Heart defects & abnormalities

Question 1

Common congenital heart defect in dogs & cats (& sheep, cattle & horses)…?

Answer 1

ventricular septal defect (VSD)

Question 2

Characteristics of ventricular septal defect (VSD)…?

Answer 2

Hole in the heart
most common congenital heart defects in sheep, cattle, horses
separation of left & right side of heart is formed by 3 parts of embryonic heart (muscular portion, downward growth of conotruncal ridges, membraneous portion of septum) - VSD can be related to any of these parts
most commonly - involve membraneous septum & muscular septum (usually farm animals - high in septum)

Question 3

Classification of VSD…? What are the 4 classes…?

Answer 3

according to anatomical location
remember PIMS
PERIMEMBRANOUS - most common ~80% humans (membranous part of ventricular septum)
INLET - located posterior & inferior to perimembranous portion 5-8% all human VSD
MUSCULAR - according to location in muscular septum (CENTRAL, APICAL, MULTIPLE - ‘Swiss cheese’) 5-20% all human VSD
SUBPULMONARY - just below pulmonary valve 5-7% all human VSD

Question 4

What are the effects of VSD…?

Answer 4

detrimental effects seen only post-natally
dev. foetus -> left & ventricular pressure equal with little flow across defect
after birth -> pulmonary vascular resistance decreases -> pressure in right heart also decreases -> shunt of blood from left -> right side thru VSD -> increased pressure R-ventricle -> R-ventricular hypertrophy -> increased pulmonary hypertension -> eccentric & concentric L-ventricular hypertrophy -> eventually R-ventricular hypertrophy -> blood shunt from R to L -> systemic hypoxia from flooding systemic circulation with venous blood

Question 5

Clinical signs of VSD - livestock…?

Answer 5

Loud, blowing pansystolic murmur audible over both sides o fchest
Most intense over L 4th intercostal & R 3rd intercostal space (more intense on R than L)

Question 6

Prognosis of VSD - livestock…?

Answer 6

determined by magnitude of shunt & degree of resistance to flow from R ventricle as determined by pulmonary vascular resistance
Large defects -> large amount of blood shunted -> animals may die at birth or show clinical signs weeks - months of age
no practical correction in largies