Features of the Cardiovascular System in Children

Functional and Extracardiac Murmurs

Children often present with functional murmurs that are not associated with organic lesions of the valvular apparatus. Based on their development mechanism, they are divided into four main groups:

• Hemodynamic (dynamic): occur due to hyperkinetic circulation (increased blood flow velocity) against the background of fever, stress, neurosis, or thyrotoxicosis. This also includes anemic murmurs caused by decreased blood viscosity combined with tachycardia.
• Musculoskeletal: a consequence of autonomic dysfunction syndrome or myocardial dystrophy. Impaired tone of the papillary muscles leads to incomplete valve closure and relative regurgitation.
• Growth heterochrony murmurs: transient in nature. They are associated with uneven, asynchronous enlargement of the heart chambers, great vessels, and chordae, which temporarily alters the resonance properties of tissues.
• Murmurs in MARS (minor cardiac structural anomalies): caused by false chordae, their atypical attachment, or specific features of the papillary muscles with completely normal hemodynamics.

During auscultation, it is important to differentiate cardiac murmurs from extracardiac ones. For example, a pericardial friction rub has a clear localization and intensifies when pressure is applied to the chest with the stethoscope. At the same time, a pleuropericardial murmur is heard along the left border of relative cardiac dullness, reaches its maximum during inspiration, and completely disappears during apnea.

Auscultation of Great Vessels: In a healthy child, two sounds are heard only over the subclavian and carotid arteries. Over the femoral artery, a single first heart sound ($S_1$) may be inconsistently detected. The remaining peripheral vessels normally remain "silent".

Age-related ECG Evolution and Extrasystoles

A child's electrocardiogram is constantly changing. This is due to changes in the anatomical position of the heart in the thoracic cavity, age-related heart rate dynamics, and the gradual shift in muscle mass balance from the right ventricle to the left.

Key Differences in Pediatric ECG:

1. Shortened time intervals and waves due to a higher pulse conduction velocity through the myocardium.
2. Pronounced parameter lability directly dependent on age and current heart rate.
3. Presence of phenomena normal for children: sinus respiratory arrhythmia and isolated incomplete right bundle branch block.

When detecting extrasystoles, the primary task is to determine their nature. Functional extrasystoles most frequently debut in the prepubertal and pubertal periods, and are of supraventricular or right ventricular origin. Their main criterion of benignity is inconsistency, as well as a decrease or complete disappearance during physical exertion and transition to orthostasis.

To rule out an organic substrate, an expanded examination is used: Holter monitoring (assessment of the circadian dependence of arrhythmia), stress tests (treadmill, bicycle ergometry), and echocardiography (EchoCG). Since arrhythmias often have an extracardiac genesis, assessment of the neurological status and consultations with related specialists (neurologist, endocrinologist, ENT specialist) are indicated.

Acute Carditis in Children

Acute carditis can occur at any age, but children of the first three years of life are most vulnerable. The disease manifests against the background of an ongoing infection or shortly after it. Coxsackie viruses pose a particular danger, capable of causing severe combined lesions of the heart and central nervous system (manifested by seizures, pronounced cyanosis, and dyspnea).

Clinical Presentation develops gradually and includes:

• Nonspecific symptoms: lethargy, pallor, nausea, vomiting, abdominal pain, encephalitic reactions.
• Respiratory syndrome: obsessive cough that intensifies with changes in body position, attacks of cyanosis.
• Left ventricular failure: progressive tachycardia, dyspnea, moist congestive rales in the lungs.

Objective examination reveals a weakened apex beat, low-amplitude pulse, and cardiomegaly (mainly due to leftward border expansion). Auscultation reveals muffled heart sounds (especially the first sound), and a gallop rhythm is possible. An important diagnostic sign is the absence of a systolic murmur at the onset of the disease, while its appearance indicates the development of mitral regurgitation.

Instrumental diagnostics:

• Radiography: cardiomegaly, venous congestion in the pulmonary circulation, decreased amplitude of systolo-diastolic fluctuations, and occasionally thymomegaly.
• ECG: decreased voltage of the QRS complex, signs of ventricular overload, impaired repolarization processes (ST segment displacement, flattened or inverted T wave up to infarct-like changes), various blocks and arrhythmias.
• Echocardiography: dilatation of the left atrium and right ventricle, increased left ventricular dimensions, wall hypokinesia, a clinically significant drop in the ejection fraction, and the presence of pericardial effusion.

Class and exam questions

What else to study on this topic

• Assessment of autonomic regulation using cardiointervalography.
• Pharmacological tests in pediatric cardiology (atropine, propranolol, isoprenaline).
• The role of neurophysiological studies (EEG, EchoEEG, REG) in rhythm disturbances.
• Specifics of combined myocardial and central nervous system lesions in Coxsackie virus infection.
• Radiological signs of carditis: venous congestion and thymomegaly.

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.