Para-Hisian Pacing During Sinus Rhythm: Establishing Threshold Values to Distinguish Nodal From Septal Pathway Conduction.

OBJECTIVES: This study sought to identify minimum threshold values below which conduction over the atrioventricular (AV) node would be unexpected. BACKGROUND: Para-Hisian pacing is used to evaluate for the presence of a septal accessory pathway (AP); however, threshold values to differentiate nodal from AP conduction are unknown. METHODS: The authors performed high- and low-output para-Hisian pacing during sinus rhythm to capture the His and para-Hisian ventricular myocardium (H+V) and para-Hisian ventricular myocardium (V) alone, respectively. The change in stimulation (stim)-to-atrial electrogram interval after loss of His bundle capture in patients with (AP+) and without (AP-) a septal AP was evaluated. Stim-to-proximal coronary sinus (PCS) and stim-to-high right atrium (HRA) intervals were measured and within-patient differences (△) for V and H+V capture were calculated. RESULTS: A total of 23 AP+ and 45 AP- patients were evaluated. The difference in stimulus to earliest atrial signal in the high right atrial catheter seen with the loss of His bundle capture (△-stim-HRA) (21 ms; interquartile range [IQR]: 3 to 43 ms vs. 64 ms; IQR: 56 to 73 ms; p < 0.001) and difference in stimulus to earliest atrial signal in the proximal coronary sinus catheter seen with the loss of His Bundle capture (△-stim-PCS) (11 ms; IQR: 0 to 30 ms vs. 61 ms; IQR: 52 to 72 ms; p < 0.001) were shorter in AP+ patients. The shortest △-stim-PCS and △-stim-HRA in AP- patients were 37 ms and 32 ms, respectively, whereas the longest corresponding intervals in AP+ patients were 51 ms and 75 ms, respectively. CONCLUSIONS: A △-stim-PCS <37 ms or △-stim-HRA <32 ms confirmed the presence of a septal AP, whereas a value >51 ms for △-stim-PCS or >75 ms for △-stim-HRA excluded it. Alternatively, the minimum △-stim-PCS with loss of His capture compatible with AV nodal conduction in isolation was 37 ms, and a △-stim-PCS >51 ms effectively ruled out the presence of a septal AP.

Catheter Ablation of Low-Voltage Areas for Persistent Atrial Fibrillation: Procedural Outcomes Using High-Density Voltage Mapping.

BACKGROUND: Several approaches have been proposed to address the challenge of catheter ablation of persistent atrial fibrillation (AF). However, the optimal ablation strategy is unknown. We sought to evaluate the efficacy of pulmonary vein isolation (PVI) plus low-voltage area (LVA) ablation using contemporary high-density mapping to identify LVA in patients with persistent AF. METHODS: Consecutive patients accepted for AF catheter ablation were studied. High-density bipolar voltage mapping data were acquired in sinus rhythm using multipolar catheters to detect LVA (defined as bipolar voltage < 0.5 mV). Semiautomated impedance-based software was used to ensure catheter contact during data collection. Patients underwent PVI + LVA ablation (if LVA present). RESULTS: A total of 145 patients were studied; 95 patients undergoing PVI + LVA ablation were compared with 50 controls treated with PVI only. Average age was 61 ± 10 years, and 80% were male. Baseline characteristics were comparable. Freedom from atrial tachycardia/AF at 18 months was 72% after PVI + LVA ablation vs 58% in controls (P = 0.022). Median procedure duration (273 [240, 342] vs 305 [262, 360] minutes; P = 0.019) and radiofrequency delivery (50 [43, 63] vs 55 [35, 68] minutes; P = 0.39) were longer in the PVI + LVA ablation group. Multivariable analysis showed that the ablation strategy (PVI + LVA) was the only independent predictor of freedom from atrial tachycardia/AF (hazard ratio, 0.53; 95% confidence interval, 0.29-0.96; P = 0.036). There were no adverse safety outcomes associated with LVA ablation. CONCLUSIONS: An individualized strategy of high-density mapping to assess the atrial substrate followed by PVI combined with LVA ablation is associated with improved outcomes. Adequately powered randomized clinical trials are needed to determine the role of PVI + LVA ablation for persistent AF.

Feasibility of complex transfemoral electrophysiology procedures in patients with inferior vena cava filters.

