One-year outcomes of pulmonary vein isolation with a novel cryoballoon: Primary results of the FROZEN AF trial.

INTRODUCTION: Cryoablation therapy for pulmonary vein isolation (PVI) to treat paroxysmal atrial fibrillation (PAF) is well established. A novel 28 mm cryoballoon system designed to operate under low pressure to safely reach a lower nadir temperature and maintain constant balloon size during cooling has not been prospectively studied in a large patient population for safety and efficacy. The FROZEN AF (NCT04133168) trial was an international multicenter, open-label, prospective, single-arm study on the safety and performance of a novel cryoballoon system for treatment of PAF. METHODS AND RESULTS: The study enrolled patients at 44 sites in 10 countries across North America, Europe, and Asia. Subjects were indicated for PVI treatment of PAF and had failed or were intolerant of one or more antiarrhythmic drugs. Procedural outcomes were defined based on the 2017 HRS consensus statement. Follow-up was performed at 7 days, 3, 6, and 12 months. Data are reported as mean ± SD or median (IQR). PVI was performed with a 28 mm cryoballoon in 325 drug refractory PAF patients. Complete PVI was achieved in 95.7% of patients. In cryoablation lesions longer than 60 s, 60.1% of PV isolations required only a single cryoballoon application. Procedure related complications included: phrenic nerve palsy [temporary 4 (1.2%), persistent 0 (0.0%)], cardiac tamponade/perforation 2 (0.6%), and air embolism 1 (0.3%). Freedom from documented atrial arrhythmia recurrence at 12 months was 79.9% (AF 82.7%, AFL 96.5%, AT 98.1%), antiarrhythmic drugs (AAD) were continued or re-initiated in 26.8% of patients after the 3-month blanking period. Additionally, an extension arm enrolled 50 pts for treatment with 28/31 mm variable size cryoballoon. A single temporary PNP occurred in this group, which resolved before discharge. Freedom from documented recurrence at 12 months in these pts was 82.0%. CONCLUSIONS: This novel cryoballoon may facilitate PVI to treat PAF, providing more options to address the variety of anatomies present in patients with PAF. This cryoballoon system proved to be safe and effective for treatment of patients with drug refractory or drug intolerant PAF.

Institutional experience report on the target contouring workflow in the radiotherapy department for stereotactic arrhythmia radioablation delivered on conventional linear accelerators.

PURPOSE: In stereotactic arrhythmia radioablation (STAR), the target is defined using multiple imaging studies and a multidisciplinary team consisting of electrophysiologist, cardiologist, cardiac radiologist, and radiation oncologist collaborate to identify the target and delineate it on the imaging studies of interest. This report describes the workflow employed in our radiotherapy department to transfer the target identified based on electrophysiology and cardiology imaging to the treatment planning image set. METHODS: The radiotherapy team was presented with an initial target in cardiac axes orientation, contoured on a wideband late gadolinium-enhanced (WB-LGE) cardiac magnetic resonance (CMR) study, which was subsequently transferred to the computed tomography (CT) scan used for treatment planning-i.e., the average intensity projection (AIP) image set derived from a 4D CT-via an axial CMR image set, using rigid image registration focused on the target area. The cardiac and the respiratory motion of the target were resolved using ciné-CMR and 4D CT imaging studies, respectively. RESULTS: The workflow was carried out for 6 patients and resulted in an internal target defined in standard anatomical orientation that encompassed the cardiac and the respiratory motion of the initial target. CONCLUSION: An image registration-based workflow was implemented to render the STAR target on the planning image set in a consistent manner, using commercial software traditionally available for radiation therapy.

Randomized Trial of Left Bundle Branch vs Biventricular Pacing for Cardiac Resynchronization Therapy.

