Conduction velocity is reduced in the posterior wall of hypertrophic cardiomyopathy patients with normal bipolar voltage undergoing ablation for paroxysmal atrial fibrillation.

OBJECTIVES: We investigated characteristics of left atrial conduction in patients with HCM, paroxysmal AF and normal bipolar voltage. BACKGROUND: Patients with hypertrophic cardiomyopathy (HCM) exhibit abnormal cardiac tissue arrangement. The incidence of atrial fibrillation (AF) is increased fourfold in patients with HCM and confers a fourfold increased risk of death. Catheter ablation is less effective in HCM, with twofold increased risk of AF recurrence. The mechanisms of AF perpetuation in HCM are poorly understood. METHODS: We analyzed 20 patients with HCM and 20 controls presenting for radiofrequency ablation of paroxysmal AF normal left atrial voltage(> 0.5 mV). Intracardiac electrograms were extracted from the CARTO mapping system and analyzed using Matlab/Python code interfacing with Core OpenEP software. Conduction velocity maps were calculated using local activation time gradients. RESULTS: There were no differences in baseline demographics, atrial size, or valvular disease between HCM and control patients. Patients with HCM had significantly reduced atrial conduction velocity compared to controls (0.44 ± 0.17 vs 0.56 ± 0.10 m/s, p = 0.01), despite no significant differences in bipolar voltage amplitude (1.23 ± 0.38 vs 1.20 ± 0.41 mV, p = 0.76). There was a statistically significant reduction in conduction velocity in the posterior left atrium in HCM patients relative to controls (0.43 ± 0.18 vs 0.58 ± 0.10 m/s, p = 0.003), but not in the anterior left atrium (0.46 ± 0.17 vs 0.55 ± 0.10 m/s, p = 0.05). There was a significant association between conduction velocity and interventricular septal thickness (slope = -0.013, R2 = 0.13, p = 0.03). CONCLUSIONS: Atrial conduction velocity is significantly reduced in patients with HCM and paroxysmal AF, possibly contributing to arrhythmia persistence after catheter ablation.

Rebooting atrial fibrillation ablation in the COVID-19 pandemic.

PURPOSE: Catheter ablation procedures for atrial fibrillation (AF) were significantly curtailed during the peak of coronavirus disease 2019 (COVID-19) pandemic to conserve healthcare resources and limit exposure. There is little data regarding peri-procedural outcomes of medical procedures during the COVID-19 pandemic. We enacted protocols to safely reboot AF ablation while limiting healthcare resource utilization. We aimed to evaluate acute and subacute outcomes of protocols instituted for reboot of AF ablation during the COVID-19 pandemic. METHODS: Perioperative healthcare utilization and acute procedural outcomes were analyzed for consecutive patients undergoing AF ablation under COVID-19 protocols (2020 cohort; n=111) and compared to those of patients who underwent AF ablation during the same time period in 2019 (2019 cohort; n=200). Newly implemented practices included preoperative COVID-19 testing, selective transesophageal echocardiography (TEE), utilization of venous closure, and same-day discharge when clinically appropriate. RESULTS: Pre-ablation COVID-19 testing was positive in 1 of 111 patients. There were 0 cases ablation-related COVID-19 transmission and 0 major complications in either cohort. Pre-procedure TEE was performed in significantly fewer 2020 cohort patients compared to the 2019 cohort patients (68.4% vs. 97.5%, p <0.001, respectively) despite greater prevalence of persistent arrhythmia in the 2020 cohort. Same-day discharge was achieved in 68% of patients in the 2020 cohort, compared to 0% of patients in the 2019 cohort. CONCLUSIONS: Our findings demonstrate the feasibility of safe resumption of complex electrophysiology procedures during the COVID-19 pandemic, reducing healthcare utilization and maintaining quality of care. Protocols instituted may be generalizable to other types of procedures and settings.

High-power, short-duration ablation for atrial fibrillation: Pros and cons.

This article reviews and compares the rationale and evidence supporting high-power, short-duration radiofrequency (RF) ablation with those of conventional-power, conventional-duration RF ablation for atrial fibrillation (AF). The pros and cons of each approach, biophysics of ablation, pre-clinical studies informing clinical utilization, and the accumulated clinical evidence are presented. Both conventional-power, conventional-duration RF ablation and high-power, short-duration ablation are similarly safe, and effective approaches for AF ablation. Theoretical advantages of high-power, short-duration ablation, including greater procedure efficiency and limited conductive heating of collateral structures, must be weighed against the narrower safety margin related to rapid energy delivery during high power ablation.

Multiple procedure outcomes for nonparoxysmal atrial fibrillation: Left atrial posterior wall isolation versus stepwise ablation.

