Left septal atrial tachycardias: electrocardiographic and electrophysiologic characterization of a paraseptal focus

A novel endocardial activation-derived predictor for focal paraseptal atrial tachycardias: evidence from a multicenter cohort study

BACKGROUND

The electrocardiogram-based algorithm for predicting para-septal atrial tachycardia (PSAT) is limited by the significant overlaps in the P-wave morphology originating from various para-septal sites.

OBJECTIVE

The aim of this study was to investigate the endocardial activation characteristics of PSAT and to seek an endocardial activation-derived predictor for the ablation site.

METHODS

Forty-four patients (11 males, average 62.6±14.7 years) with PSAT ablation in four tertiary medical centers were assigned into three groups according to the ablation site: right atrial (RA) para-Hisian region (Group 1, n=10), the noncoronary cusp (NCC) (Group 2, n=13) and left atrial (LA) para-septal areas (Group 3, n=21). Multiple-chamber activation mapping was performed guided by a 3D navigation system. The discrepancies in the earliest activation time between two of three chambers (ΔRA-LA, ΔRA-NCC and ΔLA-NCC) were calculated in each group and used for pairwise comparisons.

RESULTS

There was significant difference in ΔRA-LA, ΔRA-NCC, and ΔLA-NCC compared among three groups. ΔRA-LA was the only parameter which could consistently predict the ablation site of PSAT with good accuracy (AUC 1.000, sensitivity 100%/ specificity 100%, and cut-off value 7ms for predicting right para-Hisian or NCC ablation; AUC 0.974, sensitivity 92.3%/specificity 95.2%, and cut-off value -4 ms for predicting NCC or left para-septal ablation). Based on two cut-off values, A two-step algorithm was developed to predict the ablation site of PSAT with positive predictive value of 95.4% and negative predictive value of 97.0%.

CONCLUSIONS

ΔRA-LA is a useful endocardial activation-derived parameter for predicting the successful ablation site of PSAT.

P-Wave Morphology From Common Nonpulmonary Vein Trigger Sites Following Pulmonary Vein and Posterior Wall Isolation

BACKGROUND

Non-pulmonary vein (PV) triggers are increasingly targeted during atrial fibrillation (AF) ablation. P-wave morphology (PWM) can be useful because point mapping of AF triggers is challenging. The impact of prior ablation on PWM is yet to be determined.

OBJECTIVES

This study sought to report PWM before and after left atrial (LA) ablation and construct a P-wave algorithm of common non-PV trigger locations.

METHODS

This multicenter, prospective, observational study analyzed the paced PWM of 30 patients with persistent AF undergoing pulmonary vein isolation (PVI) and posterior wall isolation (PWI). Pace mapping was performed at the SVC, crista terminalis, inferior tricuspid annulus, coronary sinus ostium, left septum, left atrial appendage, Ligament of Marshall, and inferoposterior LA. The PWM was reported before PVI, then blinded comparisons were made post-PVI and post-PVI + PWI. A P-wave algorithm was constructed.

RESULTS

A total of 8,352 paced P waves were prospectively recorded. No significant changes in the PWM were seen post-PVI alone in 2,775 of 2,784 (99.7%) and post-PWI in 2,715 of 2,784 (97.5%). Changes in PWM were predominantly at the IPLA (53 P waves) with a positive P-wave in leads V2 to V6 before biphasic post-PWI, LA appendage (9 P waves), coronary sinus ostium (6 P waves), and ligament of Marshall (3 P waves). A PWM algorithm was created before PVI and accurately predicted the location in 93% post-PVI + PWI.

CONCLUSIONS

Minimal change was observed in PWM post-PV and PWI aside from the IPLA location. A P-wave algorithm created before and applied after PVI + PWI provided an accuracy of 93%. PWM provides a reliable tool to guide the localization of common non-PV trigger sites even after PV and PWI.

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.