BACKGROUND: Left bundle branch pacing (LBBP) is the most rapidly growing conduction system pacing technique that is capable of correcting intrinsic left bundle branch block (LBBB). As such, it is potentially an optimal alternative to cardiac resynchronization therapy (CRT) with biventricular pacing (BiVP). OBJECTIVES: The authors sought to compare the efficacy of LBBP-CRT with BiVP-CRT in patients with heart failure and reduced left ventricular ejection fraction (LVEF). METHODS: This is a prospective, randomized trial of patients with nonischemic cardiomyopathy and LBBB with 6-month preplanned follow-up. Crossovers were allowed if LBBP or BiVP were unsuccessful. The primary endpoint was the difference in LVEF improvement between 2 groups. The secondary endpoints included changes in echocardiographic measurements, N-terminal pro-B-type natriuretic peptide (NT-proBNP), New York Heart Association functional class, 6-minute walk distance, QRS duration, and CRT response. RESULTS: The study included 40 consecutive patients (20 males, mean age 63.7 years, LVEF 29.7% ± 5.6%). Crossovers occurred in 10% of LBBP-CRT and 20% of BiVP-CRT. All patients completed follow-up. Intention-to-treat analysis showed significantly higher LVEF improvement at 6 months after LBBP-CRT than BiVP-CRT (mean difference: 5.6%; 95% CI: 0.3-10.9; P = 0.039). LBBP-CRT also appeared to have greater reductions in left ventricular end-systolic volume (-24.97 mL; 95% CI: -49.58 to -0.36 mL) and NT-proBNP (-1,071.80 pg/mL; 95% CI: -2,099.40 to -44.20 pg/mL), and comparable changes in New York Heart Association functional class, 6-minute walk distance, QRS duration, and rates of CRT response compared with BiVP-CRT. CONCLUSIONS: LBBP-CRT demonstrated greater LVEF improvement than BiVP-CRT in heart failure patients with nonischemic cardiomyopathy and LBBB. (Left Bundle Branch Pacing Versus Biventricular Pacing for Cardiac Resynchronization Therapy [LBBP-RESYNC]; NCT04110431).

Spectrum of arrhythmogenic substrate post minimally invasive maze surgery in patients with recurrent.

BACKGROUND: Advancements in minimally invasive surgical ablation (MISA) have focused on improving pulmonary vein isolation. Additional ablation targets have been developed (such as posterior wall isolation). The mid- and long-term effects of current techniques (including electrophysiologic findings and recurrent arrhythmia mechanisms) have not previously been reported. METHODS: Twenty eight patients with recurrent atrial arrhythmias after bipolar clamp ablation of the pulmonary vein antrum, ganglionated plexi, posterior wall isolation (roof and floor lines to create a posterior box), and ligament of Marshall ligation/cauterization and left atrial appendage clipping underwent follow up electrophysiology study including left atrial mapping an average of 2.3 years postoperatively. RESULTS: Atrial fibrillation was the most common recurrent arrhythmia (n = 18) followed by micro-reentrant atrial tachycardia (n = 5), macro-reentry left atrial flutter (n = 3), and typical cavo-tricuspid isthmus atrial flutter (n = 2). Eighty six of 112 (77%) PVs mapped were electrically isolated, 16 (57%) patients had all four pulmonary veins (PVs) isolated. The posterior wall (PW) was completely isolated in only four (14%) patients, seven (25%) patients had normal PW voltage, while 17 (61%) patients had abnormal delayed or fractionated electrograms in the posterior wall (incomplete isolation). Abnormal PW electrograms were more frequently found in patients with complex recurrent left atrial arrhythmia (micro-reentry or left atrial macro-reentry flutter). CONCLUSION: With current surgical techniques PV isolation has improved, but PW isolation remains challenging. Incomplete PW isolation may produce arrhythmogenic substrate.

Arrhythmias in Cardiac Sarcoidosis Bench to Bedside: A Case-Based Review.

