Right ventricular function and its coupling to pulmonary circulation predicts exercise tolerance in systolic heart failure.

AIMS: Right ventricular (RV) dysfunction, pulmonary hypertension, and exercise intolerance have prognostic values, but their interrelation is not fully understood. We investigated how RV function alone and its coupling with pulmonary circulation (RV-PA) predict cardio-respiratory fitness in patients with heart failure and reduced ejection fraction (HFrEF). METHODS AND RESULTS: The Evaluation of Resynchronization Therapy for Heart Failure (EARTH) study included 205 HFrEF patients with narrow (n = 85) and prolonged (n = 120) QRS duration undergoing implantable cardioverter defibrillator implantation. All patients underwent a comprehensive evaluation with exercise tolerance tests and echocardiography. We investigated the correlations at baseline between RV parameters {size, function [tricuspid annular plane systolic excursion (TAPSE), RV fractional area change (RV-FAC), and RV myocardial performance index (RV-MPI)], pulmonary artery systolic pressure (PASP), and tricuspid regurgitation}; left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume index (LVEDVi), and left atrial volume index (LAVi); and cardiopulmonary exercise test (CPET) [peak VO2 , minute ventilation/carbon dioxide production (VE/VCO2 ), 6 min walk distance (6MWD), and submaximal exercise duration (SED)]. We also studied the relationship between RV-PA coupling (TAPSE/PASP ratio) and echocardiographic parameters in patients with both data available. Univariate and multivariate linear regression models were used. Patients enrolled in EARTH (overall population) were mostly male (73.2%), mean age 61.0 ± 9.8 years, New York Heart Association class II-III (87.8%), mean LVEF of 26.6 ± 7.7%, and reduced peak VO2 (15.1 ± 4.6 mL/kg/min). Of these, 100 had both TAPSE and PASP available (TAPSE/PASP population): they exhibited higher BNP, wider QRS duration, larger LVEDVi, with more having tricuspid regurgitation compared with the 105 patients for whom these values were not available (all P < 0.05). RV-FAC (ß = 7.5), LAVi (ß = -0.1), and sex (female, ß = -1.9) predicted peak VO2 in the overall population (all P = 0.01). When available, TAPSE/PASP ratio was the only echocardiographic parameter associated with peak VO2 (ß = 6.8; P < 0.01), a threshold ≤0.45 predicting a peak VO2  ≤ 14 mL/kg/min (0.39 for VO2  ≤ 12). RV-MPI was the only echocardiographic parameter associated with ventilatory inefficiency (VE/VCO2 ) and 6MWD (ß = 21.9 and ß = -69.3, respectively, both P ≤ 0.01) in the overall population. In presence of TAPSE/PASP, it became an important predictor for those two CPET (ß = -18.0 and ß = 72.4, respectively, both P < 0.01), together with RV-MPI (ß = 18.5, P < 0.01) for VE/VCO2 . Tricuspid regurgitation predicted SED (ß = -3.2, P = 0.03). CONCLUSIONS: Right ventricular function assessed by echocardiography (RV-MPI and RV-FAC) is closely associated with exercise tolerance in patients with HFrEF. When the TAPSE/PASP ratio is available, this marker of RV-PA coupling becomes the stronger echocardiographic predictor of exercise capacity in this population, highlighting its potential role as a screening tool to identify patients with reduced exercise capacity and potentially triage them to formal peak VO2 and/or evaluation for advanced HF therapies.

Pulmonary Vein Stenosis After Atrial Fibrillation Ablation: Insights From the ADVICE Trial.

BACKGROUND: Pulmonary vein (PV) stenosis is a complication of atrial fibrillation (AF) ablation. The incidence of PV stenosis after routine post-ablation imaging remains unclear and is limited to single-centre studies. Our objective was to determine the incidence and predictors of PV stenosis following circumferential radiofrequency ablation in the multicentre Adenosine Following Pulmonary Vein Isolation to Target Dormant Conduction Elimination (ADVICE) trial. METHODS: Patients with symptomatic AF underwent circumferential radiofrequency ablation in one of 13 trial centres. Computed tomographic (CTA) or magnetic resonance (MRA) angiography was performed before ablation and 90 days after ablation. Two blinded reviewers measured PV diameters and areas. PVs with stenosis were classified as severe (> 70%), moderate (50%-70%), or mild (< 50%). Predictors of PV stenosis were identified by means of multivariable logistic regression. RESULTS: A total of 197 patients (median age 59.5 years, 29.4% women) were included in this substudy. PV stenosis was identified in 41 patients (20.8%) and 47 (8.2%) of 573 ablated PVs. PV stenosis was classified as mild in 42 PVs (7.3%) and moderate in 5 PVs (0.9%). No PVs had severe stenosis. Both cross-sectional area and diameter yielded similar classifications for severity of PV stenosis. Diabetes was associated with a statistically significant increased risk of PV stenosis (OR 4.91, 95% CI 1.45-16.66). CONCLUSIONS: In the first systematic multicentre evaluation of post-ablation PV stenosis, no patient acquired severe PV stenosis. Although the results are encouraging for the safety of AF ablation, 20.8% of patients had mild or moderate PV stenosis, in which the long-term effects are unknown.

