complex procedure, generally requiring at least one overnight hospital stay. We investigated the safety and feasibility of early mobilization and same‐day discharge following streamlined peri‐ablation management for AF. Methods: From 2014, we offered same‐day discharge to selected patients who underwent uncomplicated AF ablation on the morning lists, with ultrasound‐guided femoral access, uninterrupted warfarin or minimal interruption in novel oral anticoagulants, and reversal of intraprocedural heparin with protamine. Patients were discharged 6‐8 h postprocedure and offered access to a dedicated nurse helpline. Results: Of 1599 AF ablation cases performed from April 2014 to March 2017, 811 (50.7%) were performed on the morning lists and 169/811 (20.8%) were discharged on the same day. Excluding 26 research cases, 1/143 (0.7%) had transient right phrenic nerve palsy and five (3.5%) cases experienced minor problems that did not preclude same‐day discharge; three (2.1%) needed rehospitalization postdischarge: one for pericarditic chest pain and two for nausea/vomiting. Compared to 642 overnight cases, day‐case procedures were shorter, more likely to be redos, to be performed under sedation rather than general anesthesia, and less likely to involve linear lesions and electrical cardioversion. There were no significant differences in patient age, gender, body mass index, CHA2DS2‐VASc, in preprocedural anticoagulation regimen (warfarin vs novel anticoagulants vs no anticoagulation) and in choice of ablation method (cryoballoon vs radiofrequency). Conclusions: Selective same‐day discharge after AF ablation is safe and feasible using a streamlined peri‐procedural care protocol. Wider adoption can potentially reduce health‐care costs while improving patient experience. [ABSTRACT FROM AUTHOR]

Background: Currently available second‐generation cryoballoon (CB2) is accepted as an effective and safe tool for pulmonary vein isolation (PVI). Although much more data exist about 1‐year outcomes of CB2 ablation, data on long‐term outcomes are scarce. Objective: We aimed to assess the long‐term outcomes of PVI using CB2 in a large‐scale symptomatic atrial fibrillation (AF) population at our tertiary referral center. Methods: In this nonrandomized prospective observational study, a total of 486 patients with paroxysmal (71%) or persistent (29%) AF who underwent index PVI using CB2 at our hospital between January 2013 and June 2017 were enrolled. Atrial tachyarrhythmia (ATa)‐free survival was defined as the absence of AF, atrial flutter, or atrial tachycardia recurrence ≥30 s following a 3 months blanking period. Predictors of recurrence were evaluated by univariate and multivariate Cox proportional hazards regression models. Results: Acute procedural success rate was 99.8% (1898/1902 PVs). Mean procedural and fluoroscopy time were 64.9 ± 9.2 and 12.1 ± 2.6, respectively. At median 39 (interquartile range: 26‐56) months follow‐up, ATa‐free survival was 78.6% after a single procedure (280/345 [81.2%] for paroxysmal AF vs. 102/141 [72.3%] for persistent AF, P =.019) and 84.4% after a mean 1.48 ± 0.42 ablations. Cox regression analysis showed that left atrium diameter, duration of AF history, and early ATa recurrence were found as the independent predictors of late recurrence. Phrenic nerve palsy was observed in 17 (3.5%) patients. Conclusions: CB2‐based PVI is effective to maintain sinus rhythm in a significant proportion of paroxysmal and persistent AF patients with an acceptable complication rate at long‐term follow‐up. [ABSTRACT FROM AUTHOR]

Background: The left atrial appendage (LAA) has been identified as a potential source of atrial fibrillation (AF) and has been described as the "fifth" pulmonary vein (PV). We report our initial experience in LAA isolation (LAAI) using the cryoballoon (CB) and data on durability of CB‐LAAI. Methods: Patients treated with a CB‐LAAI were retrospectively identified. Six weeks after electrical LAAI, patients were scheduled for staged percutaneous LAA closure. During the second procedure, a subset of patients underwent invasive remapping of the LAA. Results: A total of 32 patients (21 males, 68 ± 10 years old) were treated with CB‐LAAI. Acute LAAI was achieved in 29 of 32 (91%) patients: single‐shot LAAI was observed in 18 of 32 (56%) patients. Acute procedural sustained LAAI was related with a significantly shorter time to LAAI (sustained LAAI: 84 ± 50 s vs nonsustained LAAI: 166 ± 76 s, P = 0.004). Mean procedure and fluoroscopy time were 61 ± 29 and 8 ± 6 min, respectively. One left‐sided phrenic nerve palsy occurred. In 25 of 32 (78%) patients, a second procedure for percutaneous LAA closure device implantation was performed. In 22 patients, persistency of LAAI was tested: durable LAAI was documented in 16/22 patients (73%). Conclusion: In the present report, CB LAA isolation followed by staged LAA closure appeared to be safe and feasible but more data are required. Time to LAAI played a role in predicting acute sustained LAAI rate. CB LAA ablation leads to 73% of durable LAA isolation. [ABSTRACT FROM AUTHOR]

Background: The second‐generation cryoballoon significantly improves outcome of pulmonary vein isolation (PVI) but may cause more complications than the first generation. Currently, no consensus regarding optimal cryoballoon application time exists. The 123‐study aimed to assess the minimal cryoballoon application duration necessary to achieve PVI (primary endpoint) and the effect of application duration on prevention of phrenic nerve injury (PNI). Methods: Patients <75 years of age with paroxysmal atrial fibrillation, normal PV anatomy, and left atrial size <40 cc/m² or <50 mm were randomized to two applications of different duration: "short," "medium," or "long." A total of 222 patients were enrolled, 74 per group. Results: Duration per application was 105 (101‐108), 164 (160‐168), and 224 (219‐226) s and isolation was achieved in 79, 89, and 90% (P < 0.001) of the PVs after two applications in groups short, medium, and long, respectively. Only for the left PVs, the success rate of the short group was significantly less compared to the medium‐ and long‐duration groups (P < 0.001). PNI during the procedure occurred in 19 PVs (6.5%) in the medium and in 20 PVs (6.8%) in the long duration groups compared to only five PVs (1.7%) in the short duration group (P < 0.001). Conclusions: Short cryoballoon ablation application times, less than 2 min, did affect the success for the left PVs but not for the right PVs and resulted in less PNI. A PV tailored approach with shorter application times for the right PVs might be advocated. [ABSTRACT FROM AUTHOR]

