Safety and feasibility of cardiac electrophysiology procedures in ambulatory surgery centers.

BACKGROUND: Despite their improved safety, by and large, cardiac electrophysiology procedures including catheter ablation (CA), are presently performed in hospital outpatient departments. OBJECTIVE: This large multicenter study investigated the safety and outcomes associated with various cardiac electrophysiology procedures performed at 6 ambulatory surgery centers (ASCs), primarily during the coronavirus disease 2019 pandemic under the Center for Medicare and Medicaid Services Hospitals Without Walls program. METHODS: We retrospectively analyzed the outcomes from consecutive electrophysiology procedures performed in ASCs with same-day discharge, including transesophageal echocardiography, cardioversion, cardiac implantable electronic device (CIED) implantation, electrophysiology studies, and CA for atrial fibrillation (AF), atrial flutter (AFL)/supraventricular tachycardia, ventricular premature complexes (VPCs), and atrioventricular node. RESULTS: Altogether, 4037 procedures were performed, including 779 transesophageal echocardiography/cardioversion procedures (19.3%), 1453 CIED implantation procedures (36.0%), 26 electrophysiology studies (0.6%), and 1779 CA procedures (44.1%) for AF (75.4%), AFL/supraventricular tachycardia (18.8%), VPC (4.7%), and atrioventricular node (1.1%). Overall, 80.2% of CA procedures were for left-sided atrial arrhythmias (AF/atypical AFL) requiring transseptal catheterization. Left-sided VPC ablation procedures (42.2%) were performed using a transseptal/retrograde approach. Adverse event rates were low, but comparable between CIED implantation and CA (0.76% vs 0.73%; P = .93), as were the incidences of urgent/unplanned postprocedure hospitalization (0.48% vs 0.45%; P = .89), respectively. Moreover, the adverse event rates in ASCs vs hospital outpatient departments did not differ for CIED (0.76% vs 0.65%; P = .71) or CA (0.73% vs 0.80%; P = .79). CONCLUSION: The results from this large multicenter study suggest that ASCs represent a safe and effective setting to perform a variety of cardiac electrophysiology procedures including CA. These findings bear important implications for healthcare delivery and policy.

Initial Clinical Experience With a New Automated Antitachycardia Pacing Algorithm: Feasibility and Safety in an Ambulatory Patient Cohort.

BACKGROUND: Antitachycardia pacing (ATP) in implantable cardioverter-defibrillators (ICD) decreases patient shock burden but has recognized limitations. A new automated ATP (AATP) based on electrophysiological first principles was designed. The study objective was to assess the feasibility and safety of AATP in ambulatory ICD patients. METHODS AND RESULTS: Enrolled patients had dual chamber or cardiac resynchronization therapy ICDs, history of ≥1 ICD-treated ventricular tachycardias (VT)/ventricular fibrillation episode, or a recorded, sustained monomorphic VT. Detection was set to ventricular fibrillation number of intervals to detect=24/32, VT number of intervals to detect≥16, and a fast VT zone of 240 to 320 ms. AATP prescribed the components and delivery of successive ATP sequences in real time, using the same settings for all patients. ICD datalogs were uploaded every ≈3 months, at unscheduled visits, exit, and death. Episodes and adverse events were adjudicated by separate committees. Results were adjusted (generalized estimating equations) for multiple episodes. AATP was downloaded into the ICDs of 144 patients (121 men), aged 67.4±11.9 years, left ventricular ejection fraction 33.1±13.6% (n=137), and treated 1626 episodes in 49 patients during 14.5±5.1 months of follow-up. Datalogs permitted adjudication of 702 episodes, including 669 sustained monomorphic VT, 20 polymorphic VT, 10 supraventricular tachycardia, and 3 malsensing episodes. AATP terminated 39 of 69 (59% adjusted) sustained monomorphic VT in the fast VT zone, 509 of 590 (85% adjusted) in the VT zone, and 6 of 10 in the ventricular fibrillation zone. No supraventricular tachycardias converted to VT or ventricular fibrillation. No anomalous AATP behavior was observed. CONCLUSIONS: The new AATP algorithm safely generated ATP sequences and controlled therapy progression in all zones without need for individualized programing.

