Cardiovascular Specimens

Processing the specimen

• 1.

  Describe the specimen, including the number of fragments (carefully check lid and sides of container), size, and color (myocardium = tan, scar = white, clot = red/brown, friable).

  • Transplant biopsies (evaluation for rejection): At least three to four fragments of ≥50% myocardium should be processed for light microscopy.

  • Nontransplant biopsies: At least three to four fragments of ≥50% myocardium should be processed for light microscopy and, in some cases, additional biopsies may be processed for electron microscopy (EM) and saved frozen.

• 2.

  Wrap in lens paper and submit in one cassette. Three H&E stained sections are routinely cut on all tissue received in formalin. Masson’s trichrome, iron, or amyloid stains may be ordered if indicated.

  Additional biopsies may be submitted in order to perform special studies:

  • Electron microscopy (EM): Tissue is fixed in glutaraldehyde (Karnovsky’s fixative is often used and is a mixture of glutaraldehyde and paraformaldehyde). The laboratory prepares semithin sections.

  • Immunofluorescence (IF) microscopy or freezing: Tissue is sent from the clinic fresh on saline moistened gauze for processing for IF or freezing.

Special studies for specific diseases

• Anthracycline (Adriamycin) Cardiotoxicity. Semithin (plastic) sections prepared prior to electron microscopy are necessary for the evaluation of myocyte vacuolization and myofibrillar lysis. Histologic features of anthracycline induced cardiotoxicity are best seen on semithin sections rather than H&E.

• Amyloidosis. All forms of amyloidosis are characterized by deposition of extracellular fibrils resulting from protein misfolding into an extended β-pleated sheet. The β-pleated sheet conformation can be highlighted by Congo red staining (amyloid: orange staining with apple-green, orange, or yellow birefringence under polarized light) or sulfated Alcian Blue (amyloid: sea-foam green; myocytes: yellow; connective tissue: red-purple). The most common types of amyloid affecting the heart are:

• Determining the type of amyloid protein deposited has become increasingly important for patient treatment and prognosis.

• Histochemical stains —identify the presence of amyloid but not the type of amyloid

• • Congo red—amyloid stains orange and shows apple-green, orange, or yellow birefringence under polarized light

  • Sulfated Alcian Blue (SAB)—sea-foam green staining of amyloid, connective tissue stains red-purple, and myocytes stain yellow

  • Trichrome—amyloid stains brick red, collagen and reticular fibers stain blue-green, and myocytes stain yellow

• Immunofluorescence studies —can identify some types of amyloid

• • IgG, IgA, IgM, kappa, lambda

  • Serum amyloid A protein (SAA)

  • Transthyretin

• Mass spectroscopy —this is the best method for specific identification of the type of amyloid

• A paraffin block (with formalin or B5-fixed tissue) can be sent to Mayo Clinic Laboratories for analysis ( https://www.mayocliniclabs.com ; Email: mcl@mayo.edu; telephone: 800-533-1710 or 507-266-5700)

• Hemochromatosis and Hemosiderosis. Iron deposition can be diagnosed using iron stains on fixed tissue.

• Metabolic Disease. Frozen and/or glutaraldehyde-fixed tissue may be useful for the evaluation of metabolic disease.

• Mitochondrial Myopathies. Electron microscopy is necessary for evaluation. However, the changes in the mitochondria are typically nonspecific.

• Hypertrophic Cardiomyopathy. This disease is more appropriately diagnosed by clinical imaging studies (e.g., echocardiography), molecular genetic studies, or on an explanted heart. Biopsy material will almost never reveal diagnosable myocyte disarray due to the superficial nature of the resected myomectomy specimen. Even if disarray is present, it is not pathognomonic for hypertrophic cardiomyopathy. Occasionally, characteristic features may be present on a septal myectomy.

Pathologic features sign-out checklist

• Nontransplant

• Transplant

Sample sign-outs

• RIGHT VENTRICULAR ENDOMYOCARDIAL BIOPSY

• Six months S/P cardiac transplantation.

• No evidence of rejection; ISHLT Grade 0R.

• Old biopsy site.

• Four fragments of diagnostic myocardium.

• RIGHT VENTRICULAR ENDOMYOCARDIAL BIOPSY

• Four weeks S/P cardiac transplantation.

• Multifocal interstitial infiltrate with associated myocyte damage (ISHLT Grade 2R).

• Focal healing ischemic injury.

• Four fragments of diagnostic myocardium.

• One fragment of blood clot.

• RIGHT VENTRICULAR ENDOMYOCARDIAL BIOPSY

• Myocyte hypertrophy, moderate.

• Interstitial and/or perivascular fibrosis, mild.

• No evidence of active myocarditis, granulomatous inflammation, acute or recent myocardial infarction, amyloid heart disease or iron deposition (Congo red and iron stains examined).