Cardiac sarcoidosis is a component of an often multiorgan granulomatous disease of still uncertain cause. It is being recognized with increasing frequency, mainly as the result of heightened awareness and new diagnostic tests, specifically cardiac magnetic resonance imaging and 18F-fluorodeoxyglucose positron emission tomography scans. The purpose of this case-based review is to highlight the potentially life-saving importance of making the early diagnosis of cardiac sarcoidosis using these new tools and to provide a framework for the optimal care of patients with this disease. We will review disease mechanisms as currently understood, associated arrhythmias including conduction abnormalities, and atrial and ventricular tachyarrhythmias, guideline-directed diagnostic criteria, screening of patients with extracardiac sarcoidosis, and the use of pacemakers and defibrillators in this setting. Treatment options, including those related to heart failure, and those which may help clarify disease mechanisms are included.

Long-term durability of posterior wall isolation using the cryoballoon in patients with persistent atrial fibrillation: a multicenter analysis of repeat catheter ablations.

PURPOSE: There is a growing interest in performing pulmonary vein isolation (PVI) with concomitant posterior wall isolation (PWI) using the cryoballoon for the treatment of patients with persistent atrial fibrillation (AF). However, there is little known about the long-term durability of PWI using this approach. METHODS: In this multicenter study, we retrospectively examined the durability of PVI + PWI using the 28-mm cryoballoon by investigating the outcomes from consecutive patients referred for repeat catheter ablation. RESULTS: Altogether, 81/519 patients (15.6%) were referred for repeat catheter ablation. Repeat ablation was associated with a longer AF duration, hypertension, heart failure, multiple cardioversions, and antiarrhythmic therapy as well as larger left atrial (LA) diameters (49 ± 4 mm versus 43 ± 5 mm; P < 0.001) and greater need for "touch-up" (adjunct) radiofrequency ablation (44.4% versus 18.3%; P < 0.001). LA diameter also emerged as a significant predictor for adjunct radiofrequency ablation (P < 0.001). Durable PVI was observed in 66/81 patients (81.5%) and PWI in 67/81 patients (82.7%). Those with incomplete PWI exhibited larger LA diameters, particularly > 48 mm (negative predictive value = 89.7%). Lastly, an atypical LA posterior wall/roof flutter represented the third most common cause of arrhythmia recurrence and essentially every patient with incomplete PWI exhibited such an arrhythmia. CONCLUSION: PWI performed using a 28-mm cryoballoon in conjunction with PVI exhibits long-term durability in the vast majority of patients with persistent AF. While LA diameter (particularly > 48 mm) is a significant predictor for the need for adjunct radiofrequency ablation when performing this technique, those with incomplete PWI invariably present with an atypical flutter using this substrate.

Procedure characteristics and outcomes of atrial fibrillation ablation procedures using cryoballoon versus radiofrequency ablation: A report from the GWTG-AFIB registry.

INTRODUCTION: Cryoballoon ablation (CBA) is an alternative to radiofrequency ablation (RFA) for ablation of atrial fibrillation (AF) and real-world comparisons of this strategy are lacking. As such, we sought to compare patient and periprocedural characteristics and outcomes of CBA versus RFA in the Get With the Guidelines AFIB Registry. METHODS: Categorical variables were compared via the χ2 test and continuous variables were compared via the Wilcoxon rank-sum test. Adjusted analyses were performed using overlap weighting of propensity scores. RESULTS: A total of 5247 (1465 CBA, 3782 RFA) ablation procedures were reported from 33 sites. Those undergoing CBA more often had paroxysmal AF (60.0% vs. 48.8%) and no prior AF ablation (87.5% vs. 73.8%). CHA2 DS2 -VASc scores were similar. Among de novo ablations, most ablations involved intracardiac echocardiography and electroanatomic mapping, but both were less common with CBA (87.3% vs. 93.9%, p < .0001, and 87.7% vs. 94.6%, p < .0001, respectively). CBA was associated with shorter procedures (129 vs. 179 min, p < .0001), increased fluoroscopy use (19 vs. 11 min, p < .0001), and similar ablation times (27 vs. 35 min, p = .15). Nonpulmonary vein ablation was common with CBA: roof line 38.6%, floor line 20.4%, cavotricuspid isthmus 27.7%. RFA was associated with more total complications compared to CBA (5.4% vs. 2.3%, p < .0001), due to more volume overload and "other" events, although phrenic nerve injury was more common with CBA (0.9% vs 0.1%, p = .0001). In the adjusted model, any complication was less common among CBA cases (odds ratio, 0.45; confidence interval, 0.25-0.79, p = .0056). CONCLUSION: CBA was associated with fewer complications, and shorter procedure times, and greater fluoroscopy times, compared to RFA. Nonpulmonary vein ablation and electroanatomic mapping system use was common with CBA.

