Functional substrate mapping of atrium in patients with atrial scar: A novel method to predict critical isthmus of atrial tachycardia.

Atrial tachycardia (AT) is a common rhythm disorder, especially in patients with atrial structural abnormalities. Although voltage mapping can provide a general picture of structural alterations which are mainly secondary to prior ablations, surgery or pressure/volume overload, data is scarce regarding the functional characteristics of low voltage regions in the atrium to predict critical isthmus of ATs. Recently, functional substrate mapping (FSM) emerged as a potential tool to evaluate the functionality of structurally altered regions in the atrium to predict critical sites of reentry. Current evidence suggested a clear association between deceleration zones of isochronal late activation mapping (ILAM) during sinus/paced rhythm and critical isthmus of reentry in patients with left AT. Therefore, these areas seem to be potential ablation targets even not detected during AT. Furthermore, abnormal conduction detected by ILAM may also have a role to identify the potential substrate and predict atrial fibrillation outcome after pulmonary vein isolation. Despite these promising findings, the utility of such an approach needs to be evaluated in large-scale comparative studies. In this review, we aimed to share our experience and review the current literature regarding the use of FSM during sinus/paced rhythm in the prediction of re-entrant ATs and discuss future implications and potential use in patients with atrial low-voltage areas.

Mapping and ablation of left atrial roof-dependent tachycardias using an ultra-high resolution mapping system.

BACKGROUND: Left atrial roof-dependent tachycardias (LARTs) are common macroreentrant atrial tachycardias (ATs). We sought to characterize clinical LARTs using an ultra-high resolution mapping system. METHODS: This study included 22 consecutive LARTs in 21 patients who underwent AT mapping/ablation using Rhythmia systems. RESULTS: Three, 13, 4, and 2 LART patients were cardiac intervention naïve (Group-A), post-roof line ablation (Group-B), post-atrial fibrillation ablation without linear ablation (Group-C), and post-cardiac surgery (Group-D), respectively. The mean AT cycle length was 244 ± 43 ms. Coronary sinus activation was proximal-to-distal or distal-to-proximal in 16 (72.7%) ATs. The activation map revealed 13 (59.1%) clockwise and 9 (40.9%) counter-clockwise LARTs. A 12-lead synchronous isoelectric interval was observed in 10/19 (52.6%) LARTs. The slow conduction area was identified on the LA roof, anterior/septal wall, and posterior wall in 18, 6, and 2 ATs, respectively. Twenty concomitant ATs among 13 procedures were also eliminated, and peri-mitral AT coexisted in 7 of 9 non-group-B patients. In group-B, the conduction gap was predominantly located on the mid-roof. Sustained LARTs were terminated by a single application and linear ablation in 6 (27.3%) and 9 (40.9%), while converting to other ATs in 7 (31.8%) LARTs. Complete linear block was created without any complications in all, however, ablation at the mid-posterior wall was required to achieve block in 4 (18.2%) procedures. During 14.0 (6.5-28.5) months of follow-up, 17 (81.0%) and 19 (90.5%) patients were free from any atrial tachyarrhythmias after single and last procedures. CONCLUSIONS: The LART mechanisms were distinct in individual patients, and elimination of all concomitant ATs was required for the management.

Novel aggregated multiposition noncontact mapping of atrial tachycardia in humans: From computational modeling to clinical validation.

BACKGROUND: A novel aggregated multiposition noncontact mapping (AMP-NCM) algorithm is proposed to diagnose cardiac arrhythmias. OBJECTIVE: The purpose of this study was to computationally determine an accuracy threshold and to compare the accuracy and clinical utility of AMP-NCM to gold standard contact mapping. METHODS: In a cellular automata model, the number of catheter positions and chamber coverage were varied to establish accuracy requirements for clinically relevant AMP-NCM. This guided the clinical study protocol. In a prospective cohort of patients with atrial tachycardia (AT), noncontact mapping (NCM) recordings from a single position (SP) and multiple positions were compared to contact mapping with a high-density multipolar catheter using morphology and timing differences of reconstructed signals. Identification of AT mechanisms and ablation targets using both AMP-NCM and contact mapping were randomly evaluated by 5 blinded reviewers. RESULTS: AMP-NCM accuracy was asymptotic at 60 catheter positions in computational modeling. Twenty patients (age 65 ± 12 years; 19 male) with 26 ATs (5 focal, 21 reentrant) were studied. Morphologic correlation of signals derived from AMP-NCM was significantly better than those from SP-NCM compared to contact signals (median 0.93 vs 0.76; P <.001). AMP-NCM generated maps more rapidly than contact mapping (3 ± 1 minutes vs 13 ± 6 minutes; P <.001) and correctly diagnosed AT mechanisms in 25 of 26 maps (96%). Overall, 80% of arrhythmia mechanisms were correctly identified using AMP-NCM by blinded reviewers. CONCLUSION: Once 60 catheter positions were achieved, AMP-NCM successfully diagnosed mechanisms of AT and identified treatment sites equal to gold standard contact mapping in 3 minutes of procedural time.