Verification of a novel atrial fibrillation cryoablation dosing algorithm guided by time-to-pulmonary vein isolation: Results from the Cryo-DOSING Study (Cryoballoon-ablation DOSING Based on the Assessment of Time-to-Effect and Pulmonary Vein Isolation Guidance).

BACKGROUND: There are no recommendations on the optimal dosing for cryoablation of atrial fibrillation (Cryo-AF). OBJECTIVE: The purpose of this study was to develop and prospectively test a Cryo-AF dosing protocol guided exclusively by time-to-pulmonary vein (PV) isolation (TT-PVI) in patients undergoing a first-time Cryo-AF. METHODS: In this multicenter study, we examined the acute/long-term safety/efficacy of Cryo-AF using the proposed dosing algorithm (Cryo-AFDosing; n = 355) against a conventional, nonstandardized approach (Cryo-AFConventional; n = 400) in a nonrandomized fashion. RESULTS: Acute PV isolation was achieved in 98.9% of patients in Cryo-AFDosing (TT-PVI = 48 ± 16 seconds) vs 97.2% in Cryo-AFConventional (P = .18). Cryo-AFDosing was associated with shorter (149 ± 34 seconds vs 226 ± 46 seconds; P <.001) and fewer (1.7 ± 0.8 vs 2.9 ± 0.8; P <.001) cryoapplications, reduced overall ablation (16 ± 5 minutes vs 40 ± 14 minutes; P <.001), fluoroscopy time (13 ± 6 minutes vs 29 ± 13 minutes; P <.001), left atrial dwell time (51 ± 14 minutes vs 118 ± 25 minutes; P <.001), and total procedure time (84 ± 23 minutes vs 145 ± 49 minutes; P <.001) but similar nadir balloon temperature (-47°C ± 8°C vs -48°C ± 6°C; P = .41) and total thaw time (43 ± 27 seconds vs 45 ± 19 seconds; P = .09) as compared to Cryo-AFConventional. Adverse events (2.0% vs 2.7%; P = .48), including persistent phrenic nerve palsy (0.6% vs 1.2%; P = .33) and 12-month freedom from all atrial arrhythmias (82.5% vs 78.3%; P = .14), were similar between Cryo-AFDosing and Cryo-AFConventional. However, Cryo-AFDosing was specifically associated with fewer atypical atrial flutters/tachycardias during long-term follow-up (8.5% vs 13.5%; P = .02) as well as fewer late PV reconnections at redo procedures (5.0% vs 18.5%; P <.001). CONCLUSION: A novel Cryo-AF dosing algorithm guided by TT-PVI can help individualize the ablation strategy and yield improved procedural endpoints and efficiency as compared to a conventional, nonstandardized approach.

Catheter ablation using the third-generation cryoballoon provides an enhanced ability to assess time to pulmonary vein isolation facilitating the ablation strategy: Short- and long-term results of a multicenter study.