Effect of Direct Oral Anticoagulants, Warfarin, and Antiplatelet Agents on Risk of Device Pocket Hematoma: Combined Analysis of BRUISE CONTROL 1 and 2.

BACKGROUND: Oral anticoagulant use is common among patients undergoing pacemaker or defibrillator surgery. BRUISE CONTROL (Bridge or Continue Coumadin for Device Surgery Randomized Controlled Trial; NCT00800137) demonstrated that perioperative warfarin continuation reduced clinically significant hematomas (CSH) by 80% compared with heparin bridging (3.5% versus 16%). BRUISE-CONTROL-2 (NCT01675076) observed a similarly low risk of CSH when comparing continued versus interrupted direct oral anticoagulant (2.1% in both groups). Using patient level data from both trials, the current study aims to: (1) evaluate the effect of concomitant antiplatelet therapy on CSH, and (2) understand the relative risk of CSH in patients treated with direct oral anticoagulant versus continued warfarin. METHODS: We analyzed 1343 patients included in BRUISE-CONTROL-1 and BRUISE-CONTROL-2. The primary outcome for both trials was CSH. There were 408 patients identified as having continued either a single or dual antiplatelet agent at the time of device surgery. RESULTS: Antiplatelet use (versus nonuse) was associated with CSH in 9.8% versus 4.3% of patients (P<0.001), and remained a strong independent predictor after multivariable adjustment (odds ratio, 1.965; 95% CI, 1.202-3.213; P=0.0071). In multivariable analysis, adjusting for antiplatelet use, there was no significant difference in CSH observed between direct oral anticoagulant use compared with continued warfarin (odds ratio, 0.858; 95% CI, 0.375-1.963; P=0.717). CONCLUSIONS: Concomitant antiplatelet therapy doubled the risk of CSH during device surgery. No difference in CSH was found between direct oral anticoagulant versus continued warfarin. In anticoagulated patients undergoing elective or semi-urgent device surgery, the patient specific benefit/risk of holding an antiplatelet should be carefully considered. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifiers: NCT00800137, NCT01675076.

Lead Extraction With Baffle Stenting in Adults With Transposition of the Great Arteries.

OBJECTIVES: This study sought to assess the feasibility, safety, and outcomes of a stepwise combined percutaneous approach that includes transvenous lead extraction (TLE) followed by baffle stenting and device reimplantation in patients with D-transposition of the great arteries (D-TGA) and atrial baffle dysfunction. BACKGROUND: Management of baffle leak or stenosis in patients with D-TGA and atrial switch surgery is challenging in the presence of transvenous cardiac implantable electronic devices. Baffle complications hinder device-related interventions and addressing baffle dysfunction often requires TLE. METHODS: All consecutive patients with D-TGA and TLE followed by a percutaneous baffle intervention at the Montreal Heart Institute between 2009 and 2018 were enrolled. RESULTS: Ten patients, median 38.6 years of age (range 15.2 to 50.6 years), 5 males (50.0%) were included. Procedures were performed for a device-related indication in 5 patients (50.0%) and for baffle dysfunction in 5 patients (50.0%). A total of 19 leads (17 pacing, 2 defibrillation) were targeted, with a median time from implantation of 8.7 (range 4.3 to 22.1) years. A laser sheath was most frequently required for successful TLE, which was achieved in all patients. Immediate baffle stenting was performed in 9 patients (90.0%) and immediate device reimplantation in 6 (60.0%). During a median follow-up of 3.0 (range 0.1 to 8.2) years, the only complication was subpulmonary atrioventricular valve damage requiring surgery in 1 patient, 8 months after the procedure. CONCLUSIONS: A combined approach with TLE followed by baffle stenting and reimplantation appears to be safe and feasible in D-TGA patients with atrial switch, baffle dysfunction, and transvenous leads.

