Treatment of atrial tachycardia arising after superior transseptal approach mitral valve surgery: Insights from ultra-high-density mapping to prevent atrioventricular block.

INTRODUCTION: Mitral valve surgery employing a superior transseptal approach (STA) is associated with arrhythmogenicity and intra-atrial conduction delay, despite being optimal for visualization of the surgical field. It is sometimes difficult to treat atrial tachycardias (AT) that arise after STA. To investigate AT circuits that arise after STA in detail in order to identify the optimal ablation line, using ultra-high-resolution mapping (UHRM). METHODS: We retrospectively analyzed 12 AT from 10 patients (median age 70 years, nine males) who had undergone STA surgery. The tachycardias were mapped using the Rhythmia mapping system (Boston Scientific, Natick, Massachusetts). RESULTS: The 12 STA-related AT (STA-AT) circuits were classifiable as follows according to location of the optimal ablation line: (1) peri-septal incision STA-AT (n = 3), (2) cavotricuspid isthmus (CTI) dependent STA-AT (n = 7), and (3) biatrial tachycardia (n = 2). Radiofrequency (RF) application terminated 11 of the 12 STA-AT. We found that difference in STA-AT circuit type was due to characteristics of the septal incision line made for STA. UHRM was important in identifying optimal ablation sites that did not create additional conduction disturbances in the right atrium (RA). CONCLUSIONS: ATs after STA involve complex arrhythmia circuits due to multiple and long incision lines in the RA. Accurate understanding of the arrhythmia circuit and sinus conduction in the RA after STA is recommended for treating post-surgical tachycardia in a minimally invasive manner.

Epicardial-endocardial breakthrough site ablation: Demonstration of alternative target for perimitral atrial tachycardia.

A 62-year-old man underwent the catheter ablation for persistent atrial tachycardia (AT) with a cycle length of 357 milliseconds. An ultrahigh resolution mapping revealed that this tachycardia was a clockwise perimitral AT despite the conduction was apparently blocked across the lateral mitral isthmus line both at the endocardium and within the coronary sinus. The AT was terminated by the single radiofrequency application at the site below the mitral isthmus line where the endocardial activation breakout was seen. This case suggests that the epicardial-endocardial conduction breakthrough site may be an alternative ablation target in a difficult ablation case of perimitral AT.

Utility of low-dose adenosine triphosphate sensitivity in slow-fast atrioventricular nodal reentrant tachycardia.

PURPOSE: Low-dose adenosine triphosphate (LD-ATP) is useful for diagnosing ATP-sensitive atrial tachycardia. However, the clinical implications of the sensitivity of LD-ATP in atrioventricular nodal reentrant tachycardia (AVNRT) still remain unknown. This study aimed to evaluate the mechanism of LD-ATP sensitivity in slow-fast AVNRT. METHODS: We estimated the sensitivity of LD-ATP in slow-fast AVNRT by a 2-4-mg ATP intravenous injection during the tachycardia. We evaluated the atrial-His (A-H) interval, tachycardia termination mode, prevalence of a lower common pathway (LCP), and successful ablation site in slow-fast AVNRT with LD-ATP sensitivity. LCPs were defined as His-atrial interval differences of at least 5 ms between that during ventricular pacing at the tachycardia cycle length and that during the tachycardia. RESULTS: Twenty-eight patients (mean age = 58 ± 11 years old, 18 females) with slow-fast AVNRT, who underwent catheter ablation of the antegrade slow pathway, were enrolled. Seventeen of 28 (61%) patients had LD-ATP sensitivity defined as termination of the tachycardia and/or a prolongation of the A-H interval of over 30 ms after an LD-ATP injection. The patients with LD-ATP sensitivity had a significantly higher prevalence of an LCP than those without (15/17 vs0/11, P < 0.0001). The successful ablation site in the LD-ATP sensitive group was significantly closer to the His bundle area than that in the LD-ATP nonsensitive group (13.3 ± 3.8 vs 20.5 ± 5.4 mm; distance to His bundle area in the left anterior oblique fluoroscopic view, P < 0.0001). CONCLUSIONS: LD-ATP sensitivity in slow-fast AVNRT may suggest the existence of an LCP. The successful ablation site in patients with LD-ATP sensitivity could be closer to the His bundle region.

