String-Like Structure in the Left Atrium

A 62-year-old man experienced sudden onset of tachycardia during triathlon training. During a treadmill exercise test, atrial fibrillation (AF) started when the heart rate was approximately 140 beats/min. Due to symptomatic paroxysmal AF, the patient was admitted to our hospital for catheter ablation. Transthoracic echocardiography revealed no structural heart disease. Two- (Figure A) and 3-dimensional (Figure B) transesophageal echocardiography (TEE), contrast-enhanced computed tomography (CT) scans (Figure C) and left atrial (LA) reconstruction anatomy of CT images (Figure D–F) revealed a string-like structure extending from the posterior to the anterior side of the right inferior pulmonary vein (RIPV), across the front of the RIPV attached to the interatrial septum, which consequently interfered with right pulmonary vein (PV) isolation.

Figure.

Two- (A) and 3-dimensional (B) transesophageal echocardiography, contrast-enhanced computed tomography (CT) scans (C) and left atrial (LA) reconstruction anatomy of CT images (D–F) revealed a string-like structure (arrows) extending from the posterior to the anterior side of the right inferior pulmonary vein (RIPV), across the front of the RIPV attached to the interatrial septum. Ao, aorta; LA, left atrium; RA, right atrium; RSPV, right superior pulmonary vein.

An anomalous muscular band in the LA has been found in approximately 2% of autopsy cases¹ and in 0.1% of CT studies.² In such cases, it may be possible to accomplish PV isolation by either ostial or wide-area ablation. Radiofrequency energy ablation close to the PV orifices and/or within the PVs could result in PV stenosis. Trans-septal LA catheterization into the posterior part of this string-like structure may enable successful PV isolation. Cardiac CT and TEE provide accurate imaging of the PV and LA anatomy.³ This information is important for determining procedural strategies.

Sources of Funding

This study did not receive any specific funding.

Disclosures

K.T. has received scholarship funds from Otsuka Pharmaceutical. K.T. is a member of Circulation Reports’ Editorial Team.

IRB Information

This study was approved by Shimane University Faculty of Medicine (No. 20210106-1).

References

• 1.   Yamashita T, Ohkawa S, Imai T, Ide H, Watanabe C, Ueda K. Prevalence and clinical significance of anomalous muscular band in the left atrium. Am J Cardiovasc Pathol 1993; 4: 286–293.
• 2.   Kanaji Y, Miyazaki S, Iwasawa J, Ichihara N, Takagi T, Kuroi A, et al. Pre-procedural evaluation of the left atrial anatomy in patients referred for catheter ablation of atrial fibrillation. J Cardiol 2016; 67: 115–121.
• 3.   Tanabe K. Three-dimensional echocardiography: Role in the clinical practice and future directions. Circ J 2020; 84: 1047–1054.