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CASE REPORT
Year : 2019  |  Volume : 29  |  Issue : 1  |  Page : 32-34

A nonfatal massive pulmonary embolism in a very old patient: The protective filter-effect of the Chiari Network


1 Department of Cardiology, San Giuseppe Multimedica IRCCS Hospital, Milano, Italy
2 Department of Cardiology, Cardiology Clinic, Policlinico San Giorgio, Pordenone, Italy
3 Department of Cardiovascular, MultiMedica IRCCS, Milano, Italy

Date of Web Publication20-Mar-2019

Correspondence Address:
Andrea Sonaglioni
San Giuseppe Multimedica IRCCS Hospital, San Vittore Street 12, 20123 Milano
Italy
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcecho.jcecho_65_18

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  Abstract 


The Chiari network, a net-like structure within the right atrium, has been described as an embryonic remnant of no clinical significance. Its role in facilitating paradoxical arterial embolic events and as a potential site for thrombus formation has been reported in the literature. This case illustrates the protective filter-effect of the Chiari network in a 92-year-old women who presented with the clinical signs and symptoms of acute cor pulmonale. Transthoracic echocardiography revealed a large, S-shaped, and extremely mobile right atrial thrombus within the Chiari network. Here, the authors describe how the Chiari network may have prevented the occurrence of a fatal pulmonary embolism acting as a protective factor.

Keywords: Chiari network, pulmonary embolism, right atrial thrombus


How to cite this article:
Sonaglioni A, Nicolosi GL, Lombardo M, Anza C. A nonfatal massive pulmonary embolism in a very old patient: The protective filter-effect of the Chiari Network. J Cardiovasc Echography 2019;29:32-4

How to cite this URL:
Sonaglioni A, Nicolosi GL, Lombardo M, Anza C. A nonfatal massive pulmonary embolism in a very old patient: The protective filter-effect of the Chiari Network. J Cardiovasc Echography [serial online] 2019 [cited 2019 Apr 20];29:32-4. Available from: http://www.jcecho.org/text.asp?2019/29/1/32/254599




  Introduction Top


The Chiari network, a net-like structure within the right atrium, has been described as an embryonic remnant of no clinical significance. Its role in facilitating paradoxical arterial embolic events and as a potential site for thrombus formation has been reported in the literature. We illustrate the protective filter-effect of the Chiari network in a very old women who presented with the clinical signs and symptoms of acute cor pulmonale.


  Case Report Top


A 92-year-old woman was admitted to the emergency room, because of on-going dyspnea, tachypnea, tachycardia, and systolic blood pressure >100 mmHg. She also had nausea and vomiting. Electrocardiogram showed sinus tachycardia (heart rate: 100 bpm) with incomplete right bundle branch block and minor nonspecific ST-T alterations [Figure 1]. Arterial blood gas analysis revealed hypoxemia and hypocapnia. Blood tests evidenced markedly elevated levels of D - dimer (>20000 ng/ml), NT-proBNP (>500 pg/ml), liver transaminases (>100 U/L), C-reactive protein (>7 mg/dl), and white blood cell count (>20,000/ml). Troponin levels were slightly increased (0.1 ng/ml, range: 0–0.04 ng/ml).
Figure 1: Electrocardiogram showing sinus tachycardia (heart rate, 100 bpm) with incomplete right bundle branch block and minor nonspecific ST-T alterations

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An urgent two-dimensional-echocardiography demonstrated severe dilation of the right heart chambers with the McConnell's sign and raised systolic pulmonary artery pressure, suggesting acute cor pulmonale. Surprisingly, it was also detected a large, S-shaped and extremely mobile right atrial thrombus, tethered to Chiari network, freefloating and prolapsing through the tricuspid valve into the right ventricle [Figure 2], panel a, red arrow].
Figure 2: (Panel a) Transthoracic echocardiography in apical four-chamber view. Dilatation of right atrium and right ventricle. Large S-shaped RA thrombus (red arrow) entrapped in the Chiari network. LA = Left atrium, LV = Left ventricle, RA = Right atrium, RV = Right ventricle. (Panel b) Chest computed tomography scan with contrast showing obstructive thrombosis of the main pulmonary arteries. Ao = Aorta, PA = Pulmonary artery, T = Thrombus. (Panel c) Transthoracic echocardiography in apical four-chamber view showing the complete disappearance of the thrombus. LA = Left atrium, LV = Left ventricle, RA = Right atrium, RV = Right ventricle

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The patient rapidly underwent a thoracic computed tomography scan, which showed obstructive thrombosis of the main pulmonary arteries [Figure 2], panel b].

