Author + information
- Received July 14, 2015
- Accepted August 13, 2015
- Published online February 1, 2016.
- Takekuni Hayashi, MDa,∗ (, )
- Seiji Fukamizu, MDb,
- Takeshi Mitsuhashi, MD, PhDa,
- Takeshi Kitamura, MDb,
- Yuya Aoyama, MDb,
- Rintaro Hojo, MDb,
- Yoshitaka Sugawara, MDa,
- Harumizu Sakurada, MD, PhDc,
- Masayasu Hiraoka, MD, PhDd,
- Hideo Fujita, MD, PhDa and
- Shin-ichi Momomura, MD, PhDa
- aDivision of Cardiovascular Medicine, Saitama Medical Center, Jichi Medical University, Saitama, Japan
- bDepartment of Cardiology, Tokyo Metropolitan Hiroo Hospital, Tokyo, Japan
- cDepartment of Cardiology, Tokyo Metropolitan Health and Medical Treatment Corporation Ohkubo Hospital, Tokyo, Japan
- dToride Kitasohma Medical Center Hospital, Ibaraki, Japan
- ↵∗Reprint requests and correspondence:
Dr. Takekuni Hayashi, Division of Cardiovascular Medicine, Saitama Medical Center, Jichi Medical University, 1-847, Amanuma, Oomiya-ku, Saitama 330-8503, Japan.
Objectives The aim of this study was to determine whether re-entrant circuits were associated with the ligament of Marshall (LOM).
Background Peri-mitral atrial tachycardias (PMATs) following pulmonary vein isolation (PVI) or mitral valve surgery are common.
Methods Six PMATs involving epicardial circuits were identified from 38 patients. Of these, 4 PMATs involved the LOM (PMAT-LOM, mean cycle length 308 ± 53 ms), as confirmed by the insertion of a 2-F electrode in the vein of Marshall (VOM). All patients underwent PVI and mitral isthmus ablation. The PMAT-LOMs were diagnosed based on left atrium (LA) activation maps that covered <90% of tachycardia cycle length (TCL), and a difference between the post-pacing interval and TCL that was: 1) ≤20 ms at the VOM, the ridge between the left pulmonary vein and appendage, the anterior wall of the LA, and along the 6 to 11 o’clock direction of the mitral annulus; and 2) >20 ms at the distal coronary sinus (CS), the posterior wall of the LA, and the mitral isthmus ablation line (or noncapture). Catheter ablation was performed at the ridge for all PMAT-LOMs.
Results Three tachycardias were successfully terminated at the ridge, which showed continuous fractionated potential lasting >100 ms, confirming the bidirectional block of Marshall bundle (MB)–LA connections. The remaining tachycardia required ablation for the CS-MB connections, confirming bidirectional block of CS-MB connections.
Conclusions PMAT-LOMs following PVI or valve surgery accounted for up to 11% of PMATs. The bidirectional block of either MB-LA or CS-MB connections is required to eliminate PMAT-LOMs.
- atrial fibrillation
- epicardial mapping
- Marshall bundle
- peri-mitral atrial tachycardia
- radiofrequency catheter ablation
The ligament of Marshall (LOM) is an epicardial vestigial fold that contains the vein of Marshall (VOM) and a myocardial sleeve called the Marshall bundle (MB). The LOM has previously been implicated as a source of focal activity initiating atrial fibrillation (AF) (1–3). Radiofrequency catheter ablation (RFCA) has emerged as an effective therapy for patients with AF (4–6). Peri-mitral atrial tachycardia (PMAT) commonly develops after pulmonary vein isolation (PVI) or mitral valve surgery (7). The creation of a linear lesion from the mitral annulus (MA) to the left inferior PV, in the so-called mitral isthmus (MI), is the most common ablation strategy for PMAT. Achieving a complete ablation line (defined by a bidirectional conduction block across the MI line) is critical to eliminate PMAT, but doing so can be technically difficult and can require coronary sinus (CS) ablation of up to 70% (8). In rare cases, re-entrant circuits of PMAT involve an epicardial connection (9). This study was conducted to clarify the characteristics of PMATs that use epicardial connections, especially the LOM (PMAT-LOMs).
This study consisted of 38 consecutive patients with PMAT who underwent PVI for AF or mitral valve surgery in the Saitama Medical Center of Jichi Medical University and Tokyo Metropolitan Hiroo Hospital from March 2009 to September 2014. Of these patients, 28 underwent ablation for AF (paroxysmal AF n = 12; persistent AF lasting ≤1 year n = 2; long-standing persistent AF lasting >1 year n = 14) and 10 underwent mitral valve surgery (replacement n = 7; plasty n = 3). All patients gave signed informed consent before the procedure.