Introduction: The Medtronic SelectSecure™ (Minneapolis, MN, USA) pacing lead (SS) has theoretical advantages compared to conventional (C) transvenous pacing leads (PLs). The study purpose was to determine whether differences in electrical function and lead survival exist between these PLs in a large data set of pediatric and congenital patients. Methods: A multicenter historical longitudinal cohort study was performed comparing SS and CPL performance over a 72‐month follow‐up (FU). Ten centers provided data for both SS and CPL, matched for age, implanted pacing chamber, time period of implantation, and presence of heart disease. Results: The cohort consisted of 141 subjects in each group. No statistical differences were observed in age, gender, presence of heart disease, or pacing indication. Atrial and ventricular capture thresholds were stable throughout FU and higher in the SS group (atrial: 0.75 ± 0.02 vs 0.5 ± 0.04 V, ventricular: 1.0 ± 0.04 vs 0.75 ± 0.04 V), P < 0.001. Group PL sensing thresholds did not differ. The SS group required greater energy to pace (atrial: 0.57 ± 0.05 vs 0.32 ± 0.02 mJ, ventricular: 0.83 ± 0.05 vs 0.56 ± 0.06 mJ), P = 0.001. Early lead dislodgement and phrenic nerve stimulation were greater in the SS group (P = 0.03). Long‐term lead survival was high and similar between the two groups, P = 0.35. Conclusions: Long‐term survival of both PL was high with a low fracture rate. The SS had excellent electrical function but did show higher capture thresholds and increased energy to pace; these differences are offset by other advantages of the SS PL. [ABSTRACT FROM AUTHOR]

Introduction: A technique was developed to eliminate radiation exposure for routine atrial fibrillation (AF) ablation, to simplify the procedure and to achieve cost effectiveness. We here report the outcomes of this approach. Methods: Two hundred consecutive AF ablations (55% paroxysmal) were performed by a single operator. Pulmonary vein isolation (PVI) was achieved by antral ablation without left atrial anatomic mapping, guided by contact force sensing and intracardiac echocardiogram (ICE). All ablations were performed using three ipsilateral 8 French catheters (ICE, Lasso, and ablation). Eighty‐two percent of the patients underwent ablation of atrial flutter or non‐pulmonary vein triggers. All patients underwent provocative testing after PVI. Results: No fluoroscopy was used for the entire study. Two ablations were performed without x‐ray available due to unexpected equipment failure. The mean procedure time was 90.3 ± 17.7 (minutes) in patients who only required PVI and 106.2 ± 23.2 (minutes) for the entire cohort, with a success rate of 76% (mean follow‐up of 11 months). In contrast, the procedure time and success rate were 127.9 ± 38.2 (minutes) (P < 0.01) and 74%, respectively, for the last 50 standard ablations guided by fluoroscopy (without contact force sensing). Complications included one case of partial right phrenic nerve palsy and one case of right femoral artery pesudoaneurysm. Compared to our previous ablation approaches, the new method resulted in catheter savings of $2,168–$4,568/case. Conclusion: The new technique eliminated radiation exposure and shortened the procedure time without significant negative impact on safety or success rate. Substantial cost savings were also achieved by using a minimal number of mostly reprocessed catheters. [ABSTRACT FROM AUTHOR]

Abstract: Background: Intraoperative controlled mechanical ventilation (CMV) changes the intrathoracic geometry and may impact postoperative left ventricular (LV) lead function after CRT implantation. This multicenter study investigates the effect of intraoperative ventilation setting (spontaneous breathing [SB] vs CMV) on postoperative LV lead function taking into account patients’ body mass index (BMI). Methods: CRT implantation was performed at two centers during SB in 92 and during CMV in 73 patients. Follow‐up was carried out after 3 ± 5 and 36 ± 53 days. Functional lead parameters (FLP; pacing threshold and impedance), postoperative adverse events (A;  phrenic nerve stimulation [PNS] and lead malfunction), and patients’ BMI were assessed. Delta values of FLP between baseline and follow‐up visits were analyzed applying an analysis of covariance model to detect subclinical alterations in LV lead function. Results: AE occurred in a total of 36 (21%) patients. PNS was observed in 26 (15%) patients and LV lead repositioning due to malfunction was necessary in 10 (6%) patients. Both AE and FLP delta values between baseline and follow‐up were not associated with intraoperative ventilation settings nor the patients’ BMI. Conclusions: This study demonstrates that there is no impact of the intraoperative ventilation setting (SB vs CMV) on postoperative FLP or the occurrence of AE. This is also the case taking into account the BMI. With respect to these findings both approaches—sedation only or general anaesthesia including CMV—can be safely implemented during CRT implantation. [ABSTRACT FROM AUTHOR]

Background Phrenic nerve (PN) palsy (PNP) is the most frequent complication of cryoballoon ablation (CBA) of atrial fibrillation (AF). The major complication of this technique seems to be right-sided PN injury (PNI) following ablation of the right pulmonary veins (PVs). We sought to assess the incidence and prognosis of left-sided PNI during CBA. Methods CBA was performed in 448 patients with AF. During the ablation of the left-sided PVs, the PN was paced from the left subclavian vein with a pacing output just exceeding the threshold by 10 ∼ 20%. The right and left arm 12-lead electrocardiogram electrodes were positioned 5 cm above the xiphoid process and 16 cm along the left costal margin. The amplitude of the compound motor action potentials was recorded during the CBA. Results Two thousand one hundred seventy-eight CBA applications were delivered in 1,094 left-sided PVs. PNI occurred in 29 patients (6.5%); the PN could be captured by an increasing pacing output in 21 patients (4.7%), and premature termination of the freezing was required to avoid PNP in eight patients (1.8%). The PN function recovered before discharge; however, it took 7 months for one patient to completely recovery from the PNP. Conclusions Left-sided PNP could be provoked during a left-sided CBA procedure. Assessment of the left PN during the CBA was necessary to prevent left-sided PNP. [ABSTRACT FROM AUTHOR]

Background Sleep-disordered breathing (SDB) and Cheyne-Stokes respiration (CSR) are associated with shorter survival in patients with heart failure. A novel treatment method for this patient group is unilateral phrenic nerve stimulation by the remedē® system (Respicardia Inc., Minnetonka, MN, USA), a transvenously implantable neurostimulation device, which has recently been studied in a large randomized, controlled trial. Previous literature has shown efficacy and safety of the treatment with this first-generation device, but hardly any data are available on long-term clinical parameters, the remedē® device's battery lifetime, device exchangeability, lead position stability, surgical accessibility, and manageability. Methods We performed remedē® device replacements in consecutive patients for battery depletion, and documented clinical parameters, longevity, operation procedure, complications, and difficulties. Results All patients were on neurostimulation treatment by phrenic nerve neurostimulation when device replacement became necessary. Apnea-hypopnea index (from 45 ± 4/h to 9 ± 4/h), oxygen-desaturation index (from 35 ± 7/h to 7 ± 6/h), and time spent with oxygen saturation of <90% (T < 90% from 5 ± 7% to 0 ± 0%) were improved and improvements remained constant throughout the 4-year follow-up. Mean battery life was 4.2 ± 0.2 years and mean replacement procedure time was 25 ± 5.1 minutes. Apart from conventional X-ray documentation of stable lead positions in a long-term setting, no radiation or contrast dye usage was needed and no major complications occurred. In addition, clinical exercise capacity and sleepiness symptoms improved. Conclusions Novel remedē® device shows sustained therapy efficacy and safety in terms of stable lead positions over 4 years. Long-term phrenic nerve neurostimulation therapy for central SDB/CSR appears feasible in a clinical routine setting. [ABSTRACT FROM AUTHOR]

