Atrial tachycardias: Cause or effect with ablation of persistent atrial fibrillation?

INTRODUCTION: It is largely believed that atrial tachycardias (ATs) encountered during ablation of persistent atrial fibrillation (PsAF) are a byproduct of ablative lesions. We aimed to explore the alternative hypothesis that they may be a priori drivers of AF remaining masked until other AF sources are reduced or eliminated. METHODS AND RESULTS: Radiofrequency ablation of fibrillatory drivers mapped by electrocardiographic imaging (ECGI; ECVUE™, Cardioinsight Technologies, Cleveland, OH, USA) terminated PsAF in 198 (73%) out of 270 patients (61 ± 10 years, 9 ± 9 m). Two hundred and six ATs in 158 patients were subsequently mapped. Their anatomic relationship to the fibrillatory drivers prospectively identified by ECGI was then established. There were 26 (13%), 52 (25%), and 128 (62%) focal, localized, and macrore-entrant ATs, respectively. In focal/localized re-entrant ATs, 64 (82%) were terminated within an AF-driver region, in which 26 (81%) among 32 focal/localized ATs analyzed with 3-D-mapping system merged to driver map occurred from AF-driver regions in 1.0 ± 1.0 cm distance from the driver core. Importantly, there was no attempt at ablation of the associated AF-driver region in 25 of 64 (39%) of focal/localized re-entrant ATs. The sites of ATs origin generally had low-voltage, fractionated, and long-duration electrograms in AF. All but two focal/localized re-entrant ATs were successfully ablated. CONCLUSION: The majority of post-AF-ablation focal and localized re-entrant ATs originate from the region of prospectively established AF-driver regions. A third of these are localized to regions not subsequently submitted to ablation. These data suggest that many ATs exist, although not necessarily manifest independently, prior to ablation. They may have a role in the maintenance of PsAF in these individuals.

Alternative to left ventricular lead implantation through the coronary sinus: 1-year experience with a minimally invasive and robotically guided approach.

AIMS: Left ventricular (LV) lead implantation through the coronary sinus (CS) can be limited and sometimes not possible-alternative approaches are needed. Minimally invasive, robotically guided LV lead implantation has major advantages, but there are little published data about the short- and long-term follow-ups, in terms of feasibility, safety, electrical performance, and impact on clinical outcome. METHODS AND RESULTS: A total of 21 heart failure patients underwent robotically guided LV lead implantation using the Da Vinci Robotic System. Indications were failed implant with conventional approach through the CS (n = 16) and non-response to conventional cardiac resynchronization therapy (n = 5). During the procedure, the entire LV free wall was exposed through 3 transthoracic ports (10 mm diameter each) allowing ample choice of stimulation site and the ability to implant 2 LV leads via a Y connector. Patients were prospectively followed up for 1 year. The two LV leads were successfully implanted in all patients. No peri-procedural complications were observed. After a mean stay in the intensive care unit of 1.2 ± 4 days, the 21 patients were hospitalized in the EP department for 6.7 ± 2.9 days. Acute LV thresholds were excellent (1.0 V ± 0.6/0.4 ms) and stayed stable at 1-year follow-up (1.5 V ± 0.6/0.4 ms, P = 0.21). Four patients demonstrated an increased threshold (>2 V/0.4 ms). There was no phrenic nerve stimulation. After 12 months, in the failed implant group, 69% of the patients were echocardiographic and clinical responders. CONCLUSION: The robotic approach was feasible, safe, and minimally invasive. Accordingly, robotically guided LV lead implantation seems to offer a new alternative when conventional approaches are not suitable.

Diagnosis and management of iatrogenic cardiac perforation caused by pacemaker and defibrillator leads.