OBJECTIVE: To compare multiple-procedure catheter ablation outcomes of a stepwise approach versus left atrial posterior wall isolation (LA PWI) in patients undergoing nonparoxysmal atrial fibrillation (NPAF) ablation. BACKGROUND: Unfavorable outcomes for stepwise ablation of NPAF in large clinical trials may be attributable to proarrhythmic effects of incomplete ablation lines. It is unknown if a more extensive initial ablation strategy results in improved outcomes following multiple ablation procedures. METHODS: Two hundred twenty two consecutive patients with NPAF underwent first-time ablation using a contact-force sensing ablation catheter utilizing either a stepwise (Group 1, n = 111) or LA PWI (Group 2, n = 111) approach. The duration of follow-up was 36 months. The primary endpoint was freedom from atrial arrhythmia >30 s. Secondary endpoints were freedom from persistent arrhythmia, repeat ablation, and recurrent arrhythmia after repeat ablation. RESULTS: There was similar freedom from atrial arrhythmias after index ablation for both stepwise and LA PWI groups at 36 months (60% vs. 69%, p = .1). The stepwise group was more likely to present with persistent recurrent arrhythmia (29% vs. 14%, p = .005) and more likely to undergo second catheter ablation (32% vs. 12%, p < .001) compared to LA PWI patients. Recurrent arrhythmia after repeat ablation was more likely in the stepwise group compared to the LA PWI group (15% vs. 4%, p = .003). CONCLUSIONS: Compared to a stepwise approach, LA PWI for patients with NPAF resulted in a similar incidence of any atrial arrhythmia, lower incidence of persistent arrhythmia, and fewer repeat ablations. Results for repeat ablation were not improved with a more extensive initial approach.

Esophageal temperature dynamics during high-power short-duration posterior wall ablation.

BACKGROUND: Increased peak luminal esophageal temperature (LET) is associated with increased risk of esophageal injury after left atrial posterior wall (LAPW) ablation. The magnitude, distribution, and risk factors of LET increase with high-power short-duration (HPSD) LAPW ablation are not well understood. OBJECTIVE: The purpose of this study was to describe the spatial and temporal characteristics of LET changes associated with HPSD LAPW radiofrequency (RF) ablation. METHODS: LET was sampled at 20 Hz using a 12-point esophageal temperature monitor (CIRCA S-CATH; Circa Scientific, Inc) in 16 patients undergoing LAPW ablation. Esophageal temperature sensor position and lesion locations were recorded using an electroanatomic mapping system with fluoroscopic integration (CARTO 3, CARTOUNIVU; Biosense Webster, Inc). Point-by-point LAPW ablation was performed at 50 W for 6 seconds. The first 20 LAPW lesions were individually analyzed in each patient. RESULTS: LET increase ≥4°C (8 lesions: max LET 5.8°C), 2°-4°C (34 lesions), and 1°-2°C (58 lesions) occurred at 9 ± 2 mm, 8 ± 2 mm, and 13 ± 2 mm from sensors, respectively. Lesions placed >20 mm from a temperature sensor did not result in an LET increase ≥2°C. Temperature resolution to within 1°C of baseline occurred ∼60 seconds after cessation of RF application. Consecutive lesions resulting in additive heating of at least 1°C occurred in 17 lesion pairs with an interlesion distance of 9 ± 4 mm and interlesion time of 21 ± 4 seconds. CONCLUSION: HPSD LAPW ablation can result in severe esophageal temperature increases. Significant LET increase will be undetected when lesions are >20 mm away from a temperature sensor. Additive LET increase was observed with consecutive lesions placed <20 mm apart within 60 seconds.

Inappropriate ICD Shock as a Result of TASER Discharge.

Conducted energy weapon (commonly known as TASER) discharge in patients with implantable cardioverter-defibrillators is known to cause electromagnetic interference and inappropriate ventricular fibrillation sensing without delivery of implantable cardioverter-defibrillators therapy during conducted energy weapon application. We report the first known case of conducted energy weapon discharge resulting in inappropriate implantable cardioverter-defibrillators therapy. (Level of Difficulty: Beginner.).

Contact-force radiofrequency ablation of non-paroxysmal atrial fibrillation: improved outcomes with increased experience.

