Atrial flutter (AFL) involving the vein of Marshall (VOM) after left atrial (LA) ablation for persistent atrial fibrillation (AF) is a recognized form of atrial flutter. In one series reported by Vlachos et al,1 the Marshall bundle (MB) network participated in 30.2% of reentrant atrial tachycardias. The significance of these arrhythmias involving the MB need to be recognized to enhance the success rates of ablation, as it often poses a challenge due to the fact it is an epicardial structure.
These arrhythmias can present as macroreentrant tachycardia or localized reentrant tachycardia, and having a better understanding of them can help us to target ablation for best success.
We present 2 cases involving the MB with demonstration of pure macroreentrant circuit and combination of macro and localized reentrant circuits.
The patient is a 73-year-old male with a history of ischemic cardiomyopathy, an ejection fraction of 35%, previous implantation with a cardiac resynchronization therapy defibrillator, and persistent atrial fibrillation (including previous ablation for AF). He had wide area circumferential ablation (WACA) along with roof line, posterior box line, mitral isthmus (MI) line, complex fractionated atrial electrogram (CFAE), and inside coronary sinus (CS) triggers targeted as a part of AF ablation. He also underwent cavotricuspid isthmus ablation for typical AFL. This time, he presented with symptomatic atypical AFL. Mapping and ablation was planned, and the patient was brought to the EP laboratory. The CS was accessed using a 6 Fr Inquiry decapolar catheter (Abbott), and transseptal access was obtained using a medium curl Agilis NxT Steerable Introducer dual-reach sheath (Abbott) and 98 cm NRG Transseptal Needle (Baylis Medical) under intracardiac echo (ACUSON AcuNav Ultrasound Catheter, Biosense Webster, Inc., a Johnson & Johnson company) and biplane fluoroscopy guidance.
The patient’s rhythm was atrial tachycardia (AT) when he was brought to the EP laboratory (Figure 1A). The activation sequence was from CS distal to proximal with a cycle length (CL) of 399 ms (Figure 1B). Atrial overdrive pacing involving the CS catheter in the proximal, mid, and distal location showed concealed entrainment with post-pacing interval (PPI) equal to the tachycardia cycle length (TCL). Left atrial geometry, activation, and voltage maps were created using the Advisor HD Grid Mapping Catheter, Sensor Enabled and EnSite 3D mapping (Abbott). The voltage map with a voltage setting of 0.1 mV and 0.5 mV showed evidence of scar in the mitral isthmus region (<0.1 mV) (Figure 1D). The LA roof line between the right superior and left superior line was intact with conduction block, as demonstrated by voltage and wavefronts (Figure 1D). The activation map showed 2 missing isochrones through the endocardial map along the MI line (Figure 1D). CS venogram was performed, and the vein of Marshall (VOM) was identified. The VOM was cannulated with a balanced middleweight wire (BMW guide wire, Abbott). A balloon catheter was advanced over the wire into the VOM. The tip of the wire was exposed, and activation mapping revealed the 2 missing isochrones (Figure 1D). Overdrive pacing through the BMW wire demonstrated concealed entrainment with PPI=TCL (Figure 1C). The balloon was inflated (1.5 mm X 10 mm, Boston Scientific) for VOM occlusion, 1 cc of 98% ethanol was injected slowly, and the flutter terminated (Figure 1E). An additional 1 cc of alcohol was injected for insurance purposes after 90 seconds. Differential pacing across the mitral isthmus showed conduction block, and the flutter was not induced with pacing maneuvers.
A 72-year-old male who had persistent AF underwent WACA, roof line, and CFAE ablation at the anterior septum, atrial part of aorto-mitral continuity, anterior to the right superior pulmonary vein, and posterior inferior to the right inferior pulmonary vein, as well as the superior vena cava right atrial junction area. He returned with symptomatic AT one year after previous ablation. He had normal left ventricular function and moderate mitral regurgitation.
