Networks in the Right Side of the Heart

Abstract

Delicate networks occur in the right side of the heart at three sites: at the entry of the inferior vena cava into the atrium, at the mouth of the coronary sinus, and between the endocardial surfaces of the right ventricle. The first clear account of the fenestrated valve of the inferior vena cava and coronary sinus was by Eustachi (1563, quoted by Franklin 1948. Franklin (1948) has reviewed the historical background of these valves and the theories concerned with their origin and function. Chiari (1879) described networks formed from the valves of the inferior vena cava, and in some cases of the coronary sinus, which showed attachments beyond the usual territories of these valves. These reticular formations are now called Chiari networks. Chiari himself considered them to act as a source of pulmonary emboli. Yater (1929) suggests that they may serve as a filter for emboli arriving at the right atrium from elsewhere in the venous system. This investigation is mainly concerned with the view that the network may act as a short circuit from sinu-atrial node to atrioventricular bundle.Hearts from 300 consecutive necropsies were examined for the presence of networks in the right atrium and in the right ventricle. Of these 260 were from adults, 23 of whom were below the age of fifty; 7 were from children in the first five years of life; and 33 were from stillbirths and neonates. RESULTSIn 58 of all hearts examined, of which 38 were from children of five years or less, no valves were found of either the coronary sinus or the inferior vena cava. In 204 of 260 adult hearts examined the commonest findings were along the lateral border of the coronary sinus and in order of frequency could be divided into: (a) a conspicuous crescentic valve flap often fenestrated, (b) a valve flap that completely covered the orifice of the coronary sinus and was adherent to its medial wall except at one or two points, and (c) a single strand which was present alone in 25, or in association with a fenestrated valve of the inferior vena cava in 9 (Fig. 1). If the inferior sinus septum (Fig. 1) was absent or poorly developed, then the strands were continuous with a fenestrated valve of the inferior vena cava in five cases (Fig. 2).The next most frequent abnormality found in 75 cases was a fenestrated valve of the inferior vena cava (Fig. 1). In four cases the attachments of this valve extended up to the internal orifice of the superior vena cava and inferiorly to the atrioventricular ring near the site, anterior to the coronary sinus, of the atrioventricular node (Fig. 3). Such a valve with these attachments is called the Chiari network (Yater, 1929). Evidence will be presented to support the desirability of distinguishing it from a fenestrated valve of the inferior vena cava without such attachments.The degree of fenestration of the valve of the inferior vena cava was variable. The simplest form was a fleshy crescentic valve with a few holes in its free border (Fig.

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“…Developmentally, the embryological remnants of the right venous valve evolve into the valve of the inferior vena cava (Eustachian valve) and the valve of the coronary sinus (Thebesian valve) and Chiari Network (CN) [11,12]. Echocardiography is an excellent tool for the diagnosis of these structures, including CN.…”

Prominent prolapsing Chiari network: presentation and prognosis in paediatric patients

“…On microscopic analysis in children and adults, the Chiari network has been found to consist of strands of cardiac muscle surrounded by elastic tissue. [17][18]…”

Live/Real Time Three‐Dimensional Transthoracic Echocardiographic Visualization of Chiari Network

“…Chiari network named after Hans Chiari, results from failure of resorption of the right sided sinus venosus valve, and presents as a large fenestrated and web like membrane in the right atrium (RA) 1–6 . It has wide attachments in the RA at the crista terminalis and the interatrial septum in the region of tubercle of Lower 1,2,7 .…”

“…Chiari network named after Hans Chiari, results from failure of resorption of the right sided sinus venosus valve, and presents as a large fenestrated and web like membrane in the right atrium (RA) 1–6 . It has wide attachments in the RA at the crista terminalis and the interatrial septum in the region of tubercle of Lower 1,2,7 . On the other hand, both the eustachian and thebesian valves are typically much smaller and less extensive and result from more complete resorption of the right sinus venosus valve 2,3,6 .…”

“…[1][2][3][4][5][6] It has wide attachments in the RA at the crista terminalis and the interatrial septum in the region of tubercle of Lower. 1,2,7 On the other hand, both the eustachian and thebesian valves are typically much smaller and less extensive and result from more complete resorption of the right sinus venosus valve. 2,3,6 Chiari network also needs to be differentiated from cor triatriatum dexter which also results from incomplete resorption of the right sinus venosus valve, but is much thicker with few or no fenestrations.…”