Atrial fibrillation in young patients.

INTRODUCTION: Atrial fibrillation (AF) is the most frequent arrhythmia worldwide. While mostly seen in elderly, it can also affect young adults (≤ 45 years of age), older adolescent, and children. Areas covered: The aim of this review is to provide an overview of the current management of AF in young patients. Specific issues arise over diagnostic workup as well as antiarrhythmic and anticoagulation therapies. The future management and diagnostic strategies are also discussed. Expert commentary: Management of AF in the young adult is largely extrapolated from adult studies and guidelines. In this population, AF could reveal a genetic pathology (e.g. Brugada, Long QT or Short QT syndromes) or be the initial presentation of a cardiomyopathy. Therefore, thorough workup in the young population to eliminate potential malignant pathology.

Reducing radiation exposure during procedures performed in the electrophysiology laboratory.

INTRODUCTION: Expert societies recently published strong recommendations to reduce the exposure of patients and staff to ionizing radiation (IR) during interventional and electrophysiology (EP) procedures. However, adherence to these guidelines remains difficult and the impact of implementing such recommendations is poorly characterized. METHODS AND RESULTS: We conducted a single-center cohort study to quantify radiation exposure over time in three EP laboratories at the Montreal Heart Institute during 5,546 consecutive procedures from 2012 to 2015 by 11 primary operators. Overall, 2,618 (47.2%) procedures were catheter-based and 2,928 (52.8%) were device interventions. Interventions to reduce radiation exposure included educational initiatives to raise awareness (i.e., limiting cine acquisition, patient position, table height), slower frame rate, lower radiation dose per pulse, collimation, and integration with 3-D mapping systems and/or MediGuide technology. An 85% reduction in IR exposure was observed from 2012 to 2015, with the mean dose-area-product (DAP) decreasing from 7.65 ± 0.05 Gy·cm2 to 1.15 ± 0.04 Gy·cm2 (P < 0.001). This was true for catheter-based procedures (mean DAP 16.99 ± 0.08 to 2.00 ± 0.06 Gy·cm2 , P < 0.001) and device interventions (mean DAP 4.18 ± 0.06 to 0.64 ± 0.05 Gy·cm2 , P < 0.001). The median effective dose of IR recorded per quarter by 282 cervical dosimeters on EP staff decreased from 0.57 (IQR 0.18, 1.03) mSv in 2012 to 0.00 (IQR 0.00, 0.19) mSv in 2015, P < 0.001. CONCLUSION: Enforcing good clinical practices with simple measures and low-dose fluoroscopy settings are highly effective in reducing IR exposure in the EP lab. These promising results should encourage other EP labs to adopt similar protective measures.

Focal Transcatheter Cryoablation: Is a Four-Minute Application Still Required?

INTRODUCTION: The standard 4-minute application time for transcatheter cryoablation was determined in the 1990s when the system employed less potent chlorofluorocarbon refrigerants. The current refrigerant, nitrous oxide, generates substantially colder temperatures, with a faster cooling rate. METHODS AND RESULTS: We conducted a preclinical study on 32 mongrel dogs with stratified randomization of right atrial, right ventricular, and left ventricular chambers to 2-minute versus 4-minute application times using 8-mm electrode tip cryocatheters (Freezor Max, Medtronic CryoCath LP, Montreal, Canada). Animals were sacrificed one month after the procedure. Three-dimensional morphometric analyses were conducted in a blinded fashion. A total of 193 identified ablation lesions were processed for histological analyses, 102 with 2-minute applications and 91 with 4-minute applications. Ablation lesion surface area (167.8 ± 21.6 mm2 vs. 194.3 ± 22.6 mm2 , P = 0.40), maximum depth (4.4 ± 0.2 mm vs. 4.5 ± 0.2 mm, P = 0.71), and volume (125.7 ± 69.5 mm3 vs. 141.0 ± 83.5 mm3 , P = 0.25) were similar between groups. Overall, 90.2% of ablation lesions in the right atrium were transmural, 45.6% in the right ventricle, and 2.4% in the left ventricle, with no differences between 2-minute and 4-minute application times (P = 0.55). Thrombus was detected on the endocardial surface of 0.0% and 3.3% of ablation lesions created with 2-minute and 4-minute application times, respectively (P = 0.10). CONCLUSION: Single 2-minute and 4-minute application times result in catheter ablation lesions of similar size using the modern cryoablation system with nitrous oxide as a refrigerant. While these findings suggest the potential to reduce the standard 4-minute application time, further studies are required to compare clinical efficacy.