Electrophysiological study and ablation procedure
Antiarrhythmic drugs, excluding amiodarone, were discontinued ≥5 half-lives prior to ablation. The electrophysiological study was performed during continuous intravenous administration of propofol (3 to 6 mg/kg/min). A decapolar or multipolar catheter (Inquiry Luma-Cath, St. Jude Medical, Tokyo, Japan, or BeeAT, Japan Lifeline Co., Ltd., Tokyo, Japan) was inserted via the right subclavian vein to the CS. The left atrium (LA) and PV were explored via transseptal catheterization with 2 or 3 long sheaths. PV mapping was performed using a circular mapping catheter (Inquiry Optima, St. Jude Medical or Lasso, Biosense Webster, Inc., South Diamond Bar, California). A 3.5-mm irrigated-tip catheter (ThermoCool Navistar, Biosense Webster or Cool Path, St. Jude Medical) and a 3-dimensional anatomic mapping system (CARTO, Biosense Webster or EnSite NavX and Velocity, St. Jude Medical) were used for mapping and ablation.
AF ablation strategy
Ablation for AF was performed as previously described (10). Briefly, in patients with paroxysmal AF and persistent AF lasting ≤1 year, circumferential PVI was performed. If AF was present, sinus rhythm was restored by internal or external cardioversion. The target in this phase was the elimination of all PV potentials; once the target was attained, continuous intravenous isoproterenol (4 μg/min) was administered, a 20- to 40-mg bolus of adenosine triphosphate was injected, and further RFCA was performed to eliminate any reconduction of PV potentials or adenosine triphosphate–provoked acute dormant PV conduction. The endpoint of PVI was the establishment of a bidirectional conduction block between the LA and PV. If reproducible non-PV foci–initiated AF was identified, RFCA was attempted to eliminate the non-PV foci.
In the patients with long-lasting persistent AF lasting >1 year, PVI was performed during AF, followed by mapping of complex fractionated atrial electrograms (CFAEs) of the LA. CFAEs were defined as previously reported (11). Subsequently, linear ablation of a roof and MI line was performed. If AF persisted after linear ablation, LA CFAE ablation was performed. If the AF still persisted in this phase, internal or external cardioversion was performed. If the AF converted to atrial tachycardia (AT) after either linear or CFAE ablation, or both, mapping and ablation were performed.
Diagnosis and ablation of PMAT
Linear ablation of the MI was performed for induced or spontaneously occurring PMAT. PMAT was diagnosed using a 3-dimensional anatomic mapping system with the entrainment pacing technique. A difference between the post-pacing interval (PPI) and tachycardia cycle length (TCL) of ≤20 ms from the 4, 8, and 12 o’clock positions in the LA or CS along MA. Left-side PVI was performed in patients without AF. Subsequently, RFCA was applied from the 4 o’clock position of the MA to the bottom left-side PV with 25 to 35 W. If endocardial ablation was unable to successfully achieve a complete MI conduction block (defined by bidirectional conduction block across the MI line), further RFCA application was delivered within the CS opposite of the endocardial MI line with 20 to 25 W.
Diagnosis of PMAT using LOM
PMATs using epicardial connections were diagnosed with a 3-dimensional anatomic mapping system with the entrainment pacing technique. PMATs using epicardial connections were diagnosed based on: 1) an LA activation map of a 3-dimensional anatomic mapping system that covered <90% of the TCL; 2) a difference between PPI and TCL from the LA 6 to 11 o’clock positions of the MA that was ≤20 ms; 3) a difference between PPI and TCL from the LA 4 o’clock position of the MA or prior MI line that was >20 ms or noncapture with high-output pacing (20 mA × 2 ms); and 4) a difference between PPI and TCL from the multiple sites of CS that was ≤20 ms. Added to these observations, PMAT-LOM was diagnosed based on: 1) a difference between PPI and TCL from the 2-F octopolar electrodes (EPstar Fix, Japan Lifeline) inserted into the VOM that was ≤20 ms; 2) a difference between PPI and TCL from the CS distal beyond the bifurcation of VOM that was >20 ms; and 3) a difference between PPI and TCL from the ridge (defined as the area between the left-side PVs and left atrial appendage [LAA]) that was ≤20 ms.
Ablation of PMAT using LOM
Theoretically, creating either a bidirectional block of MB-LA or CS-MB connections without MI ablation can eliminate PMAT-LOM. Furthermore, the evaluation of differential pacing from the CS can be misleading when the existing MB epicardial connections bypass the MI. For example, when the bidirectional block of MI is incomplete, conduction time from the CS pacing site (pacing from the CS distal over VOM) to the LAA may be longer than from the CS proximal site, resulting in a pseudo-conduction block that may be misinterpreted as a complete MI block (Figure 1).