BACKGROUND: Limited data exist on cryoablation of atrial fibrillation (Cryo-AF) using the newly available third-generation (Arctic Front Advance-Short Tip [AFA-ST]) cryoballoon. OBJECTIVE: In this multicenter study, we evaluated the safety and efficacy of Cryo-AF using the AFA-ST vs the second-generation (Arctic Front Advance [AFA]) cryoballoon. METHODS: We examined the procedural safety and efficacy and the short- and long-term clinical outcomes associated with a first-time Cryo-AF performed in 355 consecutive patients (254/355 [72%] with paroxysmal AF), using either the AFA-ST (n = 102) or the AFA (n = 253) cryoballoon catheters. RESULTS: Acute isolation was achieved in 99.6% of all pulmonary veins (PVs) (AFA-ST: 100% vs AFA: 99.4%; P = .920). Time to pulmonary vein isolation was recorded in 89.2% of PVs using AFA-ST vs 60.2% using AFA (P < .001). PVs targeted using AFA-ST required fewer applications (1.6 ± 0.8 vs 1.7 ± 0.8; P = .023), whereas there were no differences in the balloon nadir temperature (AFA-ST: -47.0°C ± 7.3°C vs AFA: -47.5°C ± 7.8°C; P = .120) or thaw time (AFA-ST: 41 ± 24 seconds vs AFA: 44 ± 28 seconds; P = .056). However, AFA-ST was associated with shorter left atrial dwell time (43 ± 5 minutes vs 53 ± 16 minutes; P < .001) and procedure time (71 ± 11 minutes vs 89 ± 25 minutes; P < .001). Furthermore, Cryo-AF using AFA-ST was completed more frequently by "single-shot" PV ablation (27.4% vs 20.2%; P = .031). Persistent phrenic nerve palsy (AFA-ST: 0% vs AFA: 0.8%; P = .507) and procedure-related adverse events (AFA-ST: 1.0% vs AFA: 1.6%; P = .554) were similar, as was the freedom from recurrent atrial arrhythmias at 10 months of follow-up (AFA-ST: 81.8% vs AFA: 79.9%; P = .658). CONCLUSION: Cryo-AF using the AFA-ST cryoballoon offers an enhanced ability to assess time to pulmonary vein isolation, allowing for fewer cryoapplications and shorter left atrial dwell time and procedure time. Consequently, this allowed for procedural completion more frequently using a "single-shot" PV ablation with equivalent safety and efficacy.

Quantification of the cryoablation zone demarcated by pre- and postprocedural electroanatomic mapping in patients with atrial fibrillation using the 28-mm second-generation cryoballoon.

BACKGROUND: There are 2 Food and Drug Administration-approved catheters (ThermoCool RF and Arctic Front Advance cryoballoon) for the treatment of drug refractory and symptomatic paroxysmal atrial fibrillation. Each tool is used to ablate the area surrounding the pulmonary veins (PVs). However, no study has described and quantified the ablated surface area after the application of cryoablation lesions with the second-generation cryoballoon. OBJECTIVE: The purpose of this study was to determine the area of ablation during cryoballoon PV isolation. METHODS: Preprocedural computed tomography angiography of the left atrium (LA) was conducted in 43 patients to accurately determine spatial chamber dimensions. Before and after the ablation procedure, a detailed 3-dimensional electroanatomic map of the LA was created and merged onto the computed tomography angiogram to improve the accuracy of the data recordings. RESULTS: The posterior LA wall had a mean surface area of 31.1 (±1.6 SEM) cm(2). Left- and right-sided antral PV surface areas of cryoballoon ablation were not statistically different (P = .935), which were 11.4 (±0.8 SEM) and 11.3 (±0.8 SEM) cm(2), respectively. In total, 27% of the posterior LA wall remained unablated, electrically functional, and homogeneous with regard to voltage conductivity. This ablation strategy resulted in 95.3% freedom from atrial fibrillation at 6 months. CONCLUSION: The area of the posterior LA wall ablation with the cryoballoon catheter is wide and antral, and the resulting posterior LA wall debulking could be a part of the cryoballoon efficacy beyond discrete PV isolation.

Do omega-3 polyunsaturated fatty acids reduce risk of sudden cardiac death and ventricular arrhythmias? A meta-analysis of randomized trials.