Background Treatment of left ventricular electrode dislocation and phrenic nerve stimulation remains an issue in the era of new electrode designs. Methods Safety and efficacy of minimal invasive lead repositioning and pocket opening reposition procedures were evaluated between December 2005 and December 2012 at our center. Minimal invasive method was developed and widely utilized at our center to treat phrenic nerve stimulation. The distally positioned left ventricular lead is looped around by a deflectable catheter in the right atrium introduced from the femoral vein access and then pulled back. Coronary stent implantation was used afterwards for lead stabilization in some patients. Results 42 minimal invasive and 48 electrode repositions with pacemaker pocket opening were performed at 77 patients for left ventricular lead problems. Minimal invasive reposition could be carried out successfully in 69% of (29 patients) cases. Note that in 14.3% of the cases (six patients) minimal invasive procedures were acutely unsuccessful and crossover was necessary. In 16.6% of the cases (seven patients) lead issues were noted later during follow-up. Opening of the pocket could be carried out successfully in 81.2% (39 patients) and was unsuccessful acutely in 6.25% (three patients). Repeated dislocation was noticed, 12.5%, in this group (six patients). Complication during minimal invasive procedures was electrode injury in one case. Pocket openings were associated with several complications: atrial fibrillation, pericardial effusion, fever, hematoma, and right ventricular electrode dislodgement. Conclusion Minimal invasive procedure-as the first line approach-is safe and feasible for left ventricular electrode repositioning in selected cases. [ABSTRACT FROM AUTHOR]

Background Central sleep apnea syndrome, correlated with the occurrence of heart failure, is characterized by periods of insufficient ventilation during sleep. This acute study in 15 patients aims to map the venous system and determine if diaphragmatic movement can be achieved by phrenic nerve stimulation at various locations within the venous system. Methods Subjects underwent a scheduled catheter ablation procedure. During the procedural waiting time, one multielectrode electrophysiology catheter was subsequently placed at the superior and inferior vena cava and the junctions of the left jugular and left brachiocephalic vein and right jugular and right brachiocephalic vein, for phrenic nerve stimulation (1-2 seconds ON/2-3 seconds OFF, 40 Hz, pulse width 210 μs). Diaphragmatic movement was assessed manually and by a breathing mask. During a follow-up assessment between 2 and 4 weeks postprocedure, occurrence of adverse events was assessed. Results In all patients diaphragmatic movement was induced at one or more locations using a median threshold of at least 2 V and maximally 7.5 V (i.e., e 3.3 mA, 14.2 mA). The lowest median current to obtain diaphragmatic stimulation without discomfort was found for the right brachiocephalic vein (4.7 mA). In 12/15 patients diaphragmatic movement could be induced without any discomfort, but in three patients hiccups occurred. Conclusion Diaphragmatic stimulation from the brachiocephalic and caval veins is feasible. Potential side effects should be eliminated by adapting the stimulation pattern. This information could be used to design a catheter, combining cardiac pacing with enhancing diaphragm movement during a sleep apnea episode. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor refers to topics in the issue, including arrhythmogenic role of the LAA in mapping and ablating patients with persistent atrial fibrillation (AF) and long-standing persistent AF (LSPAF).

Background To understand the impact of a quadripolar left ventricular (LV) lead on reverse remodeling and phrenic nerve stimulation (PNS) in congestive heart failure patients treated by cardiac resynchronization therapy at 8-month follow-up (FU). Methods One hundred and fifty-eight patients received an LV Medtronic Performa lead (Medtronic Inc., Minneapolis, MN, USA) and were reevaluated at FU by echocardiography and measurement of electrical parameters. Results A targeted LV lead placement was achieved in 140 (89%) patients. Super responders and responders were 76 (50%) and 26 (18%), respectively, at FU; seven (4%) died and 13 (8%) were hospitalized for any cause. Nonischemic etiology was the only independent predictor of reverse remodeling. The configurations available only with the Performa leads reduced PNS occurrence at 8 V@0.4 ms from 43 (27%) to 14 (9%) of patients at implantation, and from 44 (28%) to 19 (12%) at last FU, compared to configurations available with bipolar leads. Patients with detectable PNS had >10/16 pacing configurations with a PNS safety margin >2 V both at implantation and at FU. During FU 16 (10%) patients had an adverse event possibly related to the lead or to modification of the underlying heart disease but 99% of these events were fixed by reprogramming of the pacing vector. Conclusions Performa Lead enables an increased capability to achieve a targeted lead positioning in the broad clinical scenario of large- and small-volume implanting centers, with a relevant impact on the occurrence of reverse remodeling compared to literature data. The enhanced management of PNS resulted in a dislodgement rate of only 1%. [ABSTRACT FROM AUTHOR]

Background Cardiac resynchronization therapy (CRT) relies on sufficient left ventricular (LV) pacing with safety margin to phrenic nerve stimulation (PNS). Previous studies introduced LV vector reprogramming in bipolar coronary sinus leads to optimize LV pacing and avoid PNS. We investigated the efficacy and reliability of quadripolar leads in CRT. Methods The EffaceQ study enrolled 344 patients with de novo CRT implantation with a quadripolar LV lead in an observational, prospective multicenter study. The study was powered to demonstrate that in at least 90% of patients with an implanted quadripolar LV lead, a viable LV pacing configuration (LVPC) is available (primary end point: LV pacing threshold ≤2.5 V/0.5 ms, sufficient PNS margin). Results Quadripolar leads were successfully implanted in 96% of patients. A total of 278 of 299 (93.0%) patients with complete data met the criteria for viable LVPC. With the use of traditional LVPCs, a viable LVPC would have been available (268 of 299 patients; P = 0.002) in significantly fewer patients (89.6%). In any LVPC, PNS was inducible in 65.0% of patients and 22.6% of patients reported PNS during ambulatory 3-month follow-up. LVPC reprogramming was performed in 49.8% of patients. PNS inducibility decreased from distal to proximal electrodes, whereas LV pacing thresholds increased from distal to proximal. At prehospital discharge, 5.9 ± 2.8 viable LVPCs were observed, stable during follow-up. The quadripolar electrode offered significantly more LVPC for LV optimization and PNS avoidance. Conclusion Quadripolar LV leads yield high numbers of patients with viable LVPCs and alternatives for noninvasive repositioning of LV pacing. [ABSTRACT FROM AUTHOR]

