Gaps after linear ablation of persistent atrial fibrillation (Marshall-PLAN): Clinical implication

BACKGROUND

Beyond pulmonary vein (PV) isolation, anatomic isthmus transection is an adjunctive strategy for persistent atrial fibrillation. Data on the durability of multiple lines of block remain scarce.

OBJECTIVE

The purpose of this study was to evaluate the impact of gaps within such a lesion set.

METHODS

We followed 291 consecutive patients who underwent (1) vein of Marshall ethanol infusion, (2) PV isolation, and (3) mitral, cavotricuspid, and dome isthmus transection. Dome transection relied on 2 distinct strategies over time: a single roof line with touch-ups applied in case of gap demonstrated by conventional maneuvers (first leg), and an alternative floor line if the roof line exhibited a gap during high-density mapping with careful electrogram reannotation (second leg).

RESULTS

Twelve-month sinus rhythm maintenance was 70% after 1 procedure and 94% after 1 or 2 procedures. Event-free survival after the first procedure was lower in case of residual gaps within the lesion set (log-rank, P = .004). Delayed gaps were found in 94% of a second procedure performed in the 69 patients relapsing despite a complete lesion set with PV gaps increasing the risk of recurrence of atrial fibrillation (67% vs 34%; P = .02) and anatomic isthmus gaps supporting a majority of atrial tachycardias (60%). Between the first leg and the second leg, a significant decrease was found in roof lines considered blocked during the first procedure (99% vs 78%; P < .001) and in delayed dome gaps observed during a second procedure (68% vs 43%; P = .05).

CONCLUSION

Gaps are arrhythmogenic and can be reduced by optimized ablation and assessment of lines of block. Closing these gaps improves sinus rhythm maintenance.

Distribution of atrial low voltage induced by vein of Marshall ethanol infusion

INTRODUCTION

Systematic and quantitative descriptions of vein of Marshall (VOM)-induced tissue ablation are lacking. We sought to characterize the distribution of low voltage observed in the left atrium (LA) after VOM ethanol infusion.

METHODS AND RESULTS

The distribution of ethanol-induced low voltage was evaluated by comparing high-density maps performed before and after VOM ethanol infusion in 114 patients referred for atrial fibrillation ablation. The two most frequently impacted segments were the inferior portion of the ridge (82.5%) and the first half of the mitral isthmus (pulmonary vein side) (92.1%). Low-voltage absence in these typical areas resulted from inadvertent ethanol infusion in the left atrial appendage vein (n = 3), initial VOM dissection (n = 3), or a "no branches" VOM morphology (n = 1). Visible anastomosis of the VOM with roof or posterior veins more frequently resulted in low-voltage extension beyond typical areas, toward the entire left antrum (19.0% vs. 1.9%, p = .0045) or the posterior LA (39.7% vs. 3.8%, p < .001) but with a limited positive predictive value ranging from 29.4% to 43.5%. Ethanol-induced low voltage covered a median LA surface of 3.6% (1.9%-5.0%) and did not exceed 8% of the LA surface in 90% of patients.

CONCLUSION

VOM ethanol infusion typically locates at the inferior ridge and the adjacent half of the mitral isthmus. Low-voltage extensions can be anticipated but not guaranteed by the presence of visible anastomosis of the VOM with roof or posterior veins.

Preoperative Personalization of Atrial Fibrillation Ablation Strategy to Prevent Esophageal Injury: Impact of Changes in Esophageal Position

INTRODUCTION

Due to changes in esophageal position, preoperative assessment of the esophageal location may not mitigate the risk of esophageal injury in catheter ablation for atrial fibrillation (AF). This study aimed to assess esophageal motion and its impact on AF ablation strategies.