AIMS: Cardiac perforations caused by pacemaker or implantable cardioverter-defibrillator (ICD) leads are uncommon but potentially fatal events. The optimal approach to such cases is unclear. The aim of this study was to identify the optimal imaging modality and management strategy for cardiac perforation. METHODS AND RESULTS: All patients presenting to a single institution with cardiac perforation >24 h since implant between 2011 and 2015 were identified retrospectively. Assessment of the diagnostic performance of pre-extraction chest radiography, transthoracic echocardiography (TTE), and computed tomography (CT) was carried out by blinded review. The method of lead extraction and any associated complications were examined. Eighteen cases of cardiac perforation were identified from 426 lead extraction procedures. Sixteen patients had abnormal electrical parameters at device interrogation. In all cases, the perforating lead was an active fixation model, and in four cases, this was an ICD coil. The accuracy of CT imaging for the diagnosis of cardiac perforation was 92.9%, with sensitivity and specificity of 100 and 85.7%, respectively. This was superior to both TTE (accuracy 62.7%, sensitivity and specificity 41.2 and 84.2%, respectively) and chest radiography (accuracy 61.1%, sensitivity and specificity 27.7 and 94.4%, respectively). Transvenous lead extraction (TLE) was performed in 17 patients, and a hybrid surgical approach in 1 patient. Of those who underwent TLE, there was 100% complete procedural success as per Heart Rhythm Society definitions. CONCLUSION: In the setting of cardiac perforation, CT is the imaging modality of choice. Transvenous lead extraction can be recommended as a safe, efficacious, and versatile intervention.

Image Integration to Guide Catheter Ablation in Scar-Related Ventricular Tachycardia.

BACKGROUND: Although multi-detector computed tomography (MDCT) and cardiac magnetic resonance (CMR) can assess the structural substrate of ventricular tachycardia (VT) in ischemic cardiomyopathy (ICM), non-ICM (NICM), and arrhythmogenic right ventricular cardiomyopathy (ARVC), the usefulness of systematic image integration during VT ablation remains undetermined. METHODS AND RESULTS: A total of 116 consecutive patients (67 ICM; 30 NICM; 19 ARVC) underwent VT ablation with image integration (MDCT 91%; CMR 30%; both 22%). Substrate was defined as wall thinning on MDCT and late gadolinium-enhancement on CMR in ICM/NICM, and as myocardial hypo-attenuation on MDCT in ARVC. This substrate was compared to mapping and ablation results with the endpoint of complete elimination of local abnormal ventricular activity (LAVA), and the impact of image integration on procedural management was analyzed. Imaging-derived substrate identified 89% of critical VT isthmuses and 85% of LAVA, and was more efficient in identifying LAVA in ICM and ARVC than in NICM (90% and 90% vs. 72%, P < 0.0001), and when defined from CMR than MDCT (ICM: 92% vs. 88%, P = 0.026, NICM: 88% vs. 72%, P < 0.001). Image integration motivated additional mapping and epicardial access in 57% and 33% of patients. Coronary and phrenic nerve integration modified epicardial ablation strategy in 43% of patients. The impact of image integration on procedural management was higher in ARVC/NICM than in ICM (P < 0.01), and higher in case of epicardial approach (P < 0.0001). CONCLUSIONS: Image integration is feasible in large series of patients, provides information on VT substrate, and impacts procedural management, particularly in ARVC/NICM, and in case of epicardial approach.

Early prosthetic aortic valve infection identified with the use of positron emission tomography in a patient with lead endocarditis.

BACKGROUND: 18-Fluorodeoxyglucose positron emission tomography/computerized tomography (FDG PET/CT) scanning has recently been proposed as a diagnostic tool for lead endocarditis (LE). OBJECTIVE: FDG PET/CT might be also useful to localize associated septic emboli in patients with LE. CASE PRESENTATION: We report an interesting case of a LE patient with a prosthetic aortic valve in whom a trans-esophageal echocardiogram did not show associated aortic endocarditis. FDG PET/CT revealed prosthetic aortic valve infection. A second TEE performed 2 weeks after identified aortic vegetation. A longer duration of antimicrobial therapy with serial follow-up echocardiography was initiated. There was also increased uptake in the sigmoid colon, corresponding to focal polyps resected during a colonoscopy. CONCLUSION: FDG PET/CT scanning seems to be highly sensitive for prosthetic aortic valve endocarditis diagnosis. This promising diagnostic tool may be beneficial in LE patients, by identifying septic emboli and potential sites of pathogen entry.

Epicardial only mapping and ablation of ventricular tachycardia: a case series.

