5.4 Investigative aids to diagnosis of CHD
Until recently, definitive diagnosis of CHD depended on the use of releatively difficult, invasive techniques such as catherterisation for angiography and measurement of chanber pressures and oxygen tension. Now, diagnosis is usually made on the basis of two-dimensional echocardiography (2DE). Doppler echo-cardiography (DE) and contrast echocardiography are also useful techniques in the diagnosis of CHD. DE is particularly useful for estimating pressure gradients, which may be directly related to the haemodynamic significance of a defect and the prognosis for that individual.
Echocardiography may also be useful to differentiate acquired heart disease from CHD. The distinction between acquired and congenital disease may affect the prognosis, influence future breeding programmes and may also be important in insured animals because many policies have an exclusion clause covering congenital disease. Acquired cardiac disease may be severe even in young aniEndocarditis has an increased incidence in foals and may affect the atrioventricular (AV) valves more often in neonates than in adults. Ruptured chordae tendineae are also reported in young animals and may result in conheart failure (CHF).
Other acquired diseases, particularly respiratory disease, may result in clinical signs which are similar to those with CHD. For example, a foal with tachypnoea and tachycardia may have heart disease or may have pneumonia. A thorough investigation of all body systems is essential so that the relative significance of different problems can be evaluated.
The effect of a congenital lesion on future use as a breeding animal, resale value and insurance certification should also be considered when advising owners.