Electrophysiological characteristics of atrial tachycardia recurrence: Relevance to catheter ablation strategies in adults with congenital heart disease.

BACKGROUND: Catheter ablation outcomes for adults with congenital heart disease (ACHD) are described, but recurrence mechanisms remain largely unknown. OBJECTIVE: The purpose of this study was to identify the electrophysiological characteristics of atrial tachycardia (AT) recurrence in ACHD. METHODS: ACHD atrial tachycardia procedures over a 10-year period were explored for AT or atrial fibrillation (AF) recurrence. RESULTS: At 299 procedures in 250 ACHD (mean age 39 ± 15 years; 130 [52%] male), 464 ATs (360 intra-atrial reentrant tachycardia, 104 focal AT; median 2 [IQR 1-3] ATs per procedure) were targeted. Complete (n = 256 [86%]) or partial (n = 37 [12%]) success was achieved in 98% of procedures. Over a median of 3.0 (IQR 1.4-5.3) years of follow-up, 67 patients (27%) developed AT/AF recurrence after the index procedure. Repeat vs index tachycardias were more often focal AT (26/69 [38%] vs 73/378 [19%]; P < .001), demonstrated longer cycle length (325 ms vs 280 ms; P = .003), required isoproterenol (34/69 [50%] vs 121/378 [32%]; P = .03), and involved the pulmonary venous atrium (PVA)/septum (26/69 [38%] vs 67/378 [18%]; P < .001). AF history (hazard ratio [HR] 2.0; interquartile range [IQR] 1.2-3.4; P = .01), incomplete success (HR 3.6; IQR 2.1-6.4; P < .001), and PVA substrate (HR 2.1; IQR 1.2-3.5; P = .006) were independently associated with AT/AF recurrence. With complete index procedure success and no AF history, 5-year actuarial freedom from AT/AF and AT alone were 77% and 80%. CONCLUSION: After catheter ablation in ACHD, repeat ATs were more frequently focal, required isoproterenol administration, or involved intra-atrial reentrant tachycardia within the PVA or atrial septum. Negative factors were partial success, index PVA substrate, and remote history of AF. These data support aggressive pharmacological provocation to eliminate all inducible tachycardias and coexisting PVA substrates at index procedures for ACHD.

Arrhythmic manifestation in ß-thalassemia cardiomyopathy: a complex management.

A young male with ß-thalassemia major was implanted with a single-chamber Implantable cardioverter-defibrillator (ICD) for a cardiac arrest due to ventricular fibrillation. He received multiple inappropriate shocks due to atrioventricular nodal re-entrant tachycardia (AVNRT) treated with radiofrequency catheter ablation and then to high-rate atrial tachycardia refractory to amiodarone and not inducible during electrophysiological study. He refused empirical pulmonary vein isolation. Upgrading to biventricular ICD and performing atrioventricular node ablation avoided further inappropriate shocks.

Electrophysiological Characteristics of Intra-Atrial Reentrant Tachycardia in Adult Congenital Heart Disease: Implications for Catheter Ablation.