AIMS: Ventricular tachycardia (VT) ablation for ventricular arrhythmias is a validated approach, typically performed endocardially, or combined with an epicardial approach if endocardial ablation failed or in case of non-ischaemic cardiomyopathy. We report our experience with epicardial only procedure in a subset of patients with incessant VT or VT storm. METHODS AND RESULTS: This was a single centre retrospective study. Between 2011 and 2014, all patients referred for VT ablation were reviewed at CHU Bordeaux. All patients with an epicardial only (anterior percutaneous approach) mapping and ablation procedure were included. In total, 296 patients underwent a VT ablation and 4 (all male, 70 ± 7 years, 27 ± 11% left ventricular ejection fraction) of them underwent an epicardial only procedure: two ischaemic patients had an endocardial left ventricular thrombus and incessant VT. One patient post-myocarditis had a failed a previous endocardial procedure without local abnormal ventricular activity (LAVA). The fourth patient had a dilated cardiomyopathy and a complicated epicardial puncture followed by mild continuous bleeding (200 mL) precluding anticoagulation associated with left ventricular endocardial access. Local abnormal ventricular activity elimination was verified only epicardially in all and obtained in two patients and non-inducibility was tested and achieved in the two patients without thrombus. No further complications occurred. After a mean follow-up of 21 ± 12 months, one patient (25%) had recurrence of VT and no patient death was observed. CONCLUSION: Epicardial only ablation seems feasible and effective and useful in a limited subset of patients with incessant VT. However, endpoints are more difficult to evaluate and long-term follow-up is needed.

Driver domains in persistent atrial fibrillation.

BACKGROUND: Specific noninvasive signal processing was applied to identify drivers in distinct categories of persistent atrial fibrillation (AF). METHODS AND RESULTS: In 103 consecutive patients with persistent AF, accurate biatrial geometry relative to an array of 252 body surface electrodes was obtained from a noncontrast computed tomography scan. The reconstructed unipolar AF electrograms acquired at bedside from multiple windows (duration, 9±1 s) were signal processed to identify the drivers (focal or reentrant activity) and their cumulative density map. The driver domains were catheter ablated by using AF termination as the procedural end point in comparison with the stepwise-ablation control group. The maps showed incessantly changing beat-to-beat wave fronts and varying spatiotemporal behavior of driver activities. Reentries were not sustained (median, 2.6 rotations lasting 449±89 ms), meandered substantially but recurred repetitively in the same region. In total, 4720 drivers were identified in 103 patients: 3802 (80.5%) reentries and 918 (19.5%) focal breakthroughs; most of them colocalized. Of these, 69% reentries and 71% foci were in the left atrium. Driver ablation alone terminated 75% and 15% of persistent and long-lasting AF, respectively. The number of targeted driver regions increased with the duration of continuous AF: 2 in patients presenting in sinus rhythm, 3 in AF lasting 1 to 3 months, 4 in AF lasting 4 to 6 months, and 6 in AF lasting longer. The termination rate sharply declined after 6 months. The mean radiofrequency delivery to AF termination was 28±17 minutes versus 65±33 minutes in the control group (P<0.0001). At 12 months, 85% patients with AF termination were free from AF, similar to the control population (87%,); P=not significant. CONCLUSIONS: Persistent AF in early months is maintained predominantly by drivers clustered in a few regions, most of them being unstable reentries.

Impact of Electrode Type on Mapping of Scar-Related VT.

BACKGROUND: Substrate-based VT ablation is mostly based on maps acquired with ablation catheters. We hypothesized that multipolar mapping catheters are more effective for identification of scar and local abnormal ventricular activity (LAVA). METHODS AND RESULTS: Phase1: In a sheep infarction model (2 months postinfarction), substrate mapping and LAVA tagging (CARTO® 3) was performed, using a Navistar (NAV) versus a PentaRay (PR) catheter (Biosense Webster). Phase2: Consecutive VT ablation patients from a single center underwent NAV versus PR mapping. Point pairs were defined as a PR and a NAV point located within a 3D-distance of ≤3 mm. Agreement was defined as both points in a pair being manually tagged as normal or LAVA. Four sheep (4 years, 50 ± 4.8 kg) and 9 patients were included (53 ± 14 years, 8 male, 6 ischemic cardiomyopathy). Mapping density was higher within the scar with PR versus NAV (3.2 vs. 0.7 points/cm2 , P = 0.001) with larger bipolar scar area (68 ± 55 cm2 vs. 58 ± 48 cm2 , P = 0.001). In total, 818 point pairs were analyzed. Using PR, far-field voltages were smaller (PR vs. NAV; bipolar: 1.43 ± 1.84 mV vs. 1.64 ± 2.04 mV, P = 0.001; unipolar; 4.28 ± 3.02 mV vs. 4.59 ± 3.67 mV, P < 0.001). More LAVA were also detected with PR (PR vs. NAV; 126 ± 113 vs. 36 ± 29, P = 0.001). When agreement on LAVA was reached (overall: 72%; both LAVA, 40%; both normal, 82%) higher LAVA voltages were recorded on PR (0.48 ± 0.33 mV vs. 0.31 ± 0.21 mV, P = 0.0001). CONCLUSION: Multipolar mapping catheters with small electrodes provide more accurate and higher density maps, with a higher sensitivity to near-field signals. Agreement between PR and NAV is low.