Comparison of Frequency of Atrial Fibrillation in Blacks Versus Whites and the Utilization of Race in a Novel Risk Score.

Blacks have a lower prevalence of atrial fibrillation (AF) compared with Whites. We sought to confirm previously reported ethnic trends in AF in Blacks and Whites in a large database, and develop a prediction score for AF. Over 330 million hospital discharges between the years 2003 to 2013 from the National Inpatient Sample database were analyzed. All hospitalizations with a diagnosis of AF formed the study cohort. Traditional risk factors for the development of AF were compared between Blacks and Whites. Univariate and multiple logistic regression analyses were used to formulate a risk score to predict AF-CHADSAVES (Congestive heart failure, Hypertension, Age>65 years, Diabetes Mellitus, prior Stroke, Age>75 years, Vascular disease, White Ethnicity, and previous cardiothoracic Surgery). AF prevalence in Whites was 11.3% vs 4.6% in Blacks (p < 0.001). Blacks were younger (33.8% vs 14.4% patients <65 years, p < 0.01) and had less males (46.3% vs 49.4%, p < 0.01). Blacks had more hypertension (71.3% vs 64.1%, p < 0.01), congestive heart failure (24.8% vs 22.6%, p < 0.01), diabetes mellitus with (7.5% vs 4.7%, p < 0.01) or without complications (30.3% vs 23.1%, p < 0.01), renal failure (29.7% vs 17.1%, p < 0.01), and obesity (13.1% vs 8.7%, p < 0.01). CHADSAVES predicted AF in the study population (NIS 2003 to 2013) with an AUC of 0.82 and verified in a validation cohort (NIS 2014) with an AUC of 0.85. In conclusion, our data confirm a significant AF ethnicity paradox. Despite a higher prevalence of traditional risk factors for AF, Blacks had >2-fold lower prevalence of AF compared with Whites. CHADSAVES can be used effectively to predict AF in inpatients.

Procedural Patterns and Safety of Atrial Fibrillation Ablation: Findings From Get With The Guidelines-Atrial Fibrillation.

BACKGROUND: Catheter ablation is an increasingly used treatment for symptomatic atrial fibrillation (AF). However, there are limited prospective, nationwide data on patient selection and procedural characteristics. This study describes patient characteristics, techniques, treatment patterns, and safety outcomes of patients undergoing AF ablation. METHODS: A total of 3139 patients undergoing AF ablation between 2016 and 2018 in the Get With The Guidelines-Atrial Fibrillation registry from 24 US centers were included. Patient demographics, medical history, procedural details, and complications were abstracted. Differences between paroxysmal and patients with persistent AF were compared using Pearson χ2 and Wilcoxon rank-sum tests. RESULTS: Patients undergoing AF ablation were predominantly male (63.9%) and White (93.2%) with a median age of 65. Hypertension was the most common comorbidity (67.6%), and patients with persistent AF had more comorbidities than patients with paroxysmal AF. Drug refractory, paroxysmal AF was the most common ablation indication (class I, 53.6%) followed by drug refractory, persistent AF (class I, 41.8%). Radiofrequency ablation with contact force sensing was the most common ablation modality (70.5%); 23.7% of patients underwent cryoballoon ablation. Pulmonary vein isolation was performed in 94.6% of de novo ablations; the most common adjunctive lesions included left atrial roof or posterior/inferior lines, and cavotricuspid isthmus ablation. Complications were uncommon (5.1%) and were life-threatening in 0.7% of cases. CONCLUSIONS: More than 98% of AF ablations among participating sites are performed for class I or class IIA indications. Contact force-guided radiofrequency ablation is the dominant technique and pulmonary vein isolation the principal lesion set. In-hospital complications are uncommon and rarely life-threatening.