Canadian Registry of Implantable Electronic Device Outcomes: Surveillance of the Riata Lead Under Advisory.

BACKGROUND: The Riata lead under advisory has posed a unique clinical scenario where inside-out abrasion results in externalization of conductor cables, with a higher risk of electrical failure. We developed a comprehensive registry to assist with clinical management of this lead. METHODS AND RESULTS: This Canadian registry reports the findings of 3763 (74.2% of all Riata leads in Canada) Riata leads under advisory, with a mean follow-up time of 8.9±1.5 years. The overall electrical failure rate was 5.2% at 8 years, with no difference between 7-French and 8-French lead models. Cable externalization was found to be more common in the 8-French model (12.3% versus 5.2%, P<0.0001) and was associated with a higher risk of electrical failure. Predictors of electrical lead failure included cable externalization, higher left ventricular ejection fraction, younger age, higher body mass index, and a passive fixation lead. One patient died due to electrical failure, a further 2 patients survived an event where the device failed to deliver high-voltage therapy. Major complications because of lead extraction were higher when compared with lead abandonment, no difference among lead model observed. Two deaths occurred as a consequence of lead extraction, in the context of an underlying infection. CONCLUSIONS: The Riata lead under advisory has a steady electrical failure rate over time. There are identifiable predictors of lead failure that can assist with clinical decisions as to whether lead revision should be performed prophylactically.

Redefining the Blanking Period After Catheter Ablation for Paroxysmal Atrial Fibrillation: Insights From the ADVICE (Adenosine Following Pulmonary Vein Isolation to Target Dormant Conduction Elimination) Trial.

BACKGROUND: Early recurrences (ERs) of atrial tachyarrhythmia are common after catheter ablation of atrial fibrillation. A 3-month blanking period is recommended by current guidelines. This study sought to investigate the significance of ER during the first 3 months post ablation in predicting late recurrences and determine whether it varies according to timing. METHODS AND RESULTS: A total of 401 patients with paroxysmal atrial fibrillation undergoing pulmonary vein isolation were followed for 12 months with transtelephonic monitoring in the ADVICE (Adenosine Following Pulmonary Vein Isolation to Target Dormant Conduction Elimination) trial. Patients with atrial tachyarrhythmia ≥30 s within the 3-month blanking period were stratified according to the timing of ER. A total of 179 patients (44.6%) experienced their last episode of ER during the first (n=53), second (n=44), or third (n=82) month of the 3-month blanking period. One-year freedom from symptomatic atrial tachyarrhythmia was 77.2% in patients without ER compared with 62.6%, 36.4%, and 7.8% in patients with ER 1, 2, and 3 months post ablation, respectively (P<0.0001). Receiver operating curve analyses revealed a strong correlation between the timing of ER and late recurrence (area under the curve 0.82, P<0.0001). Corresponding hazard ratios for ER during the first, second, and third months were 1.84, 4.45, and 9.64, respectively. CONCLUSIONS: This study validates the use of a blanking period after catheter ablation for paroxysmal atrial fibrillation but calls into question the 90-day cut-off value. In particular, >90% of patients with ER during the third month post ablation experience late recurrence by 1 year. However, pending further study, repeat ablation before 90 days cannot be routinely advocated. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01058980.

Reducing Radiation Exposure During CRT Implant Procedures: Single-Center Experience With Low-Dose Fluoroscopy Settings and a Sensor-Based Navigation System (MediGuide).

