Bi-atrial characterization of the electrical substrate in patients with atrial fibrillation.

BACKGROUND: Little is known regarding the characterization of electrical substrate in both atria in patients with atrial fibrillation (AF). METHODS: Eight consecutive patients undergoing AF ablation (five paroxysmal, three persistent) underwent electrical substrate characterization during sinus rhythm. Mapping of the left (LA) and right atrium (RA) was performed with the use of the HD Grid catheter (Abbott). Bipolar voltage maps were analyzed to search for low voltage areas (LVA), the following electrophysiological phenomena were assessed: (1) slow conduction corridors, and (2) lines of block. EGMs were characterized to search for fractionation. Electrical characteristics were compared between atria and between paroxysmal versus persistent AF patients. RESULTS: In the RA, LVAs were present in 60% of patients with paroxysmal AF and 100% of patients with persistent AF. In the LA, LVAs were present in 40% of patients with paroxysmal AF and 66% of patients with persistent AF. The areas of LVA in the RA and LA were 4.8±7.3 cm2 and 7.8±13.6 cm2 in patients with paroxysmal AF versus 11.7±3.0 cm2 and 2.1±1.8 cm2 in patients with persistent AF. In the RA, slow conduction corridors were present in 40.0% (paroxysmal AF) versus 66.7% (persistent AF) whereas in the LA, slow conduction corridors occurred in 20.0% versus 33.3% respectively (p = ns). EGM analysis showed more fractionation in persistent AF patients than paroxysmal (RA: persistent AF 10.8 vs. paroxysmal AF 4.7%, p = .036, LA: 10.3 vs. 4.1%, p = .108). CONCLUSION: Bi-atrial involvement is present in patients with paroxysmal and persistent AF. This is expressed by low voltage areas and slow conduction corridors whose extension progresses as the arrhythmia becomes persistent. This electrophysiological substrate demonstrates the important interplay with the pulmonary vein triggers to constitute the substrate for persistent arrhythmia.

Characterization of cardiac electrogram signals in atrial arrhythmias.

Despite significant advancements in 3D cardiac mapping systems utilized in daily electrophysiology practices, the characterization of atrial substrate remains crucial for the comprehension of supraventricular arrhythmias. During mapping, intracardiac electrograms (EGM) provide specific information that the cardiac electrophysiologist is required to rapidly interpret during the course of a procedure in order to perform an effective ablation. In this review, EGM characteristics collected during sinus rhythm (SR) in patients with paroxysmal atrial fibrillation (pAF) are analyzed, focusing on amplitude, duration and fractionation. Additionally, EGMs recorded during atrial fibrillation (AF), including complex fractionated atrial EGMs (CFAE), may also provide precious information. A complete understanding of their significance remains lacking, and as such, we aimed to further explore the role of CFAE in strategies for ablation of persistent AF. Considering focal atrial tachycardias (AT), current cardiac mapping systems provide excellent tools that can guide the operator to the site of earliest activation. However, only careful analysis of the EGM, distinguishing low amplitude high frequency signals, can reliably identify the absolute best site for RF. Evaluating macro-reentrant atrial tachycardia circuits, specific EGM signatures correspond to particular electrophysiological phenomena: the careful recognition of these EGM patterns may in fact reveal the best site of ablation. In the near future, mathematical models, integrating patient-specific data, such as cardiac geometry and electrical conduction properties, may further characterize the substrate and predict future (potential) reentrant circuits.

Cardiac CT With Delayed Enhancement in the Characterization of Ventricular Tachycardia Structural Substrate: Relationship Between CT-Segmented Scar and Electro-Anatomic Mapping.

OBJECTIVES: This study sought to compare myocardial scars depicted by computed tomography (CT) with electrical features from electro-anatomic mapping (EAM), assessing the potential role of CT integration in ventricular tachycardia (VT) and radiofrequency catheter ablation (RFCA) procedures. BACKGROUND: Imaging-based characterization of VT myocardial substrate is required to plan EAM and, potentially, to guide RFCA. METHODS: Forty-two consecutive patients, 35 of whom had implantable cardioverter-defibrillator, all referred for VT RFCA, underwent pre-procedural CT including an angiographic and a 10-min delayed-enhancement scan. Segmental comparison between scars segmented from CT and low voltages (bipolar voltages <1.5 mV; unipolar voltages <8 mV), late potentials, and RF ablation points on EAM, was carried out. In a subset of 16 consecutive patients, a further point-by-point analysis was performed: a CT-derived 3-dimensional structure including heart anatomy and myocardial scars was integrated with EAM for quantitative comparison. RESULTS: CT scans identified scars in 39 patients and defined left ventricular wall involvement and mural distribution. Overall segmental concordance between CT and EAM was good (κ = 0.536) despite the presence of implantable cardioverter-defibrillator, scar etiologies, and mural distribution. CT identified segments characterized by low voltages with good sensitivity (76%), good specificity (86%), and very high negative predictive value (95%). Late potentials and RF ablation points fell on scarred segments identified from CT in 79% and 81% of cases, respectively. Point-by-point quantitative comparison revealed good correlation between the average area of scar detected at CT and at bipolar mapping (CT = 4,901 mm(2), bipolar voltages-EAM = 4,070 mm(2); R = 0.78; p < 0.0001). In this study, 70% and 84% of low-amplitude bipolar points were mapped at a maximum distance of 5 mm and 10 mm from CT-segmented scar, respectively. CONCLUSIONS: CT with delayed-enhancement provides a 3-dimensional characterization of VT scar substrate together with a detailed anatomic model of the heart. This information may offer assistance to plan EAM and RFCA procedures and is potentially suitable for EAM-imaging integration.