INTRODUCTION: Clinical trials have failed to reliably show improved outcomes with utilization of contact-force sensing (CFS) radiofrequency (RF) ablation catheters. It is unknown whether the unfavorable outcomes observed in these trials are attributable to inexperience with CFS technology. OBJECTIVES: To compare catheter ablation outcomes of stepwise linear ablation with versus without CFS technology and to assess the impact of operator experience with CFS technology on procedural outcomes. METHODS: Clinical outcomes were evaluated in 228 consecutive NPAF patients undergoing first-time left atrial ablation using a stepwise linear approach. Arrhythmia recurrence was assessed using 2-week event monitors at 3-month intervals following index ablation. RESULTS: A total of 228 patients were included in our study. There was no statistically significant difference in risk of recurrent atrial arrhythmias at 12 and 24 months between CFS and non-CFS patients (p = 0.5 and p = 0.169). The time to recurrence of atrial arrhythmias at 24 months in the second half of CFS patients was significantly lower when compared to both the first half of CFS patients (p = 0.002) and non-CFS patients (p = 0.005). CONCLUSION: While there was no difference in overall outcomes between CFS and non-CFS ablation using a stepwise linear approach in patients with NPAF, procedural efficacy of the second half of CFS patients was significantly improved compared to both the first half of CFS patients and all non-CFS patients. Lack of benefit seen in clinical trials using CFS technology may be related to operator inexperience with CFS ablation catheters at the time of the trials.

Effect of CYP2C9 and VKORC1 Gene Variants on Warfarin Response in Patients with Continuous-Flow Left Ventricular Assist Devices.

Bleeding and thrombotic complications continue to plague continuous-flow left ventricular assist device (CF-LVAD) therapy in patients with end-stage heart failure. Warfarin genotyping information can be incorporated into decision making for initial dosing as recommended by the Food and Drug Administration; however, clinical utility of this data in the CF-LVAD population has not been well studied. Genotypes testing for CYP2C9 and VCORC1 polymorphisms were determined in 90 CF-LVAD patients. Outcomes studied were the association of CYP2C9 (*1, *2, or *3) and VKORC1 (-1639 G>A) gene variants with time-to-target international normalized ratio (INR), total warfarin dose, maintenance warfarin dose. Continuous-flow left ventricular assist device patients carrying a rare variant in the VKORC1 gene had a significantly lower cumulative warfarin dose until target INR achieved (18.9 vs. 35.0 mg, p = 0.002), days spent until INR target achieved (4.9 vs. 7.0 days, p = 0.021), and discharge warfarin dose (3.2 vs. 5.6 mg, p = 0.001) compared with patients with wild-type genotype. Genotype-guided warfarin dosing may lead to safer anticoagulation and potentially improve outcomes in CF-LVAD patients.

Cardiac arrhythmias in pregnancy.

As more women with repaired congenital heart disease survive to their reproductive years and many other women are delaying pregnancy until later in life, a rising concern is the risk of cardiac arrhythmias during pregnancy. Naturally occurring cardiovascular changes during pregnancy increase the likelihood that a recurrence of a previously experienced cardiac arrhythmia or a de novo arrhythmia will occur. Arrhythmias should be thoroughly investigated to determine if there is a reversible etiology, and risks/benefits of treatment options should be fully explored. We discuss the approach to working up and treating various arrhythmias during pregnancy with attention to fetal and maternal risks as well as treatment of fetal arrhythmias. Acute management in stable patients includes close monitoring and intravenous pharmacologic therapy, while DC cardioversion should be used to terminate arrhythmias in hemodynamically unstable patients. Long-term management may require continued oral antiarrhythmic therapy, with particular attention to fetal safety, to prevent complications associated with arrhythmias.

Diffuse ST depression with ST elevation in aVR: Is this pattern specific for global ischemia due to left main coronary artery disease?

BACKGROUND AND PURPOSE: We assess whether the electrocardiographic (ECG) pattern of ST depression in >7 body surface leads combined with ST elevation in aVR and V1 is predictive of left main coronary artery (LMCA) stenosis or left main equivalent (LMEQ) disease. METHODS: We collected 133 patients showing this particular ECG pattern. Patients with left bundle branch block, ventricular rhythm or ventricular paced rhythm were excluded. RESULTS: Only 28% of the patients had non-ST elevation acute coronary syndrome (NSTE-ACS). ECGs were classified as chronic, dynamic or no prior in 28%, 48% and 24%, respectively. A total of 57 patients (44%) underwent coronary angiography (CA). No significant coronary artery disease was found in 26%. LMCA/LMEQ disease was found in only 23% of these patients. The positive predictive value of the ECG pattern was not improved after exclusion of patients with intraventricular conduction abnormalities and left ventricular hypertrophy or in patients with dynamic ECG changes. CONCLUSIONS: This ECG pattern is not always caused by LMCA/LMEQ disease; therefore, the term "suspect circumferential subendocardial ischemia" may be preferred. Other medical conditions may also be associated with a similar ECG pattern.