INTRODUCTION: Cardiac resynchronization therapy (CRT) implant procedures are often complex and prolonged, resulting in substantial ionizing radiation (IR) exposure to the patient and operator. We assessed the impact of lower-dose fluoroscopy settings and a sensor-based electromagnetic tracking system (MediGuide™, MDG) on reducing IR exposure during CRT implantation. METHODS: A single-center 2-group cohort study was conducted on 348 consecutive patients, age 66.4 ± 11.0 years, 80.4% male, with CRT implant procedures from 2013 to 2015. Patients were arbitrarily assigned to MDG (N = 239) versus no MDG (N = 109) guidance. Lower-dose fluoroscopy settings were adopted in January 2015 (3 instead of 6 fps; 23 instead of 40 nGy/pulse; N = 101). RESULTS: Overall, MDG was associated with an 82.1% reduction in IR exposure (393 µGray·m2 vs. 2191 µGray·m2 , P < 0.001). Lower-dose fluoroscopy resulted in a 59.5% reduction in IR-exposure without MDG (1055 µGray·m2 vs. 2608 µGray·m2 , P < 0.001) and 81.8% reduction with MDG (108 µGray·m2 vs. 595 µGray·m2 , P < 0.001). Low-dose fluoroscopy combined with MDG was associated with a 95.9% lower exposure to IR when compared to standard fluoroscopy without MDG (108 µGray·m2 vs. 2608 µGray·m2 , P < 0.001). Procedures with MDG were shorter (96 minutes vs. 123 minutes, P < 0.001) and associated with a trend towards a higher success rate (94.6% vs. 89.0%, P = 0.062), with fewer coronary sinus cannulation failures (2.1% vs. 6.4%, P = 0.040). CONCLUSION: Low-dose fluoroscopy settings are highly effective (>50%) in reducing IR exposure during CRT implant procedures. When combined with MDG, >95% reduction in IR exposure is achieved. Moreover, MDG shortens procedural duration and may improve acute procedural outcomes.

Adenosine-guided pulmonary vein isolation for the treatment of paroxysmal atrial fibrillation: an international, multicentre, randomised superiority trial.

BACKGROUND: Catheter ablation is increasingly used to manage atrial fibrillation, but arrhythmia recurrences are common. Adenosine might identify pulmonary veins at risk of reconnection by unmasking dormant conduction, and thereby guide additional ablation to improve arrhythmia-free survival. We assessed whether adenosine-guided pulmonary vein isolation could prevent arrhythmia recurrence in patients undergoing radiofrequency catheter ablation for paroxysmal atrial fibrillation. METHODS: We did this randomised trial at 18 hospitals in Australia, Europe, and North America. We enrolled patients aged older than 18 years who had had at least three symptomatic atrial fibrillation episodes in the past 6 months, and for whom treatment with an antiarrhythmic drug failed. After pulmonary vein isolation, intravenous adenosine was administered. If dormant conduction was present, patients were randomly assigned (1:1) to additional adenosine-guided ablation to abolish dormant conduction or to no further ablation. If no dormant conduction was revealed, randomly selected patients were included in a registry. Patients were masked to treatment allocation and outcomes were assessed by a masked adjudicating committee. Patients were followed up for 1 year. The primary outcome was time to symptomatic atrial tachyarrhythmia after a single procedure in the intention-to-treat population. The trial is registered with ClinicalTrials.gov, number NCT01058980. FINDINGS: Adenosine unmasked dormant pulmonary vein conduction in 284 (53%) of 534 patients. 102 (69·4%) of 147 patients with additional adenosine-guided ablation were free from symptomatic atrial tachyarrhythmia compared with 58 (42·3%) of 137 patients with no further ablation, corresponding to an absolute risk reduction of 27·1% (95% CI 15·9-38·2; p<0·0001) and a hazard ratio of 0·44 (95% CI 0·31-0·64; p<0·0001). Of 115 patients without dormant pulmonary vein conduction, 64 (55·7%) remained free from symptomatic atrial tachyarrhythmia (p=0·0191 vs dormant conduction with no further ablation). Occurrences of serious adverse events were similar in each group. One death (massive stroke) was deemed probably related to ablation in a patient included in the registry. INTERPRETATION: Adenosine testing to identify and target dormant pulmonary vein conduction during catheter ablation of atrial fibrillation is a safe and highly effective strategy to improve arrhythmia-free survival in patients with paroxysmal atrial fibrillation. This approach should be considered for incorporation into routine clinical practice. FUNDING: Canadian Institutes of Health Research, St Jude Medical, Biosense-Webster, and M Lachapelle (Montreal Heart Institute Foundation).

Impact of a Novel Catheter Tracking System on Radiation Exposure during the Procedural Phases of Atrial Fibrillation and Flutter Ablation.