Background Ultra-high-density mapping enables detailed mechanistic analysis of atrial reentrant tachycardia but has yet to be used to assess circuit conduction velocity (CV) patterns in adults with congenital heart disease. Methods and Results Circuit pathways and central isthmus CVs were calculated from consecutive ultra-high-density isochronal maps at 2 tertiary centers over a 3-year period. Circuits using anatomic versus surgical obstacles were considered separately and pathway length <50th percentile identified small circuits. CV analysis was used to derive a novel index for prediction of postablation conduction block. A total of 136 supraventricular tachycardias were studied (60% intra-atrial reentrant, 14% multiple loop). Circuits with anatomic versus surgical obstacles featured longer pathway length (119 mm; interquartile range [IQR], 80-150 versus 78 mm; IQR, 63-95; P<0.001), faster central isthmus CV (0.1 m/s; IQR, 0.06-0.25 versus 0.07 m/s; IQR, 0.05-0.10; P=0.016), faster non-isthmus CV (0.52 m/s; IQR, 0.33-0.71 versus 0.38 m/s; IQR, 0.27-0.46; P=0.009), and fewer slow isochrones (4; IQR, 2.3-6.8 versus 6; IQR 5-7; P=0.008). Both central isthmus (R2=0.45; P<0.001) and non-isthmus CV (R2=0.71; P<0.001) correlated with pathway length, whereas central isthmus CV <0.15 m/s was ubiquitous for small circuits. Non-isthmus CV in tachycardia correlated with CV during block validation (R2=0.94; P<0.001) and a validation map to tachycardia conduction time ratio >85% predicted isthmus block in all cases. Over >1 year of follow-up, arrhythmia-free survival was better for homogeneous CV patterns (90% versus 57%; P=0.04). Conclusions Ultra-high-density mapping-guided CV analysis distinguishes atrial reentrant patterns in adults with congenital heart disease with surgical obstacles producing slower and smaller circuits. Very slow central isthmus CV may be essential for atrial tachycardia maintenance in small circuits, and non-isthmus conduction time in tachycardia appears to be useful for rapid assessment of postablation conduction block.

Mechanisms and outcomes of catheter ablation for biatrial tachycardia in adults with congenital heart disease.

BACKGROUND: Biatrial tachycardia (BiAT) is a rare form of macroreentry not previously characterized in adults with congenital heart disease (ACHD). OBJECTIVE: The purpose of this study was to determine the prevalence, mechanisms, and outcomes of catheter ablation for BiAT in ACHD. METHODS: All ACHD undergoing catheter ablation for macroreentrant atrial tachycardia over a 10-year period were evaluated for evidence of BiAT. Patients were categorized as prior Senning, Fontan, or other biventricular operation. A novel biatrial global activation histogram (GAH) analysis was used to demonstrate the presence of interatrial connections (IACs). RESULTS: Among 263 ACHD, BiAT was identified at 11 procedures in 10 patients (4.2%; median age 35 years; 30% male). The congenital category was Fontan in 6, Senning in 3, and biventricular in 2. Diagnosis of BiAT was associated with ablation era and mapping technology (P <.001) and could be confirmed with a novel GAH mapping approach for normally septated atrial connections. Catheter ablation targeted an IAC in 5 cases (Bjork Fontan and biventricular operations), a posterior isthmus in 3 (Senning operation), and the cavotricuspid isthmus or equivalent in 3 (lateral tunnel [LT] Fontan). Recurrence was isolated to ablation to sites at the expected location of the Bachmann bundle, and durable success could be achieved after repeat ablation. CONCLUSION: BiAT occurs in approximately 4% of ACHD but is likely underrecognized. BiAT could be targeted at an IAC for normally septated atria and at a conventional critical isthmus after Senning and LT Fontan operations.

Prognostic Implications of Supraventricular Arrhythmias.

The aim of this study was to establish the prevalence and prognostic implication of progressive supraventricular arrhythmias from frequent supraventricular ectopic complexes, isolated, in bi- or trigeminy, to supraventricular tachycardias with different characteristics. In the STROKESTOP I mass-screening study for atrial fibrillation (AF) in 75- and 76-year olds in Sweden, participants registered 30-second intermittent ECG twice daily for two weeks. The ECG-recordings from STROKESTOP I were re-evaluated using an automated algorithm to detect individuals with frequent supraventricular ectopic complexes or runs. Detected episodes were manually re-examined to confirm the findings. The primary endpoint was AF as ascertained from the national Swedish Patient register. Exploratory secondary endpoints were stroke and death. Median follow-up was 4.2 (interquartile range [IQR] 3.8-4.4) years. Of the examined 6,100 participants, 85% were free of significant supraventricular arrhythmia. In the 894 participants that had arrhythmia, frequent supraventricular ectopic complexes were the most common arrhythmia, n = 709 (11.6%) and irregular supraventricular tachycardias were more common than regular. Individuals with the most AF similar supraventricular tachycardias, irregular and lacking p-waves (termed micro-AF), n = 97 (1.6%) had the highest risk of developing AF (hazard ratio 4.3; 95% confidence interval [CI] 2.7-6.8). They also had increased risk of death (hazard ratio 2.0; CI 1.1-3.8). In conclusion, progression of atrial arrhythmias from supraventricular ectopic complexes to more AF-like episodes is associated with development of AF. Extended screening for AF should be considered in individuals with frequent supraventricular activity, especially in those with supraventricular tachycardias with AF characteristics.

