Can phrenic nerve injury be anticipated by larger cryoballoons?

Recently, a novel size-adjustable cryoballoon has been introduced in clinical practice, which can be inflated to two different diameters (28 and 31 mm). The 31 mm cryoballoon is specifically designed to achieve better contact with remodeled pulmonary veins (PVs) that have wider ostia while avoiding deep cannulation, thereby potentially reducing the risk of phrenic nerve injury (PNI) associated with deep balloon cannulation. However, we encountered two cases of PNI during cryoballoon ablation using the novel system among our initial 25 consecutive case series. Herein, we present two cases that exhibited PNI during freezing of the right superior PV with a size-adjustable balloon. While larger balloons are expected to create a larger area of isolation, the safety of this novel balloon system needs to be evaluated in a large-scale clinical study.

Implantable Defibrillator System Shock Function, Mortality, and Cause of Death After Magnetic Resonance Imaging.

BACKGROUND: Studies have shown that magnetic resonance imaging (MRI) does not have clinically important effects on the device parameters of non-MRI-conditional implantable cardioverter-defibrillators (ICDs). However, data on non-MRI-conditional ICD detection and treatment of arrhythmias after MRI are limited. OBJECTIVE: To examine if non-MRI-conditional ICDs have preserved shock function of arrhythmias after MRI. DESIGN: Prospective cohort study. (ClinicalTrials.gov: NCT01130896). SETTING: 1 center in the United States. PATIENTS: 629 patients with non-MRI-conditional ICDs enrolled consecutively between February 2003 and January 2015. INTERVENTIONS: 813 total MRI examinations at a magnetic field strength of 1.5 Tesla using a prespecified safety protocol. MEASUREMENTS: Implantable cardioverter-defibrillator interrogations were collected after MRI. Clinical outcomes included arrhythmia detection and treatment, generator or lead exchanges, adverse events, and death. RESULTS: During a median follow-up of 2.2 years from MRI to latest available ICD interrogation before generator or lead exchange in 536 patients, 4177 arrhythmia episodes were detected, and 97 patients received ICD shocks. Sixty-one patients (10% of total) had 130 spontaneous ventricular tachycardia or fibrillation events terminated by ICD shocks. A total of 210 patients (33% of total) are known to have died (median, 1.7 years from MRI to death); 3 had cardiac arrhythmia deaths where shocks were indicated without direct evidence of device dysfunction. LIMITATIONS: Data were acquired at a single center and may not be generalizable to other clinical settings and MRI facilities. Implantable cardioverter-defibrillator interrogations were not available for a subset of patients; adjudication of cause of death relied solely on death certificate data in a subset. CONCLUSION: Non-MRI-conditional ICDs appropriately treated detected tachyarrhythmias after MRI. No serious adverse effects on device function were reported after MRI. PRIMARY FUNDING SOURCE: Johns Hopkins University and National Institutes of Health.

Comparison of three different approaches to very high-power short-duration ablation using the QDOT-MICRO catheter.

BACKGROUND/OBJECTIVES: The QDOT-MICRO™ catheter allows very high-power and short-duration (vHPSD) ablation. This study aimed to investigate lesion characteristics using different ablation settings. METHODS: Radiofrequency applications (90 W/4 s, temperature-control mode with 55°C or 60°C target) were performed in excised porcine myocardium using three different approaches: single (SA), double nonrepetitive (DNRA), and double repetitive applications (DRA). Applications were performed with an interval of 1 min for DNRA, and without interval for DRA. RESULTS: A total of 480 lesions were analyzed. Lesion depth and volume were largest for DRA followed by DNRA and SA regardless of catheter direction (depth: 3.8 vs. 3.3 vs. 2.6 mm, p < .001 for all comparisons; volume: 176.6 vs. 145.1 vs. 97.0 mm3 , p < .001 for all comparisons). Surface area was significantly larger for DRA than for SA (45.1 vs. 38.3 mm2 , p < .001) and larger for DNRA than for SA (44.5 vs. 38.3 mm2 , p < .001), but was similar between DRA and DNRA (45.1 vs. 44.5 mm2 , p = .54). Steam-pops more frequently occurred for DRA than for SA (15.6% vs. 4.4%, p = .004) and DNRA (15.6% vs. 6.9%, p = .061), but the incidence was similar between SA and DNRA (4.4% vs. 6.9%, p = 1). Although surface area and lesion volume were larger in lesions with steam-pops than without steam-pops (46.5 vs. 38.1 mm2 , p = .018 and 128.3 vs. 96.8 mm3 , p = .068, respectively), lesions were not deeper (pop(+): 2.5 mm vs. pop(-): 2.6 mm, p = .75). CONCLUSIONS: DNRA produces larger lesions than SA without increasing the risk of steam-pops. DRA produces the largest lesions among the three groups, but with an increased risk of steam-pops. Even with steam-pops, lesions do not become deeper in vHPSD ablation.

