An infant was diagnosed prenatally with tricuspid atresia and hypoplastic right ventricle by fetal echocardiography at 22 weeks' gestation. On delivery, physical examination revealed a cyanotic female infant with an active precordium, single 1st and 2nd heart sounds, an ejection click, and a grade 1/6 low frequency systolic ejection murmur at the left upper sternal border. Prostaglandin E1 was initiated.
Two-dimensional echocardiography demonstrated tricuspid atresia, pulmonary atresia, hypoplastic right ventricle, D-transposed great arteries, and a large subaortic muscular ventricular septal defect. There was a prominent aneurysm of the atrial septum and restrictive right-to-left shunting. A Chiari's network reticulum was present in the right atrium. After cardiac catheterization and balloon atrial septostomy were performed, the interatrial gradient decreased from 10 mmHg to 0 mmHg. The prostaglandin was discontinued, and the infant underwent a modified right Blalock-Taussig shunt on day of life 5.
Chiari 1st described this fetal remnant in the right atrium over 100 years ago. 1 In early cardiac development, 2 venous valves guard the right horn of the sinus venosus. 2 The smaller left valve is incorporated into the septum secundum, and the right valve partitions the right atrium. In normal development, the right valve regresses between gestational weeks 9 and 15, its cephalic portion remaining as the crista terminalis and its caudal portion dividing to form the eustachian and thebesian valves. Failure of regression gives rise to the fenestrated Chiari's network, which attaches to the superior vena cava or crista terminalis. 3 This must be differentiated from a prominent eustachian valve, and from complete atrial partitioning as found in cor triatriatum dexter. 4
Supplementary Material
Fig. 1 Two-dimensional transthoracic apical 4-chamber view shows tricuspid atresia and hypoplastic right ventricle. Note the aneurysmal atrial septum and the Chiari's network in the right atrium.
AS = aneurysmal atrial septum; CC = Chiari's network;
RA = right atrium; RV = right ventricle
Fig. 2 A close-up apical 4-chamber view demonstrates the Chiari's network extending across the right atrium.
AS = aneurysmal atrial septum; CC = Chiari's network;
TP = tricuspid plate
Fig. 3 Subcostal view reveals the attachment of the Chiari's network to the junction of the superior vena cava and the right atrium and its extension across the right atrium.
AS = aneurysmal atrial septum; RA = right atrium;
SVC = superior vena cava
Footnotes
Address for reprints: Mark B. Lewin, MD, Division of Pediatric Cardiology, Texas Children's Hospital, 6621 Fannin, MC 2280, Houston, TX 77030
Web site: This article has also been published, with supplementary images, on the THI web site: www.texasheartinstitute.org/mcmahon.html
References
- 1.Chiari H. Ueber Netzbildungen im rechten Vorhofe des Herzens. Beitr Path Anat 1897;22:1–10.
- 2.Yater WM. Variations and anomalies of the venous valves of the right atrium of the human heart. Arch Pathol 1929;7:418–44.
- 3.Werner JA, Cheitlin MD, Gross BW, Speck SM, Ivey TD. Echocardiographic appearance of the Chiari network: differentiation from right-heart pathology. Circulation 1981;63:1104–9. [DOI] [PubMed]
- 4.Alboliras ET, Edwards WD, Driscoll DJ, Seward JB, Cor triatriatum dexter: two-dimensional echocardiographic diagnosis. J Am Coll Cardiol 1987;9:334–7. [DOI] [PubMed]
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