Background Phrenic nerve palsy (PNP) is the most frequently observed complication in the setting of cryoballoon (CB) ablation (Arctic Front, Medtronic Inc., Minneapolis, MN, USA). Although, usually transient, resolving before the end of the procedure, persistent PNP (not resolving before the end of procedure) can occur. Literature on persistent PNP after second generation CB ablation is relatively sparse. Methods A total of 316 consecutive patients having undergone large 28-mm CB ablation as index procedure in the Heart Rhythm Management Center, UZ Brussels, Belgium, from January 2009 to December 2013 were retrospectively reviewed for the study. Of these 117 patients were treated with the first generation CB (CB1) and 199 patients with the second generation CB (CB2). Results PNP occurred in 10% of the total population. Persistent PNP was only observed following CB2 ablation which occurred in 4.5% of the group. At a mean follow-up of 11 months, diaphragmatic contraction in persistent PNP patients resumed in 78% (7/9) of the patients. In a final follow-up at 5 and 20 months, PNP persisted in two patients, respectively. PNP during ablation in the right inferior pulmonary vein was only observed in the CB2 group. No predictors of persistency of PNP were observed. Conclusion Persistence of PNP only occurred in the CB2 group in 4.5% of patients. The majority of patients with persistent PNP were asymptomatic. In most of the patients having persistent PNP after ablation, complete phrenic nerve function resumed during follow-up (78%). [ABSTRACT FROM AUTHOR]

Aims This multicenter acute clinical study was designed to verify novel three-dimensional (3D) quadripolar lead designs that can achieve ≤2.5 V average pacing capture threshold (PCT) not only at the apex, but also at the base of the left ventricle with phrenic nerve stimulation (PNS) avoidance for cardiac resynchronization. Methods During the implant procedure, up to two different left ventricular investigational leads were introduced and tested in the same target coronary vein based on the coronary sinus venogram in a wedged and unwedged position. Adverse events were collected in 30 days following the procedure. Results Eighty-seven leads were tested in 50 patients. When the best performing spiral electrode was chosen from each lead testing, the average of the best PCT on spiral in a wedged position was similar to the unwedged position (1.7 ± 1.5 V vs 1.9 ± 1.5 V, P = ns) and was similar to the wedged tip electrode average PCT (1.7 ± 1.5 V vs 1.6 ± 1.6 V, P = ns). In the majority of patients (89-96%), pacing was achievable in a mid-basal ventricular location without PNS. Conclusions This acute study demonstrated that a 3D quadripolar spiral lead design can achieve acceptable PCTs and avoid PNS without repositioning the lead at implant in the vast majority of patients. It also demonstrated that this lead design can achieve mid-basal ventricular stimulation with low PCT and good acute stability. [ABSTRACT FROM AUTHOR]

Background Recognition of the potential for phrenic nerve injury (PNI) often prompts less aggressive attempts at catheter ablation of multiple forms of tachycardia or abandoning ablation altogether. Some novel techniques to avoid PNI during catheter ablation have been described. Methods Five patients (age: 13-57 years, three females) with ectopic atrial tachycardia originating from the right atrial free wall (RAFW) near the phrenic nerve underwent electrophysiology study with three-dimensional mapping and endocardial cryoablation. Upstream phrenic pacing was performed after cryoadherence was achieved, and cryoablation of ectopic foci was performed during close observation for occurrence of PNI and tachycardia elimination. Results Cryoablation acutely eliminated five of six atrial tachycardias originating close to the phrenic nerve. Transient PNI during cryothermy occurred in two patients, and resolved within 3 minutes. Patients were observed overnight on telemetry, with no early recurrences of targeted atrial tachycardias and no evidence of PNI. At last follow-up of 1-39 months, four patients were arrhythmia free on no medications. Conclusions Catheter cryoablation during simultaneous upstream phrenic nerve pacing can lead to safe and effective elimination of focal atrial tachycardias originating from the RAFW close to the phrenic nerve. [ABSTRACT FROM AUTHOR]

Background Pulmonary vein (PV) isolation with catheter ablation in treating atrial fibrillation carries the risk of injury to phrenic nerve (PN). Left PN (LPN) stimulation continues to be one of the common complications of transvenous left ventricular lead placement during cardiac resynchronization therapy (CRT). Methods and Results In 30 formalin-fixed cadavers, spatial relationship of PNs with PV ostia, left atrial appendage (LAA), and cardiac veins was observed. Segmental location of LPN and cardiac vein crossover was also noted. Right and left PNs coursed abutting the ostium of right superior and left superior PVs in five (16.6%) and one (3.33%) cases, respectively. LPN coursed along the lateral surface of LAA in 20 (66.66%) cases and behind LAA in one (3.33%) case. Out of 18 (60%) cases having two cardiac veins draining free wall of left ventricle (LV) and suitable for CRT lead placement, both cardiac veins were crossed by LPN in two (6.66%) cases. LPN-cardiac vein crossover was located in midlateral segment in 10 (33.3%) cases; mid posterolateral segment in five (16.7%) cases; apical lateral segment and apical posterolateral segment in three (10.0%) cases each. Conclusion PN is highly susceptible to either injury during catheter ablation or stimulation with LV pacing in certain critical locations. Detailed knowledge of spatial relationship of PNs with cardiac structures could help minimize inadvertent complications during these transcatheter electrophysiological procedures. [ABSTRACT FROM AUTHOR]

Background: Catheter ablation of atrial fibrillation has been associated with left-sided phrenic nerve palsy. Knowledge of the individual left phrenic nerve course therefore is essential to prevent nerve injury. The aim of this study was to test the feasibility of an intraprocedural pace mapping and reconstruction of the left phrenic nerve course and to characterize which anatomical areas are affected. Methods: In patients undergoing left atrial catheter ablation, a three-dimensional map of the left atrial anatomical structures was created. The left-sided phrenic nerve course was determined by high-output pace mapping and reconstructed in the map. Results: In this study, 40 patients with atrial fibrillation or atrial tachycardias were included. Left phrenic nerve capture was observed in 23 (57.5%) patients. Phrenic nerve was captured in 22 (55%) patients inside the left atrial appendage, in 22 (55%) in distal parts, in 21 (53%) in medial parts, and in two (5%) in ostial parts of the appendage. In three (7.5%) patients, capture was found in the distal coronary sinus and in one (2.5%) patient in the left atrium near the left atrial appendage ostium. Ablation target was changed due to direct spatial relationship to the phrenic nerve in three (7.5%) patients. No phrenic nerve palsy was observed. Conclusions: Left-sided phrenic nerve capture was found inside and around the left atrial appendage in the majority of patients and additionally in the distal coronary sinus. Phrenic nerve mapping and reconstruction can easily be performed and should be considered prior catheter ablations in potential affected areas. [ABSTRACT FROM AUTHOR]

