t ductus arteriosus (discussed later). In the mature baby the major causes of heart failure are large left-to-right shunts, obstructive left-sided lesions, myocardial disease and arrhythmias. Another clinical manifestation of CHD is cyanosis (blue-ish skin colour) which is normally due to a shunt associated with: low pulmonary blood flow (only a little oxygenated blood circulating), transposition streaming or intracardiac mixing of desaturated and saturated blood (so that some desaturated blood reaches the aorta). Cyanotic CHD is also nearly always associated with the development of digital clubbing (see appendix two – diagram one). Babies with CHD will finally often fail to thrive normally. In older children, growth and physical development may be impaired, unlike mental development, which is usually normal.
             One of the commonest forms of CHD is tetralogy of fallot (see appendix two – diagram two), which makes up 24% of cases of heart disease (see appendix two - table one). This particular lesion occurs equally in males and females. It consists of four defects that occur in the early stages of development of the embryo. The tetralogy consists of subvalvular pulmonary outflow obstruction, ventricular septal defect, overriding of the aorta and right ventricular hypertrophy/excess growth (see appendix two – diagram three). A right-sided aortic arch occurs in 25% of patients. Depending largely on the severity of right ventricular outflow obstruction, blood shunts from the right to the left across the ventricular septal defect (VSD). In cases of severe outflow obstruction, the shunt is large and resultant cyanosis is severe. A patient with tetralogy of fallot has diminished blood flow to the lungs and increased blood flow to the body.
             Tetralogy of fallot is, indeed, the most common cardiac cause of cyanosis in the first year of life. Unprovoked attacks of intense cyanosis may occur, leading to convulsions and death. In less seve...