BACKGROUND: Fluoroscopic guidance is used to position catheters during cardiac ablation. We evaluated the impact of a novel nonfluoroscopic sensor-guided electromagnetic navigation system (MG) on radiation exposure during catheter ablation of atrial fibrillation (AF) or atrial flutter (AFL). METHODS: A total of 134 consecutive patients referred for ablation of AF (n = 44) or AFL (n = 90) ablation were prospectively enrolled. In one group the MG system was used for nonfluoroscopic catheter positioning, whereas in the conventional group standard fluoroscopy was utilized. Fluoroscopy times were assessed for each stage of procedure and total radiation exposure was quantified. RESULTS: Patient characteristics were similar between the groups. The procedural end point was achieved in all. Median (interquartile range [IQR]) fluoroscopy times were 12.5 minutes (7.6, 17.4) MG group versus 21.5 minutes (15.3, 23.0) conventional group (P < 0.0001) for AF ablation, and 0.8 minutes (0.4, 2.5) MG group versus 9.9 minutes (5.1, 22.5) conventional group (P < 0.0001) for AFL ablation. Median (IQR) total radiation exposure (µGy·m(2)) was 1,107 (906, 2,033) MG group versus 2,835 (1,688, 3,855) conventional group (P = 0.0001) for AF ablation, and 161 (65, 537) MG group versus 1,651 (796, 4,569) conventional group (P < 0.0001) for AFL ablation. No difference in total procedural time was seen. CONCLUSIONS: The use of a novel nonfluoroscopic catheter tracking system is associated with a significant reduction in radiation exposure during AF and AFL ablation (61% and 90% reduction, respectively). In the era of heightened awareness of the importance of radiation reduction, this system represents a safe and efficient tool to decrease radiation exposure during electrophysiological ablation procedures.

Reducing radiation exposure during CRT implant procedures: early experience with a sensor-based navigation system.

BACKGROUND: Cardiac resynchronization therapy (CRT) implant procedures are often complex and prolonged, resulting in significant ionizing radiation (IR) exposure to the patient and operator. We report our early experience working with a novel sensor-based electromagnetic tracking system (MediGuide™, MDG, St. Jude Medical Inc., St. Paul, MN, USA), in terms of procedural IR exposure reduction. METHODS AND RESULTS: Information regarding patient demographics, procedural details, procedural duration, and IR exposure were prospectively collected on 130 consecutive CRT procedures performed between January 2013 and January 2014. Sixty procedures were performed with MDG guidance, and 70 were performed without MDG guidance. Despite a nonsignificant trend toward shorter procedure duration with the use of MDG (120 minutes vs 138 minutes with non-MDG, P = 0.088), a 66% reduction in total IR exposure (median 769 µGray · m(2) vs 2,608 µGray · m(2), P < 0.001) was found. This reduction was primarily driven by a >90% reduction in IR dose required to cannulate the coronary sinus (median 80 µGray · m(2) vs 922 µGray · m(2), P < 0.001), and to a lesser extent from a reduction in IR dose required for LV lead placement (median 330 µGray·m(2) vs 737 µGray · m(2), P = 0.059). In addition, a significant learning curve effect was observed with a significantly shorter procedural duration for the last 15 cases compared to the first 15 cases (median 98 minutes vs 175 minutes, P < 0.001). CONCLUSION: The nonfluoroscopic MDG positioning system is associated with a dramatic reduction in exposure to IR during CRT implant procedures, with a 90% decrease in the IR dose required to cannulate the coronary sinus. A steep learning curve was quantified.

Pulmonary vein isolation using "contact force" ablation: the effect on dormant conduction and long-term freedom from recurrent atrial fibrillation--a prospective study.

BACKGROUND: Atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) is associated with PV to left atrium reconduction. Effective lesion creation necessitates adequate contact force between the ablation catheter and myocardium. OBJECTIVE: The purpose of this study was to study the utility of contact force-guided ablation on immediate and long-term outcomes. METHODS: Seventy-five patients with highly symptomatic paroxysmal AF underwent wide circumferential PVI using an irrigated-tip radiofrequency catheter. In 25 patients, ablation was guided by real-time contact force measurements (CF group; SmartTouch, Biosense Webster). A control group of 50 patients underwent PVI using a standard nonforce sensing catheter (standard group; ThermoCool, Biosense Webster). After PVI, all patients underwent adenosine testing to unmask dormant conduction. Patients were followed up at 3, 6, and 12 months and by transtelephonic monitoring as well. RESULTS: Dormant conduction was unmasked and subsequently eliminated in 4 PV pairs (8%; 16% of patients) in the CF group and 35 PV pairs (35%; 52% of patients) in the standard group (P = .0004 per PV pair; P = .0029 per patient). The single-procedure, off-antiarrhythmic drug freedom from recurrent atrial arrhythmias at 1 year was 88% in the CF group vs 66% in the standard group (P = .047). Procedure duration and fluoroscopy time were significantly longer in the CF group (P = .0038 and P = .0001, respectively). CONCLUSION: The use of real-time contact force guidance results in a significant reduction in the prevalence of dormant conduction with improved long-term freedom from recurrent arrhythmias. The utility of a contact force-guided approach requires evaluation in a long-term prospective randomized study.