BACKGROUND: The presence of inferior vena cava filters (IVCFs) has been considered a relative contraindication to electrophysiology (EP) procedures that require transfemoral venous placement of multiple catheters and/or long sheaths. There are inadequate data related to complex EP procedures in this population. OBJECTIVE: The purpose of this study was to describe the experience of a single high-volume center with respect to complex EP procedures in patients with IVCFs. METHODS: Patients with IVCFs undergoing complex EP procedures between 2004 and 2018 were identified. Clinical characteristics, IVCF type, procedural findings, and complications were analyzed. RESULTS: Fifty complex ablation procedures were performed in 40 patients (mean age 63.8 ± 10.9 years; 68% men). The mean IVCF dwell time was 69.1 ± 19.1 months, and 48 patients (96%) were on chronic oral anticoagulation. Procedures included ablation of atrial fibrillation (n = 21), ventricular tachycardia (n = 20), supraventricular tachycardia (n = 3), cavotricuspid isthmus flutter (n = 3), supraventricular tachycardia and cavotricuspid isthmus flutter (n = 1), and transvenous lead extraction (n = 3). Twenty procedures included quadripolar catheters (mean 1.4 ± 0.75), and 33 procedures involved deflectable decapolar catheters (mean 1.7 ± 0.47). Long sheaths were used in 35 cases (mean 1.63 ± 0.49) and intracardiac echocardiography in 38. In 4 cases (involving 3 patients), the IVCF was occluded and could not be crossed. There were no procedural complications related to the IVCF. CONCLUSION: The substantial majority of IVCFs in patients presenting for complex EP procedures were patent and easily crossed under fluoroscopic guidance. The presence of an IVCF should not discourage operators from performing procedures that require transfemoral deployment of multiple catheters and/or sheaths.

Characterization of Low-Voltage Areas in Patients With Atrial Fibrillation: Insights From High-Density Intracardiac Mapping.

BACKGROUND: There is limited data on the scar burden in patients with atrial fibrillation (AF). In this study, we sought to evaluate the presence and extent of an abnormal left atrial (LA) substrate in patients with paroxysmal or persistent AF. METHODS: Consecutive patients who underwent initial AF catheter ablation were prospectively enrolled. Endocardial voltage mapping was acquired in sinus rhythm using multipolar mapping catheters. Automated software was used to ensure homogeneous data collection. Assessment of low-voltage area (LVA) was performed by a reviewer blinded to clinical details. RESULTS: One hundred and four patients were prospectively enrolled; 69 had paroxysmal and 35 persistent AF. The mean LA volume was 159 ± 48 mL, and the average number of LA points collected was 1308 ± 1065. Atrial LVAs were present in 23 of 69 (33%) subjects with paroxysmal and 20 of 35 (57%) with persistent AF (P = 0.02). Amongst 43 of 104 patients with scar, the average extent of LVA was 19.4 ± 21.6 cm2 and the mean percentage area was 7.6 ± 8.8%. Univariate analysis showed that age, LA volume, and persistent AF were associated with the presence of LVA. Multivariable analysis showed that age (odds ratio [OR] 1.05; 95% confidence interval [CI] 1.00-1.11; P = 0.046) and LA volume (OR 1.02; 95% CI 1.01-1.04; P < 0.001) remained predictors of LVA. AF classification (persistent vs paroxysmal) was not a predictor of an abnormal atrial substrate (OR 1.34; 95% CI 0.4-3.9; P = 0.56). CONCLUSIONS: There is wide variability in the presence and extent of LVA in patients with paroxysmal or persistent AF. Age and LA volume were predictors of LVA. There was no correlation between AF classification and the presence of LVA.

Association between transthoracic impedance and electrical cardioversion success with biphasic defibrillators: An analysis of 1055 shocks for atrial fibrillation and flutter.

BACKGROUND: The relevance of transthoracic impedance (TTI) to electrical cardioversion (ECV) success for atrial tachyarrhythmias when using biphasic waveform defibrillators is unknown. HYPOTHESIS: TTI is predictive of ECV success with contemporary defibrillators. METHODS: De-identified data stored in biphasic defibrillator memory cards from ECV attempts for atrial fibrillation (AF) or atrial flutter (AFL) over a 2-year period at our center were evaluated. ECV success, defined as arrhythmia termination and ≥ 1 sinus beat, was adjudicated by 2 blinded cardiac electrophysiologists. The association between TTI and ECV success was assessed via Cochrane-Armitage trend and Spearman rank correlation tests, as well as simple and multivariable logistic regression. The influence of TTI on the number of shocks and on cumulative energy delivered per patient was also examined. RESULTS: 703 patients (593 with AF, 110 with AFL) receiving 1055 shocks were included. Last shock success was achieved in 88.0% and 98.2% of patients with AF and AFL, respectively. In patients with AF, TTI was positively associated with last shock failure (Ptrend =0.019), the need for multiple shocks (Ptrend <0.001), and cumulative energy delivered (ρ = 0.348; P < 0.001). After adjusting for first shock energy, 10-Ω increments in TTI were associated with odds ratios of 1.36 (95% CI: 1.24-1.49) and 1.22 (95% CI: 1.09-1.37) for first and last shock failure, respectively (P < 0.001 for both). CONCLUSIONS: Although contemporary defibrillators are designed to compensate for TTI, this variable continues to be associated with ECV failure in patients with AF. Strategies to lower TTI during ECV for AF may improve procedural success.