High performances of (18)F-fluorodeoxyglucose PET-CT in cardiac implantable device infections: A study of 40 patients.

BACKGROUND: Cardiovascular implantable electronic devices (CIED) infections are life-threatening complications. The diagnosis can be difficult to establish. Our purpose is to evaluate the diagnostic value of (18)F-FDG PET. METHODS: Forty patients who received work-up for suspected CIED infection were retrospectively included (group 1) and compared with 40 controls (group 2); CIED patients were referred for oncologic PET. PET-CT data were blindly assessed. Interpretation was based on visual analysis of both attenuation-corrected and non-corrected images and a semi-quantitative analysis was performed. The gold standard was bacteriological data of explanted devices or clinical follow-up for at least 1 year. RESULTS: Infection was present in 18 out of 40 patients of group 1. Sensitivity, specificity, positive predictive value, and negative predictive value of PET-CT were 83%, 95%, 94%, and 88%, respectively. Accuracy was 90%. PET-CT revealed the presence of additional pathological hypermetabolic foci in 28% of cases. PET-CT was negative at implanted devices in all patients of group 2. CONCLUSION: (18)F-FDG PET-CT is helpful in the work-up of suspected CIED infections. It is a potential tool to make the accurate diagnosis of CIED infection and to assess the extent of infection. The promising results in this indication need to be validated in a prospective multicenter study.

A comparison of left ventricular endocardial, multisite, and multipolar epicardial cardiac resynchronization: an acute haemodynamic and electroanatomical study.

AIMS: Alternative forms of cardiac resynchronization therapy (CRT), including biventricular endocardial (BV-Endo) and multisite epicardial pacing (MSP), have been developed to improve response. It is unclear which form of stimulation is optimal. We aimed to compare the acute haemodynamic response (AHR) and electrophysiological effects of BV-Endo with MSP via two separate coronary sinus (CS) leads or a single-quadripolar CS lead. METHODS AND RESULTS: Fifteen patients with a previously implanted CRT system received a second temporary CS lead and left ventricular (LV) endocardial catheter. A pressure wire and non-contact mapping array were placed into the LV cavity to measure LVdP/dtmax and perform electroanatomical mapping. Conventional CRT, BV-Endo, and MSP were then performed (MSP-1 via two epicardial leads and MSP-2 via a single-quadripolar lead). The best overall AHR was found using BV-Endo pacing with a 19.6 ± 13.6% increase in AHR at the optimal endocardial site over baseline (P < 0.001). There was an increase in LVdP/dtmax with MSP-1 and MSP-2 compared with conventional CRT, but this was not statistically significant. Biventricular endocardial pacing from the optimal site was significantly superior to conventional CRT (P = 0.039). The AHR achieved when BV-Endo pacing was highly site specific. Within individuals, the best pacing modality varied and was affected by the underlying substrate. Left ventricular activation times did not predict the optimal haemodynamic configuration. CONCLUSION: Biventricular endocardial pacing and not MSP was superior to conventional CRT, but was highly site specific. Within individuals, however, different methods of stimulation are optimal and may need to be tailored to the underlying substrate.

Pre- and intra-procedural predictors of reverse remodeling after cardiac resynchronization therapy: an MRI study.