Clinical experience with a novel electromyographic approach to preventing phrenic nerve injury during cryoballoon ablation in atrial fibrillation.

BACKGROUND: Phrenic nerve palsy remains the most frequent complication associated with cryoballoon-based pulmonary vein (PV) isolation. We sought to characterize our experience using a novel monitoring technique for the prevention of phrenic nerve palsy. METHODS AND RESULTS: Two hundred consecutive cryoballoon-based PV isolation procedures between October 2010 and October 2013 were studied. In addition to standard abdominal palpation during right phrenic nerve pacing from the superior vena cava, all patients underwent diaphragmatic electromyographic monitoring using surface electrodes. Cryoablation was terminated on any perceived reduction in diaphragmatic motion or a 30% decrease in the compound motor action potential (CMAP). During right-sided ablation, a ≥30% reduction in CMAP amplitude occurred in 49 patients (24.5%). Diaphragmatic motion decreased in 30 of 49 patients and was preceded by a 30% reduction in CMAP amplitude in all. In 82% of cases, this reduction in CMAP amplitude occurred during right superior PV isolation. The baseline CMAP amplitude was 946.5±609.2 mV and decreased by 13.8±13.8% at the end of application. This decrease was more marked in the 33 PVs with a reduction in diaphragmatic motion than in those without (40.9±15.3% versus 11.3±10.5%; P<0.001). In 3 cases, phrenic nerve palsy persisted beyond the end of the procedure, with all cases recovering within 6 months. Despite the shortened application all veins were isolated. At repeat procedure the right-sided PVs reconnected less frequently than the left-sided PVs in those with phrenic nerve palsy. CONCLUSIONS: Electromyographic phrenic nerve monitoring using the surface CMAP is reliable, easy to perform, and offers an early warning to impending phrenic nerve injury.

Aortic coarctation and the retinal microvasculature.

BACKGROUND: Aortic coarctation has been associated with generalized vascular disease, yet little is known about retinal vascular patterns and their changes over time. OBJECTIVES: The aim of this study is to characterize the nature and extent of retinal vascular disease in adults with aortic coarctation, and explore age-related effects and associations with cardiovascular outcomes. METHODS: A prospective cross-sectional seroepidemiological study was conducted on 60 consecutive adults with repaired aortic coarctation, age 42.4±14.1 years, 61.7% male. In addition to detailed questionnaires, imaging studies, and laboratory testing, high-quality retinal images were acquired by 45° nonmydriatic digital funduscopy. RESULTS: No patient had evidence of hypertensive retinopathy. A distinctive vascular pattern characterized by bilaterally symmetric tortuosity of retinal arteries and veins was observed. Arterial tortuosity was abnormal in 98.3% of patients and decreased with age (P=0.0005). In patients≥45 years, a 1-point increase in the arterial tortuosity score was associated with a 1.5-fold higher risk of cardiovascular complications (i.e., acute coronary syndrome, stroke, cerebral aneurysm, aortic dissection/rupture) [odds ratio 1.50, 95% CI (1.01, 2.24), P=0.0496]. Abnormal venous tortuosity was present in 75.0% of patients and non-significantly correlated with higher levels of serum inflammatory markers (C-reactive protein, fibrinogen, interleukin-6, and tumor necrosis factor-alpha). A higher venous tortuosity score was likewise associated with an increased risk of cardiovascular complications [odds ratio 1.86, 95% CI (1.03, 3.35), P=0.0392]. CONCLUSIONS: Adults with repaired aortic coarctation exhibit a unique retinal vascular pattern characterized by excessive arterial and venous tortuosity that regresses with age. Greater tortuosity is associated with adverse cardiovascular outcomes in patients≥45 years.

Histopathology of cryoballoon ablation-induced phrenic nerve injury.