INTRODUCTION: Omega-3 polyunsaturated fatty acids (PUFA) have demonstrated to have antiarrhythmic properties. However, randomized studies have shown inconsistent results. OBJECTIVE: We aimed to analyze the effect of omega-3 PUFA on preventing potentially fatal ventricular arrhythmias and sudden cardiac death. METHODS: Randomized trials comparing omega-3 PUFA to placebo and reporting sudden cardiac death (SCD) or first implanted cardioverter-defibrillator (ICD) event for ventricular tachycardia or fibrillation were included in this study. A meta-analysis using a random effects model was performed and results were expressed in terms of Odds Ratio (OR) and 95% Confidence Interval (CI) after evaluating for interstudy heterogeneity using I(2). The reported data were extracted on the basis of the intention-to-treat principle. RESULTS: A total of 32,919 patients were included in nine trials; 16,465 patients received omega-3 PUFA and 16,454 received placebo. When comparing omega-3 PUFA to placebo, there was nonsignificant risk reduction of SCD or ventricular arrhythmias (OR = 0.82 [95% CI: 0.60-1.21], p = 0.21 I(2) = 49.7%). CONCLUSION: Dietary supplementation with omega-3 PUFA does not affect the risk of SCD or ventricular arrhythmias.

Histopathologic characterization of chronic radiofrequency ablation lesions for pulmonary vein isolation.

OBJECTIVES: This study describes the histopathologic and electrophysiological findings in patients with recurrence of atrial fibrillation (AF) after pulmonary vein (PV) isolation who underwent a subsequent surgical maze procedure. BACKGROUND: The recovery of PV conduction is commonly responsible for recurrence of AF after catheter-based PV isolation. METHODS: Twelve patients with recurrent AF after acutely successful catheter-based antral PV isolation underwent a surgical maze procedure. Full-thickness surgical biopsy specimens were obtained from the PV antrum in areas of visible endocardial scar. Before biopsy, intraoperative epicardial electrophysiological recordings were taken from each PV using a circular mapping catheter. RESULTS: Twenty-two PVs were biopsied from the 12 patients 8 ± 11 months after ablation. Eleven of the 22 specimens (50%) revealed transmural scar, and 11 (50%) showed viable myocardium with or without scar. Each biopsy specimen demonstrated evidence of injury, most commonly endocardial thickening (n = 21 [95%]) and fibrous scar (n = 18 [82%]). Seven of the 22 specimens (32%) showed conduction block at surgery. Transmural scar was more likely to be seen in the biopsy specimens from the PVs with conduction block than in specimens from the PVs showing reconnection. However, viable myocardium alone or mixed with scar was seen in 2 specimens from PVs with conduction block. CONCLUSIONS: PVs showing electrical reconnection after catheter-based antral ablation frequently reveal anatomic gaps or nontransmural lesions at the sites of catheter ablation. Nontransmural lesions are noted in some PVs with persistent conduction block, suggesting that lesion geometry may influence PV conduction. The histological findings show that nontransmural ablation can produce a dynamic cellular substrate with features of reversible injury. Delayed recovery from injury may explain late recurrences of AF after PV isolation.

R-wave amplitude changes measured by electrocardiography during early transmural ischemia.

BACKGROUND: Changes in the amplitude of the R wave (RWA) on the electrocardiogram (ECG) have been described during acute myocardial ischemia and infarction. However, this has not been well studied in a controlled setting. We hypothesized that significant increase in RWA occurs during early transmural myocardial ischemia. METHODS: We prospectively evaluated changes in RWA in 50 patients during brief episodes of transmural ischemia induced by first balloon occlusion (mean, 38 seconds at 6-10 atmospheric pressures) during elective percutaneous coronary intervention. We recorded 12-lead ECGs at 20-second intervals before and during balloon inflation in 16 right coronary arteries, 14 left circumflex arteries, and 20 left anterior descending arteries. R wave amplitude was digitally measured in each of the 12 leads in every ECG using the ECG interval editor (General Electric HC, Menomonee Falls, WI). Intracoronary (IC) ECGs were also recorded in 4 patients. The mean of the RWA in each lead before balloon inflation was compared to the mean RWA during balloon inflation. RESULTS: R wave amplitude significantly increased during balloon inflation from baseline in limb leads I, II, aVL, and all the precordial leads with the exception of lead V(1). The RWA increase did not reach statistical significance in leads III, aVF, and V(1). Mean RWA increase was consistent in all leads except aVR during the brief episodes of ischemia during initial balloon inflation because of the inverse polarity of this lead. The increase in RWA was seen in most patients (mean, 75%) in whom transmural ischemia was induced by first balloon inflation. Besides, the RWA showed an increase from baseline in 3 patients who had IC-lead recordings. CONCLUSION: R wave amplitude increases significantly in precordial leads (V(2)-V(6)) and limb leads (I, II, aVL) of the surface ECG during brief episodes of transmural ischemia. The increase in RWA might be consistent with the expansion of the left ventricular cavity during ischemia and/or alterations in conduction that are intrinsic to the myocardium.

