Diagnosis of Congenital heart diseases
Congenital heart diseases (CHD) defined as a structural anomaly of the heart and great vessels. Popularly, described as having a “hole in the heart”, they are the most common congenital anomaly. They are also the most common cause of death from congenital defects with many causing disability in children. It is important to note that not all CHDs are functionally disabling that is, not all will cause symptoms.
Medical practice has evolved particularly in the aspects of both palliative and corrective cardiac surgeries. These advances have improved the quality of life and life expectancy for children and adults with congenital heart diseases.
Before a decision is made for definitive/final diagnosis, a proper evaluation to identify the primary anomaly, as well as the complications from them through accurate diagnosis is the major decisive rate-limiting step. As an overall rule, making the right diagnosis cannot be overemphasized.
Current existing screening tools fail to identify up to 50% of children with CHD before discharge from the hospital, although the Pulse oximetry screening has been well studied and seems a promising screening tool.
Diagnosis of congenital heart diseases can be
- Before birth
- After birth
Diagnosis before birth entails a critical look at the fetal anomaly scan which is done at about 18-22 weeks. Ultrasound scan done at this age can detect, if present, structural cardiac defects and abnormal blood flow through the heart. Also, other congenital anomalies closely associated with congenital heart diseases can be identified.
At birth, screening for congenital heart anomalies can identify those with the disease before they manifest with complications. The combined use of pulse oximetry with fetal anomaly screening and routine newborn examination could detect the majority of critical CHDs in asymptomatic infants. A detailed history and thorough clinical examination are of paramount significance in suspected CHD in infants. A high index of suspicion with a systematic approach is vital for the timely diagnosis and appropriate management.
Common evaluation/investigations of diagnostic value to congenital heart diseases include;
- Clinical evaluation/test of cardiac functions
- Pulse oximetry
- Chest Xray
- Cardiac Magnetic resonance/Computed tomography with Angiography
- Cardiac Catheterisation
- Other ancillary investigations
The initial evaluation where CHD is suspected involves the systematic approach a doctor or paediatric cardiologist assesses newborns for the presence or absence of anomalies. He/she identifies the presence or absence of bluish discolouration of the mouth, lips, tongue or the hands/feet commonly called cyanosis. If cyanosis and or other symptoms of CHD are present, it prompts the need for further evaluation. Sometimes, a physician may hear an abnormal heart sound referred to as a murmur. This may also be a reason for further investigations. Four limb blood pressure measurements are of important but limited diagnostic value.
As the clinical presentation can mimic or overlap with other common conditions in infancy (sepsis, respiratory or metabolic condition) further investigations are required.
A general physical examination of the baby should include pulse oximetry. This test measures the level of Oxygen in peripheral blood using a finger or toe for the test. This screening, endorsed by the American Association of Paediatrics and American Heart Association, is best done by 24 and 48 hr of life and before the discharge of newborns without any symptoms. A pulse oximetry saturation <90% in the right hand or either foot requires urgent echocardiography. A pulse oximetry saturation <95% in either location or a saturation difference >3% between the right hand and either foot is considered a positive test and should be repeated in an hour; if positive again, it should be repeated in another hour. If it remains positive, echocardiography is indicated.
A Chest Xray is a common investigation which makes use of radiation to outline the size and shape of the heart. It may show evidence of increased, normal, or decreased lung vascular markings. This is representative of the amount of blood flowing through the lungs due to the CHD and its shunting effects. Increased blood flow in the lungs can predict the possibility of recurrent chest infections.
An electrocardiogram measures electrical impulses generated in the heart, that controls the contraction of the heart. Cardiac electrocardiogram helps in only few diagnoses during infancy.
Echocardiography remains the gold standard investigation but is not always available. When used with Doppler(a measure of flow), it provides real-time images of the heart chambers, the movement of the valves and presence of any structural anomalies e.g hole in the heart. It can also assess the flow of blood through the heart chambers and valves.
Cardiac Magnetic resonance/Computed tomography with Angiography
It shows the spatial arrangement and overall relationship between the vessels and heart. Heart chamber sizes can also be evaluated as well as abnormal connections to and from the heart.
It is an invasive investigation to assess the different aspects of the heart’s structure and function by passing a tube (catheter) through large blood vessels in the groin which are then threaded till they get to the baby’s heart.
Other additional investigations
These include baseline investigations such as Full blood count, C reactive protein, test of kidney functions (Electrolytes, Urea, Creatinine), Test of liver functions, clotting profiles.
Investigations needed for the diagnosis of Congenital heart diseases are prerequisite in the identification, treatment and supporting outcomes of these precious children. One could mean the world to their parents, community and the world at large.