Cardiac Resynchronization Therapy in Patients With Nonischemic Cardiomyopathy Using Left Bundle Branch Pacing.

OBJECTIVES: The aim of this study was to assess the feasibility and efficacy of left bundle branch pacing (LBBP) using a novel intraseptal technique to deliver cardiac resynchronization therapy (CRT) in patients with left bundle branch block (LBBB) and nonischemic cardiomyopathy. BACKGROUND: His bundle pacing to correct LBBB is a viable alternative approach to achieve CRT but is limited by suboptimal lead delivery and high thresholds. METHODS: This was a prospective, multicenter study performed between June 2017 and August 2018 at 6 centers. Patients with nonischemic cardiomyopathy, complete LBBB, and left ventricular ejection fractions (LVEFs) ≤50% who had indications for CRT and/or ventricular pacing in whom LBBP was attempted were included. Success rates, QRS duration, LVEF, left ventricular end-systolic volume, and improvement in functional class were assessed. RESULTS: LBBP was successful in 61 of 63 patients (97%, mean age 68 ± 11 years, 52.4% men). During LBBP, QRS duration narrowed from 169 ± 16 to 118 ± 12 ms (p < 0.001). Pacing threshold and R-wave amplitude remained stable at 1-year follow-up compared with implantation values (0.5 ± 0.15 V/0.5 ms vs. 0.58 ± 0.14 V/0.5 ms and 11.1 ± 4.9 mV vs. 13.3 ± 5.3 mV, respectively). LVEF increased significantly (33 ± 8% vs. 55 ± 10%; p < 0.001), with a reduction in left ventricular end-systolic volume (123 ± 61 ml vs. 67 ± 39 ml; p < 0.001). LVEF had normalized (≥50%) in 75% of patients at 1 year. New York Heart Association functional class improved significantly from 2.8 ± 0.6 at baseline to 1.4 ± 0.6 at 1 year. No deaths or heart failure hospitalizations were observed during follow-up. CONCLUSIONS: LBBP is a feasible and effective method for achieving electric resynchronization of LBBB, with resultant improvements in left ventricular structure and function. Low and stable pacing thresholds may be advantageous over His bundle pacing for CRT in patients with LBBB and nonischemic cardiomyopathy.

Cryoballoon ablation dosing: From the bench to the bedside and back.

To date, multiple modes of research have been leveraged to study the optimal cryoballoon ablation parameters to safely, effectively, and efficiently isolate the pulmonary veins for the treatment of atrial fibrillation. Basic scientific investigation, preclinical studies, clinical observations, trials, and, more recently, computational modeling have helped to generate and test new hypotheses for the advancement of cryoballoon treatment in patients with atrial fibrillation. In this review, we examine the data and evidence that have contributed to the development of patient-tailored dosing strategies that are currently used for pulmonary vein isolation by using the Arctic Front series of cryoballoon ablation catheters.

Vitamin C Intravenous Treatment In the Setting of Atrial Fibrillation Ablation: Results From the Randomized, Double-Blinded, Placebo-Controlled CITRIS-AF Pilot Study.

