Paced P-wave morphology templates to guide atrial tachycardia localization: A derivation and validation study.

BACKGROUND: Surface ECG is a useful tool to guide mapping of focal atrial tachycardia (AT). OBJECTIVES: We aimed to construct 12-lead ECG templates for P-wave morphology (PWM) during endocardial pacing from different sites in both atria in patients with no apparent structural heart disease (derivation cohort), with the goal of creating a localization algorithm, which could subsequently be validated in a cohort of patients undergoing catheter ablation of focal AT (validation cohort). METHODS: We prospectively enrolled consecutive patients who underwent electrophysiology study, had no structural heart disease and no atrial enlargement. Atrial pacing, at twice diastolic threshold, was carried out at different anatomical sites in both atria. Paced PWM and duration were assessed. An algorithm was generated from the constructed templates of each pacing site. The algorithm was applied on a retrospective series of successfully ablated AT patients. Overall and site-specific accuracy were determined. RESULTS: Derivation cohort included 65 patients (25 men, age 37 ± 13 years). Atrial pacing was performed in 1025 sites in 61 patients (95%) in RA and in 15 patients (23%) in LA. The validation cohort included 71 patients (28 men, age 52 ± 19 years). AT were right atrial in 66.2%. The algorithm successfully predicted AT origin in 91.5% of patients (100% in LA and 87.2% in RA). It was off by one adjacent segment in the remaining 8.5%. CONCLUSIONS: A simple ECG algorithm based on paced PWM templates was highly accurate in localizing site of origin of focal AT in patients with structurally normal hearts.

Successful treatment of the focal ectopic atrial tachycardia in an infant with a single dose of ivabradin.

We report on a 12-month-old boy with an ectopic atrial tachycardia successfully treated with the ivabradine that acts on cardiac pacemaker cells by selectively inhibiting the If channel. The patient was diagnosed with supraventricular tachycardia in another centre, and multi-drug therapy was unsuccessful to restore sinus ryhthm, so he was sent to our hospital for catheter ablation. We stopped the medications the patient was taking and started using ivabradine. Sinus rhythm was restored 2 hours after ivabradine treatment was started.

10-year single center experience of catheter ablation of focal atrial tachycardia.

BACKGROUND: Focal atrial tachycardias (ATs) represent 5-15% of sustained supraventricular tachycardias (SVTs). Characteristic distribution of sites of origin and detailed electrophysiologic characterization of AT from specific sites of origin (SOO) have been described. Acute success and recurrence are less favorable than for other SVTs. In this series, we present our experience of focal AT ablation over a 10-year period. METHODS: We undertook a retrospective review of an electronically maintained database of all patients undergoing AT ablation at our institution between January 2011 and December 2020. Demographic, procedural, and outcomes data were reviewed. RESULTS: A total of 293 distinct atrial tachycardias were treated during 279 procedures in 256 patients, including 207 first AT ablations. Acutely successful AT suppression was achieved in 91% of first-time ablations. Acute success was dependent on SOO of AT with lowest rates of acute suppression in the para-Hisian region and the crista terminalis (CT). The most common reason for failure to acutely suppress the AT was proximity to a critical structure (phrenic nerve, sinus node, and AV node). 8.9% of patients in this series presented with a tachycardia-mediated cardiomyopathy (TCM). 48% of TCM patients underwent an ablation attempt during an acute medical admission. Among the TCM group, median LV ejection fraction increased from 25% (range 10-50%) to 55% (range 35-65%) with successful treatment of AT. Five patients undergoing a repeat procedure had planned pericardial access for displacement of the phrenic nerve to permit ablation of the AT, which was successful in all cases. Among patients without a pre-existing diagnosis of AF, peri-procedural AF was not associated with a higher incidence of a subsequent diagnosis of AF (odds ratio 1.169, 95% CI 0.4058-3.475, p = 0.7628). Median duration of follow-up was 832 days. By Kaplan-Meier estimate, recurrence-free survival was 78% (95% CI 67-88%). CONCLUSIONS: In this series, focal AT ablation is associated with good acute results and a low rate of complications, but outcomes remain less favorable than previously reported for other forms of SVT.

Three-dimensional activation maps of sinus rhythm and focal atrial tachycardia in a dog.

A five-year-old, female-spayed boxer was referred for frequent and medically refractory paroxysmal supraventricular tachycardia. Diagnostic evaluation found no underlying structural heart or systemic diseases. Three-dimensional electroanatomical mapping and radiofrequency ablation were pursued. Activation mapping of normal sinus rhythm demonstrated the location of the sinus node in the posterolateral region of the right atrium. Activation mapping of the tachyarrhythmia identified a centrifugal activation pattern originating from the right atrium at the posterolateral aspect of the tricuspid valve orifice, suggestive of focal atrial tachycardia. A total of 10 ablation lesions were delivered to the earliest activation site. The dog recovered without complications and no recurrence of supraventricular tachycardia was noted on subsequent follow-ups.