Electrical superior vena cava isolation using a novel pace-and-ablate technique under diaphragmatic electromyography monitoring.

BACKGROUND: Diaphragmatic compound motor action potential (CMAP) amplitude monitoring is a standard technique to anticipate phrenic nerve injury during cryoballoon ablation. OBJECTIVE: The purpose of this study was to evaluate the feasibility of a novel superior vena cava isolation (SVCI) technique using simultaneous pacing and ablation through the tip of a single mapping/ablation catheter. METHODS: Fifty-four patients with atrial fibrillation were included. Radiofrequency energy was delivered point by point uniformly for 20 seconds with a power of 20 W until achieving SVCI. Diaphragmatic CMAPs were obtained from modified surface electrodes by high-output pacing from the mapping/ablation catheter throughout the procedure (pace-and-ablate group). Applications were interrupted if CMAP amplitudes significantly decreased without fluoroscopy. The data were compared with those of the 54 patients undergoing conventional SVCI (conventional group). RESULTS: Successful SVCI procedures were achieved in all with a mean of 10.3 ± 2.9 applications. In total, among 559 ablation sites, CMAPs were recorded at 95 (17.0%) with baseline amplitudes of 0.45 ± 0.23 mV. In 10 patients (18.5%), isolation was achieved without any radiofrequency deliveries at CMAP-recorded sites. Among the 95 applications, 6 (6.3%) were interrupted because of CMAP amplitude reductions. At the remaining 88 sites, 20-second radiofrequency applications were delivered without any amplitude decrease (from 0.45 ± 0.21 to 0.46 ± 0.23 mV; P = .885). Phrenic nerve injury occurred in 1 patient in the pace-and-ablate group, which recovered 3 months later, and in 3 conventional group patients, of whom 1 recovered 1 month later (P = .308). The total procedure time tended to be shorter (14.5 ± 6.3 minutes vs 16.7 ± 9.2 minutes; P = .153) and fluoroscopy time significantly shorter (3.9 ± 3.0 minutes vs 6.7 ± 5.7 minutes, P = .002) in the pace-and-ablate group than in the conventional group. CONCLUSION: A novel and simple pace-and-ablate technique under diaphragmatic electromyography monitoring might be feasible for an electrical SVCI.

Five-year follow-up outcome after catheter ablation of persistent atrial fibrillation using a sequential biatrial linear defragmentation approach: What does atrial fibrillation termination during the procedure imply?

BACKGROUND: A paucity of data exists about long-term outcomes after catheter ablation of persistent atrial fibrillation (AF). The mechanisms of AF are still unclear. OBJECTIVE: The purpose of this study was to evaluate the 5-year outcome after persistent AF ablation using sequential defragmentation approaches and to identify the prognostic factors. METHODS: One hundred thirty-five patients with persistent AF (age 62 ± 9 years, 76 longstanding persistent AF) underwent catheter ablation using biatrial linear defragmentation approaches consisting of substrate modification for eliminating AF after pulmonary vein antrum isolation. Procedures were stopped when AF terminated; however, AF termination was not pursued after predetermined substrate modification. RESULTS: AF terminated in 69 patients (51%). Total procedural and fluoroscopic times were 145.4 ± 36.1 minutes and 35.1 ± 14.3 minutes, respectively. Median [25th, 75th percentiles] follow-up was 60 [26.0-64.0] months, with 1.9 ± 0.8 procedures per patient. Arrhythmia-free survival after multiple procedures was 86.8%, 73.1%, 62.6%, and 53.8% (39 patients on antiarrhythmic drug therapy) at 1, 2, 3, and 5 years, respectively. Multivariate analyses revealed that AF termination (hazard ratio [HR] 3.043, 95% confidence interval [CI] 1.605-5.767, P = .001) was the sole independent predictor of long-term arrhythmia freedom, and arrhythmia freedom at 5 years was 70.0% and 31.8% in patients with and without AF termination (P = .0007). Five-year freedom from crossover to rate control strategies was 86.5%, and AF termination (HR 3.558, 95% CI 1.171-10.812, P = .025) was also the sole predictor. CONCLUSION: Catheter ablation of persistent AF using the sequential defragmentation approach provided limited long-term freedom of arrhythmias often requiring multiple procedures. AF termination was the sole factor predicting freedom from both arrhythmia recurrence and crossover to rate control strategies during long-term follow-up.