Background Catheter ablation is an effective treatment for atrial fibrillation (AF), but high levels of post-procedure inflammation predict adverse clinical events. Ascorbic acid (AA) has shown promise in reducing inflammation but is untested in this population. We sought to test the feasibility, safety, and preliminary effects on inflammatory biomarkers in the CITRIS-AF (Vitamin C Intravenous Treatment In the Setting of Atrial Fibrillation Ablation) pilot study. Methods and Results Patients scheduled to undergo AF ablation (N=20) were randomized 1:1 to double-blinded treatment with AA (200 mg/kg divided over 24 hours) or placebo. C-reactive protein and interleukin-6 levels were obtained before the first infusion and repeated at 24 hours and 30 days. Pain levels within 24 hours and early recurrence of AF within 90 days were recorded. Median and interquartile range were aged 63 (56-70) years, 13 (65%) men, and 18 (90%) white. Baseline data were similar between the 2 groups except ejection fraction. Baseline C-reactive protein levels were 2.56 (1.47-5.87) mg/L and similar between groups (P=0.48). Change in C-reactive protein from baseline to 24 hours was +10.79 (+6.56-23.19) mg/L in the placebo group and +3.01 (+0.40-5.43) mg/L in the AA group (P=0.02). Conversely, change in interleukin-6 was numerically higher in the AA group, though not statistically significant (P=0.32). One patient in each arm developed pericarditis; no adverse events related to the infusions were seen. There were no significant differences between aggregated post-procedure pain levels within 24 hours or early recurrence of AF (both P>0.05). Conclusions High-dose AA is safe and well tolerated at the time of AF ablation and may be associated with a blunted rise in C-reactive protein, although consistent findings were not seen in interleukin-6 levels. Further studies are needed to validate these findings and explore the potential benefit in improving clinically relevant outcomes. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT03148236.

Fluoroscopy reduction during device implantation by using three-dimensional navigation. A single-center experience.

BACKGROUND AND OBJECTIVES: The use of nonfluoroscopic three-dimensional electroanatomic mapping (3DM) systems reduces radiation exposure during ablation procedures. In this study, we sought to determine the value of 3DM during routine device implant procedures. METHODS: Seventy nonselected patients underwent implantation of a single chamber, dual chamber, or biventricular device guided by Ensite (Abbott Laboratories) to limit fluoroscopy use and compared with 70 consecutive patients, who underwent matching procedures with standard fluoroscopy use (FL) in the period immediately preceding the use of 3DM. The venous anatomy, right atrium, and ventricle and coronary sinus were mapped with 0.035 inch J-wire, quadripolar catheter, and/or angioplasty wire. The leads were advanced under real-time visualization in Ensite. RESULTS: 3DM reduced both fluoroscopy time and dose. Median fluoroscopy time for FL vs 3DM was 5.5 minutes (interquartile range [IQR]: 3.8-8.1) vs 0.9 minutes (IQR: 0.6-1.9) (P < .001) for single chamber devices, 6.3 minutes (IQR: 5.1-7.9) vs 3.3 minutes (IQR: 1.9-4) (P < .001) for dual-chamber devices, and 28.6 minutes (IQR: 19.6-36.2) to 14.7 minutes (IQR: 10.4-22.3) (P = .009) for biventricular devices, respectively. The median air kerma for FL vs 3DM was 15.4 mGy (IQR: 8.1-30.2) vs 4 mGy (IQR: 1.8-8) (P < .001) for single chamber devices, 16 mGy (IQR: 12-18.5) to 9.4 mGy (IQR: 7.5-11.3) (P = .001) for dual-chamber devices, and 324 mGy (IQR: 143-668.7) to 115 mGy (IQR:77-204) (P = .014) for biventricular devices, respectively. There were no procedural complications. At 3-month follow-up, there was no difference in voltage threshold measurements between the groups. CONCLUSION: The use of 3DM leads to significantly reduced fluoroscopy time and fluoroscopy dose during routine device implantation.

Epicardial injection of nanoformulated calcium into cardiac ganglionic plexi suppresses autonomic nerve activity and postoperative atrial fibrillation.