METHODS AND RESULTS

Ninety-seven AF patients underwent 2 computed tomography (CT) scans. The area at risk of esophageal injury (AAR) was defined as the left atrial surface ≤3 mm from the esophagus. On CT1, ablation lines were drawn blinded to the esophageal location to create 3 ablation sets: individual pulmonary vein isolation (PVI), wide antral circumferential ablation (WACA), and WACA with linear ablation (WACA+L). Thereafter, ablation lines for WACA and WACA+L were personalized to avoid the AAR. Rigid registration was performed to align CT1 onto CT2, and the relationship between ablation lines and the AAR on CT2 was analyzed. The esophagus moved by 3.6 [2.7 to 5.5] mm. The AAR on CT2 was 8.6 ± 3.3 cm² , with 77% overlapping that on CT1. High body mass index was associated with the AAR mismatch (standardized β 0.382, P <0.001). Without personalization, AARs on ablation lines for individual PVI, WACA, and WACA+L were 0 [0-0.4], 0.8 [0.5-1.2], 1.7 [1.2-2.0] cm² . Despite the esophageal position change, the personalization of ablation lines for WACA and WACA+L reduced the AAR on lines to 0 [0-0.5] and 0.7 [0.3-1.0] cm² (P <0.001 for both).

CONCLUSION

The personalization of ablation lines based on a preoperative CT reduced ablation to the AAR despite changes in esophageal position. This article is protected by copyright. All rights reserved.

Genome-wide association analyses identify new Brugada syndrome risk loci and highlight a new mechanism of sodium channel regulation in disease susceptibility

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel Na_V1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on Na_V1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings.

Optimized Computed Tomography Acquisition Protocol for Ethanol Infusion Into the Vein of Marshall

OBJECTIVES

This study sought to introduce a computed tomography (CT) protocol for optimal planning of vein of Marshall (VOM) catheterization.

BACKGROUND

Ethanol infusion into the VOM (Et-VOM) is increasingly used in atrial fibrillation ablation.

METHODS

Preprocedural CT was performed with either a conventional (conv-CT; n = 132) or an optimized CT protocol (VOM-CT; n = 126) designed for obtaining on a single image both left atrial and coronary sinus (CS) enhancement. The detection rate and anatomical features of the CT-derived VOM were analyzed and the utility of VOM-CT protocol was assessed by comparing the procedural data.

RESULTS

VOM was detected in 35% in conv-CT versus 63% in VOM-CT (P < 0.001). The VOM-CT protocol did not impair the assessment of left atrial anatomy and appendage patency. In VOM-CT, the detection of the VOM was related to body mass index and width of epicardial space on posterior wall. Mean distance between CS ostium and VOM was 36 ± 7 mm. Mean VOM diameter was 1.6 ± 0.3 mm. On the CS circumference, the VOM emerged superiorly in 68% and postero-superiorly in 32%. Ethanol infusion into the VOM was attempted in 165 patients (77 conv-CT, 70 VOM-CT, and 18 without-CT). After registration in CARTO, the VOM segmented on CT matched its location on venography in all cases. As compared with conv-CT and without-CT, procedures guided by VOM-CT showed significantly shorter radiation time, shorter procedure time, lower amount of the contrast medium, and fewer contrast injections to obtain VOM catheterization.

CONCLUSIONS

The proposed CT protocol allows for improved visualization of the VOM, translating into easier VOM catheterization.

Sinus node exit, crista terminalis conduction, interatrial connection and wavefront collision: key features of human atrial activation in sinus rhythm

BACKGROUND

An understanding of normal atrial activation during sinus rhythm can inform catheter ablation strategies to avoid deleterious impacts of ablation lesions on atrial conduction and mechanics.

OBJECTIVE

To describe how the sinus node impulse originates, propagates, and collides in right and left atria with normal voltage.

METHODS

Fifty consecutive patients undergoing catheter ablation of atrial fibrillation with endocardial atrial voltage > 0.5 mV during high-density 3D-mapping were studied.

RESULTS

Sinus node exits varied between patients along a lateral oblique arc extending from the anterior aspect of the superior vena cava (SVC) to the mid-posterior wall of the right atrium (RA). Conduction slowing or block at one of the smooth components that faces the crista terminalis was observed in 54% of cases, including complete block at the SVC musculature and the systemic venous sinus in 6% of cases. Depending on these two key features of RA activation, interatrial conduction was mediated by the Bachmann bundle (64%) and posterior bundles (54%), with an overlap of the resulting LA breakthrough location. Wavefront collision was consistently observed at three sites: the septal aspect of the cavotricuspid isthmus; and the lower aspects of the dome and of the mitral isthmus.