For the reasons stated above, RFCA was applied at the ridge (i.e., MB-LA connections site) with 30 to 35 W. Ablation endpoint was a complete block of MB-LA connections (defined by bidirectional conduction block across the MB-LA connections). If endocardial ablation was unable to successfully achieve an MB-LA block, further RFCA was delivered to the bifurcation of the CS and VOM with 20 to 25 W. In such cases, the ablation endpoint was a complete block of CS-MB connections.
PMATs using epicardial connections were identified in 6 patients. The baseline characteristics of these patients are listed in Table 1. Of these cases, 2 PMATs involved the CS, which bypassed the LA endocardium scar area of the MI line. RFCA was applied in the CS without LA endocardium ablation, and tachycardia was successfully terminated (cases 1 and 2).
Characteristics of PMAT using LOM
Four PMAT-LOMs were identified in the remaining 4 patients. The mean TCL was 308 ± 53 ms (range 260 to 380 ms). Three patients underwent catheter ablation for long-standing persistent AF. Of these patients, 2 patients underwent prior catheter ablation (PVI, roof line, MI, and LA CFAE ablation; cases 3 and 4) and 1 patient had no prior ablation. In the 2 patients with prior ablation, PMAT-LOM lasted from the beginning of the procedure. In the patient with long-standing persistent AF without prior ablation (case 5), AF was converted to PMAT-LOM after PVI, roof line, and MI ablation (including CS ablation). The remaining patient had a prior myocardial infarction with a history of paroxysmal AF and underwent catheter ablation for multiple AT (case 6). The macro–re-entrant AT (TCL 260 ms) originating from the anterior wall of the LA at the beginning of the procedure changed to roof-dependent AT (TCL 380 ms) after LA anterior ablation. Subsequently, AT changed to PMAT-LOM (TCL 380 ms) after roof and MI line ablation following left-side PV isolation (no PV potential in right-side PV).
The 3-dimensional anatomic activation map showed either clockwise or counterclockwise PMAT pattern (Figure 2). However, only 79 ± 1% (range 78% to 81%) of the TCL was covered by the activation map. This finding suggested the existence of epicardial circuits. Using both the 3-dimensional anatomic activation map and PPI technique revealed the circuits of PMAT-LOM (Figures 2 and 3). The circuits of clockwise PMAT-LOM were as follows: 1) the wave front propagated from the 5 to 11 o’clock positions of the LA endocardium around the mitral valve and proceeded vertically across the anterior wall of the LA from bottom to roof; 2) the activation was unable to proceed across the posterior wall of the LA due to the blocked line of the roof, and it moved to the ridge; and 3) the wave front proceeded across the epicardium via MB bridging the endocardium over the MI, and it broke out from the 5 to 6 o’clock positions of the LA endocardium around the mitral valve via the CS. The counterclockwise PMAT-LOMs followed the reversed circuit of the clockwise PMAT-LOMs.
Catheter ablation of PMAT using LOM
RFCA was applied at the ridge in which the difference between PPI and TCL was ≤20 ms in all patients. Three PMAT-LOMs were terminated by the ridge ablation. Local electrograms of tachycardia termination sites showed continuous fractionated potential in the diastole phase during AT in 3 cases (cases 3 to 5) (Figure 3). Further RFCA was applied at the ridge to create a block in the MB-LA connections, and bidirectional conduction block across the MB-LA connection was confirmed in these cases (Figure 4). Bidirectional block of MI line was confirmed in these 3 cases after bidirectional block of the MB-LA connections. The tachycardia was not terminated by ridge ablation in the remaining patient. RFCA was delivered to the bifurcation of the CS and VOM, and PMAT-LOM was successfully terminated. Further RFCA was applied to this area to create a block in the CS-MB connections, and bidirectional block of CS-MB connections was confirmed (Figure 5). Interestingly, in this case, incomplete MI block was demonstrated after bidirectional block of the CS-MB connections was created. Furthermore, MB-LA connections still remained.
In the patients with PMAT-LOM, 1 case had recurrence of paroxysmal AF within 1 month after the procedure during a mean follow-up period of 15 ± 6 months. No patients had recurrence of AT.
The present study demonstrated that:
1. The re-entrant circuits of PMATs following PVI for AF or mitral valve surgery involved epicardial connections bypassing the MI in 16% of patients (6 of 38); the majority of these (4 of 38) involved the MB epicardial connection.
2. The local electrograms of PMAT-LOM termination sites of the ridge showed fractionated potential lasting >100 ms in 3 of 4 patients.