Background Stability of threshold currents during long-term use of phrenic nerve stimulation has been questioned. Methods and Results Between January 5, 1988, and March 5, 2008, 49 patients with functional C2-tetraplegia received an Atrostim PNS (Atrotech Ltd., Tampere, Finland) as treatment of their respiratory insufficiency; a follow-up of 35 of such patients was carried out exclusively in our institution for 6.3 (4.44) 0.04-15.75 years (mean [standard deviation (SD)] range). The device employed four-pole sequential nerve stimulation, which provided four threshold currents subsequently evaluated for each phrenic nerve. Stimulation data were prospectively recorded. The differences between threshold currents recorded 1 year after implantation and the last recorded values were 0.33-0.43 (0.44-0.63) 0-2.9 mA. After having excluded the data of eight patients with values >1 mA (= mean + SD), we registered the differences for the remaining patients of 0.15-0.24 (0.14-0.24) 0-0.95 mA, which is just twice the adjustment accuracy of the device. Out of the eight problem cases one had, and two were suspected to have, surgical trauma; all three nerves recovered. In two cases the values steadily increasing over years might have been caused by unspecific foreign body reaction. Two cases with values >1mA for different durations at different electrodes might be caused by biofilm, and one patient displaying steadily increasing values lived, unwilling to live, only 2 years after the implantation. Conclusion Thus, there was no permanent nerve injury and in 77% of the presented cases threshold currents remained stable. [ABSTRACT FROM AUTHOR]

Recent clinical and preclinical studies have demonstrated that cryothermal ablation using a balloon catheter (Artic Front®, Medtronic CryoCath LP, Pointe-Claire, Canada) provides an effective means of achieving pulmonary vein isolation. This review explores the biophysics and biomechanics of cryoballoon ablation. Components of the cryoballoon catheter system are examined, mechanisms of cryothermal injury are summarized, and potential advantages of cryoballoon technology over standard radiofrequency ablation in isolating pulmonary veins are discussed. Practical aspects of biophysics and biomechanics relevant to the clinical electrophysiologist are emphasized, particularly with regards to the selection of the most appropriate cryoballoon catheter and minimizing peri-procedural complications. (PACE 2012; 35:1162-1168) [ABSTRACT FROM AUTHOR]

Background: Phrenic nerve (PN) injury is a potential complication that can occur during superior vena cava (SVC) isolation to cure atrial fibrillation (AF). Avoiding radiofrequency (RF) energy delivery is the safer alternative but may result in failed isolation. High-output PN pacing above the ablation site (upstream PN pacing) to confirm whether the PN is intact is a promising technique to avoid PN injury. This study was conducted to elucidate the safety of delivering RF energy at the site of capture of the right PN using upstream high-output pacing during electrical SVC isolation. Methods: SVC isolation was conducted in 41 drug-resistant AF patients. When high-output pacing (25 mA) from the distal tip of the ablation catheter captured the PN at the right atrial-SVC junction, upstream PN pacing (cycle length: 1000-1500 ms) was applied during RF delivery. The application of RF energy was stopped upon the failure or weakness of diaphragmatic twitching. The feasibility of SVC isolation using upstream PN pacing was investigated. Results: In all 41 patients, SVC isolation was successfully achieved. RF energy was delivered at the PN capture site in 26 patients (154 ± 138 second, 18 ± 5 W), and upstream PN pacing was successfully applied in all of the patients. Out of 46 SVC isolations, including five repeated sessions, PN injury occurred in one patient, who recovered spontaneously within 2 weeks. Conclusions: Upstream PN pacing may be effective for the safe completion of SVC isolation and to reduce the severity of PN injury. (PACE 2012; 35:1053-1060) [ABSTRACT FROM AUTHOR]

Background: Phrenic stimulation (PS) may cause intolerable symptoms and prevent CRT delivery in 2-5% of patients. We sought to ensure effective cardiac resynchronization therapy (CRT) delivery by management of PS at the left ventricular (LV) target site. Methods and Results : Two hundred and eleven consecutive patients received a CRT device despite PS occurrence at the LV target site at implantation, when a PS-LV difference >2V was achieved by LV stimulation programming (cathode, pacing vector). PS management strategy both at implantation and at follow-up (FU) aimed to keep the target LV implantation site. LV reverse remodeling was assessed by echocardiography before implantation and at follow-up. LV lead placement was lateral/posterolateral in all the 211 patients; 51 of 211 had detectable PS at FU, 26 of 211 (12.3%) were symptomatic. Symptoms occurred more frequently when PS-LV difference was <3V (16/16 vs 10/35, P < 0.001). Cathode and pacing vector reprogramming improved the PS-LV difference and symptoms in 14 of 23 patients. LV output as threshold +0.5V was helpful to manage PS symptoms in patients with a PS-LV ≤2V at FU. Median FU was 34.9 (16-50) months: 12 patients had tolerable PS symptoms, 76% (39/51) were objective responders at echocardiography compared to 74% (119/160) in patients without PS (P = NS). Conclusions : CRT delivery at long term is feasible despite PS at the target LV site. PS management is mandatory in about 12.3% of patients at FU, with 6.6% remaining symptomatic. Symptoms improve at FU when a PS-LV >3V is achieved. Further improvement in lead manufacturing and pacing electronics are awaited to meet this clinical need. (PACE 2011; 34:1201-1208) [ABSTRACT FROM AUTHOR]

