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Congenital Heart Defects

Vitium cordis congenitum

For medical students2 min readUpdated 2026-10-10

Congenital heart defects (CHDs) are a heterogeneous group of structural abnormalities of the cardiovascular system originating during embryonic development. The clinical presentation, severity of hemodynamic impairment, and prognosis directly depend on the specific type of defect, the anatomical site of the lesion, and the size of the anatomical opening.

Genetic factorHheritability plays a decisive role in the formation of atrial septal defects.
Viral infectionsMaternal infection during pregnancy acts as a potent teratogenic factor.
HemodynamicsLarge defects provoke a pathological left-to-right shunt and myocardial hypertrophy.
TranspositionUncorrected transposition is entirely incompatible with life without additional shunts.

Etiology: Heredity and Teratogens

The development of vitium cordis congenitum is always viewed as the result of a complex interaction between genetic predispositions and aggressive environmental factors.

First, genetic factors play a monumental role. It is well established that genetic mutations are fundamental in the genesis of atrial septal defects. Interestingly, the genetic influence on ventricular septal defects is less definitive and significantly less pronounced.

Second, the teratogenic impact of external factors on the pregnant woman is of critical importance. The most hazardous triggers include:

Pathophysiology and Clinical Manifestations

The severity of the disease and the prominence of the clinical presentation directly correlate with the size of the anatomical defect.

When defects are small, the condition may remain completely asymptomatic for a long period. Patients report no symptoms, and hemodynamic disturbances are minimal, successfully compensated by the body.

A completely different picture emerges with large defects. In such cases, pronounced circulatory disorders develop. The key pathophysiological mechanism is a massive left-to-right blood shunt. Due to constant volume and pressure overload, compensatory hypertrophy of the myocardium of both ventricles develops. Upon physical examination and auscultation, the physician typically detects a harsh systolic murmur, often accompanied by a palpable thrill on the chest wall.

Atrial Septal Defects

Among all variations of structural compromise of the septum separating the right and left atria, defects localized in the middle and upper sections of this anatomical structure are most frequently encountered in clinical practice.

Transposition of the Great Arteries

This is a severe structural malformation characterized by an abnormal, altered spatial arrangement of the major blood vessels relative to the heart chambers. Generally, two forms of the pathology are distinguished: corrected and uncorrected.

In uncorrected transposition, the great arteries are displaced in such a way that the systemic and pulmonary circulations become completely isolated from one another:

  1. The aorta anatomically arises from the right ventricle. Consequently, it delivers venous, oxygen-depleted blood into the systemic circulation.
  2. The pulmonary artery originates from the left ventricle. It directs arterial (already oxygen-saturated) blood back into the pulmonary circulation, i.e., into the lungs.

Such an anatomical arrangement is incompatible with the newborn's life. Survival is possible exclusively if additional pathways for blood mixing (shunts between the circulatory loops) are present within the heart. Accompanying ventricular or atrial septal defects, or a patent ductus arteriosus, can serve as these life-saving shunts.

Mnemonic

To understand the hemodynamics of uncorrected transposition, imagine two isolated loops: the right ventricle idly pumps dark venous blood through the body, while the left pumps bright red arterial blood through the lungs. Without a "bridge" (shunt defect), the system is doomed.

Frequently asked questions

What forms of transposition of the great arteries exist and what is their anatomical basis?

There are two main forms of transposition of the great arteries: uncorrected and corrected.

  • Uncorrected form — the aorta arises from the right ventricle containing venous blood, and the pulmonary artery originates from the left ventricle with arterial blood.
  • Corrected form (CCTGA) — characterized by atrioventricular and ventriculoarterial discordance. The aorta arises from the right-sided ventricle containing arterial blood, and the pulmonary artery originates from the left-sided ventricle containing venous blood.

The uncorrected form creates a parallel circulation incompatible with life without a shunt, whereas in the corrected form, physiological circulation is maintained.

Which specific maternal viral infections have a proven teratogenic effect on the fetal heart?

Rubella virus has a proven teratogenic effect on the fetal heart. When the mother is infected during the first trimester of pregnancy, this virus causes the classic congenital rubella syndrome, which includes the triad of cataracts, deafness, and congenital heart defects. The most frequent cardiovascular anomalies associated with rubella include:

  • Patent ductus arteriosus — persistence of the ductus arteriosus.
  • Pulmonary stenosis.
  • Ventricular septal defects — the presence of a communication between the ventricles.

Additionally, viral damage in the first trimester is described as causing non-reactive necrosis in the endocardium and subendocardial layers.

What anatomical variants of ventricular septal defects are distinguished based on their localization?

Based on localization, two main anatomical variants of ventricular septal defects are distinguished: perimembranous and muscular.

  • Perimembranous defects — the most frequent location, accounting for about 80% of all cases. Many small defects in this area can close spontaneously.
  • Muscular defects — located in the muscular portion of the septum, which is anatomically divided into three parts:
  • Inlet;
  • Outlet, or subarterial;
  • Midmuscular and apical.

Patient management directly depends on the type and size of the identified defect.

What developmental anomalies comprise the classic tetralogy of Fallot?

The classic tetralogy of Fallot comprises four anatomical components.

  • Ventricular septal defect — usually a large, high septal defect.
  • Dextroposition of the aorta («overriding aorta») — displacement of the aorta to the right, positioning it directly over the septal defect to receive blood from both ventricles.
  • Pulmonary stenosis — narrowing of the pulmonary outflow tract or right ventricular infundibulum.
  • Right ventricular hypertrophy.

This symptom complex is the most common cyanotic ("blue") heart defect and presents with pronounced cyanosis, the degree of which depends on the severity of the pulmonary outflow obstruction.

What is the role of genetics in the development of various cardiac septal defects?

Genetic factors have a primary, decisive role in the formation of atrial septal defects. In contrast, their influence is significantly weaker in ventricular septal defects.

How does the size of the defect affect the clinical presentation of the anomaly?

The size of the defect is the primary determinant of disease severity. Small anomalies may cause no clinical symptoms, whereas large ones lead to pronounced circulatory disorders, hypertrophy of both ventricles, a systolic murmur, and a thrill.

What is the core mechanism of uncorrected transposition of the great arteries?

In this defect, the aorta arises from the right ventricle and delivers venous blood to the body, while the pulmonary artery originates from the left ventricle, returning arterial blood to the lungs. The systemic and pulmonary circulations are completely parallel and isolated.

How is infant survival possible in uncorrected transposition of the great vessels?

Patient survival is only possible if there is additional shunting between the systemic and pulmonary circulations. This blood mixing occurs through accompanying atrial or ventricular septal defects, or via a patent ductus arteriosus.

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