Then, she was admitted to the department of pneumology and was treated with subcutaneous unfractionated heparin (enoxaparin sodium 6000 IU SC) twice daily.

A deep venous thrombosis (DVP) of the left popliteal vein was also diagnosed by a Doppler ultrasound imaging of the lower extremities.

During the following days, the echocardiographic reevaluation revealed the complete resolution of the thrombus from still enlarged right heart cavities [Figure 2], panel c]. The patient completely recovered and was discharged from the hospital on the 15th day.

The Chiari network, an embryonic remnant from the persistence of the right valve of the sinus venosus, was first described in 1897.[1] Its present in only 1.5%–3% of adults. It originates from the eustachian valve, an embryological remnant of the inferior vena cava (IVC), runs along the posterior wall of the right atrium, and has the role of directing blood from the IVC toward the foramen ovale in fetal life.[2]

Echocardiography is an excellent tool for the diagnosis of the Chiari network. In transthoracic echocardiography, this network presents as a highly reflectant echo target in several locations in the right atrium, sometimes highly mobile.[3]

The Chiari network is mostly an incidental finding, and itself bears no major clinical significance.

Its presence was recognized as a potential risk factor for paradoxical arterial embolic events since the network may encourage blood flow away from the IVC and toward the interatrial septum causing right-to-left shunting.[4]

In addition to its role as a risk factor for arterial embolic events, it has been suggested that the Chiari network may act as a nidus for thrombus formation and a part of the strands may embolize.[5],[6],[7] By initially entrapping the fragments of thrombi from a DVP an even bigger clot may develop, which once the filter-like effect of the Chiari network is overcome, could result in a fatal massive pulmonary embolism (PE).[8]

Interestingly, the Chiari network has been described to play a protective role in special situations, holding thrombo-emboli from the leg or pelvic veins in the network and preventing pulmonary embolization.[9],[10],[11]

The present case supports the action of this embryonic remnant as a protective filter, which may have prevented the occurrence of a fatal PE in a very old patient.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Loukas M, Sullivan A, Tubbs RS, Weinhaus AJ, Derderian T, Hanna M, et al. Chiari's network: Review of the literature. Surg Radiol Anat 2010;32:895-901.  Back to cited text no. 1
    
2.
Obaji SG, Cooper R, Somauroo J. Chiari network: A protective filter against pulmonary embolism in a case of polycythaemia. BMJ Case Rep 2012;2012. pii: bcr0520114289.  Back to cited text no. 2
    
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.  Back to cited text no. 3
    
4.
Schneider B, Hofmann T, Justen MH, Meinertz T. Chiari's network: Normal anatomic variant or risk factor for arterial embolic events? J Am Coll Cardiol 1995;26:203-10.  Back to cited text no. 4
    
5.
Yater WM. The paradox of Chiari's network. Review and report of a case of Chiari's network ensnaring a large embolus. Am Heart J 1936;11:542-52.  Back to cited text no. 5
    
6.
Powell ED, Mullaney JM. The Chiari network and the valve of the inferior vena cava. Br Heart J 1960;22:579-84.  Back to cited text no. 6
    
7.
Schwimmer-Okike N, Niebuhr J, Schramek GG, Frantz S, Kielstein H. The presence of a large Chiari network in a patient with atrial fibrillation and stroke. Case Rep Cardiol 2016;2016:4839315.  Back to cited text no. 7
    
8.
Casazza F, Becattini C, Guglielmelli E, Floriani I, Morrone V, Caponi C, et al. Prognostic significance of free-floating right heart thromboemboli in acute pulmonary embolism: Results from the Italian pulmonary embolism registry. Thromb Haemost 2014;111:53-7.  Back to cited text no. 8
    
9.
Motovska Z, Widimsky P, Bilkova D, Penicka M, Linkova H, Kautznerova D, et al. An embolus in the right atrium caught in the Chiari network and resistant to thrombolysis. J Thromb Thrombolysis 2010;30:114-8.  Back to cited text no. 9
    
10.
Goedde TA, Conetta D, Rumisek JD. Chiari network entrapment of thromboemboli: Congenital inferior vena cava filter. Ann Thorac Surg 1990;49:317-8.  Back to cited text no. 10
    
11.
Rizzello V, Lombardo A, Colizzi C, Pennestrì F. Entrapment of a floating thrombus in the right atrium by persistent Chiari's network: A barrier to massive pulmonary embolism. Int J Cardiol 2009;132:e40-1.  Back to cited text no. 11
    


    Figures

  [Figure 1], [Figure 2]



 

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