The Quartet model 1458Q (St. Jude Medical, Sylmar, CA, USA) lead is a quadripolar left ventricular (LV) lead with pace/sense capability from four electrodes (tip and three rings). The lead is capable of pacing in 10 different configurations rather than the three that are available in conventional bipolar pacing leads. We describe a single-center initial experience of the use of this lead in patients undergoing cardiac resynchronization therapy (CRT). Twenty-eight patients for a CRT with cardiac defibrillator were implanted between October 2009 and May 2010 with a Quartet lead . Lead position, pacing parameters, stability, complications, and presence of phrenic nerve stimulation (PNS) data were collected at implant and predischarge. Follow-up data were collected at 15 ± 8 weeks for all patients. A Quartet lead was successfully implanted in 96% (27/28) of patients (age 61 ± 15 years; 82% male; ischemic etiology 50%; mean left ventricular [LV] ejection fraction 25 ± 7%; left bundle branch block 68%). PNS was seen at implant in 11 patients (41%) with at least one vector. In eight of these cases (72%), the need for lead repositioning was averted by programming LV pacing utilizing the additional vectors available with the Quartet lead. These initial data suggest that pacing with the Quartet lead is associated with a high implant success rate and stable pacing parameters acutely and at short-term follow-up. The 10 LV pacing vectors available with this lead may allow PNS and capture threshold problems to be easily overcome. (PACE 2011; 34:484-489) [ABSTRACT FROM AUTHOR]

Background: Implantation procedures for cardiac resynchronization therapy (CRT) remain challenging with regard to coronary sinus (CS) cannulation and left ventricular (LV) lead positioning. Technologic advances in catheter design may facilitate CS cannulation and LV lead placement. Aims: To evaluate two different telescoping dual-catheter systems, RAPIDO Guiding Catheter System (Group R) and RAPIDO ADVANCE Guiding Catheter System (Group A) (Guidant Inc. , St. Paul, MN, USA), during implantation of a CRT device. Methods: Seventy-four consecutive patients randomly received a CRT device using the R or A system. Results: An LV lead was successfully implanted in 74 patients (100%). (1) Median times for CS cannulation in groups R and A were 0.3 minutes (range from 0.05 to 14 minutes) and 0.5 minutes (range from 0.05 to 9 minutes), respectively (P = NS). (2) Median times for LV lead placement were 8 minutes (range from 0.8 to 100 minutes) and 3.5 minutes (range from 0.25 to 30 minutes), respectively, for groups R and A (P = 0.032). (3) Median total fluoroscopy times were 12.33 minutes (range from 5 to 70 minutes) and 14.33 minutes (range from 6 to 53 minutes) for groups R and A, respectively (P = NS). (4) Median procedural times for CRT implantation were 80 minutes (range from 40 to 200 minutes) and 75 minutes (range from 45 to 180 minutes) (P = NS) in groups R and A, respectively. There were no major complications. Conclusion: CS cannulation and LV lead placement with a telescopic dual-catheter system is a safe and feasible approach that may reduce fluoroscopy and overall CRT implantation times. Our observations suggest that the RAPIDO ADVANCE System is faster than the RAPIDO System in terms of median time for LV lead positioning. [ABSTRACT FROM AUTHOR]

Background: High left ventricular pacing (LVP) thresholds and phrenic nerve stimulation (PNS) are common problems with cardiac resynchronization (CRT). Newer systems capable of multiple LVP configurations may help overcome these problems without the need for reoperation. Methods: CRT systems capable of multiple LVP configurations (Guidant models H155 and H145) were implanted in 43 patients (study group). An additional 49 patients (control group) received CRT systems (Guidant, Medtronic, Biotronik, St. Jude Medical, various models) lacking this feature. Results: Overall, acute high (≥2.5 V/0.5 ms) LVP thresholds were encountered in 13 (30%) of the study group, and 25 (50%) of control group patients (P = 0.03). PNS was encountered in 5 (12%) of the study group and 12 (24%) of control group patients (P = 0.13). All cases of high LVP thresholds and PNS in the study group were managed by switching to a different LVP configuration, while high thresholds remained in control group patients, and PNS was managed by replacing the lead. The CS lead was successfully placed in a lateral branch in 95% of study group, compared to only 77% of control group patients (P = 0.004). Conclusions: Multiple LVP configurations were clinically useful in a significant number of patients undergoing CRT system implantation by helping to overcome high LVP thresholds and PNS, and by providing more flexibility in placing the LV lead. [ABSTRACT FROM AUTHOR]

SCHUCHERT, A.,et al.: Two-Year Performance of a Preshaped Lead for Left Ventricular Stimulation. Important goals, when implanting a cardiac resynchronization therapy (CRT) system, are to reach a stable LV lead position in a suitable coronary sinus (CS) tributary associated with a low capture threshold and no extracardiac stimulation. The aim of this study was to assess the 2-year performance of a new preshaped lead designed for LV stimulation. The study enrolled 102 patients with heart failure and bundle branch block who underwent implantation of a CRT system, including a sheath-guided, unipolar, S-shaped LV lead placed in a CS tributary. At each follow-up the electrical parameters and CRT system related adverse events were recorded. Eight patients who underwent LV stimulation alone, versus 88 patients who received biventricular CRT systems, were analyzed separately. Access to the CS was reached in 98 patients, and the lead was permanently implanted in 96 (94%) patients. The overall procedural time was 98± 28 minutes. During follow-up, three patients underwent reinterventions for phrenic nerve stimulation (n= 2) and hematoma (n= 1). The capture threshold at implantation was 1.4± 0.9 V with LV versus 1.7± 0.5 V with biventricular stimulation, and after a transient increase, remained between 1.6 and 1.9 V in both configurations. The device measured impedance was significantly higher with LV than with biventricular stimulation at the time of CRT system implantation (698± 296Ω vs 380± 67Ω, P<0.05) and during follow-up. The initial R wave amplitude was 14.3± 5.9 mV in LV versus 8.9± 3.2 V in the biventricular configuration (NS) and 13.8± 7 mV in LV versus 12.8± 4.8 mV in the biventricular configuration at 24 months (NS). Implantation of the S-shaped LV lead for CRT was safe, expeditious, and associated with a high success rate and reliable long-term performance.(PACE 2004; 27:1610–1614) [ABSTRACT FROM AUTHOR]

Temporary epicardial pacing wires are routinely placed in patients undergoing cardiac surgery. Eighteen suitable patients undergoing elective surgery were prospectively studied. Their sensing and stimulating characteristics were studied at various locations. Subepicardial pacing leads were applied to the lateral wall of the LV, apex of the LV, anterior wall of the RV, diaphragmatic wall of the fly, and diaphragmatic wall of the LV. Impedance, B wave amplitude, slew rate, and stimulation thresholds were measured on postoperative days 1 and 5. Impedance remained unchanged in time with no significant differences between locations. B waves and slew rates were significantly lower in the anterior RV wall. Stimulation thresholds displayed no differences on day 1, but they increased significantly in all locations on day 5. These thresholds were significantly lower in the lateral and diaphragmatic LV walls on day 5, and the rate of voltage increase was also lower in these two locations. Five patients presented phrenic nerve stimulation when stimulating the lateral LV wall. The authors advocate the diaphragmatic wall of the LV as the best location for placing temporary leads. The anterior wall of the RV is not recommended for pacing purposes. [ABSTRACT FROM AUTHOR]