3. Bidirectional blocks of either MB-LA connections or CS-MB connections are feasible and effectively cure PMAT-LOMs.
Re-entrant circuits of PMAT using LOM
The 3-dimensional activation mapping showed a noncentrifugal pattern, and the activation of LA endocardium covered only 79% of the TCL. The remaining 21% of noncovered re-entrant circuits presented in the LOM of the epicardium. Although the local electrograms of PMAT-LOM termination sites of the ridge showed fractionated potential at the early- to mid-diastole phase in 3 of 4 patients, the tachycardia was clearly distinguished from localized reentry originating from the ridge by the entrainment pacing technique. In cases 3 and 4, small fractionated continuous potentials following the large spiky potentials were recorded in the distal site of the VOM (VOM 1 to 2), whereas only large spiky potentials were recorded in the proximal VOM. These findings indicated that the area of slow conduction was not the main body of MB but the connection site of MB-LA. There was a possibility that previous left-side PVI line including ridge ablation led to the slow conduction zone in the connection site of MB-LA.
Ablation strategy of PMAT using LOM
Previous reports showed that PMAT-LOM, which includes the MB epicardial connections bypassing previous endocardial MI lines, was terminated by the creation of a bidirectional block of MI using ethanol infusion into the VOM; however, the previous reports did not evaluate bidirectional blocks of either the MB-LA or CS-MB connections (12,13). In the present study, 3 of 4 PMAT-LOMs were terminated by the creation of a bidirectional block of the MB-LA connections. The remaining case of tachycardia was terminated by the creation of a bidirectional block of the CS-MB connection without MI block. Our data indicate that it is not always necessary to create bidirectional blocks of MI for terminating PMAT-LOM. Furthermore, evaluation of the MI block may be misleading when MB epicardial connections bypass the MI. Accurate evaluations of the MB connections are necessary to eliminate PMAT-LOM. Bidirectional block of either the MB-LA or CS-MB connections is necessary to eliminate PMAT-LOM. Han et al. (14) reported 3 electrophysiological types of MB-LA connections: single, double, and multiple connections. Creating a bidirectional block of the MB-LA connections in patients with multiple connections is technically difficult. However, ablation should be initially attempted at the ridge for creating blocks in the MB-LA connections because creating CS-MB blocks has potential complications, such as coronary occlusion. Creating CS-MB connections block is an alternative strategy in cases in which blocking MB-LA connections is difficult.
PMATs using epicardial connections including the LOM can develop after AF ablation or mitral valve surgery. When the difference between PPI and TCL is >20 ms at the ablation site of endocardial MI lines, the possibility of PMAT is easy to exclude. However, in this situation, PPI mapping should be undertaken at the CS, including the VOM. For accurate diagnosis of PMAT-LOM, a 2-F electrode needs to be inserted in the VOM. However, when it is technically difficult to insert the 2-F electrode in the VOM or when the VOM is absent in cases of suspected PMAT-LOM, RFCA should be attempted at the ridge in which the difference between PPI and TCL is ≤20 ms.
First, the ridge ablation was performed during left-side PVI in all patients. The ridge ablation naturally led to the disconnection of the MB-LA connections. Furthermore, the majority of patients underwent RFCA in the CS for the creation of MI block, and CS ablation can disconnect CS-MB connections. Procedures of PVI and MI ablation, including CS, both carry the possibility of disconnecting the MB epicardial connections that bypass the MI. Furthermore, a 2-F electrode was not inserted in all patients, and we were unable to insert it in patients without VOM. Finally, because these patients underwent extensive previous LA ablation, a long PPI could be obtained due to delayed conduction with misleading entrainment results. Therefore, the real percentage of PMAT-LOM may not be accurate.
The re-entrant circuits of PMATs following PVI for AF or mitral valve surgery involved epicardial connections bypassing the MI in 16% of patients, the majority of which involved MB epicardial connections. Bidirectional block of either the MB-LA or CS-MB connections was feasible and effectively cured PMAT-LOMs.
COMPETENCY IN MEDICAL KNOWLEDGE: The re-entrant circuits of PMATs following PVI for AF or mitral valve surgery involved epicardial connections bypassing the MI in 16% of patients, the majority of which involved MB epicardial connections. Bidirectional block of either the MB-LA or CS-MB connections is feasible and effectively cures PMAT-LOMs.
TRANSLATIONAL OUTLOOK: Prospective clinical trials are needed to assess the real percentage of PMAT-LOM prevalence.
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- atrial fibrillation
- atrial tachycardia
- complex fractionated atrial electrogram
- coronary sinus
- left atrial/atrium
- left atrial appendage
- ligament of Marshall
- mitral annulus
- Marshall bundle
- mitral isthmus
- peri-mitral atrial tachycardia
- post-pacing interval
- pulmonary vein isolation
- radiofrequency catheter ablation
- tachycardia cycle length
- vein of Marshall
- Received July 14, 2015.
- Accepted August 13, 2015.
- American College of Cardiology Foundation
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