Atrial Arrhythmia Ablation in Patients With D-Transposition of the Great Arteries and Atrial Switch.

BACKGROUND: Patients with D-transposition of the great arteries and atrial switch have a high incidence of atrial arrhythmias. We sought to analyze the arrhythmia substrate, ablation strategies, and outcomes for catheter ablation in this population. METHODS: An in-depth analysis of all clinical and procedural data in patients with D-transposition of the great arteries, atrial baffles, and atrial arrhythmia ablation was performed. RESULTS: A cohort of 32 patients (72% male, mean age 38±7 years) underwent ablation for non-AV nodal reentrant tachycardia atrial arrhythmias, and 4 patients underwent AV nodal reentrant tachycardia ablation. Cavotricuspid isthmus flutter (CTI-flutter) was the most common arrhythmia, encountered in 75% of patients, followed by scar-related intraatrial reentrant tachycardia (non-CTI intraatrial reentrant tachycardia, 53%) and focal atrial tachycardia (focal atrial tachycardia, 6%). Among the 32 patients, 26 underwent 31 procedures at our institution. For patients with prior outside intervention, the index ablation at our institution revealed CTI-dependent flutter in 3/5 cases. However, redo ablation after an index ablation with demonstrated bidirectional CTI block revealed different/new arrhythmia substrates (80% non-CTI intraatrial reentrant tachycardia, 40% focal atrial tachycardia). Achieving bidirectional block across the CTI often required ablating on both sides of the baffle (retroaortic access, 81%; using a baffle leak, 11.5%; or transbaffle puncture, 7.7%). Combined approaches were necessary in 19% to reach the critical tissue. Acute procedural success was 81%, and recurrence was documented in 58% of patients. Despite recurrence, clinical arrhythmia burden was significantly reduced post-ablation (P<0.001), with rare episodes, amenable to antiarrhythmic therapy. Redo ablation was required in 5 (19%) patients and uncovered new arrhythmia substrates. AV nodal reentrant tachycardia ablation also required transbaffle approaches in 3/4 patients. CONCLUSIONS: CTI-dependent flutter was the most common arrhythmia in patients with Dextro-Transposition of the Great Arteries and atrial switch. Transbaffle approaches were often necessary, and, provided that bidirectional CTI block was achieved at the index ablation, late recurrence was due to different arrhythmia mechanisms. Despite recurrence, ablation was associated with significant clinical improvement.

Intuitive diagnosis of complex atrial tachycardia mechanisms using a novel histogram module of an ultra-high-resolution mapping system.

PURPOSE: The LUMIPOINT™ software module was developed to aid the physician in determining the mechanism of individual atrial tachycardias (ATs). The purpose of this study was to assess the clinical utility of the SKYLINE™ histogram that is a part of LUMIPOINT™. METHODS: This study included consecutive patients with iatrogenic sustained AT who underwent catheter ablation using conventional mapping (RHYTHMIA™). SKYLINE™ patterns were analyzed offline and classified into two types: (1) focal type (type-F) exhibiting a low-amplitude (relative activating surface area < 10%) plateau period and (2) reentrant type (type-R) showing no plateau period. How well the two patterns distinguished between focal and macroreentrant ATs as determined by conventional mapping was evaluated. RESULTS: We studied 101 iatrogenic ATs in 91 patients (female: 24, mean age: 67.3 ± 9.1 years). Activation mapping revealed 79 (78.2%) macroreentrant, 6 (5.9%) localized reentrant, and 16 (15.8%) focal ATs. Among the 72 type-R ATs, the mechanism was truly a macroreentry in 70 ATs. However, one focal AT and one localized reentrant AT displayed a type-R pattern (pseudo-reentry pattern). In the 29 type-F ATs, nine macroreentrant ATs were recognized (pseudo-focal pattern). Using SKYLINE™ type-R to differentiate macroreentrant AT from AT with centrifugal activation (focal or localized reentry), the sensitivity and specificity were 88.6% and 90.9%, respectively. Even when the SKYLINE™ type did not match the mapping-based AT mechanism, all discrepancies were electrophysiologically explicable using the SKYLINE™ histograms. CONCLUSIONS: SKYLINE™ histograms are a useful tool for the intuitive diagnosis of AT mechanisms.

Ripple mapping-guided atrial tachycardia ablation following open-heart surgery.