• Four fragments of diagnostic myocardium.

Note: These findings are entirely nonspecific and could result from the right-sided changes secondary to left-sided heart disease of numerous etiologies (e.g., ischemic heart disease, valvular heart disease), a global cardiac process such as idiopathic dilated cardiomyopathy, or the right-sided changes secondary to primary pulmonary disease.

Specimen examination, dictation, and processing

• 1.

  Examine the specimen grossly and determine the type of valve (aortic, mitral, pulmonic, or tricuspid).

  Leaflets or cusps: Number of recognizable leaflets (atrioventricular valves) or cusps (semilunar valves), size, consistency (thickened, fibrotic, calcified, thinned, redundant (ballooned), perforated), additional fragments. If an abnormality is present describe the distribution (focal or diffuse), surface (atrial or ventricular or both), and location (free edge or base).

  Commissures: Relationship to each other (not fused, fused completely, fused partially).

  Chordae tendineae (tendinous cords): Length (shortened, elongated), status (intact, thickened, ruptured, fused). Mitral and tricuspid valves, but not aortic or pulmonic valves, have cords.

  Papillary muscles: Dimensions, abnormalities (hypertrophied, elongated, scarred).

  Vegetations: Color, size, location, consistency (firm, friable), presence or absence of destruction of underlying tissue.

  Endocarditis is a life-threatening disease and any indication that acute endocarditis is present should be immediately brought to the attention of the clinician if not already clinically known (see description under “Gross Differential Diagnosis”). Histologic stains for bacteria and fungi should be ordered if there is a possibility of endocarditis, either from clinical information or after gross or histologic examination.

• 2.

  Submit one cassette with representative sections taken from the free edge to the annulus. It may be necessary to decalcify some specimens.

Gross differential diagnosis

The gross evaluation is important for determining the etiology of valvular disease ( Tables 13.1 and 13.2 ; and Figs. 13.1 , 13.2 , and 13.3 ).

• Calcific aortic valve stenosis. Calcific deposits are present within the cusps, primarily at the base (attachment margin). The free cuspal edges are usually not involved. The cusps may be heavily fibrosed and thickened but are not fused.

• Congenital bicuspid valves are predisposed to degenerative calcification. Usually one of the cusps is larger with a midline raphe resulting from the incomplete separation of two cusps. The raphe extends from the base of the cusps at the aortic wall toward the edge, but does not reach the free edge. The free edge is often horizontal without an indentation. Less frequently the cusps may be of equal size. The raphe is often a site of extensive calcification.

• An acquired bicuspid valve results fusion of two normal cusps due to inflammation (see “aortic postinflammatory scarring” below). The two fused cusps are two times the size of the remaining cusp. The fibrocalcific ridge at the site of the fusion extends from the base to the free edge and the free edge usually shows an indentation between the fused cusps.

• Mitral Annular Calcification. Calcifications occur in the annulus of the mitral valve. The chordae are uninvolved.

• Myxomatous Degeneration of the Mitral Valve. The leaflet is enlarged, thickened, and redundant. The cords may be elongated and thinned and sometimes ruptured.

• Aortic Postinflammatory Scarring (Rheumatic Type). The cusps are fused at the commissures. Diffuse thickening and calcification is rather evenly distributed and includes the free cuspal edges. The mitral valve is also involved in the majority of patients.

• Mitral Postinflammatory Scarring (Rheumatic Type). The leaflets are thickened and there is commissural fusion and shortening ( Fig. 13.1 ). The cords are thickened and fused. Calcification is often present. Small warty vegetations are present along the lines of closure of the valve leaflets.

• Endocarditis. The types of endocarditis have different gross appearances ( Fig. 13.1 ). In acute bacterial endocarditis, large friable vegetations are found on the valves and may be single or multiple. They may extend onto the chordae. There is often perforation or erosion of the underlying valve. The vegetations of nonbacterial thrombotic endocarditis (NBTE) are small, bland, and typically attached at the line of closure on the flow surfaces of the valve. Systemic lupus erythematosus may be associated with small to medium size bland vegetations that can be located on both surfaces of the valve or on the cordae (Libman–Sacks endocarditis).

Sample dictations

Pathologic features sign-out checklist

Sample sign-outs

• Mitral Valve

  Diffuse leaflet thickening, commissural fusion, and chordae fibrosis; transmural fibrosis and neovascularization, consistent with postinflammatory scarring, rheumatic type.

• Aortic Valve

  Calcific degeneration.

  Probable congenitally bicuspid aortic valve.

• Aortic Valve

  ENDOCARDITIS, ACTIVE

  Valve with extensive necrosis, acute inflammation, and neovascularization.

  Gram-positive cocci identified (Gram and MSS stains examined).