Sensing failure associated with the Medtronic Sprint Fidelis defibrillator lead.

INTRODUCTION: The diameter of implantable cardioverter-defibrillator (ICD) leads has become progressively smaller over time. However, the long-term performance characteristics of these smaller ICD leads are unknown. METHODS: We retrospectively evaluated 357 patients who underwent implantation of a Medtronic Sprint Fidelis defibrillating lead at two separate centers between September 2004 and October 2006. Lead characteristics were measured at implant, at early follow-up (1-4 days post implant), and every 3-6 months thereafter. RESULTS: During the study period, 357 patients underwent implantation of the Medtronic Sprint Fidelis lead. The mean R-wave measured at implant through the device was not different (P = NS) when compared with that measured at first follow-up (10.5 +/- 5.0 mV vs 10.7 +/- 5.1 mV). Forty-one patients (13%) had an R-wave amplitude

Cryoablation inside the pulmonary vein after failure of radiofrequency antral isolation.

BACKGROUND: Antral pulmonary vein (PV) ablation with radiofrequency (RF) energy has become widely used as a curative approach for the treatment of atrial fibrillation. In some patients, despite antral ablation, PV entry and exit conduction block (BDB) cannot be achieved with RF energy. Cryoablation inside the PV may be an effective method to achieve BDB. OBJECTIVE: This study sought to describe a strategy of cryoablation within the PV to produce BDB in patients in whom antral RF ablation has failed. METHODS: In 15 of 148 consecutive patients (57 +/- 8.9 years old, 80% male) with atrial fibrillation (14 paroxysmal, 1 chronic) undergoing PV isolation cryoablation (CryoCath Technologies, Inc., Montreal, Canada) was performed 12 +/- 2 mm inside the PV after RF antral isolation failed. Nine patients were undergoing a repeat PV isolation procedure. Procedural and follow-up data were recorded and collected. RESULTS: In these 15 patients, BDB could not be achieved in 23 veins (12 left superior PV) with antral or ostial ablation alone. After cryoablation inside the vein, all patients had documented PV BDB and were in normal sinus rhythm at the end of the procedure. The average PV diameter before and after the procedure was unchanged (1.77 +/- 0.18 vs 1.74 +/- 0.19, P = .641). The average fluoroscopic and procedure times were 57 +/- 16 min and 5.3 + 1.2 hours, respectively. At 1-year follow-up, 75% of patients remained in sinus rhythm off antiarrhythmic medication; 7 of 9 patients undergoing a repeat procedure were in sinus rhythm at 1 year off antiarrhythmics. None of the patients had clinical evidence of PV stenosis after cryoablation. CONCLUSION: Cryoablation inside the PV after failed antral isolation with RF is a safe and effective method to achieve acute BDB.

Prolongation of the QTc interval is seen uniformly during early transmural ischemia.