Impact of filter configurations on bipolar EGMs: An optimal filter setting for identifying VT substrates.

BACKGROUND: The impact of filtering on bipolar electrograms (EGMs) has not been systematically examined. We tried to clarify the optimal filter configuration for ventricular tachycardia (VT) ablation. METHODS: Fifteen patients with VT were included. Eight different filter configurations were prospectively created for the distal bipoles of the ablation catheter: 1.0-250, 10-250, 100-250, 30-50, 30-100, 30-250, 30-500, and 30-1000 Hz. Pre-ablation stable EGMs with good contact (contact force > 10 g) were analyzed. Baseline fluctuation, baseline noise, bipolar peak-to-peak voltage, and presence of local abnormal ventricular activity (LAVA) were compared between different filter configurations. RESULTS: In total, 2276 EGMs with multiple bipolar configurations in 246 sites in scar and border areas were analyzed. Baseline fluctuation was only observed in the high-pass filter of (HPF) ≤ 10 Hz (p < .001). Noise level was lowest at 30-50 Hz (0.018 [0.012-0.029] mV), increased as the low-pass filter (LPF) extended, and was highest at 30-1000 Hz (0.047 [0.041-0.061] mV) (p < .001). Conversely, the HPF did not affect the noise level at ≤30 Hz. As the HPF extended to 100 Hz, bipolar voltages significantly decreased (p < .001), but were not affected when the LPF was extended to ≥100 Hz. LAVAs were most frequently detected at 30-250 Hz (207/246; 84.2%) and 30-500 Hz (208/246; 84.6%), followed by 30-1000 Hz (205/246; 83.3%), but frequently missed at LPF ≤ 100 Hz or HPF ≤ 10 Hz (p < .001). A 50-Hz notch-filter reduced the bipolar voltage by 43.9% and LAVA-detection by 34.5% (p < .0001). CONCLUSION: Bipolar EGMs are strongly affected by filter settings in scar/border areas. In all, 30-250 or 30-500 Hz may be the best configuration, minimizing the baseline fluctuation, baseline noise, and detecting LAVAs. Not applying the 50-Hz notch filter may be beneficial to avoid missing VT substrate.

Comparison of lesion characteristics using temperature-flow-controlled versus conventional power-controlled ablation with fixed ablation index.

INTRODUCTION: The QDOT-MicroTM catheter is a novel irrigated contact force (CF) sensing catheter which benefits from thermocouples for temperature monitoring, allowing temperature-flow-controlled (TFC) ablation. We compared lesion metrics at fixed ablation index (AI) value during TFC-ablation and conventional power-controlled (PC)-ablation. METHODS: A total of 480 RF-applications were performed on ex-vivo swine myocardium with predefined AI targets (400/550) or until steam-pop occurred, using the QDOT-MicroTM (TFC-ablation) and Thermocool SmartTouch SFTM (PC-ablation). RESULTS: Both TFC-ablation and PC-ablation produced similar lesions in volume (218 ± 116 vs. 212 ± 107 mm3 , p = .65); however, lesions using TFC-ablation were larger in surface area (41.3 ± 8.8 vs. 34.8 ± 8.0 mm2 , p < .001) and shallower in depth (4.0 ± 1.0 vs. 4.2 ± 1.1 mm, p = .044). Average power tended to be lower in TFC-alation (34.2 ± 8.6 vs. 36.9 ± 9.2, p = .005) compared to PC-ablation due to automatic regulation of temperature and irrigation-flow. Although steam-pops were less frequent in TFC-ablation (24% vs. 15%, p = .021), they were particularly observed in low-CF (10 g) and high-power ablation (50 W) in both PC-ablation (n = 24/240, 10.0%) and TFC-ablation (n = 23/240, 9.6%). Multivariate analysis revealed that high-power, low-CF, long application time, perpendicular catheter orientation, and PC-ablation were risk factors for steam-pops. Furthermore, activation of automatic regulation of temperature and irrigation-flow was independently associated with high-CF and long application time while ablation power had no significant relationship. CONCLUSIONS: With a fixed target AI, TFC-ablation reduced the risk of steam-pops, producing similar lesions in volume, but with different metrics in this ex-vivo study. However, lower CF and higher power in fixed-AI ablation may increase the risk of steam-pops.

