Heart Disease - Screening for Congenital Heart Disease: Implications and Strategies

Article by Prof William Yip Chin Ling

Heart Disease - Screening for Congenital Heart Disease: Implications and Strategies

Prof William Yip Chin Ling

Paediatrician
University of Singapore
Royal Colleges of Physicians of United Kingdom
Royal Colleges of Physicians of London
Academy of Medicine Singapore
Royal College of Physicians of Edinburgh
 
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Why is screening for CHD important?

Congenital heart disease (CHD), with its incidence around 1 per 100 live born, is the most common congenital malformation. Missing CHD has potentially serious consequences, including death, especially in the newborn. Delayed diagnosis may lead to complications like frequent chest infections, cardiac failure, pulmonary hypertension, and Eisenmenger’s syndrome. Failure to thrive and effort intolerance contribute to suboptimal quality of life. Other issues include genetic risk to the next sibling, insurance dispute and law suits.

Why do we fail to diagnose CHD?
If CHD is not suspected or actively looked for, it will be missed. The symptoms and signs may be mild or even absent, especially in the newborn. If appropriate tests like pulse oximetry and echocardiography are not performed, the diagnosis can be missed. Finally if doctors assume no responsibility to screen for CHD, more cases will be missed.

When do we screen for CHD?
The following situations are opportunities for screening for CHD: newborn examination, pre-adoption checkup, postnatal follow-up, routine medical visits, school health screening, pre-enlistment national service, pre-sport participation, specific consultations for suspected cardiac condition (including sudden death of family member). Problems of screening for CHD in the newborn & strategy Critical cyanotic CHD may be clinically silent. Visual diagnosis of cyanosis is unreliable. Ductal dependent CHD, like pulmonary atresia and aortic interruption may be missed for a few days. Non ductal dependent cyanotic lesions, like total anomalous pulmonary venous return, may even present days or weeks later. Hence pulse oximetry is proposed recently as a screening test. A reading of at least 95% with a right upper and lower limb reading difference of less than 3% is considered normal. Any persistent deviation warrants a cardiac consultation.

An estimated 0.1% of all live born have critical CHDs which include: hypoplastic left heart syndrome, pulmonary atresia, severe tetralogy of Fallot, total anomalous pulmonary venous return, transposition of great arteries, tricuspid atresia, and truncus arteriosus. The incidence of these 7 conditions is estimated to be about 11.6 per 10,000 newborns. Infants with these conditions who are diagnosed late have higher mortality and poorer surgical outcomes.

Who is at risk of CHD?
Important clues for cardiac referral are: cyanosis, poor effort tolerance, family history of sudden death and cardiomyopathy, exertional chest pain, syncope (especially during exercise), palpitation (especially sustained or exercise-induced), cardiac murmur, abnormal pulse, heart sound and click, Marfan syndrome & suspected Marfan syndrome, and abnormal ECG and CXR.

What is the significance of cardiac murmur detected during screening?
To differentiate between pathological from innocent murmur is not always easy. Some patients with “innocent sounding” murmur may have very serious lesions. Indeed dangerous cardiac lesions, like aberrant left coronary artery from pulmonary artery, idiopathic cardiomyopathy, Ebstein anomaly, coarctation of aorta, total anomalous pulmonary venous drainage, and Loeys-Dietz syndrome, may have no murmur in children.

As a guide, when a cardiac murmur is heard in the first 24 hours of life, there is 1:12 risk of CHD. At 6 months and 12 months, the risk is 1:7 and 1:50, respectively. When the cardiac murmur is detected at birth and still present at 12 months, the risk is roughly 3:5.

How do we screen for and diagnose CHD?
A detailed history and a thorough clinical examination are of utmost importance. ECG may reveal rate, rhythm and electrical axis abnormalities, conduction anomalies, volume and pressure overload signs in the atria and ventricles and signs of ischaemia. CXR is not very useful for specific diagnosis of CHD, but may reveal associated lung pathology. Echocardiography is the first modality of choice for diagnostic and functional assessment. Additional tests may include: Holter monitoring, cardiac catheterization, cardiopulmonary exercise stress test, CT angiography and MR imaging.

Summary
CHD is the most common congenital malformation. Missing it has dire consequences. Screening for CHD is mandatory in the newborn and detection of CHD should be in the mind of all physicians who treat children as well as adult.