INTRODUCTION: Response rate after cardiac resynchronization therapy (CRT) remains suboptimal. We sought to identify pre- and intraprocedural predictors of response using MRI. METHODS AND RESULTS: Sixty patients underwent MRI before CRT. Left ventricular (LV) volumes and ejection fraction were assessed on cine images. Intra-LV dyssynchrony was defined as the maximal delay between first peaks of radial wall motion over 20 segments. Myocardial scar extent was quantified using delayed-enhanced MRI. After CRT, the paced LV segment was characterized on preprocedural MRI with respect to presence of scar and mechanical delay, the latter being quantified using time to first peak of wall motion, expressed in percentage of the total LV activation. Echocardiography was performed before and 6 months after CRT to quantify reverse remodeling (RR). Mean RR at 6 months was 30 ± 29% of baseline LV end-systolic volume. At univariate analysis, RR related to baseline LV end-diastolic and end-systolic volumes (R(2) = 0.101, P = 0.01; R(2) = 0.072, P = 0.04), intra-LV mechanical dyssynchrony (R(2) = 0.351, P < 0.0001), scar extent (R(2) = 0.273, P < 0.0001), and presence of scar at pacing site (R(2) = 0.100, P = 0.01). QRS duration and mechanical delay at pacing site were not found related to RR (R(2) = 0.041, P = 0.12 and R(2) = 0.012, P = 0.4, respectively). At multivariate analysis intra-LV mechanical dyssynchrony, scar extent, and LV end-diastolic volume were independent predictors of RR (R(2) = 0.307, P = 0.001; R(2) = 0.096, P = 0.002, R(2) = 0.078, P = 0.005, respectively). CONCLUSION: Intra-LV dyssynchrony and scar extent are independent predictors of RR after CRT. Scar at pacing site is associated to a lesser response to CRT. Mechanical delay at this site has no impact on the response.

CLOSE-Guided Pulmonary Vein Isolation to Treat Persistent Atrial Fibrillation: 1-Year Outcome.

BACKGROUND: CLOSE-guided pulmonary vein isolation (PVI) is based on contiguous and optimized (Ablation Index-guided) radiofrequency lesions. The efficacy of CLOSE-guided PVI in persistent atrial fibrillation (AF) treatment has been poorly evaluated. METHODS: In two centers, 50 patients eligible for persistent AF ablation underwent CLOSE-guided PVI (Ablation Index ≥ 450 at the anterior wall, ≥300 at posterior wall, intertag distance ≤ 6 mm). If PVI failed to restore sinus rhythm (SR), electrical cardioversion (ECV) was performed. Atrial substrate modification (ASM) was performed only if PVI and ECV failed to restore SR. Recurrence was defined as any recorded episode of AF, atrial tachycardia (AT) or atrial flutter (AFL) > 30 s on Holter electrocardiographs at 3, 6 and 12 months. RESULTS: From the 50 patients (64 ± 10 years, 14% long-standing persistent AF), SR was restored by ECV in 34 patients (68%) 56 ± 38 days prior to ablation. On the day of ablation, 42 patients (84%) were on class I-III anti-arrhythmic drug therapy (ADT) and the rhythm was AF in 23/50 patients. PVI was achieved in all patients; after PVI, ECV was required in 21 patients and ASM in 1 patient. The mean procedure time, radiofrequency time and fluoroscopy time were 141 ± 33 min, 23 ± 7 min and 7 ± 6 min, respectively. At 12 months, single-procedure freedom from AF/AT/AFL was 80%, with 19 patients (38%) receiving class I-III ADT. CONCLUSIONS: In a population of patients with persistent AF monitored with intermittent cardiac rhythm recordings, CLOSE-guided PVI resulted in high single-procedure arrhythmia-free survival at 1 year. Future large-scale studies involving continuous cardiac monitoring are necessary.

The interaction of QRS duration with cardiac magnetic resonance derived scar and mechanical dyssynchrony in systolic heart failure: Implications for cardiac resynchronization therapy.

