2.4.1 Gross post-mortem examination of the heart
A complete examination of the body is essential in all cases; however, specific attention must be paid to dissection of the heart when cardiac disease is suspected. A systematic method of inspecting the heart at post-mortem is essential in order that minor changes are not overlooked. In addition, it is very easy to damage structures during dissection so that it is unclear if the lesion is real or iatrogenic. The following protocol is relatively simple to follow.
- Note the presence of any pleural or pericardial fluid before the heart is removed from the thoracic cavity.
- Inspect the condition of the pericardium.
- Examine the epicardial surface of the heart
- Trim fat away from the heart.
- Carefully divide the pulmonary artery and the aorta, noting the condition of the ligamentum arteriosum.
- Free the pulmonary artery from the atria and cut down its length. Inspect the pulmonary valve. A little gentle washing may be needed at this point to see the valve clearly.
- Divide the pulmonary valve by cutting between the leaflets and continue the incision along the junction of the right ventricular free-wall and the inter-ventricular septum, until the incision extends to the base of the tricuspid valve annulus. Inspect the condition of the myocardium, the moderator bands and the tricuspid valve If a ventricular septal defect is present it may be hidden under the septal leaflet of the tricuspid valve.
- Make an incision from the caudal vena cava along the base of the right atrium, and from the cranial vena cava to join this. Extend the incision into the right atrial appendage. Inspect the endocardiurn of the right atrium for jet lesions.
- Cut down the length of the aorta and inspect the aortic valve. Take culture samples at this point if aortic valve endocarditis is suspected. Gentle washing may again be needed at this point to see the valve clearly.
- Open the left atrium by cutting between the pulmonary veins and extend the incision into the left atrial appendage. Inspect the endocardial surface for jet lesions and note the position of any lesions relative to the mitral valve leaflets. Jet lesions are rough patches of fibrin deposit on the endocardial surface, but can look like fleshy projections if they are more severe and long-standing (Figure 2.1). Gently wash the mitral valve and note any flailing of leaflets as water fills the ventricle. This can also be done by filling the ventricle via the aortic valve.
- Cut down the length of the coronary arteries from the sinus of Valsalva.
- Divide the aortic valve between the right and left coronary cusps and cut to the level of the left coronary groove. Divide the myocardium carefully with a scalpel to penetrate into the ventricle without damaging any structures. Extend the incision between the papillary muscles to the base of the mitral valve annulus Minor moderator bands may need to be cut. Inspect the condition of the myocardium and endocardium. Inspect the aortic valve and the mitral valve. Pay particular note to the origins and insertions of the chordae tendineae. A ruptured chorda tendinea may curl up onto the leaflet or papillary muscle (Figure 2.2). If a ventricular septal defect is present it will usually be just below the right coronary cusp of the aortic valve, right at the top of the septum.
- Once the chordae have been inspected, divide the caudal mitral leaflet between the chordae from the right and left papillary muscles, leaving the chordae intact. This allows the mitral annulus to be laid out for close inspection of the valve.