Etiology and pathogenesis
The anatomical basis of the defect is the persistence of fetal circulatory pathways, hypoplasia or hypertrophy of the ventricles, as well as anomalies of the valve apparatus. It is practically impossible to establish a single exact cause. Almost 90% of cases are explained by a polygenic-multifactorial impact—the overlap of exogenous triggers on genetic predisposition.
Key factors disrupting normal embryogenesis include:
- Genetic disorders: quantitative and structural chromosomal anomalies (trisomies of chromosomes 13, 18, 21; Down syndrome, Turner syndrome).
- Environment and infections: maternal viral illnesses during pregnancy, radiation exposure.
- Toxins and medications: parental harmful habits, use of teratogenic drugs (lithium preparations, warfarin, anticonvulsants).
- Parental status: maternal age over 35 years, chronic endocrine or autoimmune pathologies.
Classification and hemodynamic features
In clinical practice, defects are grouped by two criteria: the nature of blood flow changes (overload or depletion) and the presence of cyanosis ("blue" and "pale" CHD).
- With pulmonary circulation overload (up to 80% of all CHDs). Blood is shunted from left to right, overloading the right chambers of the heart. This leads to their hypertrophy and a high risk of bronchopulmonary complications. This group includes septal defects (ASD, VSD), patent ductus arteriosus (ductus arteriosus) — these are "pale" forms. Transposition of the great vessels also belongs to this group, but presents with cyanosis.
- With diminished pulmonary blood flow. Occurs due to obstruction in the pathway to the pulmonary artery. Blood flow in the lungs is reduced, causing persistent hypoxemia and cyanosis (e.g., Tetralogy of Fallot).
- With diminished systemic blood flow. A barrier arises for blood ejection into the systemic circulation (coarctation of the aorta, aortic stenosis). They are characterized by regional hypertension: high pressure in the upper extremities and inadequate blood supply to the lower half of the body. Such defects typically manifest at school age (8–12 years).
Clinical presentation and diagnostics
Due to fetal compensatory mechanisms, defects may be asymptomatic in the first weeks of life, but then hemodynamic disorders go through three phases: primary adaptation, relative compensation, and the terminal phase.
Symptoms are grouped into four leading syndromes: cardiac (murmurs, cardiomegaly), heart failure (hypoxic-cyanotic spells), chronic hypoxia (developmental delay, clubbing of fingers), and respiratory disorders.
Confirmation of the diagnosis is based on an instrumental triad:
- Echocardiography (EchoCG): the key method that directly demonstrates the defect and abnormal blood shunting (Doppler sonography).
- Electrocardiography (ECG): reflects overload of the right (in "blue" defects) or left (in "pale" defects) chambers of the heart.
- Radiography: evaluates the state of the pulmonary vascular pattern and the configuration of the cardiac silhouette (e.g., the "wooden shoe" shape in Tetralogy of Fallot).
Principles of CHD treatment
The definitive method of treatment is surgical correction. Modern cardiac surgery aims for the earliest possible interventions. Operations can be either traditional (open-heart surgery with cardiopulmonary bypass) or minimally invasive endovascular procedures (placement of occluders, stenting).
Conservative treatment is supportive. It includes a sparing regimen, measured activity, and pharmacological support (metabolic drugs, diuretics, beta-blockers for spell prevention). An exception is an isolated patent ductus arteriosus — it can be closed medically using prostaglandin synthesis inhibitors (non-steroidal anti-inflammatory drugs) that prevent ductal wall spasm and promote its obliteration.
To remember the hemodynamics of aortic coarctation, imagine a "waterfall": high pressure accumulates before the narrowing (head and arms), while below the narrowing (legs) blood flow is insufficient, resulting in hypotension.
Class and exam questions
What early signs can suggest CHD in a newborn?
First and foremost, these include transient or persistent cyanosis, tachypnea (shortness of breath), pallor, poor weight gain, edema, and the detection of a harsh systolic murmur radiating to the back.
What is a hypoxic-cyanotic spell?
This is a severe condition typical of young children with "blue" defects. It occurs due to a sudden spasm of the right ventricular outflow tract, leading to acute cerebral ischemia, worsening cyanosis, and agitation.
Is surgery always necessary for congenital heart disease?
No, not always. Some defects, such as small muscular ventricular septal defects (Tolochinov-Roguet disease) or small atrial septal defects, are capable of spontaneous closure.
What else to study on this topic
- Anatomical features of fetal circulation
- Differential diagnosis of CHD and minor heart anomalies (MHA)
- Radiological cardiac silhouettes in various CHDs
- Contraindications to cardiac glycosides in pediatric cardiology
- Mechanism of action of prostaglandin inhibitors in patent ductus arteriosus
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Other topics in "Chapter 6. Diseases of the Cardiovascular System"
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