Atria and Pulmonary Veins










  • Magnetic resonance angiography (MRA) is an excellent imaging modality for defining pulmonary venous anatomy before pulmonary vein isolation for treatment of atrial fibrillation.



  • Pulmonary vein stenosis, a possible side effect of atrial fibrillation ablation, is associated with dyspnea, cough, or hemoptysis and can be diagnosed with MRA.



  • Esophageal perforation, another feared complication of catheter ablation for atrial fibrillation, typically presents with dysphagia. Early recognition and treatment is of paramount importance and can be facilitated by cardiac magnetic resonance (CMR) imaging.



  • Transesophageal echocardiography (TEE) is the current standard of care for ruling out the presence of thrombus in the left atrial appendage before cardioversion or catheter ablation. The noninvasive nature of CMR compared with TEE suggests promise for its future use in thrombus evaluation.



  • Because of its superior soft tissue resolution, CMR is an ideal tool for diagnosis, staging, and preprocedural planning for treatment of cardiac mass lesions.



KEY POINTS




Case 1


A 65-year-old man with history of highly symptomatic persistent atrial fibrillation refractory to antiarrhythmic therapy presented for pulmonary vein isolation. Preprocedural TEE ruled out the presence of left atrial thrombus. CMR was performed prior to the procedure to plan lesion sets and obtain baseline pulmonary vein diameters ( Figure 6-1 ). The MRA revealed a right middle pulmonary vein.




Figure 6-1


A, MRA showing pulmonary vein variant anatomy with a separate ostium for the right middle pulmonary vein. The right atrium and ventricle are visualized at the top of the image and the left atrium and ventricle at the bottom. The pulmonary veins and their tributaries are readily visualized. B, Three-dimensional reconstruction of MRA of left atrial anatomy in another patient with a separate ostium for the right middle pulmonary vein. Segmented three-dimensional reconstructions of the left atrium are registered with catheter positions in the left atrium and within pulmonary veins during atrial fibrillation ablation to enable accurate real-time tracking of catheter movements with respect to the preacquired image. Using the electroanatomic system’s catheter positioning information, the operator can avoid delivering lesions deep in the pulmonary veins or at the ostia of small branches, thus avoiding pulmonary vein stenosis or occlusion. LA, left atrium; LV, left ventricle; RSPV, right superior pulmonary vein; RMPV, right middle pulmonary vein; RIPV, right inferior pulmonary vein.


Right Middle Pulmonary Vein


Comments


Atrial fibrillation is the most common sustained cardiac arrhythmia and is associated with increased morbidity and mortality. The identification of focal pulmonary vein triggers for atrial fibrillation has led to surgical and catheter-based ablation techniques to treat atrial fibrillation through electrical isolation of pulmonary veins from the atria. To guide the intricate lesion sets required for isolation, MRA images of the left atrium and pulmonary veins are often acquired before catheter-based pulmonary vein isolation procedures for atrial fibrillation. Three-dimensional reconstructions of such images can be merged with an electroanatomic mapping system to provide catheter positioning information during the procedure and help guide the targeting of lesions sets. Information about variant anatomic features such as a right middle lobe pulmonary vein can change procedural plans. For example, ablation between the superior and inferior pulmonary veins is commonly performed, may cause occlusion of the right middle branch, and is best avoided in patients with such variant anatomy. Lack of information about such anatomic detail may result in pulmonary vein stenosis or occlusion, often presenting with dyspnea, cough, and/or hemoptysis.




Case 2


A 39-year-old man with a 3-year history of highly symptomatic paroxysmal atrial fibrillation underwent catheter-directed pulmonary vein isolation using radiofrequency energy. Follow-up CMR images revealed mild narrowing of all pulmonary vein ostia, and occlusion of the superior branch of the left inferior pulmonary vein ( Figure 6-2 ).




Figure 6-2


A, Preprocedural MRA of the left atrium and pulmonary veins. On this posterior view, the aortic arch and pulmonary artery are seen at the top of the image with the descending aorta’s caudal course in front of the left atrium. The left inferior pulmonary vein and a small ostial branch are easily visualized. B, Corresponding image following radiofrequency ablation. The descending aorta is not visible allowing better visualization of the posterior left atrium and pulmonary veins. Mild narrowing of all pulmonary vein ostia and occlusion of the superior branch of the left inferior pulmonary vein is readily appreciated. C, Three-dimensional “catheter view” reconstruction of the preprocedural MRA of the left atrium and pulmonary veins. The view shows the ostia of the left superior and inferior pulmonary veins. Secondary branches within the left inferior pulmonary vein are appreciated from the internal view of the chamber. D, Corresponding image after radiofrequency ablation. Stenosis of the left inferior pulmonary vein ostium is readily appreciated and the ostial secondary branch to the right of the left inferior pulmonary vein orifice in ( C ) is no longer visible. LIPV, left inferior pulmonary vein.

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Feb 1, 2019 | Posted by in MAGNETIC RESONANCE IMAGING | Comments Off on Atria and Pulmonary Veins
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