Ripple mapping can make the visualization of activation conduction on a 3-dimensional voltage map and is useful tool for scar-related organized atrial tachycardia (AT). This study sought to assess the efficacy of ripple mapping for interpreting reentrant circuits and critical isthmus in postoperative ATs. 34 consecutive patients with a history of mitral valve surgery (mean age, 54.5 ± 12.4 years) underwent high density (HD) RM during ATs with CARTO3v4 CONFIDENSE system. The voltage activation threshold was determined by RM over a bipolar voltage map. The identification of underlying mechanisms and ablation setting was based on RM without reviewing activation mapping. A total of 41 ATs (35 spontaneous, 6 induced) were characterized. 39 reentry circuits were successfully mapped (cycle length, 256 ± 43 ms). Of the 41 ATs, 28 were confirmed by ripple mapping alone (68%), and 12 (29%) by ripple mapping and entrainment mapping. Of 12 ATs in the left atrium, 9 (75%) needed entrainment to confirm, compared with 5 (17.8%) in the right atrium. Primary endpoint after initial ablation set was achieved in 32 of the 34 patients (94.1%). Freedom from atrial arrhythmias was 79.4% after the follow-up of 12 ± 5 months. Of the seven patients with recurrence, three underwent the repeated catheter ablation. Ripple mapping precisely delineated reentrant circuits in post-cardiac surgery AT resulting in a high success rate of ablation. Entrainment maneuvers remain useful for elucidation of complex AT circuits.

Focal atrial tachycardia-the localization differences between men and women: A study of 487 consecutive patients.

OBJECTIVE: The preferential sites for focal atrial tachycardia (FAT) are mainly in the right atrium in both sexes. However, a limited number of studies have indicated that sex differences in the localization of FAT. This study investigated possible sex differences in the distribution of FAT in a large cohort of patients referred for ablation. METHODS: From 2004 to 2019, 487 patients (298 women) were referred to our institution for ablation of FAT. A standard electrophysiological study was conducted, and isoproterenol or atropine was given when needed. Conventional catheter mapping, electroanatomic contact mapping, and noncontact mapping were used to assess the origin of ectopic atrial tachycardia. RESULTS: Overall, 451 foci were successfully ablated in 436 patients (90%). Although the foci located along the crista terminalis were more common in women than in men (42% vs. 29%; p=0.023), the opposite were found in the foci located along the tricuspid annulus (5% vs. 11%; p=0.032) and the right atrial appendage (RAA) (1% vs. 3%; p=0.032). Other locations were similarly distributed in men and women. In addition, the presence of persistent FAT was more frequent in men than in women (22% vs. 5%; p<0.001). Finally, the difference in the induction pattern of FAT was also remarkable between sexes. CONCLUSION: The distribution of FAT in women and men is different. In addition, persistent FAT seems more often in men than in women. The different distribution, persistency, and induction pattern of FAT should be considered in the successful management of this type of tachycardia.

Biophysical properties, efficacy, and lesion characteristics of a new linear cryoablation catheter in a canine model.

BACKGROUND: The cryoballoon (CB) catheter is an established tool for pulmonary vein isolation (PVI), but its use is limited for that purpose. OBJECTIVE: The purpose of this study was to investigate the biophysical properties of a newly developed linear cryoablation catheter for creation of linear ablation lesions in an in vivo model. METHODS: Twenty-nine dogs (14 acutely ablated, 15 chronically followed) underwent cryoablation using the linear cryoablation catheter. Regions of interest included the cavotricuspid isthmus (CTI), mitral isthmus (MI), left atrial (LA) roof, and LA posterior wall in an acute study. Cryoablations for CTI and MI were performed in 14 atrial fibrillation animals after PVI and followed over 1 month in the chronic study. Tissue temperature during cryoablation was monitored using implanted thermocouples in the regions of interest. Gross and microscopic pathologic characteristics of the lesions were assessed. RESULTS: In acute animals, lesion length (transmurality) was CTI 34 ± 4 mm (89% ± 11%); MI 29 ± 4 mm (90% ± 13%); LA roof 19 ± 3 mm (90% ± 8%); and LA posterior wall 19 ± 2 mm (81% ± 13%), with 1 or 2 freezes. Chronic bidirectional block was achieved in 13 of 14 CTI (93%) and 10 of 14 MI (71%) ablations after 1-month follow-up and was consistent with lesion continuity and transmurality upon pathology. The lowest tissue temperature correlated well with the closest distance to the linear cryocatheter (r = 0.688; P <.001). CONCLUSION: This linear cryocatheter created continuous and transmural linear lesions with "single-shot" cryoenergy application and has the potential for clinical use in the setting of various arrhythmias.

Successful Ablation of Atrial Tachycardia Originating from Inside the Single Atrium and Conduit After a Fontan Operation.