BACKGROUND: Imbalanced activation of the cardiac autonomic nervous system triggers postoperative atrial fibrillation (POAF). Neuronal calcium overload induces apoptosis. We hypothesize that epicardial injection of timed-release nanoformulated CaCl2 (nCaCl2) into left atrial ganglionic plexi (GP) modulates autonomic function and suppresses POAF. OBJECTIVE: The purpose of this study was to determine whether nCaCl2 GP therapy suppresses POAF. METHODS: We used a novel canine model of POAF with implanted radiotelemetry to record nerve activity (NA) from the left stellate ganglion (SNA), left cardiac vagus nerve, and GP. At week 3, nCaCl2 (n = 7) or vehicle control (sham; n = 3) was injected into left pulmonary vein GP (LGP), followed by right pulmonary vein GP at week 4. Atrial effective refractory period (AERP) and atrial fibrillation vulnerability (AFV) were assessed in vivo. Resting and exercise NA and heart rate (HR) were assessed before and after LGP treatment. RESULTS: AERP decreased (P < .0001) and AFV increased (P = .008) at week 3 vs baseline. However, nCaCl2-LGP treatment reversed these changes and restored them to baseline after 1 week (P = .04). Subsequent nCaCl2-right pulmonary vein GP treatment further reduced AFV (P = .03). In contrast, AFV increased (P = .001) and AERP remained decreased (P = .01) 1 week after sham-LGP treatment vs baseline. nCaCl2-LGP treatment reduced NA from GP (P < .02) and NA from the left cardiac vagus nerve (P < .05) and increased SNA (P < .02). Despite increased SNA, HR was decreased (P < .01) with loss of HR-SNA correlation (R = 0.62). After sham-LGP treatment, NA was unchanged and HR-SNA remained correlated (R = 0.95). Histology confirmed nCaCl2-GP colocalization, apoptosis, and loss of immunoreactivity in nCaCl2-treated somas. CONCLUSION: Epicardial injection of nCaCl2 into left atrial GP induced neuroapoptosis and modulated autonomic function. This reversed a postoperative reduction in AERP and suppressed POAF.

Low Fluoroscopy Permanent His Bundle Pacing Using Electroanatomic Mapping: A Feasibility Study.

BACKGROUND: Conventional permanent His Bundle pacing (PHBP) can be challenging and associated with high fluoroscopy exposure. The aim of this study was to assess the feasibility and safety of performing low fluoroscopy PHBP using 3-dimensional electroanatomic mapping and comparing outcomes with conventional fluoroscopy guided PHBP implants. METHODS: PHBP was performed at 2 centers using electroanatomic mapping-guided low fluoroscopy implantation in 10 patients using a novel protocol (group 1) and conventional fluoroscopy guided implantation in 20 patients (group 2). The primary end point was feasibility of achieving PHBP with low/zero fluoroscopy and safety end points included total radiation exposure (fluoroscopy time and dose area product), procedure-related complications associated with lead implantation or need for lead revisions. RESULTS: PHBP was successful in 9 of 10 patients (90%) in group 1 and 100% successful in the group 2 patients. The mean His lead fluoroscopy time was significantly lower in group 1 (0.2±0.2 minutes) compared with 8±7 minutes in group 2 ( P=0.002) as was the total fluoroscopy time (0.8±0.3 versus 13±8 minutes, P=0.003) and the dose area product (96±83 versus 1531±923 microGy/m2, P=0.003). The HB capture threshold was lower in group 1 (0.7±0.4 at 1 ms) compared with patients in group 2 (1.15±0.7 at 1 ms) P=0.04. There were no procedure-related complications or lead dislodgements in either group. There was an increase in HB capture threshold in 1 patient (5%) in group 2 at 1-month follow-up. CONCLUSIONS: Electroanatomic mapping-guided PHBP is feasible can be performed safely and results in a significant reduction in fluoroscopy duration and exposure.