Main criticisms about single-pass VDD stimulation in patients with AV block and normal sinus node function concern atrial undersensing in a lead with floating atrial electrodes, and loss of AV synchrony if sinus node dysfunction develops after implantation. We evaluated the concept of a preshaped singlepass lead designed to place the atrial ring electrodes in a constant position close to, or in contact with, the atrial wall. A preshaped lead (Model 2775, Medtronic Inc.) was implanted in 14 patients and followed for up to 2 years. Mean P wave amplitudes (PWAs) were 3.1 mVat implantation, 1.2 mV at predischarge, and 1.3 mV after 12 months. In all patients, minimal PWAs were well above maximal atrial sensitivity of the pacemaker in all body positions during the complete follow-up; atrial undersensing was not observed. Effective atrial stimulation was possible in all patients at implantation (mean stimulation threshold 2.5 V at 0.50 ms), in 11 patients on the first day after implant (mean stimulation threshold 0.22 ms at 5.0 V), in 10 patients after 1 month (mean stimulation threshold 0.57 ms at 5.0 V), and in 10 patients after 1 year (mean stimulation threshold 0.65 ms at 5.0 V). Intermittent phrenic nerve stimulation could be provoked in six patients. In conclusion, the concept of a preshaped single-pass lead facilitated implantation, improved atrial sensing performance, and allowed atrial stimulation in some patients. Still, further improvements are necessary to decrease the atrial stimulation thresholds to acceptable values in all patients. [ABSTRACT FROM AUTHOR]

A multi-channel phrenic nerve stimulator developed in Tampere has been implanted into seven patients with C2-tetraplegia and into three patients with central sleep apneas. Six bipolar cuff electrodes were implanted bilaterally into the neck. Two four-pole cuff and 14 four-pole noncuff electrodes were used in seven patients and to replace one bipolar electrode. Four-pole electrodes were implanted within the thorax. Seven patients achieved total independence from conventional ventilators within 4 months of implantation, and one for 18 hours each day. Two patients died 12 days and 3 months after implantation and two patients after having achieved independence from mechanical ventilators from causes unrelated to the stimulators. Reoperations were necessary because of dislocation of receivers, electrodes, electrode lesions, nerve injuries, and technical failures in seven patients. Most of the problems appeared in two patients with obesity and in three patients with very thin phrenic nerves. Single unit prototypes failed technically more frequently than units of prototype serial fabrication. New electrode design, progress in the manufacture of receivers, and improved implantation technique should help to deminish failures in future. [ABSTRACT FROM AUTHOR]

Presents alternative techniques for electrically activating muscles of the respiratory system and their application in patients with chronic ventilatory insufficiency. Electrical activation of the phrenic nerve using an intramuscular stimulating electrode that is implanted in the diaphragm near the entry point of the phrenic nerve; Electrical activation of intercostals motor units via a single electrode placed on the upper thoracic cervical spinal cord; Electrical activation of the abductor muscles of the vocal cords.

A review of the electrical design of a r/inductively coupled phrenic nerve stimulator/or the diaphragm developed in our laboratories will be discussed. Modifications of the original circuit are based on long-term laboratory and clinical studies. A total implant battery powered stimulator was designed exclusively for animal studies to evaluate the effects of several stimulating parameters on diaphragm fatigue and neuromuscular structure. On the basis of these studies the optimum current level, stimulus frequency, respiratory rate, electrode configuration, and waveform were selected for clinical use to pace the diaphragm. A multiprogrammable dual output stimulator responsive to interrogation has been constructed and used in the experimental laboratory in anticipation of clinical application. There was an insignificant difference between the effect on neural structure or diaphragm function of stimulation with pulse width modulated constant voltage or with amplitude-modulated constant current. Demand pacing: maintenance of normal PACO2 by monitoring ET PACO2 with feedback to the diaphragm pacemaker to adjust the pacing rate has been successful in the experimental animal. [ABSTRACT FROM AUTHOR]

Records were reviewed of 477 patients who had diaphragm pacemakers implanted for treatment of chronic hypoventilation. Three groups were established for comparison. (1) Center group: 165 patients operated on in six medical centers participating in a cooperative study; (2) Noncenter group, sufficient data available: 203 patients operated on by surgeons with experience limited to a few cases; (3) Nonstudy group, minimal data available: 109 patients operated on as in group 2; vital statistics only were contributed. The protocol for data gathering was comprised of 154 major variables. Basic data on age, sex, diagnosis and etiology were analyzed for homogenicity of data among the groups. A comprehensive analysis of the pacing methods, complication and results from the Center group yielded information on the early experience with diaphragm pacing important to its future application. [ABSTRACT FROM AUTHOR]

Since 1976 we have implanted bilateral diaphragm pacers in 34 infants and children: 26 with central hypoventilation syndrome (CHS), three with myelomeningocele, and five with quadriplegia. Compared to adults, several modifications have been necessary to achieve effective ventilation in infants and younger children. In all instances, a tracheostomy has been necessary due to impaired neuromuscular control of upper airway patency during pacing. Bilateral pacing has been necessary to achieve adequate ventilation; in the CHS children with normal awake ventilation, bilateral pacing during sleep eliminates the need for positive pressure ventilation. For the remaining children, adequate awake ventilation is achieved with bilateral pacing, thus permitting substantially greater mobility and limiting use of the ventilator to sleep time. Our longest survivor has now been paced for 10.7 years, and in no instance has phrenic nerve damage occurred secondary to electrical stimulation. Our current pacing regime is characterized by moderate respiratory rates (21 breaths/min), long interpulse intervals (95 ms), and short inspiratory times (0.6 sec], resulting in 50%-75% fewer stimuli/min compared to our previous regime. For all infants and children requiring 24-hour ventilatory assistance, our recent successes in maintaining ventilation using significantly fewer stimuli suggest that long-term continuous pacing is a realistic future goal. [ABSTRACT FROM AUTHOR]

Phrenic nerve stimulators (diaphragm pacers) were implanted in 20 patients with partial or total respiratory insufficiency of central nervous origin and chronic singultus. A 2-84 months follow-up (M = 41), 10 patients are entirely independent of a conventional respirator, two patients are partially dependent on respirator, three patients are dead, and five patients including two with hiccups had limited or no help from diaphragm pacing. [ABSTRACT FROM AUTHOR]

The article focuses on phrenic electrostimulation. Probably the first successful restoration of normal breathing through electrotherapy was achieved in 1807. The major impetus to phrenic electrostimulation endeavors came, however, from complications entrained by chloroform anesthesia. Indeed, the obligatory inclusion of electroresuscitation equipment in operating theaters derives directly from that epoch. The majority, by far, of circumstances dictating recourse to phrenic electrostimulation have been acute in nature, with corresponding restriction of therapy to mere minutes or hours.

