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Pathophysiology · Additional topics

Tachycardia Syndromes

Tachycardia

Tachycardia is an accelerated heart rate resulting from dysfunction in the generation of electrical impulses or the cardiac conduction system. Depending on the level of signal generation, nomotopic and heterotopic (ectopic) forms are distinguished, which often have an asymptomatic course, especially in children.

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Asymptomatic courseIn 40% of cases, arrhythmias in children are detected incidentally during screening or following acute respiratory viral infections (ARVI)
Cause of arrhythmiasExcess catecholamines and active forms of vitamin D
SymptomatologyDizziness and syncopal episodes are possible with decreased cerebral blood flow
ClassificationNomotopic, heterotopic, blocks, and combined rhythm disorders
2 min readFor medical studentsUpdated 10.10.2026
Material prepared by WhiteCoat Pro editorial team based on platform study guidesPending instructor review

Pathogenesis and developmental factors

The development of tachycardia syndromes and other arrhythmias is based on myocardial instability and dysfunction of the cardiac conduction system. A key role is played by a failure in sympathoadrenal regulation and the gradual depletion of the functional reserves of the heart muscle.

Endocrine and metabolic disorders have a significant impact on the heart rhythm. For instance, in hypercatecholanemia (characteristic of pheochromocytoma), an excess of catecholamines causes pronounced cardiovascular reactions, including rhythm disorders, hypertension, and orthostatic collapse. Toxic effects are also possible in hypervitaminosis D: cholecalciferol overdosage provokes hypercalcemia, which in turn causes arrhythmias and seizure disorders.

Classification of rhythm disorders

Depending on the localization of the rhythm source and its mechanism of formation, arrhythmias, including tachycardia, are divided into several groups:

  1. Disorders of automatism (nomotopic arrhythmias).

The impulse source is located in the normal site—the sinoatrial (sinus) node. This group includes sinus tachycardia (acceleration of contractions), as well as sinus bradycardia and arrhythmia.

  1. Ectopic (heterotopic) rhythms.

The function of the pacemaker is assumed by lower-lying (accessory) automatism centers. These include:

  • Accelerated ectopic rhythms.
  • Replacement (escape) slow complexes.
  • Paroxysmal and non-paroxysmal tachycardias.
  • Atrial and ventricular flutter and fibrillation (merger/quivering).
  • Migration of the supraventricular pacemaker.
  1. Combined forms.

They include sick sinus syndrome (SSS), AV dissociation, and ventricular pre-excitation syndromes.

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Clinical presentation in children

Symptoms of rhythm disorders in children have distinct features. A specific premorbid background is characteristic: burdened heredity, frequent infections, signs of connective tissue dysplasia, and an unfavorable perinatal history.

Specific manifestations:

  • Latent course. In 40% of cases, the pathology is detected incidentally (ECG screening).
  • Scarcity of complaints. Children rarely complain of palpitations or skipped heartbeats, even in severe arrhythmias.
  • Age-related features. In the prepubertal and pubertal periods, psycho-vegetative disorders join in: cardialgia, insomnia, excitability, and weather sensitivity.
  • Hemodynamic disturbances. In paroxysmal tachycardias or SSS, cerebral blood flow may decrease, manifesting as weakness, dizziness, and fainting (syncope).

Objectively, pulse palpation reveals accelerated, irregular, or dropped pulse waves. Blood pressure measurement and auscultation are necessary to rule out primary organic pathology.

Class and exam questions

What are nomotopic arrhythmias?

These are rhythm disorders in which the impulse source remains the sinus node (e.g., sinus tachycardia or bradycardia).

How does hypercatecholaminemia affect the heart rhythm?

Excess catecholamines cause persistent rhythm disorders, arterial hypertension, hypertensive crises, and metabolic shifts (hyperglycemia, hyperlipidemia).

How often are arrhythmias in children asymptomatic?

About 40% of cardiac rhythm disorders in childhood are asymptomatic and are discovered incidentally during an ECG examination.

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What else to study on this topic

  • Mechanisms of extrasystole
  • Conduction disorders (blocks)
  • Sick sinus syndrome (SSS)
  • The role of the autonomic nervous system in the genesis of arrhythmias

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