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Number 10-14: Persistent Left SVC Complicating Atrial Fibrillation Ablation
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Number 10-14: Persistent Left SVC Complicating Atrial Fibrillation Ablation

Case from:  Vikas K. Rathi1, Robert W.W. Biederman1, June Yamrozik1, Ronald Williams1, William Belden2
1Center for Cardiovascular MRI and 2Electrophysiology Lab, Division of Cardiology, Gerald McGinnis Cardiovascular Institute, Allegheny General Hospital, Pittsburgh, PA, USA.  

Clinical history: A 50 year old male with history of persistent atrial fibrillation and three failed electrical cardioversion attempts in the past 2 years was being evaluated for a pulmonary vein isolation (PVI) procedure.  The day prior to ablation he underwent cardiovascular MRI (CMR) to identify the 3D anatomy and location of the pulmonary veins in order to assist the electrophysiologist in the planned PVI procedure.

 

 

Figure 1

 

CMR imaging: The initial cine 2-chamber view demonstrated a markedly dilated coronary sinus (Fig 1). Coronal and sagittal cine images revealed a persistent left superior vena cava (pLSVC) communicating with the coronary sinus which drained into the right atrium (Movies 1 and 2).

 


 

 Movie 1


 

  

Movie 2

 

An oblique peri-axial image perpendicular to the long-axis of the pLSVC at the level of left pulmonary veins was acquired which demonstrated the pLSVC coursing between the left atrial appendage and the left superior pulmonary vein completely adjacent to the walls of these structure (Movie 3). There was no communication between the pLSVC and the pulmonary veins or left atrial appendage. A 3D MRA demonstrated four pulmonary veins draining into the left atrium (Movie 4). No anomalous pulmonary venous return or sinus venosus defect were seen. He also had a bicuspid aortic valve with mildly dilated ascending aorta and aneurysmal origin of the left subclavian artery (Movies 2 and 3).

 

  

Movie 3

 

Following morphologic and anatomic imaging, the patient underwent 3D magnetic resonance angiography (MRA) with gadolinium chelate (Gd) injected into the right antecubital vein. The first phase acquisition was targeted for pulmonary vein filling and demonstrated four pulmonary veins draining into the left atrium.  As expected, the pLSVC was not visualized on first phase images due to the IV administration of Gd in the right antecubital vein and the absence of bridging vein to the left side (common in pLSVC cases) (Movie 4).  A second (venous) phase was acquired to demonstrate pLSVC filling (Movie 5)

 

      

Movie 4                                                          Movie 5

 

Electrophysiology Study: A lasso catheter was passed across the interatrial septum and into the left atrium followed by a venogram of the pLSVC which was accessed through the coronary sinus (Movie 6).  The lasso catheter was then passed through the coronary sinus into the distal end of the pLSVC.  The bipole electrodes LS 1 to 10 on this lasso catheter recorded significant electrical activity originating in the distal LSVC (Fig 2). Since the pLSVC was adjacent to the left atrial wall and the left superior pulmonary vein, the electrical activity within the pLSVC was able to conduct into these structures thereby potentially initiating atrial fibrillation. The pLSVC was rendered electrically inactive after ablation performed within the pLSVC (Fig 3).  The electroanatomic map created during the PVI procedure demonstrated ablation lines within the pLSVC, left atrium and pulmonary veins (Movie 7).

 

 

Movie 6

 

 

Figure 2 - Pre ablation

 

 

Figure 3 - Post ablation

 

 

 

Movie 7

 

Discussion: The major thoracic veins, with their specific electrical properties, have an established role in the genesis and maintenance of atrial fibrillation1,2.  The vein of Marshall and pLSVC which drains into the coronary sinus as well as the ligament of Marshall have all been implicated in the cause for premature atrial complexes and initiation of atrial fibrillation3,4.  Identification of their presence along with demonstration of electrical activity within such structures is key to successful ablation of atrial fibrillation5.

Of note, a pLSVC most commonly drains into the coronary sinus (as in this case) but it can rarely drain straight into the roof of the left atrium causing a right to left shunt and may also be associated with partial or complete unroofing of the coronary sinus leading to a large left to right shunt.

Perspective: This case highlights the complimentary role of CMR in identifying the anatomy of pulmonary veins, left atrium and surrounding venous structures prior to PVI.  Identifying anomalous anatomic structures is critical to successful ablation of all the foci of aberrant electrical activity.  Non contrast cine images in multiple planes are as important as contrast 3D pulmonary vein angiograms to display accurate anatomic relationships.  Injection of contrast into the right antecubital vein would miss the diagnosis in early phases of 3D aquisition.  Visualization of the pLSVC can be demonstrataed by inspection of the later 3D aqusition phases or by injection of contrast into the left antecubital vein.

 

References: 

1. Chen PS, Wu TJ, Hwang C, et al. Thoracic veins and the mechanisms of non-paroxysmal atrial fibrillation. Cardiovasc Res. 2002; 54: 295-301.

2. Zipes DP, Knope RF. Electrical properties of the thoracic veins. Am J Cardiol. 1972; 29: 372-376.

3. Hwang C, Wu TJ, Doshi RN, et al. Vein of Marshall cannulation for the analysis of electrical activity in patients with focal atrial fibrillation. Circulation. 2000; 101: 1503-1505.

4. Morgan DR, Hanratty CG, Dixon LJ, et al. Anomalies of cardiac venous drainage associated with abnormalities of cardiac conduction system. Europace. 2002; 4: 281-287.

5. Hsu LF, Jaïs P, Keane D, Wharton JM, Deisenhofer I, Hocini M, Shah DC, Sanders P, Scavée C, Weerasooriya R, Clémenty J, Haïssaguerre M. Atrial fibrillation originating from persistent left superior vena cava. Circulation. 2004 Feb 24;109(7):828-32.

 


COTW handling editor: Kevin Steel

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