Emergent Zero-Fluoroscopy Mapping and Thoracoscopic Ectomy of Appendage in Pregnant Women with Life-Threatening Atrial Tachycardia: A Case Report and Literature Review

Background: Focal atrial tachycardia (AT) originating from the right atrial appendage (RAA), often persistent and refractory, is clinically rare in pregnant woman, and the therapy is much more challenging. We report that a pregnant woman presented with hypotension due to persistent and refractory atrial tachycardia and was successfully cured by a multidisciplinary treatment (MDT) approach, consisting of a combination of zero-fluoroscopy mapping and thoracoscopic atrial appendectomy. We also carried out a literature review of this topic. Methods and Results: A 26-year-old woman in pregnancy at 21 weeks presented with severe palpitation and hypotension due to persistent rapid supraventricular tachycardia (SVT). Since adenosine triphosphate could not terminate the tachycardia, a catheter ablation procedure was planned and finally canceled when the zero-fluoroscopy mapping using Carto 3^TM system revealed an atrial tachycardia originating from the RAA. Thoracoscopic RAA ectomy was recommended after multidisciplinary consultation and successfully performed without fluoroscopy. Ensite^TM velocity mapping system was used for accurately locating the origin of the arrhythmia during ectomy. The woman finally produced a healthy baby during follow-up. Conclusions: Focal AT originating from appendage in pregnant patients can be persistent, refractory, and life-threatening; traditional strategies, such as medicine or catheter ablation, are limited in this situation. MDT measures, using a thoracoscopic ectomy and zero-fluoroscopy three-dimensional electroanatomical mapping technique, is minimally invasive and a promising strategy.

P-Wave Morphology in Focal Atrial Tachycardia: An Updated Algorithm to Predict Site of Origin

OBJECTIVES

This study sought to report P-wave morphology (PWM) from a series of paraseptal (PS) atrial tachycardia (AT), revise then prospectively evaluate a simplified PWM algorithm against a contemporary consecutive cohort with focal AT.

BACKGROUND

The 2006 PWM algorithm was useful in predicting the origin of focal AT. An updated algorithm was developed given advances in multipolar 3-dimensional mapping, potential limitations of PWM in separating PS sites, and a renewed interest in the P-wave in mapping non-pulmonary vein triggers.

METHODS

The PWM from a consecutive series of 67 patients with PS AT were analyzed. PS sites included were coronary sinus ostium, perinodal, left and right septum, septal tricuspid annulus, superior mitral annulus, and noncoronary cusp. Next the P-wave algorithm was revised and prospectively evaluated by 3 blinded assessors.

RESULTS

The P-wave for PS sites was neg/pos (n = 50), iso/pos (n = 10), or isoelectric (n = 4) in lead V₁ (96%). The P-wave algorithm was modified and prospectively applied to 30 consecutive patients with focal AT who underwent successful ablation. Foci (n = 30) originated from the right atrium (33.3%), left atrium (30%), and PS (36.7%). Using the PW algorithm, the correct anatomic location was identified in 93%. Incorrect interpretation of the terminal positive P-wave component (n = 3) and initial negative P-wave deflection (n = 1) in lead V₁ misidentified 4 paraseptal cases.

CONCLUSIONS

The revised PWM algorithm offers a simplified and accurate method of localizing the responsible site for focal AT. The P-wave remains an important first step in mapping atrial arrhythmias.

Atrial Tachycardias and Atypical Atrial Flutters: Mechanisms and Approaches to Ablation

Atrial tachycardias (ATs) may be classified into three broad categories: focal ATs, macroreentry and localised reentry – also known as ‘microreentry’. Features that distinguish these AT mechanisms include electrogram characteristics, responses to entrainment and pharmacological sensitivities. Focal ATs may occur in structurally normal hearts but can also occur in patients with structural heart disease. These typically arise from preferential sites such as the valve annuli, crista terminalis and pulmonary veins. Macro-reentrant ATs occur in the setting of atrial fibrosis, often after prior catheter ablation or post atriotomy, but also de novo in patients with atrial myopathy. High-resolution mapping techniques have defined details of macro-reentrant circuits, including zones of conduction block, scar and slow conduction. Localised reentry occurs in the setting of diseased atrial myocardium that supports very slow conduction. A characteristic feature of localised reentry is highly fractionated, low-amplitude electrograms that encompass most of the tachycardia cycle length over a small diameter. Advances in understanding the mechanisms of ATs and their signature electrogram characteristics have improved the efficacy and efficiency of catheter ablation.

Should the Aortic Root Be the Preferred Route for Ablation of Focal Atrial Tachycardia Around the AV Node?: Support From Intracardiac Echocardiography

OBJECTIVES

The purpose of this study was to determine the optimal approach to focal atrial tachycardia originating from around the atrioventricular node.

BACKGROUND

Focal atrial tachycardia (FAT) demonstrating earliest activation around the atrioventricular (AV) node during right atrial (RA) mapping has been eliminated by ablation at the RA para-Hisian region, from the left atrium (LA) or the noncoronary aortic cusp (NCC). However the optimal approach has not been determined.

