Prominent Crista Terminalis: As An AnatomicStructure Leading to Atrial Arrhythmias and

Mimicking Right Atrial MassMurat 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 theposterolateral region of the right atrium (RA).Superiorly localized prominent crista terminaliscan mimic pathologic RA mass on transthoracicechocardiograms. Transesophageal echocardiog-raphy can be used to differentiate nonpathologic

structures from pathologic ones. Besides mimick-

doi:10.1016/j.echo.2006.08.037

ing RA mass, crista terminalis is an importantanatomic structure responsible for paroxysmalatrial fibrillation and atrial flutter by initiatingectopic atrial beats. In this case we discuss apatient with atrial arrhythmias who had promi-nent crista terminalis misdiagnosed as RA mass.

(J Am Soc Echocardiogr 2007;20:197.e9-e10.)

CASE SUMMARY

A 51-year-old woman was referred to our clinic withdiagnosis of right atrial (RA) thrombus. Her symptomswere dyspnea and palpitation for 2 years. On physicalexamination, blood pressure was 130/80 mm Hg andpulse was regular at 82/min. Chest examination revealedprolongation of expiration and bilateral rhonchi. Otherfindings of physical examination were normal. Laboratoryfindings revealed anemia with hemogram and hematocritlevels of 11 g/dL and 33%, respectively, and no otherpathologic findings were detected including thyroid func-tions.

On telecardiogram, there were no pathologic findings.Electrocardiography showed no significant change. Trans-thoracic echocardiogram (TTE) revealed a RA mass. It wasround, 15 mm in diameter, immobile, not calcified, andlocated at the posterior region of RA (Figure 1). Trans-esophageal echocardiography (TEE) showed prominentcrista terminalis superiorly located beneath superior venacava in the RA at 130 degrees midesophageal position(Figure 2). There were no other pathologic findings onTEE. Magnetic resonance imaging showed no abnormalityexcept prominent crista terminalis. On 24-hour Holtermonitoring, atrial ectopic beats (100/24 h) were detected(Figures 1 and 2, Videos 1 and 2).

From the Ankara Ataturk Education and Research Hospital, De-partment of Cardiology.Reprint requests: Murat Akcay, MD, Umit mah. Kermes Sitesi.1.Blok No:20, Umitkoy 06800 Ankara, Turkey (E-mail:drmuratakcay@yahoo.com).0894-7317/$32.00Copyright 2007 by the American Society of Echocardiography.

DISCUSSION

The crista terminalis is a fibromuscular ridge at theposterolateral region of the RA. It is originated fromregression of the septum spirium as the sinus veno-sus is incorporated into the RA wall. Thus, theregression of the crista terminalis shows wide vari-ations, and so does its prominence.1 Crista termina-lis may achieve a thickness of 3 to 6 mm in adoles-cents and adults.2 It separates the smooth posteriorregion of the RA from a more muscular anteriorregion. There is no study evaluating the prevalenceof the crista terminalis during TTE examination.However, Meier and Hartnell1 and Mirowitz andGutierrez3 searched the prevalence of the promi-nent crista terminalis during magnetic resonanceimaging. Mirowitz and Gutierrez3 defined crista ter-minalis as a soft tissue structure along the posteriorlateral wall between the superior and inferior venacava in 90% of cases. In the study of Meier andHartnell1 the frequency of a prominent crista termi-nalis was approximately 40%. Pharr et al4,5 reportedtwo cases of prominent crista terminalis that werefirst diagnosed as RA mass on TTE. In the first case,during TEE, the diagnosis was corrected as promi-nent crista terminalis. In the other case, prominentcrista terminalis with lipomatous hypertrophy ofatrial septum was reported. In our case, the thick-ness of crista terminalis was measured as 15 mm.This thickness was more than 2-fold of the thicknessthat was reported in the literature.2 In our case cristaterminalis seems to be more prominent than thecases that were reported by Pharr et al.4,5 Severalcongenital structures and normal variants such asChiari’s network, eustachian and thebesian valves,and atrial septal aneurysms may simulate pathologic

RA masses such as RA thrombus or myxomas.6

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Journal of the American Society of Echocardiography197.e10 Akcay et al February 2007

Superiorly localized prominent crista terminalis canalso mimic pathologic RA mass on TTE when imagedtangentially.5 TEE can be used to differentiate non-pathologic structures from pathologic ones. Thus,echocardiographers and cardiologists must pay at-tention while performing TEE to recognize theseanatomic structures.

Crista terminalis forms one of the tracts for inter-nodal conduction. It is also important to explain thereason of atrial fibrillation and atrial flutter by initi-

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

Figure 2 Transesophageal echocardiogram shows promi-nent crista terminalis (CT). LA, Left atrium; RA, rightatrium; VCS, vena cava superior.

ating ectopic atrial beat.7,8 In the study of Lin et al,7

crista terminalis was the origin of ectopic beats andatrial fibrillation in 3.7% of paroxysmal atrial fibrilla-tion. In the literature a relationship between atrialarrhythmias and prominent crista terminalis seen onTTE has not been reported yet. Although our patienthad anemia and mild obstructive lung disease toexplain the reason of the atrial arrhythmias, promi-nent crista terminalis may also be the other reason toexplain this situation.

Conclusion

In this case we want to emphasize that prominentcrista terminalis can mimic RA mass and may lead toatrial arrhythmias. TEE can be used to differentiatenormal structures from pathologic ones and furtherinvestigation to explain the relationship betweenthe prominent crista terminalis seen on TTE andatrial arrhythmias is warranted.

REFERENCES

1. Meier RA, Hartnell GG. MRI of the right atrial pseudomass: isit really a diagnostic problem? J Comp Assoc Tomogr 1994;18:398-401.

2. Edwards WD. Cardiac anatomy and examination of cardiacspecimens. In: Allen HD, Gutgesell HP, Clark EB, Driscoll DJ,editors. Heart disease in infants, children and adolescents. 6thed. Philadelphia: Lippincott Williams and Wilkins; 2001. p. 89.

3. Mirowitz SA, Gutierrez FR. Fibromuscular elements of theright atrium: pseudomass at MR imaging. Radiology 1992;182:231-3.

4. Pharr JR, West MB, Kusumoto FM, Figueredo VM. Prominentcrista terminalis appearing as a right atrial mass on transthoracicechocardiogram. J Am Soc Echocardiogr 2002;15:753-5.

5. Pharr JR, Figueredo VM. Lipomatous hypertrophy of the atrialseptum and prominent crista terminalis appearing as a rightatrial 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 echocardiogra-phy. 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 bynon-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 com-plex atrial arrhythmias from crista terminalis. Pacing Clin Elec-trophysiol 2004;27:1231-9.

SUPPLEMENTARY DATA

Supplementary data associated with this article canbe found, in the online version, at 10.1016/j.

echo.2006.08.037.