Impact of a chronic total occlusion in an infarct-related artery on the long-term outcome of ventricular tachycardia ablation.

INTRODUCTION: In patients with a prior myocardial infarction (MI), angiographic predictors of ventricular tachycardia (VT) recurrence after ablation are lacking. Recently, a proarrhythmic effect of a chronic total occlusion (CTO) in a coronary artery has been suggested. METHODS AND RESULTS: A total of 191 patients with prior MI were referred to our Hospital between 2010 and June 2013 for a first ablation of VT. Of these, 84 patients (44%) with stable coronary artery disease that underwent a coronary angiography during the index hospitalization were included in this study. A CTO in an infarct-related artery (IRA-CTO) was present in 47 patients (56%). Patients with and without IRA-CTO did not differ in terms of comorbidities, severity of heart failure, presentation of VT or acute outcome of ablation, that was completely successful in 93% of cases. At electroanatomic mapping, IRA-CTO was associated with greater scar and especially with greater area of border zone (34 cm(2) vs. 19 cm(2) , P = 0.001). Median follow-up was 19 months (IQR 18). At follow-up, patients with IRA-CTO had a significantly higher rate of VT recurrence (47% vs. 16%, P = 0.003). At multivariate analysis, IRA-CTO resulted to be an independent predictor of VT recurrence after ablation (HR 4.05, P = 0.004). CONCLUSIONS: IRA-CTO is an independent predictor of VT recurrence after ablation and identifies a subgroup of patients with high recurrence rate despite a successful procedure. IRA-CTO is associated with greater scars and border zone area; however, this association does not completely justify its proarrhythmic effect.

Electrical storm induced by cardiac resynchronization therapy is determined by pacing on epicardial scar and can be successfully managed by catheter ablation.

BACKGROUND: The mechanism of cardiac resynchronization therapy (CRT)-induced proarrhythmia remains unknown. We postulated that pacing from a left ventricular (LV) lead positioned on epicardial scar can facilitate re-entrant ventricular tachycardia. The aim of this study was to investigate the relationship between CRT-induced proarrhythmia and LV lead location within scar. METHODS AND RESULTS: Twenty-eight epicardial and 63 endocardial maps, obtained from 64 CRT patients undergoing ventricular tachycardia ablation, were analyzed. A positive LV lead/scar relationship, defined as a lead tip positioned on scar/border zone, was determined by overlaying fluoroscopic projections with LV electroanatomical maps. CRT-induced proarrhythmia occurred in 8 patients (12.5%). They all presented early with electrical storm (100% versus 39% of patients with no proarrhythmia; P<0.01), requiring temporary biventricular pacing discontinuation in half of cases. They more frequently presented with heart failure/cardiogenic shock (50% versus 7%; P<0.01), requiring intensive care management. Ventricular tachycardia was re-entrant in all. The LV lead location within epicardial scar was significantly more frequent in the proarrhythmia group (60% versus 9% P=0.03 on epicardial bipolar scar, 80% versus 17% P=0.02 on epicardial unipolar scar, and 80% versus 17% P=0.02 on any-epicardial scar). Ablation was performed within epicardial scar, close to the LV lead, and allowed CRT reactivation in all patients. CONCLUSIONS: CRT-induced proarrhythmia presented early with electrical storm and was associated with an LV lead positioning within epicardial scar. Catheter ablation allowed for resumption of biventricular stimulation in all patients.

Late potentials abolition as an additional technique for reduction of arrhythmia recurrence in scar related ventricular tachycardia ablation.

RATIONALE: To evaluate the efficacy of radiofrequency ventricular tachycardia (VT) ablation targeting complete late potential (LP) activity. METHODS AND RESULTS: Sixty-four consecutive patients (pts) with recurrent VTs and coronary artery disease or idiopathic dilated cardiomyopathy were evaluated. Fifty patients (47 male; 66.2 ± 10.1 years) had LPs at electroanatomical mapping; 35 patients had at least 1 VT inducible at basal programmed stimulation. After substrate mapping, radiofrequency ablation was performed with the endpoint of all LPs abolition. LPs could not be abolished in 5 patients despite extensive ablation, in 1 patient because of localization near an apical thrombus, and in 2 patients because of possible phrenic nerve injury. At the end of procedure, prevention of VT inducibility was achieved in 25 of 35 patients (71.4%) with previously inducible VT; VT was still inducible in 5 of 8 patients with incomplete LP abolition; and in 5 of 42 patients (16.1%) with complete LP abolition (P < 0.01). After a follow-up of 13.4 ± 4.0 months, 10 patients (20.0%) had VT recurrences and one of them died after surgical VT ablation; VT recurrence was 9.5% in patients with LPs abolition (4/42 pts) and 75.0% (6/8 pts) in those with incomplete abolition [positive predictive value (PPV): 75%, negative predictive value (NPV): 90.4%, sensibility: 60.0%, and specificity: 95.0%, P < 0.0001); although it was 12.5% (5/40 pts) in patients without inducibility VT after the ablation, and 50% (5/10 pts) in those with inducible VT (PPV: 50%, NPV: 87.5%, sensitivity: 50.0%, and specificity: 87.5%, P = 0.008). CONCLUSIONS: LP abolition is an effective endpoint of VT ablation and its prognostic value compares favorably to that achieved by programmed electrical stimulation.