Impact of baseline pool impedance on lesion metrics and steam pops in catheter ablation.

INTRODUCTION: Little is known about the impact of blood-pool local impedance (LI) on lesion characteristics and the incidence of steam pops. METHODS: Radiofrequency applications at a range of powers (30, 40, and 50 W), contact forces (CF) (5, 15, and 25 g), and durations (15, 30, 45, and 120 s) using perpendicular/parallel catheter orientation were performed in 40 excised porcine preparations, using a catheter capable of monitoring LI (StablePoint©, Boston Scientific). To simulate the variability in blood-pool impedance, the saline-pool LI was modulated by calibrating saline concentrations. Lesion characteristics were compared under three values of saline-pool LI: 120, 160, and 200 Ω. RESULTS: Of 648 lesions created, steam pops occurred in 175 (27.0%). When power, CF, time, and catheter orientation were adjusted, ablation at a saline-pool impedance of 160 or 200 Ω more than doubled the risk of steam pops compared with a saline-pool impedance of 120 Ω (Odds ratio = 2.31; p = .0002). Lesions in a saline-pool impedance of 120 Ω were significantly larger in surface area (50 [38-62], 45 [34-56], and 41 [34-60] mm2 for 120, 160, and 200 Ω, p < .05), but shallower in depth (4.0 [3-5], 4.4 [3.2-5.3], and 4.5 [3.8-5.5] mmfor 120, 160, and 200 Ω, respectively, p < .05) compared with the other two settings. The correlation between the absolute LI-drop and lesion size weakened as the saline-pool LI became higher (e.g., 120 Ω group (r2 = .30, r2 = .18, and r2 = .16, respectively for 120, 160, and 200 Ω), but the usage of %LI-drop (= absolute LI-drop/initial LI) instead of absolute LI-drop may minimize this effect. CONCLUSIONS: In an experimental model, baseline saline-pool impedance significantly affects the lesion metrics and the risk of steam pops.

Transcoronary mapping with an over-the-wire multielectrode catheter in scar-related ventricular tachycardia patients.

AIMS: The usefulness of coronary venous system mapping has been reported for assessing intramural and epicardial substrates in patients with scar-related ventricular tachycardia (VT). However, there has been little data on mapping from coronary arteries. We investigated the safety and utility of mapping from coronary arteries with a novel over-the-wire multielectrode catheter in scar-related VT patients. METHODS AND RESULTS: Ten consecutive scar-related VT patients with non-ischaemic cardiomyopathy who underwent mapping from a coronary artery were analysed. Six patients underwent simultaneous coronary venous mapping. High-density maps were created by combining the left ventricular endocardium and coronary vessels. Substrate maps were created during the baseline rhythm with 2438 points (IQR 2136-3490 points), including 329 (IQR 59-508 points) in coronary arteries. Abnormal bipolar electrograms were successfully recorded within coronary arteries close to the endocardial substrate in seven patients. During VT, isthmus components were recorded within the coronary vessels in three patients with no discernible isthmus components on endocardial mapping. The ablation terminated the VT from an endocardial site opposite the earliest site in the coronary arteries in five patients. CONCLUSION: The transcoronary mapping with an over-the-wire multielectrode catheter can safely record abnormal bipolar electrograms within coronary arteries. Additional mapping data from the coronary vessels have the potential to assess three-dimensional ventricular substrates and circuit structures in scar-related VT patients.

Detailed analysis of tachycardia cycle length aids diagnosis of the mechanism and location of atrial tachycardias.