Recurrent atrial arrhythmias in the setting of chronic pulmonary vein isolation.

BACKGROUND: Atrial arrhythmias may still occur in patients after durable pulmonary vein isolation (PVI). OBJECTIVE: The purpose of this study was to examine the incidence of patients undergoing ablation for recurrent arrhythmia despite chronic PVI and their clinical outcomes. METHODS: Patients undergoing repeat left atrial ablation procedures were selected from a prospective registry. From this population, we identified patients with chronic PVI. Clinical characteristics, ablation strategies, and outcomes were analyzed. RESULTS: Between January 2003 and December 2013, 1045 patients underwent 1298 repeat left atrial procedures. Of these, 900 patients had atrial fibrillation (AF) and 145 had atrial flutter (AFL)/atrial tachycardia (AT). Fifty-two patients (5.0%; 27 with AF and 25 with AFL/AT) had chronic PVI and were included in the study. Patients were followed for 19.7 ± 5.6 months. In patients with AF, 11 (41%) had a non-PV trigger identified. Ablation strategies included non-PV trigger ablation (n = 11), empiric trigger-site ablation (n = 3), provoked arrhythmia ablation (n = 9), complex fractionated atrial electrogram ablation (n = 2), and linear ablation (n = 2). During follow-up, 9 (33%) had no recurrence, 7 (26%) had rare AF (≤2 episodes during follow-up ≥1 year), and 11 (41%) had AF recurrence. In patients with AFL/AT, 12 (48%) had no recurrence, 4 (16%) had rare recurrence (≤2 episodes during follow-up ≥1 year), and 9 (36%) had recurrence. CONCLUSION: In patients with PVI undergoing a repeat procedure during the time period studied, only a small portion had chronic PVI. A strategy of targeting non-PV triggers for AF and linear/focal ablation for AFL/AT may achieve long-term arrhythmia control in the majority of patients.

Radiation safety and ergonomics in the electrophysiology laboratory: update on recent advances.

PURPOSE OF REVIEW: Risks associated with exposure to ionizing radiation in patients undergoing electrophysiology procedures and interventional cardiac electrophysiologists performing these procedures are a serious concern. Strategies to reduce radiation exposure are of obvious importance. In addition, interventional cardiac electrophysiologists have to perform procedures wearing heavy lead protection for prolonged periods, making them prone to cervical and lumbar spinal injuries. RECENT FINDINGS: Recently developed technologies, such as low-exposure radiographic imaging, novel radiographic imaging protection systems, nonfluoroscopic mapping systems using image integration, and remote catheter manipulation systems have been successful in reducing ionizing radiation exposure in the electrophysiology laboratory. The efficacy and safety of these technologies are being evaluated in clinical trials. In addition, economic analyses are being performed to evaluate these novel systems. The use of nonweight-bearing radiation protection devices and ergonomic design of the electrophysiology laboratory aim to reduce the incidence of occupational injuries in interventional cardiac electrophysiologists. SUMMARY: There is need for ongoing development and evaluation of new technologies to minimize exposure to ionizing radiation during electrophysiologic procedures. In addition, ergonomic planning of the electrophysiology laboratory and training of interventional cardiac electrophysiologists are crucial to occupational injury prevention.

Ablation of ventricular arrhythmias.

Ventricular arrhythmias (VAs) commonly occur in patients with structural heart disease and may present as ventricular premature depolarizations (VPDs), monomorphic ventricular tachycardia (VT), or polymorphic VT/ventricular fibrillation. Idiopathic VAs can also occur in patients with normal hearts. This review explores the etiology, clinical presentation, and management strategies for different types of VAs. Medical and invasive treatment strategies are discussed, and different approaches to catheter ablation are outlined. While ablation of VPDs and idiopathic VT provides a cure for the majority of patients, investigation is ongoing to define the optimal ablation strategy for patients with scar-related VT.