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Background Clinical utility of irrigation-tip ablation catheters for cavo-tricuspid isthmus (CTI) ablation is established. Recently, new-generation enhanced-cooling irrigation-tip catheters were introduced into clinical use. This study compared the performance of different types of novel irrigation-tip catheters in CTI ablation. Methods One hundred patients undergoing CTI ablation with novel irrigated-tip catheters were included. Ablation was performed with a power output of 30–35 W using either 4-mm flexible tip catheters [FlexAbility (FAs) St. Jude Medical, St. Paul, MN, USA] or 3.5-mm enhanced-cooling ring-tip catheters without [ThermoCool SurroundFlow (SFs), Biosense Webster, Diamond Bar, CA, USA] and with contact force sensing [ThermoCool SmartTouch SurroundFlow (STSFs), Biosense Webster] in 32, 34, and 34 patients, respectively. Results The successful CTI block creation rate was significantly higher for FAs than SFs/STSFs [32/32 (100%), 30/34 (88.2%), and 27/34 (79.4%), p = 0.006]. In all 11 failed procedures, block was created by additional 5 (2–7) applications with 8-mm tip catheters. The radiofrequency (RF) application number ( p = 0.001) and energy ( p = 0.021) were significantly lower, and total RF time ( p = 0.005) and procedure time ( p = 0.036) significantly shorter in the FA than SF/STSF groups. The FA catheter was associated with significantly higher tip temperature readings (34.9 °C vs. 32.0/33.0 °C, p < 0.001) and lower initial impedances than SF/STSF catheters (both p < 0.001). The tip temperature reached the maximum temperature setting in 15/295 (5.1%) FA catheter applications among 11 (34.3%) patients, 0/521 (0%) ST applications, and 0/448 (0%) STSF applications. The mean RF power achieved during RF applications was significantly lower for FA than SF/STSF catheters (28.6 W vs. 30.4/30.8 W, p < 0.001). Audible steam pops were detected in 1/448 applications in only the STSF group. Conclusions In human CTI ablation, flexible irrigation-tip catheters showed a significantly better performance than rigid enhanced-cooling irrigation-tip catheters. [ABSTRACT FROM AUTHOR]

The mitral isthmus is a part of the postero-inferior area of the lateral left atrial wall located between the mitral annulus and the left inferior pulmonary vein ostium. Linear ablation lesions are created within the mitral isthmus for the invasive treatment of left atrial arrhythmias. However, the anatomy of this region is not fully understood. The aim of this study has been to provide a detailed morphometric description of the mitral isthmus region and to propose another possible isthmus within the investigated heart area that may serve as a potential new ablation target. Two hundred autopsied, non-atrial fibrillation hearts (23.5% deriving from females) whose donors were a mean of 47.6 ± 17.6 years old were investigated. We macroscopically assessed the anatomy of the postero-inferior area of the lateral left atrial wall. The mean mitral isthmus length was 28.8 ± 7.0 mm and was significantly longer than the left atrial appendage (LAA) isthmus (14.2 ± 4.8 mm) (p = .00). The distance between the LAA orifice and the left inferior pulmonary vein ostium (18.4 ± 4.8 mm) was longer than the LAA isthmus (p = .00) and shorter than the mitral isthmus (p = .00). The LAA isthmus was longer in hearts with a common left pulmonary vein (p = .037). In 65.5% of all cases the area between the right and left mitral isthmus lines was completely smooth. In the remaining hearts, crevices and diverticula (18.0%), intertrabecular recesses (7.0%), trabecular bridges (3.5%), or co-existence of these structures (6%) could be observed. The LAA isthmus line was smooth in 95.5% of all cases, with only small crevices in the remaining 4.5%. In conclusion, regardless of the anatomical variants of the left-sided pulmonary veins, the mitral isthmus area is quite uniform in size. The LAA isthmus is considerably shorter than the mitral isthmus. The mitral isthmus line has many unwanted structures that may entrap the catheter, which is not the case for the LAA isthmus. We proposed the LAA isthmus line for potential clinical use. [ABSTRACT FROM AUTHOR]

