Cyanotic congenital heart diseases (CHD) such as tetralogy or pentalogy of Fallot, L- or D- transposition of great arteries, total anomalous pulmonary venous connection, truncus arteriosus or tricuspid valve abnormalities are severe, potentially life-threatening conditions. Clinical presentation may differ, as newborns may be discharged from the hospital before they develop symptoms, thus delaying diagnosis.
Parents should be alarmed by unsatisfactory ponderal gain, cyanosis (permanent or due to the effort of feeding), profuse perspiration, apathy, fast or difficult breathing, persistent wheezing or coughing in the supine position. Infants may sleep more than normal and have diminished activity in general .
A particular problem is represented by tet spells. These appear in children with cyanotic CHD such as tetralogy of Fallot, severe pulmonary stenosis or atresia or other decreased pulmonary blood flow malformations. Tet spells consist of inconsolable crying with increasing cyanosis and hyperpnoea and may lead to the loss of consciousness and even death. Older children instinctively adopt a squatting position, thus increasing systemic vascular resistance and blood flow to the lungs .
Blood saturation may differ in different regions of the body, so upper extremities may be more pink than lower extremities (differential cyanosis, found in patent ductus arteriosus with pulmonary hypertension or preductal coarctation of the aorta associated with patent ductus arteriosus ) or more bluish than the lower extremities (reversed differential cyanosis, found in transposition of the great arteries with patent ductus arteriosus and elevated pulmonary vascular resistance or in TGA with PDA and preductal aortic interruption or coarctation .
Presentation of children with ductal-dependent CHD dramatically changes as the ductus arteriosus changes. Thus, symptoms depend on whether the pulmonary circulation or the systemic circulation depend on the patency of the ductus arteriosus.
The clinician should take a short history about the presence of CHD or sudden death in other family members. Inspection and palpation may reveal a hyperactive precordium, dextrocardia, heart enlargement or thrill. The heart impulse might be displaced (if the right ventricle is overloaded) or prominent (when the left ventricle has a pressure or volume overload). Auscultation findings may include tachycardic or bradycardic sounds;
heart murmurs- their location, intensity, musical qualities and lack of variability with respiratory movements may suggest the underlying defect; paradoxically or fixed split, single or inaudible sounds: S2 may be single in conditions associated with pulmonary hypertension or great vessels valve abnormalities: aortic or pulmonary atresia or severe stenosis or truncus arteriosus; abnormal supplementary heart sounds: early systolic (aortic or pulmonary stenosis) or mid systolic clicks (mitral valve prolapse, Ebstein’s anomaly), atrial or ventricular gallop may also occur. Pericardial friction rubs suggest pericarditis, while murmurs may be absent in the presence of severe ventricular dysfunction or pulmonary hypertension   .
Liver enlargement should also be evaluated, keeping in mind that the inferior edge is normally felt 1-3 cm below the rib cage in newborns. The symmetry and amplitude of pulses should be routinely observed, in order not to miss associated abnormalities such as coarctation of the aorta or interrupted aortic arch.
Numerous professional cardiology associations recommend routine pulse oximetry newborn screening. The sensor should be placed on the right hand (to measure preductal saturation) or the foot (to measure postductal saturation)      .
Thoracic radiography should be used to evaluate the location of the heart, vascular pulmonary markings, and cardiac silhouette: "boot" shape in tetralogy of Fallot, "egg-on-string" in transposition of great arteries, or "snowman" in total anomalous pulmonary venous return.
Echocardiography is performed in patients with signs of cardiogenic shock or abnormal findings on the ECG or thoracic radiography. Echocardiography is able to accurately measure cavities and walls, pressure gradients and velocities, and describe defects or exclude CHD as the cause of cyanosis.
If doubt arises from echocardiographic studies or if symptoms do not match echocardiographic data, cardiac computer tomography and magnetic resonance might be useful. However, these are not available in all centers, especially in underdeveloped countries. In this situation and in cases where it is necessary to measure pulmonary vascular resistance to determine if surgery is appropriate, cardiac catheterization is indicated. However, given that this method involves radiation exposure, it should only be used in cases where cardiac anatomy or function is not properly defined by less invasive methods, such as low flow lesions that make pulmonary resistance calculation difficult .