An 18-year-old male who had a past medical history of an intracardiac total cavopulmonary connection (TCPC) operation was referred to our hospital for radiofrequency catheter ablation (RFCA) of supraventricular tachycardia (SVT). Two types of SVTs were induced, and 3-dimensional (3D) maps were created using an ultra-high-density 3-dimensional mapping system (Rhythmia). The earliest atrial activation site (EAAS) of SVT1 was at the superior part of the conduit, and the EAAS of SVT2 was at the inferior part of the single atrium (SA). The SVTs were terminated by energy deliveries to the EAAS from the conduit in SVT1 and from inside the single atrium in SVT2. Detailed maps of the SVTs were important to understand the mechanisms of the SVTs. The Rhythmia system was useful for the detailed mapping of complex arrhythmias. The use of Rhythmia in patients after a TCPC is difficult, because puncturing the TCPC conduit and proceeding and manipulating the Orion catheter via a narrow puncture hole are difficult. We were the first to succeed in ablating two atrial tachycardias (ATs) originating from the inside and outside of the conduit after a TCPC operation by using an ultra-high-density 3-dimensional mapping system.

A challenging ECG: a case of a lengthening PR interval.

A 62-year-old man presented to the emergency department with shortness of breath and chest tightness. His initial ECG appeared to have an ectopic P-wave with a lengthening PR interval consistent with second degree AV block - Mobitz Type I. But closer inspection showed a faster, independent atrial rate. The patient was diagnosed with ectopic atrial bradycardia with complete AV block and junctional escape, and was ultimately referred for pacemaker.

Characteristics, Mechanism and Long-Term Ablation Outcome of Atrial Tachycardias After Mitral Valvular Surgery and Concomitant Cox-MAZE IV Procedure.

The incidence of atrial tachycardia (AT) after rheumatic mitral valvular (RMV) surgery has been well described. However, there have been few reports on the characteristics, mechanism, and long-term ablation outcome of ATs after RMV surgery and concomitant Cox-MAZE IV procedure.The present study reviewed consecutive patients who underwent AT ablation between May 2008 and July 2013. All patients were refractory to antiarrhythmic drugs (AADs) and had a history of RMV surgery and Cox-MAZE IV procedure. A total of 34 patients underwent AT ablation after RMV surgery and concomitant Cox-MAZE IV procedure, and presented 57 mappable and 2 unmappable ATs. The 57 mappable ATs included 14 focal-ATs and 43 reentry-ATs. Ten of the 14 focal-like ATs were located at the pulmonary vein (PV) antrum and border of a box lesion. Of the 43 reentry-ATs, 16 were marco-reentrant around the mitral annulus (MA) and 16 around the tricuspid annulus. There were 41 atypical ATs (non-cavotricuspid isthmus related) including 16 ATs related to the box lesion and 21 ATs related to other Cox-MAZE IV lesions. The AT were successfully terminated in 33 (97.1%) patients. After mean follow-up of 46.9 ± 15.7 months, 25 (73.5%) patients maintained sinus rhythm without AADs after a single procedure and 28 (82.4%) patients after repeated procedures.The recurrent ATs after RMV surgery and concomitant Cox-MAZE IV were mainly reentry mechanism, and largely related to LA. An incomplete lesion or re-conductive gaps in a prior lesion might be the predominant mechanisms for these ATs. Catheter-based mapping and ablation of these ATs seems to be effective and safe during a long-term follow-up.

Centrifugal wave-front propagation speed for localizing the atrial tachycardia origin.

BACKGROUND: The earliest activation site (EAS) on a centrifugally-propagated atrial tachycardia (AT) map may represent the true AT origin (true-focal pattern), or the earliest site resulting from passive activation of AT originating from neighboring tissue (pseudo-focal pattern). We assessed the benefits of using the wave-front propagation speed to distinguish between the true- and the pseudo-focal pattern. METHODS: AT mapping was performed using a novel ultra-high resolution mapping system with a 64-electrode mini-basket catheter. The true AT origin was defined as the site where radiofrequency application eliminated AT. The wave-front propagation speed was estimated from the area surrounded by the centrifugally-propagated wave front over a specific time interval. RESULTS: Total of 46 centrifugally propagated AT maps from 34 patients were analyzed, including 18 true-focal and 28 pseudo-focal pattern. The area surrounded by the propagated wave front was significantly smaller for the true-focal pattern than for the pseudo-focal pattern, 1-20 msec after the earliest activation. The true-focal pattern was identified by the area 13 msec after the earliest activation, with the best cut-off area value of <4.5 cm2. CONCLUSION: The presence or absence of a true origin of AT at the EAS on centrifugally-propagated AT maps can be distinguished using a wave-front propagation speed.