Prospective blinded evaluation of smartphone-based ECG for differentiation of supraventricular tachycardia from inappropriate sinus tachycardia.

INTRODUCTION: Supraventricular tachycardias (SVT) are often difficult to document due to their intermittent, short-lasting nature. Smartphone-based one-lead ECG monitors (sECG) were initially developed for the diagnosis of atrial fibrillation. No data have been published regarding their potential role in differentiating inappropiate sinus tachycardia (IST) from regular SVT. If cardiologists could distinguish IST from SVT in sECG, economic health care burden might be significantly reduced. METHODS: We prospectively recruited 75 consecutive patients with known SVT undergoing an EP study. In all patients, four ECG were recorded: a sECG during SVT and during sinus tachycardia and respective 12-lead ECG. Two experienced electrophysiologists were blinded to the diagnoses and separately evaluated all ECG. RESULTS: Three hundred individual ECG were recorded in 75 patients (47 female, age 50 ± 18 years, BMI 26 ± 5 kg/m2, 60 AVNRT, 15 AVRT). The electrophysiologists' blinded interpretation of sECG recordings showed a sensitivity of 89% and a specificity of 91% for the detection of SVT (interobserver agreement κ = 0.76). In high-quality sECG recordings (68%), sensitivity rose to 95% with a specificity of 92% (interobserver agreement of κ = 0.91). Specificity increased to 96% when both electrophysiologists agreed on the diagnosis. Respective 12-lead ECG had a sensitivity of 100% and specificity of 98% for the detection of SVT. CONCLUSION: A smartphone-based one-lead ECG monitor allows for differentiation of SVT from IST in about 90% of cases. These results should encourage cardiologists to integrate wearables into clinical practice, possibly reducing time to definitive diagnosis of an arrhythmia and unnecessary EP procedures. A smartphone-based one lead ECG device (panel A) can be used reliably to differentiate supraventricular tachycardia (panel B) from inappropriate sinus tachycardia when compared to a simultaneously conducted gold-standard electrophysiology study (panels C, D).

Longitudinal Measures of Blood Pressure and Subclinical Atrial Arrhythmias: The MESA and the ARIC Study.

Background High blood pressure (BP) is a well-known risk factor for atrial fibrillation (AF), but a single BP measurement may provide limited information about AF risk in older adults. Methods and Results This study included 1256 MESA (Multi-Ethnic Study of Atherosclerosis) and 1948 ARIC (Atherosclerosis Risk in Communities) study participants who underwent extended ambulatory electrocardiographic monitoring and who were free of clinically detected cardiovascular disease, including AF. Using BP measurements from 6 examinations (2000-2018 in MESA and 1987-2017 in ARIC study), we calculated individual long-term mean, trend, and detrended visit-to-visit variability in systolic BP and pulse pressure for each participant. Outcomes, assessed at examination 6, included subclinical AF and supraventricular ectopy. Results from each study were combined with inverse variance-weighted meta-analysis. At examination 6, the mean age was 73 years in MESA and 79 years in ARIC study, and 4% had subclinical AF. Higher visit-to-visit detrended variability in systolic BP was associated with a greater prevalence of subclinical AF (odds ratio [OR], 1.20; 95% CI, 1.02-1.38) and with more premature atrial contractions/hour (geometric mean ratio, 1.08; 95% CI, 1.01-1.15). For pulse pressure as well, higher visit-to-visit detrended variability was associated with a greater prevalence of AF (OR, 1.18; 95% CI, 1.00-1.37). In addition, higher long-term mean pulse pressure was associated with a greater prevalence of subclinical AF (OR, 1.36; 95% CI, 1.08-1.70). Conclusions Antecedent visit-to-visit variability in systolic BP and pulse pressure, but not current BP, is associated with a higher prevalence of subclinical atrial arrhythmias. Prior longitudinal BP assessment, rather than current BP, may be more helpful in identifying older adults who are at higher risk of atrial arrhythmias.