BACKGROUND: Trials using echocardiographic mechanical dyssynchrony (MD) parameters in narrow QRS patients have shown a negative response to CRT. We hypothesized MD in these patients may relate to myocardial scar rather than electrical dyssynchrony. METHODS: We determined the prevalence of cardiac magnetic resonance (CMR) derived measures of MD in 130 systolic heart failure patients with both broad (≥ 130 ms - BQRS) and narrow QRS duration (< 130 ms - NQRS). We assessed whether late gadolinium enhancement derived scar might explain the presence of MD amongst narrow QRS patients. Dyssynchrony was calculated on the basis of a systolic dyssynchrony index (SDI). RESULTS: Fifty-nine patients (45%) had a NQRS and the remaining had QRS ≥ 130 ms (BQRS group). 25% of NQRS patients had MD based on SDI. In all narrow and broad QRS patients with MD there was a significantly lower scar volume than those without MD (7.4 ± 10.5% vs 13.7 ± 13.3% vs. p < 0.01). This was the case in the BQRS group with a significantly lower scar burden in patients with MD (5.0 ± 7.7% vs 15.4 ± 15.6%, p < 0.01). Notably in the NQRS group this difference was absent with an equal scar burden in patients with MD 13.3 ± 13.9% and without MD 12.5 ± 11%, p = 0.92. CONCLUSIONS: 25% of patients with systolic heart failure and a NQRS (< 130 ms) have CMR derived mechanical dyssynchrony. Our findings suggest MD in this group may be secondary to myocardial scar rather than electrical dyssynchrony and therefore not amenable to correction by CRT. This may give insight into non-response and potential harm from CRT in this group.

Revisiting anatomic macroreentrant tachycardia after atrial fibrillation ablation using ultrahigh-resolution mapping: Implications for ablation.

BACKGROUND: Anatomic macroreentrant atrial tachycardias (MATs) are conventionally reported to depend on the cavotricuspid isthmus, the mitral isthmus, or the left atrial roof, and are commonly seen following catheter ablation for atrial fibrillation. OBJECTIVES: To define the precise circuits of anatomic MAT with ultrahigh-resolution mapping. METHODS: In 57 patients (mean age, 62 years; 10 female) who developed ≥1 anatomic MAT, we analyzed 88 MAT circuits including 16 peritricuspid, 42 perimitral, and 30 roof-dependent circuits, using high-density mapping and entrainment. RESULTS: Of 16 peritricuspid atrial tachycardias (ATs), 8 (50.0%) showed a circuit not limited to the tricuspid annulus. However, cavotricuspid isthmus ablation terminated the tachycardia in all patients. Similarly, 26 of 42 perimitral ATs (61.9%) showed a circuit not limited to the mitral annulus, and a low-voltage zone <0.1 mV around the mitral annulus was associated with nontypical perimitral ATs (P < .0001). The practical isthmus was not in the mitral isthmus in 13 of these 26 perimitral ATs (50%). Finally, 22 of 30 roof-dependent ATs (73.3%) had a circuit not rotating around both pairs of pulmonary veins. Brief assessment of the activation direction on the posterior wall in relation to that on the septal, anterior, and lateral wall helped deduce the circuit of roof-dependent AT in 27 of 30 (90.0%). Practical isthmus was not in the roof in 8 of 22 (36.4%). Practical isthmuses mapped with the system were significantly shorter than the usual anatomic isthmuses (16.1 ± 8.2 mm vs 33.7 ± 10.4 mm) (P < .0001). CONCLUSIONS: High-density mapping successfully identified the precise circuits and the practical isthmus of anatomic MATs in patients with prior atrial fibrillation ablation.

Electrogram signature of specific activation patterns: Analysis of atrial tachycardias at high-density endocardial mapping.

BACKGROUND: The significance of fractionated electrograms (EGMs) is object of debate, with multiple mechanisms described. OBJECTIVE: Using Rhythmia, a high-density mapping system, we sought to investigate the relationship between specific electrophysiological phenomena and EGM characteristics at those sites. METHODS: Twenty-five consecutive patients underwent high-density atrial mapping during atrial tachycardias. Bipolar EGMs were recorded with a 64-electrode basket catheter. The following atrial phenomena were identified: slow conduction (SC) areas, lines of block (LB), wavefront collisions (WFC), pivot sites (PS), and gaps. EGMs collected at these predefined areas were analyzed in terms of amplitude, duration, and morphology. RESULTS: Twenty-five atrial maps with 195 sites of interest (1755 EGMs) were object of our analysis. Thirty-five percent were sites of SC: fractionation had low amplitude (0.16 ± 0.07 mV) and long duration (87.8 ± 10.7 ms); wavefront collisions were seen in 38% of sites with EGMs shorter in duration (46.5 ± 4.5 ms) and higher in voltage (0.58 ± 0.13 mV); 17% were lines of block, never responsible for fractionation (0.13 ± 0.05 mV; 122.4 ms ± 24.8 ms); 9% were PS with a high degree of fractionation (0.55 ± 0.15 mV; 85.8 ± 7.9 ms). Two gaps were identified (1%) with a low degree of fractionation. CONCLUSION: Specific EGM characteristics in atrial tachycardia can be reproducibly linked to electrophysiological mechanisms. High-voltage and short-duration EGMs are associated with collision sites and PS that are unlikely to form critical sites for ablation; long-duration, low-voltage EGMs are associated with SC. However, not all SC regions will lie within the critical circuit and identification by only EGM characteristics cannot guide ablation.