CONCLUSION

During sinus rhythm, atrial activation occurs via distinct sequences mediated by a complex interaction of anatomic factors.

OUP accepted manuscript

Aims

Mapping data of human ventricular fibrillation (VF) are limited. We performed detailed mapping of the activities underlying the onset of VF and targeted ablation in patients with structural cardiac abnormalities.

Methods and results

We evaluated 54 patients (50 ± 16 years) with VF in the setting of ischaemic (n = 15), hypertrophic (n = 8) or dilated cardiomyopathy (n = 12), or Brugada syndrome (n = 19). Ventricular fibrillation was mapped using body-surface mapping to identify driver (reentrant and focal) areas and invasive Purkinje mapping. Purkinje drivers were defined as Purkinje activities faster than the local ventricular rate. Structural substrate was delineated by electrogram criteria and by imaging. Catheter ablation was performed in 41 patients with recurrent VF. Sixty-one episodes of spontaneous (n = 10) or induced (n = 51) VF were mapped. Ventricular fibrillation was organized for the initial 5.0 ± 3.4 s, exhibiting large wavefronts with similar cycle lengths (CLs) across both ventricles (197 ± 23 vs. 196 ± 22 ms, P = 0.9). Most drivers (81%) originated from areas associated with the structural substrate. The Purkinje system was implicated as a trigger or driver in 43% of patients with cardiomyopathy. The transition to disorganized VF was associated with the acceleration of initial reentrant activities (CL shortening from 187 ± 17 to 175 ± 20 ms, P < 0.001), then spatial dissemination of drivers. Purkinje and substrate ablation resulted in the reduction of VF recurrences from a pre-procedural median of seven episodes [interquartile range (IQR) 4–16] to 0 episode (IQR 0–2) (P < 0.001) at 56 ± 30 months.

Conclusions

The onset of human VF is sustained by activities originating from Purkinje and structural substrate, before spreading throughout the ventricles to establish disorganized VF. Targeted ablation results in effective reduction of VF burden.

Key question

The initial phase of human ventricular fibrillation (VF) is critical as it involves the primary activities leading to sustained VF and arrhythmic sudden death. The origin of such activities is unknown.

Key finding

Body-surface mapping shows that most drivers (≈80%) during the initial VF phase originate from electrophysiologically defined structural substrates. Repetitive Purkinje activities can be elicited by programmed stimulation and are implicated as drivers in 37% of cardiomyopathy patients.

Take-home message

The onset of human VF is mostly associated with activities from the Purkinje network and structural substrate, before spreading throughout the ventricles to establish sustained VF. Targeted ablation reduces or eliminates VF recurrence.

Right ventricular outflow tract electroanatomical abnormalities in asymptomatic and high-risk symptomatic patients with Brugada syndrome: Evidence for a new risk stratification tool?

INTRODUCTION

Microstructural abnormalities at the epicardium of the right ventricular outflow tract (RVOT) may provide the arrhythmia substrate in Brugada syndrome (BrS). Endocardial unipolar electroanatomical mapping allows the identification of epicardial abnormalities. We evaluated the clinical implications of an abnormal endocardial substrate as perceived by high-density electroanatomical mapping (HDEAM) in patients with BrS.

METHODS

Fourteen high-risk BrS patients with aborted sudden cardiac death (SCD) (12 males, mean age: 41.9 ± 11.8 years) underwent combined endocardial-epicardial HDEAM of the right ventricle/RVOT, while 40 asymptomatic patients (33 males, mean age: 42 ± 10.7 years) underwent endocardial HDEAM. Based on combined endocardial-epicardial procedures, endocardial HDEAM was considered abnormal in the presence of low voltage areas (LVAs) more than 1 cm² with bipolar signals less than 1 mV and unipolar signals less than 5.3 mV. Programmed ventricular stimulation (PVS) was performed in all patients.