AIMS: Although the mechanism of an atrial tachycardia (AT) can usually be elucidated using modern high-resolution mapping systems, it would be helpful if the AT mechanism and circuit could be predicted before initiating mapping. OBJECTIVE: We examined if the information gathered from the cycle length (CL) of the tachycardia can help predict the AT-mechanism and its localization. METHODS: One hundred and thirty-eight activation maps of ATs including eight focal-ATs, 94 macroreentrant-ATs, and 36 localized-ATs in 95 patients were retrospectively reviewed. Maximal CL (MCL) and minimal CL (mCL) over a minute period were measured via a decapolar catheter in the coronary sinus. CL-variation and beat-by-beat CL-alternation were examined. Additionally, the CL-respiration correlation was analysed by the RhythmiaTM system. : Both MCL and mCL were significantly shorter in macroreentrant-ATs [MCL = 288 (253-348) ms, P = 0.0001; mCL = 283 (243-341) ms, P = 0.0012], and also shorter in localized-ATs [MCL = 314 (261-349) ms, P = 0.0016; mCL = 295 (248-340) ms, P = 0.0047] compared to focal-ATs [MCL = 506 (421-555) ms, mCL = 427 (347-508) ms]. An absolute CL-variation (MCL-mCL) < 24 ms significantly differentiated re-entrant ATs from focal-ATs with a sensitivity = 96.9%, specificity = 100%, positive predictive value (PPV) = 100%, and negative predictive value (NPV) = 66.7%. The beat-by-beat CL-alternation was observed in 10/138 (7.2%), all of which showed the re-entrant mechanism, meaning that beat-by-beat CL-alternation was the strong sign of re-entrant mechanism (PPV = 100%). Although the CL-respiration correlation was observed in 28/138 (20.3%) of ATs, this was predominantly in right-atrium (RA)-ATs (24/41, 85.7%), rather than left atrium (LA)-ATs (4/97, 4.1%). A positive CL-respiration correlation highly predicted RA-ATs (PPV = 85.7%), and negative CL-respiration correlation probably suggested LA-ATs (NPV = 84.5%). CONCLUSION: Detailed analysis of the tachycardia CL helps predict the AT-mechanism and the active AT chamber before an initial mapping.

Superiority of the Combination of Input and Output Parameters to the Single Parameter for Lesion Size Estimation.

BACKGROUND: For lesion size prediction, each input parameter, including ablation energy (AE), and output parameter, such as impedance, is individually used. We hypothesize that using both parameters simultaneously may be more optimal.Methods and Results: Radiofrequency applications at a range of power (30-50 W), contact force (10 g and 20 g), duration (10-60 s), and catheter orientation with normal saline (NS)- or half-normal saline (HNS)-irrigation were performed in excised porcine hearts. The correlations, with lesion size of AE, absolute impedance drop (∆Imp-drop), relative impedance drop (%Imp-drop), and AE*%Imp-drop were examined. Lesion size was analyzed in 283 of 288 lesions (NS-irrigation, n=142; HNS-irrigation, n=141) without steam pops. AE*%Imp-drop consistently showed the strongest correlations with lesion maximum depth (NS-irrigation, ρ=0.91; HNS-irrigation, ρ=0.94), surface area (NS-irrigation, ρ=0.87; HNS-irrigation, ρ=0.86), and volume (NS-irrigation, ρ=0.94; HNS-irrigation, ρ=0.94) compared with the other parameters. Moreover, compared with AE alone, AE*%Imp-drop significantly improved the strength of correlation with lesion maximum depth (AE vs. AE*%Imp-drop, ρ=0.83 vs. 0.91, P<0.01), surface area (ρ=0.73 vs. 0.87, P<0.01), and volume (ρ=0.84 vs. 0.94, P<0.01) with NS-irrigation. This tendency was also observed with HNS-irrigation. Parallel catheter orientation showed a better correlation with lesion depth and volume using ∆Imp-drop, %Imp-drop, and AE*%Imp-drop than perpendicular orientation. CONCLUSIONS: The combination of input and output parameters is more optimal than each single parameter for lesion prediction.

Demonstration of the discrepancy between AT-wave morphology on 12-lead ECG and AT mechanism in scar-related AT.

The 12-lead electrocardiogram (ECG) is a fundamental modality to help determine the mechanism and the localization of atrial tachycardias (ATs). Although macroreentrant ATs and focal ATs typically show F-waves and discrete P-waves respectively on the 12-lead ECG, this is not universally the case in scar-related ATs.1, We present three cases clearly showing the discrepancy between the AT morphology on the 12-lead ECG and the AT-mechanism.