Discrimination of thoracic vein potentials facilitated by atrial pacing during the isolation.

BACKGROUND: Although electrical thoracic vein (TV) isolation is an established strategy during atrial fibrillation (AF) ablation, discriminating TV potentials from far-field signals is critical for the achievement. METHODS AND RESULTS: One hundred consecutive drug-refractory symptomatic paroxysmal AF patients who underwent AF catheter ablation were included. All patients underwent circumferential pulmonary vein (PV) isolation during distal coronary sinus (CS) pacing with a cycle length of 600 ms. A superior vena cava (SVC) isolation was added during high right atrial (HRA) pacing with the same cycle length in 79 patients in whom SVC potentials were identified. The interval between the near-field PV potentials and far-field atrial signals significantly prolonged more during distal CS pacing than sinus rhythm (SR) in the left superior (26.0 [18.5-32.8] ms to 36.0 [24.3-55.5] ms, P < 0.01) and left inferior PVs (21.0 [14.0-30.0] ms to 40.0 [23.0-56.0] ms, P < 0.01), but not in the right superior (34.0 [20.0-40.0] ms to 23.0 [18.0-36.0] ms, P = 0.13) and right inferior PVs (22.0 [16.0-28.0] ms to 25.0 [18.0-38.0] ms, P = 0.05). The interval between the SVC potentials and far-field atrial signals significantly prolonged more during HRA pacing than SR (20.0 [0-32.0] ms to 34.0 [24.0-46.0] ms, P < 0.01). Electrical isolation was successfully achieved in all TVs without any complications except for transient right phrenic nerve palsy in two patients. CONCLUSIONS: Discrimination of ipsilateral left PVs and SVC potentials is facilitated by pacing from the distal CS and HRA, respectively. Better recognition of TV potentials would help to achieve electrical isolation.

Discrete prepotential as an indicator of successful ablation in patients with coronary cusp ventricular arrhythmia.

BACKGROUND: Although coronary cusp (CC) ventricular arrhythmia (VA) can be treated by catheter ablation, reliable indicators of successful ablation sites have not been fully identified. METHODS AND RESULTS: This study comprised 392 patients undergoing radiofrequency catheter ablation for outflow tract-VA at 3 institutions from January 2007 to August 2012. The successful ablation site was on the left CC or right CC in 35 (8.9%) of the 392 patients. In 9 (26%) of these 35 patients, a discrete prepotential was recognized, 5 of whom had left CC-VAs and 4 of whom had right CC-VAs. Radiofrequency catheter ablation was successful at the site of the prepotential in all 9 of these patients. The duration of the isoelectric line between the end of the discrete prepotential and the onset of the ventricular electrogram was 27±13 ms. The time from onset of the discrete prepotential at the successful ablation site on the CC to the QRS onset (activation time) was 69±20 ms (range, 50-98 ms). Pace mapping was graded as excellent at the successful ablation site in only 1 patient. No discrete prepotential was recorded in any successful right outflow tract-VA ablation case in this study. CONCLUSIONS: A discrete prepotential was seen in 9 (26%) of 35 patients with CC-VA. In left and right CC-VA, the site of a discrete prepotential with ≥50 ms activation time may indicate a successful ablation site.

Sequential biatrial linear defragmentation approach for persistent atrial fibrillation.