OBJECTIVES: In order to more clearly understand the electrocardiographic manifestations of early transmural ischemia, we studied electrocardiograms (ECGs) in patients undergoing balloon angioplasty. BACKGROUND: Decisions regarding reperfusion strategies in patients with acute myocardial infarction rely largely on the presence of ST-segment elevation (STE) in the ECG, consequently with significant limitations. Studies of the "ischemic cascade" show that ST-segment changes occur well after the onset of wall motion abnormalities. METHODS: We prospectively analyzed ECGs obtained at 20-s intervals in 74 patients undergoing elective balloon angioplasty. The ECGs were analyzed using 3 methodologies. In 74 patients, the ST-segment, the T-wave, and the QT-interval were analyzed using the MUSE (General Electric HC, Menomonee Falls, Wisconsin) automated system (MUSE). Fifty patients were also analyzed using the Interval Editor automated system (IE; General Electric HC). In 20 patients, measurements were made manually. RESULTS: Transmural ischemia prolonged the QTc interval (using the Bazett's formula) in 100% of patients. In all 74 patients analyzed with MUSE, QTc interval prolonged from 423 +/- 25 ms to 455 +/- 34 ms (p < 0.001). In the 50 patients analyzed with IE, QTc interval prolonged in 50 of 50 (100%) patients (from 424 +/- 27 ms to 458 +/- 33 ms [p < 0.001]). Mean time to maximal QTc interval prolongation, changes in T-wave polarity, > or =1 mm STE, and ST-segment depression (STD) were 22, 24, 29, and 35 s, respectively. Although QTc interval prolonged in 100% of patients, T-wave changes, STE, and STD (> or =1 mm) occurred in 7%, 15%, and 7%, respectively. CONCLUSIONS: The QTc interval prolongs in 100% of patients with early transmural ischemia. When compared with clinically accepted indexes of transmural ischemia (i.e., STD and STE [> or =1 mm]) it is the earliest ECG abnormality.

Accuracy of intracardiac echocardiography for assessing the esophageal course along the posterior left atrium: a comparison to magnetic resonance imaging.

BACKGROUND: Atrioesophageal fistula is a potentially fatal complication of ablation in the left atrium (LA) to treat atrial fibrillation. OBJECTIVE: The objective of our study was to systematically evaluate the diagnostic potential of intracardiac echocardiography (ICE) for accurately assessing the esophageal course along the posterior LA. METHODS: Thirty-five patients underwent magnetic resonance imaging (MRI) before and ICE during pulmonary vein (PV) isolation to visualize the esophagus. The location of the esophagus was determined in relation to the PVs and anatomic regions of the LA by both ICE and MRI. Using the MRI images as a reference, the accuracy of ICE localization was assessed. RESULTS: The most common location for the esophagus to appear was the mid-posterior wall (80% of patients by ICE, 71% of patients by MRI), followed by the left posterior wall (71% of patients by ICE, 63% of patients by MRI) and the right posterior wall (60% of patients by ICE, 51% of patients by MRI). The esophagus was seen to course near the left PV antrums (left superior PV antrum 34% of patients by ICE and MRI; left inferior PV antrum 34% of patients by ICE, 37% of patients by MRI), left superior PV (17% of patients by ICE, 20% of patients by MRI), left inferior PV (17% of patients by ICE and MRI), right inferior PV antrum (29% of patients by ICE, 37% of patients by MRI) and the right inferior PV (3% of patients by ICE, 17% of patients by MRI). The sensitivity for esophageal location by ICE compared to that by MRI ranged between 33% (right inferior PV) and 92% (left superior PV antrum, left inferior PV antrum, and mid-posterior wall). The specificity for esophageal location by ICE compared to that by MRI ranged between 60% (mid-posterior wall) and 100% (right inferior PV). The positive predictive value ranged between 80% (left inferior PV) and 100% (right inferior PV). The negative predictive value ranged between 84% (right inferior PV antrum) and 96% (left superior PV antrum). CONCLUSION: Phased array ICE provides rapid, real-time localization of the esophagus during LA ablation that is comparable to MRI.

Paradoxical undersensing during atrial flutter: what is the mechanism?

A patient with congenital complete heart block underwent implantation of a dual-chamber pacemaker. He presented to the emergency room with fatigue and was found to be in atrial flutter. Device interrogation revealed undersensing of 5 mV flutter waves at a programmed sensitivity of 0.5 mV. Due to undersensing, mode switch did not occur. This case illustrates apparently paradoxical undersensing of atrial flutter waves by a dual-chamber pacemaker and can be explained by a phenomenon known as "quiet timer blanking."