Prominent Crista Terminal Is Vs Right Atrial Mass-jse 2007-piis089473170600887x

Prominent Crista Terminalis: As An Anatomic Structure Leading to Atrial Arrhythmias and Mimicking Right Atrial Mass Murat Akcay, MD, Emine Senkaya Bilen, MD, Mehmet Bilge, MD, Tahir Durmaz, MD, and Mustafa Kurt, MD, Ankara, Turkey

Crista terminalis is a fibromuscular ridge at the posterolateral region of the right atrium (RA). Superiorly localized prominent crista terminalis can mimic pathologic RA mass on transthoracic echocardiograms. Transesophageal echocardiography can be used to differentiate nonpathologic structures from pathologic ones. Besides mimick-

ing RA mass, crista terminalis is an important anatomic structure responsible for paroxysmal atrial fibrillation and atrial flutter by initiating ectopic atrial beats. In this case we discuss a patient with atrial arrhythmias who had prominent crista terminalis misdiagnosed as RA mass. (J Am Soc Echocardiogr 2007;20:197.e9-e10.)

CASE SUMMARY

DISCUSSION

A 51-year-old woman was referred to our clinic with diagnosis of right atrial (RA) thrombus. Her symptoms were dyspnea and palpitation for 2 years. On physical examination, blood pressure was 130/80 mm Hg and pulse was regular at 82/min. Chest examination revealed prolongation of expiration and bilateral rhonchi. Other findings of physical examination were normal. Laboratory findings revealed anemia with hemogram and hematocrit levels of 11 g/dL and 33%, respectively, and no other pathologic findings were detected including thyroid functions. On telecardiogram, there were no pathologic findings. Electrocardiography showed no significant change. Transthoracic echocardiogram (TTE) revealed a RA mass. It was round, 15 mm in diameter, immobile, not calcified, and located at the posterior region of RA (Figure 1). Transesophageal echocardiography (TEE) showed prominent crista terminalis superiorly located beneath superior vena cava in the RA at 130 degrees midesophageal position (Figure 2). There were no other pathologic findings on TEE. Magnetic resonance imaging showed no abnormality except prominent crista terminalis. On 24-hour Holter monitoring, atrial ectopic beats (100/24 h) were detected (Figures 1 and 2, Videos 1 and 2).

The crista terminalis is a fibromuscular ridge at the posterolateral region of the RA. It is originated from regression of the septum spirium as the sinus venosus is incorporated into the RA wall. Thus, the regression of the crista terminalis shows wide variations, and so does its prominence.1 Crista terminalis may achieve a thickness of 3 to 6 mm in adolescents and adults.2 It separates the smooth posterior region of the RA from a more muscular anterior region. There is no study evaluating the prevalence of the crista terminalis during TTE examination. However, Meier and Hartnell1 and Mirowitz and Gutierrez3 searched the prevalence of the prominent crista terminalis during magnetic resonance imaging. Mirowitz and Gutierrez3 defined crista terminalis as a soft tissue structure along the posterior lateral wall between the superior and inferior vena cava in 90% of cases. In the study of Meier and Hartnell1 the frequency of a prominent crista terminalis was approximately 40%. Pharr et al4,5 reported two cases of prominent crista terminalis that were first diagnosed as RA mass on TTE. In the first case, during TEE, the diagnosis was corrected as prominent crista terminalis. In the other case, prominent crista terminalis with lipomatous hypertrophy of atrial septum was reported. In our case, the thickness of crista terminalis was measured as 15 mm. This thickness was more than 2-fold of the thickness that was reported in the literature.2 In our case crista terminalis seems to be more prominent than the cases that were reported by Pharr et al.4,5 Several congenital structures and normal variants such as Chiari’s network, eustachian and thebesian valves, and atrial septal aneurysms may simulate pathologic RA masses such as RA thrombus or myxomas.6