BACKGROUND: The strategy for catheter ablation of persistent atrial fibrillation (AF) and the procedural end point remain controversial. OBJECTIVE: To evaluate the feasibility of a sequential defragmentation approach. METHODS: One hundred thirty-five patients (aged 62.4 ± 9 years; 76 long-standing persistent AF) underwent first ablation procedure for persistent AF. With an end point of AF termination, the ablation procedure was performed sequentially in the following order: pulmonary vein antrum isolation, linear defragmentation of complex fractionated electrograms at left atrial (LA) roof, bottom, septum, inferior LA, base of LA appendage, anterior LA, right atrial septum, crista terminalis, and base of right atrial appendage. Ensuing atrial tachycardias (ATs) were mapped and ablated. RESULTS: AF termination was achieved in 69 (51%) patients (59 in the left atrium and 10 in the right atrium). The total procedure and fluoroscopic times were 145.4 ± 36.1 and 35.1 ± 14.3 minutes, respectively. At median 19.0 months, 105 (78%) patients demonstrated recurrent atrial tachyarrhythmia necessitating repeat ablation procedure(s). With mean 1.7 ± 0.7 procedures per patient, 100 (74%) patients were free from atrial tachyarrhythmia at median 15.0-month follow-up. Among 73 mappable ATs, 49 were macroreentrant ATs. On multivariate Cox regression analysis, greater LA diameter (hazard ratio 1.10; 95% confidence interval 1.04-1.17; P = .0004) and non-AF termination (hazard ratio 1.50; 95% confidence interval 1.01-2.36; P = .036) were independent predictors of AF recurrence after single and multiple ablation procedures, respectively. CONCLUSIONS: Pulmonary vein antrum isolation followed by biatrial substrate modification in a predetermined order of linear ablation of specific anatomical regions with predilection for complex fractionated atrial electrograms is a feasible alternative persistent AF ablation strategy.

Conduction recovery after electrical isolation of superior vena cava--prevalence and electrophysiological properties.

BACKGROUND: Superior vena cava (SVC) is an infrequent yet an important source of atrial fibrillation (AF). The data on SVC reconnection are limited. METHODS AND RESULTS: Following pulmonary vein (PV) antrum isolation for AF, SVC isolation was systemically performed under angiographic and mapping guidance using 4-mm non-irrigated tip catheter. SVC reconnection could be evaluated in 76 consecutive patients (65 ± 9 years, 59 male) who underwent repeat AF ablation after 16 ± 16 months. SVC was isolated at the 1(st), 2(nd), 3(rd) and 4(th) AF ablation procedure in 63, 7, 5 and 1 patient by 7.3 ± 3.1 radiofrequency applications. SVC reconnection was observed in 56 patients (74%). In the majority, the conduction gap was located at the anterolateral SVC-right atrium (RA) junction. After re-isolation of SVC, 2/7 patients (29%) had reconnection at the following procedure. Among 63 patients who underwent PV and SVC isolation at the initial procedure, the prevalence of reconnection for PV and that for SVC were similar (53/63, 84% vs. 46/63, 73%; P=0.129). Dissociated activity, however, was more frequently observed in the PVs than in the SVC (47/63, 73% vs. 10/63, 16%; P<0.0001). During the procedure, AF initiation from a thoracic vein was identified in 19/63 patients (30%). CONCLUSIONS: SVC reconnection is common after 1 or more previous isolation procedures undertaken for AF ablation. Its prevalence is similar to that of PV reconnection. The location of the conduction gap varies widely but is most frequently found at the anterolateral SVC-RA junction.

Clinical implication of adenosine test at repeat atrial fibrillation ablation procedure: the importance of detecting dormant thoracic vein conduction.