Safety verification of a novel irrigation catheter with flexible tip of laser-cut kerfs and contact force sensor.

BACKGROUND AND AIMS: The safety evaluation of TactiFlex, a novel contact-force sensing catheter with a flexible 4-mm tip irrigated through laser-cut kerfs, has been ongoing. This study aimed to verify the safety of this type of catheter. METHODS: Study 1: Radiofrequency (RF) applications at a range of powers (30-50 W), contact forces (10-20 g), and durations (10-60 s) using perpendicular/parallel catheter orientation with half-normal (HNS) or normal saline irrigation were compared between TactiFlex (4-mm tip) and TactiCath (3.5-mm tip) with temperature-controlled mode in excised porcine hearts. Study 2: The relation between RF applications using TactiFlex and the incidence of steam-pops in the real clinical cases were examined. RESULTS: Study-1: 576 RF lesions were examined. TactiFlex demonstrated a significantly lower risk of steam-pops (5[1.7%] vs. 59[20.5%], p < .0001). Compared to 3.5-mm-tip catheter (TactiCath), 4-mm-tip catheter (TactiFlex) produced smaller lesion volume at perpendicular (193[98-554]mm3 vs. 263[139-436]mm3 , p < .0001), but relatively similar lesion volume at parallel contact (243[105-443]mm3 vs. 278[180-440]mm3 , p = .06). HNS-irrigation tended to increase the lesion volume in both catheters and to increase the incidence of steam-pops with TactiCath, but not with TactiFlex. The cut-off value of %impedance-drop ( = absolute impedance-drop/initial impedance) of 20% predicted steam-pops with a sensitivity = 100% and specificity = 89.6% in TactiFlex. Study-2: 5496 RF applications in 84 patients (51AFs/8ATs/3AVNRTs/4AVRTs/17PVCs/4VTs) using TactiFlex were analyzed. Four steam-pops (0.07%) in three patients with pericardial effusion were observed (%impedance-drop = 24%/26%/29%/35%, respectively). The cut-off value of %impedance-drop = 20%, derived from ex-vivo study, showed sensitivity = 100% and specificity = 90.1% in detecting steam-pops. CONCLUSION: TactiFlex reduced the risk of steam-pops than TactiCath. %impedance-drop ≤ 20% may be reasonable for safely use with a sufficient safety margin. For 4-mm-tip catheter, parallel-contact may be recommended for larger lesion creation.

Usefulness of the over-the-wire microelectrodes catheter in treatment of ventricular arrhythmia arising from the left ventricular summit.

BACKGROUND: This study was aimed to investigate the efficacy of the over-the-wire (OTW) microelectrodes catheter in coronary venous system (CVS) mapping and treatment of outflow tract ventricular arrhythmia (OTVA) arising from the vicinity of the left ventricular summit (LVS). METHODS: Consecutive 62 patients with idiopathic OTVA in whom the OTW microelectrodes catheter was routinely used for CVS mapping were analyzed. CVS mapping was performed for both main trunk (from great cardiac vein to anterior interventricular vein) and branches including the annular branch or septal branch. RESULTS: The earliest activation site (EAS) was within the CVS in 21 patients. Among them, the EAS was within the main trunk of the CVS in seven (33%) and within the branch of the CVS in 14 (67%) patients. Radiofrequency catheter ablation was started at an anatomically adjacent site to the EAS, which eliminated OTVA in 16 (76%) patients　(the endocardial LVOT in 10 and the aortic sinus of Valsalva in six patients). For the remaining five patients with unsuccessful catheter ablation at an anatomically adjacent site, targeted OTVA was eliminated by catheter ablation at the EAS within the CVS in two patients and by chemical ablation with ethanol injection in one patient, resulting in the overall success rate of 90% (19/21). CONCLUSION: The OTW microelectrodes-guided ablation of OTVA from the vicinity of the LVS was effective. In maximizing the efficacy of ablation, CVS branch mapping is important since the earliest activation was commonly recorded not in the main trunk but within the branch of the CVS.

Acute enhancement of necrotic radio-frequency ablation lesions in left atrium and pulmonary vein ostia in swine model with non-contrast-enhanced T1 -weighted MRI.