From the Ankara Ataturk Education and Research Hospital, Department of Cardiology. Reprint requests: Murat Akcay, MD, Umit mah. Kermes Sitesi. 1.Blok No:20, Umitkoy 06800 Ankara, Turkey (E-mail: [email protected]). 0894-7317/$32.00 Copyright 2007 by the American Society of Echocardiography. doi:10.1016/j.echo.2006.08.037

197.e9

197.e10 Akcay et al

Journal of the American Society of Echocardiography February 2007

crista terminalis was the origin of ectopic beats and atrial fibrillation in 3.7% of paroxysmal atrial fibrillation. In the literature a relationship between atrial arrhythmias and prominent crista terminalis seen on TTE has not been reported yet. Although our patient had anemia and mild obstructive lung disease to explain the reason of the atrial arrhythmias, prominent crista terminalis may also be the other reason to explain this situation. Conclusion

Figure 1 Transthoracic echocardiogram reveals right atrial (RA) mass. Arrow, Crista terminalis (CT ). LA, Left atrium; LV, left ventricle; RV, right ventricle.

In this case we want to emphasize that prominent crista terminalis can mimic RA mass and may lead to atrial arrhythmias. TEE can be used to differentiate normal structures from pathologic ones and further investigation to explain the relationship between the prominent crista terminalis seen on TTE and atrial arrhythmias is warranted. REFERENCES

Figure 2 Transesophageal echocardiogram shows prominent crista terminalis (CT ). LA, Left atrium; RA, right atrium; VCS, vena cava superior.

Superiorly localized prominent crista terminalis can also mimic pathologic RA mass on TTE when imaged tangentially.5 TEE can be used to differentiate nonpathologic structures from pathologic ones. Thus, echocardiographers and cardiologists must pay attention while performing TEE to recognize these anatomic structures. Crista terminalis forms one of the tracts for internodal conduction. It is also important to explain the reason of atrial fibrillation and atrial flutter by initiating ectopic atrial beat.7,8 In the study of Lin et al,7

1. Meier RA, Hartnell GG. MRI of the right atrial pseudomass: is it really a diagnostic problem? J Comp Assoc Tomogr 1994;18: 398-401. 2. Edwards WD. Cardiac anatomy and examination of cardiac specimens. In: Allen HD, Gutgesell HP, Clark EB, Driscoll DJ, editors. Heart disease in infants, children and adolescents. 6th ed. Philadelphia: Lippincott Williams and Wilkins; 2001. p. 89. 3. Mirowitz SA, Gutierrez FR. Fibromuscular elements of the right atrium: pseudomass at MR imaging. Radiology 1992; 182:231-3. 4. Pharr JR, West MB, Kusumoto FM, Figueredo VM. Prominent crista terminalis appearing as a right atrial mass on transthoracic echocardiogram. J Am Soc Echocardiogr 2002;15:753-5. 5. Pharr JR, Figueredo VM. Lipomatous hypertrophy of the atrial septum and prominent crista terminalis appearing as a right atrial mass. Eur J Echocardiogr 2002;3:159-61. 6. Errichetti A, Weyman AE. Cardiac tumors and masses. In: Weyman AE, editor. Principles and practice of echocardiography. 2nd ed. Philadelphia: Lea and Febiger Publishing Co; 1994. p. 1169. 7. Lin WS, Tai CT, Hsieh MH, Tsai CF, Lin YK, Tsao HM, et al. Catheter ablation of paroxysmal atrial fibrillation initiated by non-pulmonary vein ectopy. Circulation 2003;107:3176-83. 8. Lin YJ, Tai CT, Liu TY, Higa S, Lee PC, Huang JL, et al. Electrophysiological mechanisms and catheter ablation of complex atrial arrhythmias from crista terminalis. Pacing Clin Electrophysiol 2004;27:1231-9.

SUPPLEMENTARY DATA Supplementary data associated with this article can be found, in the online version, at 10.1016/j. echo.2006.08.037.