BACKGROUND: Pulmonary vein reconnection after electrical isolation is commonly observed in the context of atrial fibrillation ablation and is associated with recurrent atrial tachyarrhythmias. Adenosine test was been performed to identify acute dormant conduction immediately after pulmonary vein isolation at index procedure. However, the utility of adenosine test at repeat procedure has not been reported. METHODS AND RESULTS: We report 5 paroxysmal atrial fibrillation cases without any structural heart disease in which dormant thoracic vein conduction was associated with recurrent atrial tachyarrhythmias. All patients had undergone circumferential ipsilateral pulmonary vein isolation at the index procedure. Superior vena cava isolation was performed if superior vena cava-triggered atrial fibrillation was identified. At the index procedure, adenosine test did not provoke venous reconduction. At the repeat procedure, adenosine provoked clinical arrhythmia in 4 out of 5 cases after transient reconnection between culprit thoracic vein and atrium despite absence of reconnection at the start of the procedure. After the elimination of the dormant conduction gaps, all patients were free from recurrent arrhythmia. CONCLUSIONS: Adenosine provokes dormant thoracic vein conduction associated with the late recurrence of atrial tachyarrhythmias after previous thoracic vein isolation. Thus, adenosine provocation test can specifically help identify and target the cause of recurrent atrial arrhythmia.

Two distinct electrocardiographic forms of idiopathic ventricular arrhythmia originating in the vicinity of the His bundle.

AIM: The objective is to assess electrocardiographic characteristics predicting the precise location of ventricular arrhythmia (VA) origin within the right ventricle (RV) close to the His bundle (HB) region. METHODS AND RESULTS: Twenty-five patients (14 men, age 65 ± 14 years) underwent successful catheter ablation of para-Hisian VA. Ventricular arrhythmias were considered to arise in the vicinity of the HB region based on the criteria that mapping exhibited the earliest RV activation before QRS onset in the HB region. Surface 12-lead electrocardiogram during the para-Hisian VAs was analysed. Of the 25 patients, 8 originated from the RV antero-septum just above the HB region, and 17 arose from the RV mid-septum just below the HB region. There was no significant difference in precedence of the local ventricular electrogram of the HB region from the onset of surface QRS during VAs. Surface electrocardiographic findings were characterized according to R-wave amplitude in lead I (0.43 ± 0.18 vs. 0.67 ± 0.19 mV, P = 0.005), mean R-wave amplitude in inferior leads (1.12 ± 0.32 vs. 0.71 ± 0.24 mV, P = 0.002), R-wave amplitude ratio of leads III/II (0.77 ± 0.10 vs. 0.50 ± 0.23, P = 0.005), incidence of S-wave in lead III [1/8 (13%) vs. 16/17 (94%), P < 0.001], and QS morphology in lead V1 [3/8 (38%) vs. 17/17 (100%), P = 0.001]. CONCLUSIONS: Despite their adjacent locations, para-Hisian VAs could be classified into two subgroups with distinctive electrocardiographic characteristics according to origin either above or below the HB region. The present findings can be helpful for planning catheter ablation of para-Hisian VAs, and can reduce the risk of inadvertent atrioventricular block.

Clinical characteristics of patients with persistent atrial fibrillation successfully treated by left atrial ablation.

BACKGROUND: We sought to characterize patients with persistent atrial fibrillation (AF) who were successfully treated by ablation targeting the left atrium (LA). METHODS AND RESULTS: Ninety-three patients (58±10 years, 79 male) undergoing ablation of persistent AF were studied. During the first procedure, ablation was performed in the LA and coronary sinus, consisting of pulmonary vein isolation, linear ablation, and electrogram-based ablation. During follow-up after the first procedure, 35 patients (38%) remained free from tachyarrhythmias, 27 patients (29%) had atrial tachycardia, and 31 patients (33%) had AF. Duration of persistent AF according to medical history and whether AF was terminated by ablation were associated with the outcome (P=0.005, P=0.004, respectively). In multivariate analysis, the duration of persistent AF was the only predictor of freedom from AF (sinus rhythm or atrial tachycardia) (odds ratio, 0.80 for a 1-year increase; 95% confidence interval, 0.67 to 0.95; P=0.01). Of 31 patients in whom AF recurred during follow-up, electrogram-based ablation was performed in the right atrium in 26 patients. Sixteen of those patients (62%) remained free from AF during follow-up. Overall, 82% of patients were free from any tachyarrhythmias at 2-year follow-up after a median of 2 procedures. CONCLUSIONS: Patients with shorter duration of persistent AF were more likely to be free from AF by LA ablation. Right atrial ablation may provide incremental efficacy in patients who are refractory to LA ablation.