The patient underwent an EP study, and CS activation showed CS proximal to distal with a cycle length of 313 ms. Atrial overdrive pacing from CS proximal demonstrated concealed entrainment with a PPI of 314 ms (Figure 2A). CS distal overdrive pacing demonstrated PPI=TCL (Figure 2B). Electroanatomic mapping using PENTARAY high-density mapping and CARTO (Biosense Webster) demonstrated peri-mitral isthmus atrial flutter (Figure 2C). Radiofrequency ablation with Surround Flow using a 3.5 mm CARTO NAVISTAR Catheter (Biosense Webster) from the mitral annulus and left inferior pulmonary vein was performed without termination of flutter. A CS angiogram was performed to demonstrate VOM, which overlayed the area of ablation. A 0.014-inch VisionWire (BIOTRONIK) with a 15 mm exposed tip and insulated body was used to cannulate the VOM, and overdrive pacing demonstrated concealed entrainment with PPI=TCL (Figure 2D). A 1.5 mm X 10 mm occlusive balloon (Boston Scientific) was advanced over the 0.014-inch BMW wire, and after occlusion of VOM, 98% ethanol (2 cc) was infused. The CL increased from 313 to 400 ms, but the activation sequence changed from CS distal to proximal. Activation mapping was performed to demonstrate a long fractionated signal between the left atrial appendage and left superior pulmonary vein and localized reentrant flutter. Ablation of a long fractionated site terminated the tachycardia (Figure 2E).
Left atrial ablation for AF with pulmonary vein isolation is the mainstay of therapy for symptomatic patients who fail medical therapy. Ablation with incomplete lesions with gaps or healed lesions creating channels could potentially result in proarrhythmia. Ablation by creating lines involving roof or mitral isthmus or any linear ablations without overlapping lesions or leaving gaps between anatomical structures or ablation lines could result in reentrant tachycardias. De novo left atrial flutters may also occur if there is significant remodeling due to atrial dilatation as a result of long-standing AF. Mitral isthmus line pseudoblock is due to a cooling effect either attributed to coronary sinus flow to subjacent atrial tissue. Alternatively, the MB may form a potential route through which reentrant ATs may occur.2 MB tachycardias as described in a distinctive group of tachycardia by Vlachos et al is seen commonly after ablation of persistent AF patients. The tachycardias among these series were demonstrated to be localized reentry at the MB-left atrial junction (73.3%), MD-CS junction (8.3%), and VOM itself (15%). While entrainment maps help to localize around peri-mitral regions, the diagnosis solidifies if entrainment is performed with PPI <20 ms from VOM. If there are missing isochrones with activation mapping using 3D mapping, it gives a clue to look for activation within VOM.
Our patients demonstrated atrial reentrant tachycardias with the following findings. Case #1 demonstrated 2 missing isochrones after mitral annular reentrant tachycardia was considered by entrainment at the ridge area. After mapping within the VOM, these 2 missing isochrones were uncovered. Entrainment within the VOM confirmed the protected isthmus and alcohol infusion terminated reentrant tachycardia without recurrence.
Case #2 demonstrated two interesting findings. After demonstrating that the atrial reentrant tachycardia was peri-mitral by entrainment and activation mapping, mitral isthmus ablation didn’t terminate the flutter. Entrainment mapping at the VOM identified the circuit. Although alcohol infusion terminated the flutter involving VOM, the tachycardia changed into 400 ms CS distal to proximal tachycardia. Activation maps demonstrated localized reentrant tachycardia with long fractionated electrograms in the region at the posterior portion of the left atrial appendage over the ridge anterior to the left superior pulmonary vein. Ablation at this site restored sinus rhythm. This location was the landing zone of the MB into the left atrium, demonstrating both VOM macroreentrant atrial flutter and localized reentry tachycardia at the landing zone of the MB to the LA. While ethanol infusion among patients with VOM tachycardias was successful in 56% of patients in one cohort,3 radiofrequency ablation at the CS-VOM junction or MB-LA landing zone is also effective.
Left atrial ablation, especially persistent type, may potentially present with reentrant tachycardias involving the MB. Identification through missing isochrones, mapping within the VOM, anatomically at the entry point from the CS-VOM and MB-LA landing zone, may help to target therapy for successful outcomes.
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Disclosures: The authors have no conflicts of interest to report regarding the content herein.
- Vlachos K, Denis A, Takigawa M, et al. The role of Marshall bundle epicardial connections in atrial tachycardias after atrial fibrillation ablation. Heart Rhythm. 2019;16:1341-1347.
- Fujisawa T, Kimura T, Nakajima K, et al. Importance of the vein of Marshall involvement in mitral isthmus ablation. Pacing Clin Electrophysiol. 2019;42:617-624.
- Kitamura T, Vlachos K, Denis A, et al. Ethanol infusion for Marshall bundle epicardial connections in Marshall bundle-related atrial tachycardias following atrial fibrillation ablation: the accessibility and success rate of ethanol infusion by using a femoral approach. J Cardiovasc Electrophysiol. 2019;30:1443-1451.