PURPOSE: To evaluate non-contrast-enhanced MRI of acute radio-frequency ablation (RFA) lesions in the left atrium (LA) and pulmonary vein (PV) ostia. The goal is to provide a method for discrimination between necrotic (permanent) lesions and reversible injury, which is associated with recurrence after treatment of atrial fibrillation. METHODS: Fifteen normal swine underwent RFA around the right-superior PV ostia. Electrical pulmonary vein isolation (PVI) was verified by electro-anatomic mapping (EAM) and pacing. MRI was carried out using a 3D respiratory-gated T1 -weighted long inversion time (TWILITE) sequence without contrast agent. Key settings were: inversion time 700 ms, triggering over 2 cardiac cycles, pixel size 1.1 mm3 . Contrast-enhanced imaging and T2 -weighted imaging were carried out for comparison. Six animals were sacrificed on ablation day for TTC-stained gross pathology, 9 animals were sacrificed after 2-3 mo after repeat EAM and MRI. Image intensity ratio (IIR) was used to measure lesion enhancement, and gross pathology was used to validate image enhancement patterns and compare lesion widths. RESULTS: RFA lesions exhibited unambiguous enhancement in acute TWILITE imaging (IIR = 2.34 ± 0.49 at 1.5T), and the enhancement patterns corresponded well with gross pathology. Lesion widths in MRI correlated well with gross pathology (R2 = 0.84), with slight underestimation by 0.9 ± 0.5 mm. Lesion enhancement subsided chronically. CONCLUSION: TWILITE imaging allowed acute detection of permanent RFA lesions in swine LA and PV ostia, without the need for contrast agent. Lesion enhancement pattern showed good correspondence to gross pathology and was well visualized by volume rendering. This method may provide valuable intra- or post-procedural assessment of RFA treatment.

Pulmonary vein narrowing after visually guided laser balloon ablation: Occurrence and clinical correlates.

INTRODUCTION: There are limited data focusing on pulmonary vein (PV) narrowing following ablation using a visually guided laser balloon (VGLB). We sought to assess the frequency and predictors of PV narrowing after VGLB ablation. METHODS AND RESULTS: Patients with paroxysmal atrial fibrillation treated with VGLB were screened. Study participants underwent contrast-enhanced computed tomography (CT) scanning before and 6 months after the procedure. We defined 25% to 49%, 50% to 74%, and 75% to 100% reduction in PV cross-sectional area as mild, moderate, and severe narrowing, respectively. Of 146 PVs in 38 patients analyzed, severe narrowing developed in two right superior and one right inferior PV. Moderate or severe narrowing occurred in 40 veins (27% of all PVs, 50% of the right superior, 22% of the right inferior, 21% of the left superior, and 14% of the left inferior PV). In PVs with moderate-severe narrowing, the baseline orifice area was significantly larger (4.1 [interquartile range, 3.2-4.8] vs 2.5 [1.9-3.3] cm2 , P < .0001), the narrowest region of stenosis was significantly more distal into the vessel (1.9 [0.7-2.9] vs 0 [0-1.7] mm from the orifice, P = .0006) and the total amount of energy delivered per vein was significantly greater (5190 ± 970 vs 4626 ± 1573 J, P = .018) than in PVs with mild or no significant narrowing. The baseline orifice area independently predicted moderate-severe narrowing in multivariate analysis (odds ratio, 1.8 [1.3-2.5] per 1 cm2 increase, P = .0003). No patient exhibited any signs or symptoms of PV stenosis. CONCLUSIONS: Baseline PV orifice area, ablating distally inside the veins, and total amount of laser energy are associated with PV narrowing after VGLB ablation.

Clinical outcome of pulmonary vein isolation alone ablation strategy using VISITAG SURPOINT in nonparoxysmal atrial fibrillation.