INTRODUCTION: Hemi-diaphragmatic paralysis is the most common complication associated with cryoballoon ablation for atrial fibrillation, yet the histopathology of phrenic nerve injury has not been well described. METHODS AND RESULTS: A preclinical randomized study was conducted to characterize the histopathology of phrenic nerve injury induced by cryoballoon ablation and assess the potential for electromyographic (EMG) monitoring to limit phrenic nerve damage. Thirty-two dogs underwent cryoballoon ablation of the right superior pulmonary vein with the objective of inducing phrenic nerve injury. Animals were randomized 1:1 to standard monitoring (i.e., interruption of ablation upon reduction in diaphragmatic motion) versus EMG guidance (i.e., cessation of ablation upon a 30% reduction in the diaphragmatic compound motor action potential [CMAP] amplitude). The acute procedural endpoint was achieved in all dogs. Phrenic nerve injury was characterized by Wallerian degeneration, with subperineural injury to large myelinated axons and evidence of axonal regeneration. The degree of phrenic nerve injury paralleled the reduction in CMAP amplitude (P = 0.007). Animals randomized to EMG guidance had a lower incidence of acute hemi-diaphragmatic paralysis (50% vs 100%; P = 0.001), persistent paralysis at 30 days (21% vs 75%; multivariate odds ratio 0.12, 95% confidence interval [0.02, 0.69], P = 0.017), and a lesser severity of histologic injury (P = 0.001). Mature pulmonary vein ablation lesion characteristics, including circumferentiality and transmurality, were similar in both groups. CONCLUSION: Phrenic nerve injury induced by cryoballoon ablation is axonal in nature and characterized by Wallerian degeneration, with potential for recovery. An EMG-guided approach is superior to standard monitoring in limiting phrenic nerve damage.

The time course of exit and entrance block during cryoballoon pulmonary vein isolation.

AIMS: The dynamic time course of entrance and exit block during pulmonary vein isolation (PVI) is unknown. The purpose of this series was to dynamically evaluate the manifestation of entrance and exit conduction block during simultaneous circumferential PVI. METHODS AND RESULTS: Pacing manoeuvres were performed during cryoballoon ablation of left-sided pulmonary veins (PVs) in 30 consecutive patients with a history of drug-refractory paroxysmal atrial fibrillation. At the onset of ablation continuous pacing was performed from the PV at a cycle length of 600 ms until the appearance of exit block. Once exit block was demonstrated, uninterrupted pacing was immediately transitioned to the distal coronary sinus (CS) catheter and continued at 600 ms throughout the rest of the cryoapplication. The timing of exit block, entrance block, and corresponding cryoballoon temperature were noted for all patients. In the 45 PVs when real-time PV recordings were available during cryothermal ablation, the presence of exit block was reliably demonstrated to precede entrance block (P < 0.0001) by a median of 5 s [interquartile range (IQR) 3, 12; median temperature at isolation -39°C (IQR -30, -45); nadir ablation temperature -53°C (IQR -48, -59)]. In all cases, when uninterrupted pacing was transitioned from the PV to the distal CS, entrance conduction from the left atrium to PV remained intact. CONCLUSION: Circumferential PV ablation results in progressive PVI, beginning with unidirectional exit block, and followed by entrance block. As exit block reliably precedes entrance block, we are able to provide justification for the exclusive use of entrance conduction block as the endpoint of cryoballoon-based PVI.

Effect Of Catheter Ablation On Quality Of Life In Atrial Fibrillation.

Atrial fibrillation (AF) is the most common sustained arrhythmia seen in clinical practice, affecting approximately 1% of the overall population. While rarely life-threatening, AF is almost universally associated with increased morbidity and mortality, predominantly through an increased risk of thromboembolic events, left ventricular dysfunction, as well as significant impairments in functional capacity and health-related quality of life (HRQOL).[1-8] Improvement in HRQOL, with a secondary reduction of disability and health-care resource utilization, is one of the major therapeutic goals in the management of AF.

Canadian Cardiovascular Society guidelines on the use of cardiac resynchronization therapy: implementation.

Recent studies have provided the impetus to update the recommendations for cardiac resynchronization therapy (CRT). This article provides guidance on the implementation of CRT and is intended to serve as a framework for the implementation of CRT within the Canadian health care system and beyond. These guidelines were developed through a critical evaluation of the existing literature, and expert consensus. The panel unanimously adopted each recommendation. The 9 recommendations relate to patient selection in the presence of comorbidities, delivery and optimization of CRT, and resources required to deliver this therapy. The strength of evidence was weighed, taking full consideration of any risk of bias, and any imprecision, inconsistency, and indirectness of the available data. The strength of each recommendation and the quality of evidence were adjudicated. Trade-offs between desirable and undesirable consequences of alternative management strategies were considered, as were values, preferences, and resource availability. These guidelines were externally reviewed by experts, modified based on those reviews, and will be updated as new knowledge is acquired.