The article reports that diaphragm pacemaker consists of four parts: a radiofrequency transmitter, an external coil or antenna, a radiofrequency (RF) receiver, and one or two phrenic nerve electrodes. The programmed RF pulses are transmitted via the antenna through the intact skin to the subcutaneously placed RF receiver where they are converted to electrical pulses and delivered via wire electrodes to the phrenic nerve. The electronic apparatus has been described in detail elsewhere. Pacing will also fail in conditions marked by progressive disease or injury to the phrenic nerves, lungs and diaphragm.

Interruption of atrial flutter and fibrillation by RF catheter ablation may be favored by large, elongated lesions. We administered RF current in unipolar and bipolar mode in porcine right atrium. Bipolar ablation was performed between the tip electrodes of two serially coupled catheters. With 4-mm tip electrodes in vitro, lesion length increased from a mean (SD) of 7.9 (1.2) mm at 3 mm interelectrode distance (IED) to 13.3 (3.3) mm at 9-mm IED, but decreased at 12-mm IED due to nonconfluent lesions (P < 0.0001). With 4 mm distal electrodes and 8 mm IED, bipolar lesions were 65% longer than corresponding unipolar ablations. Switching to bipolar mode increased the lesion length more than increasing electrode tip length to 6 mm in unipolar mode. Power and temperature controlled ablation created equally sized lesions. Twelve anesthetized pigs were randomized to unipolar or two catheter bipolar temperature controlled ablation of the right atrial free wall. Bipolar ablation created confluent lesions with endocardial length × width of 13.5(5.8) × 7.3 (3.7) mm, unipolar ablation 6.4(2.8) × 4.6 (1.4) mm (P < 0.001 when comparing length and P = 0.013 for lesion width). The atrial lesions in both groups were transmural and extended into hilar lung lesions with maximal depth of 3.0 (1.1) and 2.6 (1.0) mm, respectively (P = 0.44). Five bipolarly and four unipolarly ablated pigs developed right diaphragmal paresis. We conclude that bipolar ablation may be preferable in situations where large, elongated lesions are favorable. The two catheter technique is feasible in porcine right atrium. Both bipolar and unipolar ablation of the porcine right atria! free wall may frequently be complicated by injury to the phrenic nerve and adjacent lung tissue. [ABSTRACT FROM AUTHOR]

We sought to determine the international experience with the quadripolar diaphragm pacer system and to test two hypotheses: the incidence of pacer complications would be (1) increased among pediatric as compared to adult patients; and (2) highest among active pediatric patients with idiopathic congenital central hypoventilation syndrome (CCHS). Data were collected via a questionnaire coupled with the Atrotech Registry data for a total of 64 patients (35 children and 29 adults)from 14 countries. Thoracic implantation of electrodes and bilateral pacer use each occurred in 94% of all subjects. Tetraplegic (vs pediatric CCHS) patients were more typically paced 24 hours/day (P = 0.001). Pacing duration averaged 2.0 ± 1.0 years among children and 2.2 ± 1.1 years among adults. Infections occurred among 2.9% of surgical procedures, all in pediatric CCHS patients (vs pediatric tetraplegic patients, P = 0.01). The incidence of mechanical trauma was 3.8%, without significant differences among patient groups. The incidence of presumed electrode and receiver failure were 3.1% and 5.9%, respectively, with internal component failure greater among pediatric CCHS than pediatric tetraplegic patients (P < 0.01). Intermittent or absent function of 0–4 electrode combinations occurred among 19% of all patients, with increased frequency among pediatric CCHS than pediatric tetraplegic patients (P < 0.03). Complication-free successful pacing occurred in 60% of pediatric and 52% of adult patients. In all, 94% of the pediatric and 86% of the adult patients paced successfully after the necessary intervention. Although pacer complications were not increased among pediatric as compared to adult patients, the incidence of complications was highest among the active pediatric patients with CCHS. Longitudinal study of these patients will provide invaluable information for modification and improvement of the quadripolar system. [ABSTRACT FROM AUTHOR]

Diaphragmatic stimulation as a complication of cardiac pacing due to right ventricular perforation of an endocardial lead or penetration of a screw-in lead along the right atrial free wall, adjacent to the right phrenic nerve, has previously been described. A case of diaphragmatic pacing due to inadvertent insertion of a temporary pacing lead into the left pericardiophrenic vein via the left internal jugular vein is presented and anatomical considerations are discussed. [ABSTRACT FROM AUTHOR]

Transcatheter ablation of the pulmonary veins (PVs) has been established as a therapeutic option for patients with symptomatic atrial fibrillation. Cryothermal energy is an alternative energy source that has been developed to overcome some of the disadvantages of radiofrequency ablation. The major complication of the cryoballoon technique seems to be right-sided phrenic nerve injury (PNI) following ablation of the right superior PV. This case report describes a left-sided PNI after cryoballoon ablation of the left superior PV. (PACE 2012; 35:e334-e336) [ABSTRACT FROM AUTHOR]

The authors reflect on phrenic nerve pacing during atrial ablation and on the article "Electrical Isolation of the Superior Vena Cava Using Upstream Phrenic Pacing to Avoid Phrenic Nerve Injury" by T. Kimura et al. They suggest that Kimura et al should be congratulated on informing readers about the benefits of using phrenic nerve pacing to avoid phrenic nerve injury during ablation. They argue that physicians who perform ablation should be familiar with the benefits of phrenic pacing.

Although transvenous access to the coronary veins has considerably simplified left ventricular (LV) pacing, it can remain a time consuming and arduous task achieving satisfactory pacing positions for the LV electrode. Common problems include negotiating small veins with adequate guide catheter stability, pacing electrode stability once positioned, and phrenic nerve stimulation. We report a case where use of the pacing lead guidewire resulted in a dramatic reduction in the pacing threshold of the LV lead, and saved the patient the need to undergo thoracotomy placement. [ABSTRACT FROM AUTHOR]

LEE, B.-K.,et al.: Right Phrenic Nerve Injury Following Electrical Disconnection of the Right Superior Pulmonary Vein. This report describes a case of transient paresis of the right diaphragm following the transcatheter radiofrequency ablation for the electrical disconnection of pulmonary veins, which recovered completely during the observational period in a 61-year-old woman with paroxysmal atrial fibrillation. For electrical disconnection of pulmonary veins, careful preventive measures for phrenic nerve damage are required.(PACE 2004; 27:1444–1446) [ABSTRACT FROM AUTHOR]