Cardiovascular Images
Cardiovascular images: vascular hamartoma of the mitral valve in a horse,☆☆

https://doi.org/10.1016/j.jvc.2018.09.002Get rights and content

Abstract

An 8-month-old Hanoverian gelding was presented with a history of cardiac murmurs that were not apparent as a foal nor reported at the time of castration. Major echocardiographic findings included mitral valvular thickening, functional stenosis, and mitral regurgitation of sufficient severity to cause diastolic and systolic cardiac murmurs, left-sided volume overload, and pulmonary hypertension. Due to the hemodynamic severity of the lesion and poor prognosis for future performance and longevity, euthanasia was elected. On gross postmortem examination, there was focal fibrous epicarditis affecting the heart base, and the left atrium was moderately dilated. The mitral valve surface was irregular and contained several nodules along the atrial face of the cusp. Histologically, this lesion was diagnosed as a vascular hamartoma, which is rarely reported in veterinary species and has not been described in heart valves. This benign proliferative lesion, and concurrent valvular dysfunction, was associated with an unusual manifestation of clinically evident disease and should be differentiated from common incidental valvular lesions such as hematocysts.

Section snippets

Echocardiogram

Echocardiographic findings included subjectively mildly thickened mitral valve leaflets with a lack of systolic coaptation and reduced diastolic leaflet excursion. The left ventricle and atrium were moderately to severely dilated for a gelding of this relatively small size (Fig. 1 and Video 1)

Severe mitral regurgitation (MR) was diagnosed based on color and spectral Doppler imaging characteristics of wide vena contracta and jet area, as well as low peak velocity of MR (<4 m/s) with an early

Focal fibrous epicarditis with pericardial adhesions

On gross examination, the epicardial surface of the left ventricular free wall had a single 3-mm diameter, well-demarcated depression that extended into the myocardium. Thick strands of tan fibrous tissue were adherent to the overlying visceral pericardium (fibrous pericarditis, chronic). Additional gross findings included a markedly dilated left atrium and mildly dilated pulmonary artery (Fig. 2).

Mitral valve septal leaflet

Gross examination of the mitral valve demonstrated two mitral leaflets connected to two papillary muscles through normal-appearing chordal attachments. The orifice was not obviously stenotic. The septal leaflet of the mitral valve revealed approximately 10 pink-tan to gray, firm, well-demarcated nodules of 1–2 mm in diameter. The margins of the mitral valve leaflets were irregularly scalloped and thickened. There were few slightly raised linear foci on the endocardial surface of the left

Histopathology of mitral valve septal leaflet (hematoxylin and eosin stain (H&E))

On histologic examination, the septal leaflet of the mitral valve was multifocally expanded by cystic structures resembling vascular profiles lined by well-differentiated endothelium surrounded by circumferential smooth muscle (confirmed by smooth muscle actin immunohistochemistry, not pictured) and myxomatous matrix. The vascular lumina were variably filled with erythrocytes and acellular basophilic granular material, interpreted as mineral (Fig. 4).

Histopathology of epicardial lesion (H&E)

A region of the left ventricular myocardium underlying the focal epicardial depression had a paucity of cardiomyocytes with expansion of the area by dense fibrous connective tissue (confirmed by Masson's trichrome stain, not pictured), consistent with epicardial fibrosis (Fig. 5).

Immunohistochemistry for CD31 (A) and CD3 (B). (C) Verhoeff-van Gieson (elastin) stain on the mitral valve septal leaflet

Immunohistochemistry was performed on the mitral valve using an automated immunostainer to assess for a marker of vascular endothelium: CD31 (Abcam, catalog no. ab-28364) and lymphocytic inflammatory infiltrate: CD3 (Dako, catalog no. A0452). Antigen retrieval was performed according to the manufacturer's instructions. A Verhoeff-van Gieson elastin stain was performed to assess the elastin content within the walls of the vascular profiles. Staining for CD31 revealed strong positive staining of

Discussion

Based on the gross and histopathologic findings, a diagnosis of vascular hamartoma of the mitral valve was made. While atrioventricular valve hematocysts are similarly lined by the endothelium, the lesion in this case was differentiated by the presence of elastin and smooth muscle within the walls of the vascular profiles. Hematocysts are considered clinically incidental and have not been reported in association with valvular dysfunction.

Possible etiologies in this case include vascular

Conflicts of Interest Statement

The authors do not have any conflicts of interest to disclose.

Acknowledgments

The authors would like to thank the Comparative Pathology and Mouse Phenotyping Shared Resource at Ohio State University for their support in providing histologic sections and immunohistochemical stains for this report.

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A unique aspect of the Journal of Veterinary Cardiology is the emphasis of additional web-based images permitting the detailing of procedures and diagnostics. These images can be viewed (by those readers with subscription access) by going to http://www.sciencedirect.com/science/journal/17602734. The issue to be viewed is clicked and the available PDF and image downloading is available via the Summary Plus link. The supplementary material for a given article appears at the end of the page. Downloading the videos may take several minutes. Readers will require at least Quicktime 7 (available free at http://www.apple.com/quicktime/download/) to enjoy the content. Another means to view the material is to go to http://www.doi.org and enter the doi number unique to this paper which is indicated at the end of the manuscript.

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A unique aspect of the Journal of Veterinary Cardiology is the emphasis of additional web-based materials permitting the detailing of procedures and diagnostics. These materials can be viewed (by those readers with subscription access) by going to http://www.sciencedirect.com/science/journal/17602734. The issue to be viewed is clicked and the available PDF and image downloading is available via the Summary Plus link. The supplementary material for a given article appears at the end of the page. To view the material is to go to http://www.doi.org and enter the doi number unique to this paper which is indicated at the end of the manuscript.

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