METHODS

We conducted a retrospective analysis of a consecutive series of 148 patients undergoing catheter ablation for FAT between 2006 and 2014 in our institution.

RESULTS

Earliest activation was recorded in the peri-AV nodal region during RA mapping in 34 patients (23%). Of these, 7 patients (20.5%) had successful ablation at the RA septum, using either radiofrequency (n = 4) or cryoenergy (n = 3). Seven FATs (20.5%) were ablated from the LA at the region of the aortomitral continuity, and 20 patients (59%) had successful ablation in the NCC, including 1 patient with a recurrence after a temporarily successful cryoablation from the RA. The proportion of the 3 approaches in this series showed a significant temporal evolution and overall frequency favoring ablation in the NCC (p = 0.011 for time trend and 0.013 for actual vs. expected frequencies). Intracardiac echocardiography proved superior catheter stability with the NCC approach. There were 2 cases of atrioventricular block and 1 recurrence after RA ablation versus no complications or recurrent FAT with NCC and LA approaches.

CONCLUSIONS

Most peri-AV nodal FATs can be safely and effectively ablated from the NCC. The strategy of preferential NCC approach avoids RA para-Hisian ablation with the accompanying risk of AV block.

P wave morphology in guiding the ablation strategy of focal atrial tachycardias and atrial flutter

Focal atrial tachycardias arise preferentially from specific locations within the atria. Careful analysis of the P wave can provide useful information about the chamber and likely site of origin within that chamber. Macro-reentrant atrial flutter also tends to occur over a limited number of potential circuits. In this case, the ECG usually gives a guide to the chamber of origin, but unless it shows a specific morphology it is less useful in delineating the circuit involved. Nonetheless, prior knowledge of the likely chamber of origin helps to plan the ablation strategy.

Atrial tachycardias arising from the atrial appendages and aortic sinus of valsalva

Focal atrial tachycardias arising from the atrial appendages and the aortic sinuses of Valsalva are less frequently encountered in clinical practice. This review article describes the clinical presentation, surface P wave morphology, electrophysiologic characteristics and treatment of these arrhythmias. Catheter ablation of these focal tachycardias has a high success rate. It is however important to be aware of specific anatomic considerations in these locations for optimal treatment outcomes with low complication rates.

Mapping strategies in focal atrial tachycardias demonstrating early septal activation: distinguishing left from right

Determining the chamber of origin of focal atrial tachycardias (FATs) arising at or close to the septum might require biatrial mapping. This review focuses on the available tools and methods used to distinguish right atrial from left atrial origin before left atrial access is obtained. These include analysis of P wave morphology, assessing the timing of right atrial septal activation, the sequence of right atrial and/or biatrial activation and analysis of earliest electrogram morphology. The electroanatomical properties of the interatrial septum and coronary sinus that provide the basis for the above mentioned tools have also been briefly described.

Evidence of specialized tissue in human interatrial septum: histological, immunohistochemical and ultrastructural findings

Background

There is a paucity of information on structural organization of muscular bundles in the interatrial septum (IAS). The aim was to investigate histologic and ultrastructural organization of muscular bundles in human IAS, including fossa ovalis (FO) and flap valve.

Methods

Macroscopic and light microscopy evaluations of IAS were performed from postmortem studies of 40 patients. Twenty three IAS specimens underwent serial transverse sectioning, and 17 - longitudinal sectioning. The transverse sections from 10 patients were immunolabeled for HCN4, Caveolin3 and Connexin43. IAS specimens from 6 other patients underwent electron microscopy.

Results

In all IAS specimens sections the FO, its rims and the flap valve had muscle fibers consisting of working cardiac myocytes. Besides the typical cardiomyocytes there were unusual cells: tortuous and horseshoe-shaped intertangled myocytes, small and large rounded myocytes with pale cytoplasm. The cells were aggregated in a definite structure in 38 (95%) cases, which was surrounded by fibro-fatty tissue. The height of the structure on transverse sections positively correlated with age (P = 0.03) and AF history (P = 0.045). Immunohistochemistry showed positive staining of the cells for HCN4 and Caveolin3. Electron microscopy identified cells with characteristics similar to electrical conduction cells.

Conclusions

Specialized conduction cells in human IAS have been identified, specifically in the FO and its flap valve. The cells are aggregated in a structure, which is surrounded by fibrous and fatty tissue. Further investigations are warranted to explore electrophysiological characteristics of this structure.