Background Recurrent perimitral atrial tachycardia (AT) is a challenging arrhythmia and is frequently encountered in the context of atrial fibrillation (AF) ablation. Objective The purpose of this study was to investigate the clinical characteristics and the procedural and clinical outcomes in patients with recurrent perimitral atrial tachycardia (PMAT) after AF ablation. Methods Among 520 consecutive ablation procedures for recurrent AT/AF after AF ablation, 40 procedures (patients) were performed for clinically recurrent PMAT 12.1 ± 13.6 months after the last procedure (total 2.2 ± 1.3 procedures). Previously, mitral isthmus (MI) linear ablation was performed in 26 of 40 procedures, including 13 procedures with complete block and 13 with 159.0 ± 23.0 ms of conduction delay without block. As a reference group, conduction delay was evaluated in 55 patients with incomplete MI block and absence of spontaneous PMAT during the follow-up period. Results Recurrent PMATs were terminated by MI linear ablation in 26 of 40 patients. Bidirectional block across the MI and anterior line joining the mitral annulus and left atrial roof was achieved in 33 (82.5%) and 2 (5%) patients, respectively. At mean follow-up of 26.7 ± 14.5 months, 2 patients (5%) underwent reablation for spontaneously recurrent PMAT. At 12 months after the ablation procedure for PMAT, 73.5% of the patients were free from AT/AF. Conduction delay >149 ms predicted the occurrence of spontaneous PMAT with 80.0% sensitivity and 87.3% specificity. Conclusion PMAT can recur even after successful bidirectional MI linear block. Substantial conduction delay without block across the MI from a previous procedure(s) could predispose to recurrent PMAT. Although most clinical PMATs can be successfully treated by catheter ablation, very late recurrence is possible. [ABSTRACT FROM AUTHOR]

Background: While macroreentrant atrial tachycardias (ATs) have been reasonably well described, little is known about small reentrant circuits. Objective: To compare characteristics of large and small reentrant circuits after ablation of persistent atrial fibrillation. Methods: Seventy-seven patients (age 61±10 years; left atrium 46±6 mm; ejection fraction 0.52±0.13) underwent a procedure for postablation AT. The p-wave duration, circuit size, electrogram characteristics, and conduction velocity were determined. Results: AT was due to macroreentry in 62 (80%) patients, a small reentrant circuit in 13 (17%), and a focal mechanism in 2 (3%). The p-wave duration during small reentrant ATs was shorter than that during macroreentry (174±12 ms vs 226±22 ms; P<.0001). The duration of fractionated electrograms at the critical site was longer in small vs large circuits (167±43 ms vs 98±38 ms, respectively; P<.0001) and accounted for a greater percentage of the tachycardia cycle length (59%±18% vs 38%±14%, respectively; P<.0001). The mean diameters of macroreentrant and small reentrant circuits were 44±7 and 26±11 mm, respectively (P<.0001). The mean conduction velocity along the small circuits was lower (0.5±0.2 m/s vs 1.2±0.3 m/s; P<.0001). Catheter ablation eliminated the AT in all 77 patients. Conclusions: AT due to a small reentrant circuit after ablation of atrial fibrillation may be distinguished from macroreentry by a shorter p-wave duration and the presence of long-duration electrograms at the critical site owing to extremely slow conduction. These features may aid the clinician in the mapping of postablation ATs. [ABSTRACT FROM AUTHOR]

The article seeks to understand clinically encountered pitfalls in the assessment of transmitral conduction block using differential coronary sinus and appendage pacing techniques in patients with left mitral isthmus linear ablation. It concludes that every fifth assessment of bidirectional block across mitral isthmus linear lesion encountered a pitfall. The article suggests that recognition of pitfall during the procedure is feasible and necessitates distinction of far-field left atrium.

Abstract: Non-pharmacological rhythm control of atrial fibrillation (AF) is becoming increasingly important in our aging society. Advancement of catheter ablation techniques in the last decade has provided a cure for AF patients, with a nearly established efficiency for paroxysmal cases. However, since ablation of persistent/chronic AF cases is still challenging, early treatment of paroxysmal AF before transformation to the persistent/chronic form is mandatory. Although there is a consensus that pulmonary vein isolation is the first-line approach for ablation of long-standing persistent AF, similar to that for paroxysmal AF, there are still wide variations in the adjunctive approach to modify the atrial substrate of persistent AF (anatomical linear ablation, electrogram-based complex fractionated atrial electrogram ablation, ganglionated plexus ablation, etc.). Since data comparing the effectiveness of these adjunctive approaches are still lacking, large-scale controlled trials evaluating the effect of catheter ablation in diverse patient populations on a long-term basis are needed to establish the appropriate approach for long-standing persistent AF. Furthermore, the development of de novo ablation methods (new energies, new targets, etc.) is expected to improve ablation outcome in patients with long-standing persistent AF. [Copyright &y& Elsevier]

The article discusses a research which investigated preprocedural variables and perimitral conduction time (PMCT) quantum in patients with confirmed biodirectional blocked mitral isthmus (MI). Prior to ablation, all antiarrhythmic medications have been discontinued and radiofrequency application was used to perform pulmonary vein isolation (PVI). Clinical characteristics of patients including age, sex and structural heart disease information are also provided.