RESULTS

The endocardial unipolar LVAs were colocalized with epicardial bipolar LVAs (p = .0027). Patients with aborted SCD exhibited significantly wider endocardial unipolar (p < .01) and bipolar LVAs (p < .01) compared with asymptomatic individuals. A substrate size of unipolar LVAs more than 14.5 cm² (area under the curve [AUC]: 0.92, p < .001] and bipolar LVAs more than 3.68 cm² (AUC: 0.82, p = .001) distinguished symptomatic from asymptomatic patients. Patients with ventricular fibrillation inducibility (23/54) demonstrated broader endocardial unipolar (p < .001) and bipolar LVAs (p < .001) than noninducible patients. The presence of unipolar LVAs more than 13.5 cm² (AUC: 0.95, p < .001) and bipolar LVAs more than 2.97 cm² (AUC: 0.78, p < .001) predicted a positive PVS.

CONCLUSION

Extensive endocardial electroanatomical abnormalities identify high-risk patients with BrS. Endocardial HDEAM may allow risk stratification of asymptomatic patients referred for PVS.

Effect of electrode size and spacing on electrograms: Optimized electrode configuration for near-field electrogram characterization

BACKGROUND

Detailed effects of electrode size on electrograms (EGMs) have not been systematically examined.

OBJECTIVES

We aimed to elucidate the effect of electrode size on EGMs and investigate an optimal configuration of electrode size and interelectrode spacing for gap detection and far-field reduction.

METHODS

This study included 8 sheep in which probes with different electrode size and interelectrode spacing were epicardially placed on healthy, fatty, and lesion tissues for measurements. Between 3 electrode sizes (0.1 mm/0.2 mm/0.5 mm) with 3 mm spacing. As indices of capability in gap detection and far-field reduction, in different electrode sizes (0.1 mm/0.2 mm/0.5 mm) and interelectrode spacing (0.1 mm/0.2 mm/0.3 mm/0.5 mm/3 mm) and the optimized electrode size and interelectrode spacing were determined. Compared between PentaRay and the optimal probe determined in study 2.

RESULTS

Study 1 demonstrated that unipolar voltage and the duration of EGMs increased as the electrode size increased in any tissue (P < .001). Bipolar EGMs had the same tendency in healthy/fat tissues, but not in lesions. Study 2 showed that significantly higher gap to lesion volume ratio and healthy to fat tissue voltage ratio were provided by a smaller electrode (0.2 mm or 0.3 mm electrode) and smaller spacing (0.1 mm spacing), but 0.3 mm electrode/0.1 mm spacing provided a larger bipolar voltage (P < .05). Study 3 demonstrated that 0.3 mm electrode/0.1 mm spacing provided less deflection with more discrete EGMs (P < .0001) with longer and more reproducible AF cycle length (P < .0001) compared to PentaRay.

CONCLUSION

Electrode size affects both unipolar and bipolar EGMs. Catheters with microelectrodes and very small interelectrode spacing may be superior in gap detection and far-field reduction. Importantly, this electrode configuration could dramatically reduce artifactual complex fractionated atrial electrograms and may open a new era for AF mapping.

Purkinje triggers of ventricular fibrillation in patients with hypertrophic cardiomyopathy

INTRODUCTION

Ventricular fibrillation (VF) is the main mechanism of sudden cardiac death in patients with hypertrophic cardiomyopathy (HCM). The origin of VF and the success of catheter ablation to eliminate recurrent episodes in this population are poorly understood.

METHODS AND RESULTS

From 2010 to 2014, five patients with HCM (age 21 ± 9 years, three female) underwent invasive electrophysiological studies and ablation at our center after resuscitation from recurrent (9 ± 7) episodes of VF. Ventricular premature beats (VPBs), seen to initiate VF in certain cases, were recorded noninvasively before the ablation procedure. Postprocedural computed tomography (CT) was performed to correlate ablation sites with myocardial hypertrophy in three patients. Outcomes were assessed by clinical follow-up and implantable cardioverter-defibrillator interrogations. VPB triggers were localized invasively to the distal left Purkinje conduction system (left posterior fascicle [2], left anterior fascicle [1], and both fascicles [2]). All targeted VF triggers were successfully eliminated by radiofrequency ablation in the left ventricle. Among patients with postablation CT imaging, 93 ± 12% of ablation sites corresponded to hypertrophied segments. Over 50 ± 38 months, four of five patients were free from primary VF without antiarrhythmic drug therapy. One patient who had 13 episodes of VF before ablation had a single recurrence.

