Pathophysiology

The embryonic cardiovascular system is functional by 21 days. Cardiac anomalies can be congenital or acquired, but this system is highly susceptible to abnormalities when exposed to teratogens in early pregnancy. Congenital heart disease (CHD) affects about 1 in 145 babies, but half of these will not require treatment; many will be treated with medication and/or surgery. Congenital heart defects are usually described as cyanotic or acyanotic.

• Acyanotic: left to right shunting will not cause cyanosis because blood flows from the systemic to the pulmonary system.
  
• Cyanotic: right to left shunting results in blood flowing from the right side of the circulation to the systemic circulation (i.e. de-oxygenated blood mixes with oxygenated blood causing cyanosis, even when nursed in 100% oxygen).

Diagnosis

Taking a detailed history is vital: family history (other siblings); prenatal history, any illnesses, medications, complications in pregnancy, labour or delivery; and the baby’s condition since birth in relation to feeding, observations, weight gain and general health.

Cardiac problems can present in four ways: colour change (cyanosis), respiratory distress, collapse or the baby may be asymptomatic.

Genetic syndromes: babies with trisomy 21 (Down’s syndrome) have a higher risk of multiple cardiac defects. Look for unusual features.

Colour: central cyanosis – blue lips, mucous membranes and nail beds. If colour improves with oxygen, the condition is more likely to be respiratory. Heart failure usually results in increasing pallor as the blood pressure falls, peripheries become cold.

Respiratory rate increases, as does effort. Flared nostrils, subcostal and intracostal retractions, grunting and/or wheezing sounds.

Capillary refill time (CRT)