BACKGROUND: Recent studies have shown the improvement in long-term effectiveness with standardized pulmonary vein isolation (PVI) aimed at creating durable and contiguous lesions with VISITAG SURPOINT (VS) in paroxysmal atrial fibrillation (PAF). OBJECTIVE: We aimed to assess efficacy of PVI alone strategy using VS in non-PAF patients and evaluate factors associated with corresponding clinical outcomes. METHODS: Consecutive patients who underwent PVI for persistent/long-standing persistent AF between May 2017 to July 2019 were studied retrospectively. PVI was performed with 30-50 W guided by VS (posterior target: 400-500, anterior target: 500). Left atrial voltage maps were created during atrial pacing after PVI. RESULTS: A total of 140 patients (119 males, age 62 ± 10 years, long-standing persistent AF: 35) were included and followed for median of 454 days. No adverse events were reported in any patients during periprocedural and follow-up period of up to 28 months. Kaplan-Meier analysis estimated that freedom from atrial tachycardia or AF (AT/AF) without antiarrhythmics at 1-year was 70%. Radiofrequency delivery with higher power was associated with increased first-pass isolation rate, but not with freedom from AT/AF. In multivariate analysis, long-standing persistent AF and % low-voltage zone (%LVZ) were independent predictors of clinical outcome. The best cut-off value of %LVZ for predicting AT/AF recurrence was 3.24%. Freedom from AT/AF was 88% in patients with persistent AF and %LVZ < 3.24%, while 27% in those with long-standing persistent AF and %LVZ ≥ 3.24%. CONCLUSIONS: PVI alone using VS was associated with excellent 1-year success in patients with persistent AF and %LVZ < 3.24%, but was insufficient in those with long-standing persistent AF and/or %LVZ ≥ 3.24%.

Association between interatrial block, left atrial fibrosis, and mechanical dyssynchrony: Electrocardiography-magnetic resonance imaging correlation.

INTRODUCTION: Advanced interatrial block (IAB) on a 12-lead electrocardiogram (ECG) is a predictor of stroke, incident atrial fibrillation (AF), and AF recurrence after catheter ablation. The objective of this study was to determine which features of IAB structural remodeling is associated with left atrium (LA) magnetic resonance imaging structure and function. METHODS/RESULTS: We included 152 consecutive patients (23% nonparoxysmal AF) who underwent preprocedural ECG and cardiac magnetic resonance (CMR) in sinus rhythm before catheter ablation of AF. IAB was defined as P-wave duration ≥120 ms, and was considered partial if P-wave was positive and advanced if P-wave had a biphasic morphology in inferior leads. From cine CMR and late gadolinium enhancement, we derived LA maximum and minimum volume indices, strain, LA fibrosis, and LA dyssynchrony. A total of 77 patients (50.7% paroxysmal) had normal P-wave, 52 (34.2%) partial IAB, and 23 (15.1%) advanced IAB. Patients with advanced IAB had significantly higher LA minimum volume index (25.7 vs 19.9 mL/m2 , P = .010), more LA fibrosis (21.9% vs 13.1%, P = .020), and lower LA maximum strain rate (0.99 vs 1.18, P = .007) than those without. Advanced IAB was independently associated with LA (minimum [P = .032] and fibrosis [P = .009]). P-wave duration was also independently associated with LA fibrosis (ß = .33; P = .049) and LA mechanical dyssynchrony (ß = 2.01; P = .007). CONCLUSION: Advanced IAB is associated with larger LA volumes, lower emptying fraction, and more fibrosis. Longer P-wave duration is also associated with more LA fibrosis and higher LA mechanical dyssynchrony.

Non-contrast-enhanced T1 -weighted MRI of myocardial radiofrequency ablation lesions.

PURPOSE: To demonstrate imaging of radiofrequency ablation lesions with non-contrast-enhanced T1 -weighted (T1w) MRI. METHODS: Fifteen swine underwent left ventricular ablation followed by MRI using different preparations: endocardial or epicardial ablation of naïve animal, or endocardial ablation of animal with myocardial infarction. Lesion imaging was performed using free-breathing, non-contrast-enhanced, T1w sequence with long inversion time (TI). Also acquired were T1 maps and delayed contrast-enhanced (DCE) imaging. Hearts were excised for ex vivo imaging, and sliced for gross pathology and histology. RESULTS: All ablations were visibly enhanced in non-contrast-enhanced T1w imaging using TI = 700 ms. T1w enhancement agreed with regions of necrosis in gross pathology and histology. Enhanced lesion cores were surrounded by dark bands containing contraction band necrosis, hematoma, and edema. In animals with myocardial infarction, chronic scar was hypointense in T1w, whereas acute ablations were enhanced, allowing discrimination between chronic scar and acute lesions, unlike DCE. Contrast was sufficient to create 3D volume renderings of lesions after minor postprocessing. CONCLUSIONS: Non-contrast-enhanced T1w imaging with long TI promises to be an effective method for visualizing necrosis within radiofrequency ablation lesions. Enhancement is more specific and stationary than that from DCE. The imaging can be repeated as needed, unlike DCE, and may be especially useful for assessing ablations during or after a procedure. Magn Reson Med 79:879-889, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Is human atrial fibrillation stochastic or deterministic?-Insights from missing ordinal patterns and causal entropy-complexity plane analysis.

