Page 570 - The Veterinary Laboratory and Field Manual 3rd Edition

Necropsy guidelines 507

• Endocardium: The inner surface of the heart WEIGHInG tHE HEart
should be diffusely glistening and translucent • Once the heart has been thoroughly exam-
with the myocardium visible underneath. ined it can be excised from the pluck by
Post-mortem clotted blood should be dif- incising the aorta and pulmonic artery just
ferentiated from significant pre-mortem above the pulmonic and aortic valves and cut-
thrombosis. Post-mortem clots can easily be ting through the atria.
removed from the heart leaving the endo- • Gently rinse any clotted blood from the
cardium intact. Thrombosis occurs when lumen and weigh the heart whole.
the endocardium is damaged and so will be • Values for normal heart weights by species
adherent and leave a defect when removed. are published, but a good rule of thumb is
• Great vessels: The aorta and pulmonic artery that the heart should be between 0.5–1% of
are thick walled elastic vessels. Walls should body weight.
be homogenously tan-white with consider- • In cats, any heart > 17 g is considered
able elasticity. enlarged.
• Increased heart weight is indicative of myo-
• Aberrant vessels: Persistence of the ductus cardial hypertrophy and should be noted.
arteriosus, the embryological vessel which
allows blood to bypass the foetal lung in SaMPLInG
utero is the most common aberrant vascu- Formalin:
lar anomaly. In animals, greater than a few
hours old (one week on equine neonate) • A 0.5 cm thick transverse section comprising
the ductus should be closed and after this interventricular septum and the root of the
gradually fibroses to form the ligamentum left and right ventricles (T-piece section).
arteriosum. In young animals check that • A 0.5 cm thick section of the papillary muscle
no communication exists between the of the left ventricle.
aorta and pulmonic artery just distal to • A longitudinal section through the right
the semilunar valves. ventricular free wall encompassing a part of
atrioventricular valve.
SEPtaL dEFEctS
• Atrial septal defect: arises from failure of the Fresh-fixed:
foramen ovale to close post-natally. The fora-
men ovale allows communication between • A larger piece of ventricle for bacterial cul-
the atria. Atrial septal defect will be found ture/ancillary testing.
in the caudal part of the interatrial septum.
• Ventricular septal defect: This lesion occurs as
a result of failure of the endocardial cushion 13 Examining the liver
to completely fuse. These are embryological
structures which form the interventricular • Knowledge of the liver anatomy of the species
septum. Septal defects are most commonly under examination is imperative to com-
seen high in the interventricular septum pletely examine the liver.
adjacent to the septal leaflet of the mitral • The liver should be diffusely dark red/orange,
valve. soft to firm with sharp caudal borders. Large
blood vessels enter at the hilus and arborize
into the periphery.

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