Relationship Between Fibrosis Detected on Late Gadolinium-Enhanced Cardiac Magnetic Resonance and Re-Entrant Activity Assessed With Electrocardiographic Imaging in Human Persistent Atrial Fibrillation.

OBJECTIVES: This study sought to assess the relationship between fibrosis and re-entrant activity in persistent atrial fibrillation (AF). BACKGROUND: The mechanisms involved in sustaining re-entrant activity during AF are poorly understood. METHODS: Forty-one patients with persistent AF (age 56 ± 12 years; 6 women) were evaluated. High-resolution electrocardiographic imaging (ECGI) was performed during AF by using a 252-chest electrode array, and phase mapping was applied to locate re-entrant activity. Sites of high re-entrant activity were defined as re-entrant regions. Late gadolinium-enhanced (LGE) cardiac magnetic resonance (CMR) was performed at 1.25 × 1.25 × 2.5 mm resolution to characterize atrial fibrosis and measure atrial volumes. The relationship between LGE burden and the number of re-entrant regions was analyzed. Local LGE density was computed and characterized at re-entrant sites. All patients underwent catheter ablation targeting re-entrant regions, the procedural endpoint being AF termination. Clinical, CMR, and ECGI predictors of acute procedural success were then analyzed. RESULTS: Left atrial (LA) LGE burden was 22.1 ± 5.9% of the wall, and LA volume was 74 ± 21 ml/m2. The number of re-entrant regions was 4.3 ± 1.7 per patient. LA LGE imaging was significantly associated with the number of re-entrant regions (R = 0.52, p = 0.001), LA volume (R = 0.62, p < 0.0001), and AF duration (R = 0.54, p = 0.0007). Regional analysis demonstrated a clustering of re-entrant activity at LGE borders. Areas with high re-entrant activity showed higher local LGE density as compared with the remaining atrial areas (p < 0.0001). Failure to achieve AF termination during ablation was associated with higher LA LGE burden (p < 0.001), higher number of re-entrant regions (p < 0.001), and longer AF duration (p = 0.008). CONCLUSIONS: The number of re-entrant regions during AF relates to the extent of LGE on CMR, with the location of these regions clustering to LGE areas. These characteristics affect procedural outcomes of ablation.

Myocardial wall thinning predicts transmural substrate in patients with scar-related ventricular tachycardia.

BACKGROUND: Scar-related ventricular tachycardia (VT) arises from specific substrate according to etiology. OBJECTIVE: The purpose of this study was to evaluate the relationship between wall thinning (WT) on multidetector computed tomography (MDCT) and local abnormal ventricular activity (LAVA) in patients with ischemic cardiomyopathy (ICM), postmyocarditis (PMC), and dilated cardiomyopathy (DCM). METHODS: Forty-two patients (40 male, age 58 ± 13 years, 22 ICM, 11 PMC, 9 DCM) underwent MDCT before a combined endo-/epicardial VT ablation procedure. WT (<5 mm) and severe wall thinning (SWT) (<2 mm) area on MDCT were compared to the prevalence of endo-/epicardial LAVA during sinus rhythm. RESULTS: WT and SWT were found on MDCT in 36 (86%) and 20 (48%) with 42 ± 37 cm2 and 26 ± 24 cm2, respectively. SWT was frequently detected in ICM (ICM 77% vs PMC 27% vs DCM 0%, P <.001). LAVA were frequently observed on the endocardium in ICM and on the epicardium in PMC. Endo-/epicardial facing LAVA were frequently found within SWT areas (91% in <2 mm, 9% in 2-5 mm, and 0% in >5 mm, P < .001). In SWT areas, the presence of endocardial LAVA in ICM and epicardial LAVA in PMC predicted opposite facing LAVA with sensitivity and specificity of 78% and 48% and 79% and 98%, respectively. SWT predicted epicardial LAVA in ICM and endocardial LAVA in PMC with sensitivity and specificity of 89% and 100%, and 100% and 100%, respectively. CONCLUSION: SWT is frequently found in ICM and PMC but is not common in DCM. SWT predicts LAVA on the opposite side of the wall (epicardial in ICM and endocardial in PMC), indicating transmural VT substrate. MDCT is useful for identifying VT substrate and helpful for understanding the mechanisms of the location of VT substrate domain.