CONCLUSION

In our study of patients with HCM and recurrent VF, VF was not initiated from the myocardium but rather from Purkinje arborization. These sources colocalized with the hypertrophic substrate, suggesting electromechanical interaction. Focal ablation at these sites was associated with a marked reduction in VF burden.

Use of high-density activation and voltage mapping in combination with entrainment to delineate gap-related atrial tachycardias post atrial fibrillation ablation

AIMS

An incomplete understanding of the mechanism of atrial tachycardia (AT) is a major determinant of ablation failure. We systematically evaluated the mechanisms of AT using ultra-high-resolution mapping in a large cohort of patients.

METHODS AND RESULTS

We included 107 consecutive patients (mean age: 65.7 ± 9.2 years, males: 81 patients) with documented endocardial gap-related AT after left atrial ablation for persistent atrial fibrillation (AF). We analysed the mechanism of 134 AT (94 macro-re-entries and 40 localized re-entries) using high-resolution activation mapping in combination with high-density voltage and entrainment mapping. Voltage in the conducting channels may be extremely low, even <0.1 mV (0.14 ± 0.095 mV, 51 of 134 AT, 41%), and almost always <0.5 mV (0.03-0.5 mV, 133 of 134 AT, 99.3%). The use of multipolar Orion, HDGrid, and Pentaray catheters improved our accuracy in delineating ultra-low-voltage areas critical for maintenance of the circuit of endocardial gap-related AT. Conventional ablation catheters often do not detect any signal (noise level) even using adequate contact force, and only multipolar catheters of small electrodes and shorter interelectrode space can detect clear fractionated low-amplitude and high frequency signals, critical for re-entry maintenance. We performed a diagnosis in 112 out of 134 AT (83.6%) using only activation mapping and in 134 out of 134 AT (100%) using the combination of activation and entrainment mapping.

CONCLUSION

High-resolution activation mapping in combination with high-density voltage and entrainment mapping is the ideal strategy to delineate the critical part of the circuit in endocardial gap-related re-entrant AT after AF ablation.

Local catheter impedance drop during pulmonary vein isolation predicts acute conduction block in patients with paroxysmal atrial fibrillation: initial results of the LOCALIZE clinical trial

Aims

Radiofrequency ablation creates irreversible cardiac damage through resistive heating and this temperature change results in a generator impedance drop. Evaluation of a novel local impedance (LI) technology measured exclusively at the tip of the ablation catheter found that larger LI drops were indicative of more effective lesion formation. We aimed to evaluate whether LI drop is associated with conduction block in patients with paroxysmal atrial fibrillation (AF) undergoing pulmonary vein isolation (PVI).

Methods and results

Sixty patients underwent LI-blinded de novo PVI using a point-by-point ablation workflow. Pulmonary vein rings were divided into 16 anatomical segments. After a 20-min waiting period, gaps were identified on electroanatomic maps. Median LI drop within segments with inter-lesion distance ≤6 mm was calculated offline. The diagnostic accuracy of LI drop for predicting segment block was assessed using receiver operating characteristic analysis.

For segments with inter-lesion distance ≤6 mm, acutely blocked segments had a significantly larger LI drop [19.8 (14.1–27.1) Ω] compared with segments with gaps [10.6 (7.8–14.7) Ω, P < 0.001). In view of left atrial wall thickness differences, the association between LI drop and block was further evaluated for anterior/roof and posterior/inferior segments. The optimal LI cut-off value for anterior/roof segments was 16.1 Ω (positive predictive value for block: 96.3%) and for posterior/inferior segments was 12.3 Ω (positive predictive value for block: 98.1%) where inter-lesion distances were ≤6 mm.

Conclusion

The magnitude of LI drop was predictive of acute PVI segment conduction block in patients with paroxysmal AF. The thinner posterior wall required smaller LI drops for block compared with the thicker anterior wall.