Background: There has been growing concern that linear ablation is associated with an increased risk of iatrogenic arrhythmias in patients undergoing ablation for atrial fibrillation (AF). Therefore, we compared circumferential pulmonary vein ablation plus left atrial linear ablation (CPVA+LALA) with segmental pulmonary vein isolation (PVI)in patients with paroxysmal AF. Methods and Results: Sixty-six consecutive patients with paroxysmal AF were prospectively randomly assigned to receive PVI versus CPVA+LALA (consisting of encircling lesions around the pulmonary veins), a roof line, and a mitral isthmus line with documentation of bidirectional mitral isthmus block. All patients were seen at 1, 3, 6, and every 12 months after ablation, with 14-day continuous ECG monitoring every 6 months. At 16.4+/-6.3 months after 1 ablation procedure, 19 patients (58%) remained free of atrial arrhythmias after PVI versus 17 patients (51%) after CPVA+LALA (P=0.62). After PVI, 14 patients had recurrent paroxysmal AF, whereas after CPVA+LALA, 8 patients had recurrent AF, 6 had atypical left atrial flutter (LAFL), and 2 had both AF and LAFL (P=0.32 between PVI versus CPVA+LALA for AF but P=0.002 for LAFL). Twenty-eight patients (85%) remained arrhythmia-free after 1.3+/-0.5 PVI procedures versus 28 patients (85%) after 1.4+/-0.6 CPVA+LALA procedures (P=NS). Fluoroscopy time was longer after CPVA+LALA versus PVI (91 versus 73 minutes, P=0.04). Conclusions: As an initial ablation approach in patients with paroxysmal AF, more LAFL occurred after CPVA+LALA and fluoroscopy times were longer compared with segmental PVI. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the feasibility and outcome of ablation to transect the anterior left atrium (LA) in patients with atrial fibrillation (AF).Background: While the Maze procedure is effective in maintaining sinus rhythm in patients with AF, it is associated with significant morbidity. This prospective clinical study evaluates the feasibility and consequences of limited LA linear ablation to transect the anterior LA in patients with AF.Methods: Twenty-four patients (51.2 +/- 7.3 years) with paroxysmal (n = 16) or chronic (n = 8) AF resistant to pulmonary vein (PV) isolation were studied. To transect the anterior LA, linear ablation was performed joining the superior PVs; this line was then connected to the anterior mitral annulus. Pulmonary vein isolation and cavotricuspid isthmus ablation were performed in all cases. Ablation was performed using an irrigated catheter with the endpoint of achieving complete linear block demonstrated by online double potentials, differential pacing techniques, and an activation detour.Results: Of 20 patients in AF prior to linear ablation, arrhythmia terminated in 12 (60%), including half the patients with chronic AF, during ablation. Despite repeated ablation, complete linear block was achieved in only 14 of 24 patients (58%). Complete linear conduction block resulted in an activation detour around the mitral annulus and PVs with a delay of 158 +/- 30 ms (P = .0001), significantly delayed activation of the lateral LA with prolongation of P-wave duration (P = .002), and characteristic change in P-wave morphology during sinus rhythm (P = .002). Of the 14 with anterior LA transection, 4 (29%) have had regular atrial tachycardias due to macroreentry through recovered gaps. Nine of these 14 (64%) have remained arrhythmia-free without antiarrhythmics compared to 3 of 10 (30%) with incomplete block at 28 +/- 4 months following their last procedure (P = .2).Conclusions: This study demonstrates the feasibility of catheter ablation to transect the anterior LA in humans. While being effective in the termination of AF, this configuration of linear lesions is technically challenging to complete, results in significant delayed LA activation, and is associated with modest long-term arrhythmia suppression. [ABSTRACT FROM AUTHOR]