Complexity and Distribution of Drivers in Relation to Duration of Persistent Atrial Fibrillation.

BACKGROUND: The underlying mechanisms sustaining human persistent atrial fibrillation (PsAF) is poorly understood. OBJECTIVES: This study sought to investigate the complexity and distribution of AF drivers in PsAF of varying durations. METHODS: Of 135 consecutive patients with PsAF, 105 patients referred for de novo ablation of PsAF were prospectively recruited. Patients were divided into 3 groups according to AF duration: PsAF presenting in sinus rhythm (AF induced), PsAF <12 months, and PsAF >12 months. Patients wore a 252-electrode vest for body surface mapping. Localized drivers (re-entrant or focal) were identified using phase-mapping algorithms. RESULTS: In this patient cohort, the most prominent re-entrant driver regions included the pulmonary vein (PV) regions and inferoposterior left atrial wall. Focal drivers were observed in 1 or both PV regions in 75% of patients. Comparing between the 3 groups, with longer AF duration AF complexity increased, reflected by increased number of re-entrant rotations (p < 0.05), number of re-entrant rotations and focal events (p < 0.05), and number of regions harboring re-entrant (p < 0.01) and focal (p < 0.05) drivers. With increased AF duration, a higher proportion of patients had multiple extra-PV driver regions, specifically in the inferoposterior left atrium (p < 0.01), superior right atrium (p < 0.05), and inferior right atrium (p < 0.05). Procedural AF termination was achieved in 70% of patients, but decreased with longer AF duration. CONCLUSIONS: The complexity of AF drivers increases with prolonged AF duration. Re-entrant and focal drivers are predominantly located in the PV antral and adjacent regions. However, with longer AF duration, multiple drivers are distributed at extra-PV sites. AF termination rate declines as patients progress to longstanding PsAF, underscoring the importance of early intervention.

Distinctive Left Ventricular Activations Associated With ECG Pattern in Heart Failure Patients.

BACKGROUND: In contrast to patients with left bundle branch block (LBBB), heart failure patients with narrow QRS and nonspecific intraventricular conduction delay (NICD) display a relatively limited response to cardiac resynchronization therapy. We sought to compare left ventricular (LV) activation patterns in heart failure patients with narrow QRS and NICD to patients with LBBB using high-density electroanatomic activation maps. METHODS AND RESULTS: Fifty-two heart failure patients (narrow QRS [n=18], LBBB [n=11], NICD [n=23]) underwent 3-dimensional electroanatomic mapping with a high density of mapping points (387±349 LV). Adjunctive scar imaging was available in 37 (71%) patients and was analyzed in relation to activation maps. LBBB patients typically demonstrated (1) a single LV breakthrough at the septum (38±15 ms post-QRS onset); (2) prolonged right-to-left transseptal activation with absence of direct LV Purkinje activity; (3) homogeneous propagation within the LV cavity; and (4) latest activation at the basal lateral LV. In comparison, both NICD and narrow QRS patients demonstrated (1) multiple LV breakthroughs along the posterior or anterior fascicles: narrow QRS versus LBBB, 5±2 versus 1±1; P=0.0004; NICD versus LBBB, 4±2 versus 1±1; P=0.001); (2) evidence of early/pre-QRS LV electrograms with Purkinje potentials; (3) rapid propagation in narrow QRS patients and more heterogeneous propagation in NICD patients; and (4) presence of limited areas of late activation associated with LV scar with high interindividual heterogeneity. CONCLUSIONS: In contrast to LBBB patients, narrow QRS and NICD patients are characterized by distinct mechanisms of LV activation, which may predict poor response to cardiac resynchronization therapy.