The mechanism of atrial fibrillation (AF) maintenance in humans is yet to be determined. It remains controversial whether cardiac fibrillatory dynamics are the result of a deterministic or a stochastic process. Traditional methods to differentiate deterministic from stochastic processes have several limitations and are not reliably applied to short and noisy data obtained during clinical studies. The appearance of missing ordinal patterns (MOPs) using the Bandt-Pompe (BP) symbolization is indicative of deterministic dynamics and is robust to brief time series and experimental noise. Our aim was to evaluate whether human AF dynamics is the result of a stochastic or a deterministic process. We used 38 intracardiac atrial electrograms during AF from the coronary sinus of 10 patients undergoing catheter ablation of AF. We extracted the intervals between consecutive atrial depolarizations (AA interval) and converted the AA interval time series to their BP symbolic representation (embedding dimension 5, time delay 1). We generated 40 iterative amplitude-adjusted, Fourier-transform (IAAFT) surrogate data for each of the AA time series. IAAFT surrogates have the same frequency spectrum, autocorrelation, and probability distribution with the original time series. Using the BP symbolization, we compared the number of MOPs and the rate of MOP decay in the first 1000 timepoints of the original time series with that of the surrogate data. We calculated permutation entropy and permutation statistical complexity and represented each time series on the causal entropy-complexity plane. We demonstrated that (a) the number of MOPs in human AF is significantly higher compared to the surrogate data (2.7 ± 1.18 vs. 0.39 ± 0.28, p < 0.001); (b) the median rate of MOP decay in human AF was significantly lower compared with the surrogate data (6.58 × 10-3 vs. 7.79 × 10-3, p < 0.001); and (c) 81.6% of the individual recordings had a rate of decay lower than the 95% confidence intervals of their corresponding surrogates. On the causal entropy-complexity plane, human AF lay on the deterministic part of the plane that was located above the trajectory of fractional Brownian motion with different Hurst exponents on the plane. This analysis demonstrates that human AF dynamics does not arise from a rescaled linear stochastic process or a fractional noise, but either a deterministic or a nonlinear stochastic process. Our results justify the development and application of mathematical analysis and modeling tools to enable predictive control of human AF.

Impaired left atrial function predicts inappropriate shocks in primary prevention implantable cardioverter-defibrillator candidates.

INTRODUCTION: Inappropriate implantable cardioverter-defibrillator (ICD) shocks, commonly caused by atrial fibrillation (AF), are associated with an increased mortality. Because impaired left atrial (LA) function predicts development of AF, we hypothesized that impaired LA function predicts inappropriate shocks beyond a history of AF. METHODS AND RESULTS: We prospectively analyzed the association between LA function and incident inappropriate shocks in primary prevention ICD candidates. In the Prospective Observational Study of ICD (PROSE-ICD), we assessed LA function using tissue-tracking cardiac magnetic resonance (CMR) prior to ICD implantation. A total of 162 patients (113 males, age 56 ± 15 years) were included. During the mean follow-up of 4.0 ± 2.9 years, 26 patients (16%) experienced inappropriate shocks due to AF (n = 19; 73%), supraventricular tachycardia (n = 5; 19%), and abnormal sensing (n = 2; 8%). In univariable analyses, inappropriate shocks were associated with AF history prior to ICD implantation, age below 70 years, QRS duration less than 120 milliseconds, larger LA minimum volume, lower LA stroke volume, lower LA emptying fraction, impaired LA maximum and preatrial contraction strains (Smax and SpreA ), and impaired LA strain rate during left ventricular systole and atrial contraction (SRs and SRa ). In multivariable analysis, impaired Smax (hazard ratio [HR]: 0.96, P = 0.044), SpreA (HR: 0.94, P = 0.030), and SRa (HR: 0.25, P < 0.001) were independently associated with inappropriate shocks. The receiver-operating characteristics curve showed that SRa improved the predictive value beyond the patient demographics including AF history (P = 0.033). CONCLUSION: Impaired LA function assessed by tissue-tracking CMR is an independent predictor of inappropriate shocks in primary prevention ICD candidates beyond AF history.