The place of pathology in the structure of rhythm disorders
Rhythm and conduction disorders are based on the instability of the myocardium and its conduction system. This is inevitably accompanied by the depletion of the heart's functional reserves and a failure in sympathoadrenal regulation. Globally, all such pathologies are divided into three branches depending on the mechanism of development.
- Disorders of automatism. They can be nomotopic (the source of the impulse remains the sinus node: sinus tachycardia, bradycardia, or arrhythmia) and heterotopic (ectopic foci arise: extrasystole, paroxysmal tachycardias, atrial fibrillation).
- Conduction disorders (blocks). It is to this group that intraatrial block belongs. Depending on the anatomical level of damage, sinoatrial, atrioventricular (AV block), and intraventricular blocks are also distinguished.
- Combined arrhythmias. Include associated disorders, such as sick sinus syndrome (SSS) and ventricular pre-excitation syndromes.
Diagnostic significance in inflammatory diseases
The detection of intraatrial block plays a critically important role in the differential diagnosis of cardiac pathology. In particular, this type of conduction disorder acts as a key criterion in distinguishing acute isolated myocarditis from acute pericarditis (dry and effusive).
Various cardiac arrhythmias, as well as intraatrial and intraventricular blocks detected on ECG, are specific for myocarditis. At the same time, such conduction disorders are atypical for isolated pericarditis. It is worth noting that the specificity of the rheumatic process lies in the combined involvement of the heart membranes, which is why in practice clinicians most often diagnose «myopericarditis».
Clinical presentation and age-related features
The symptomatology of rhythm and conduction disorders has pronounced specific features in pediatric patients. Unlike adults, the pathology in children is often characterized by a latent course. About 40% of cases become an absolute incidental finding during routine ECG screening or during a planned examination after suffering an acute respiratory viral infection (ARVI). Children much less frequently complain of heart palpitations or «skipping beats», even in the presence of severe forms.
The situation changes in the prepubertal and pubertal periods. The clinical picture acquires a rich emotional coloring due to the addition of psychovegetative disorders. Patients complain of chest pain (cardialgia), increased excitability, sleep disorders (insomnia), and weather sensitivity. If the block becomes hemodynamically significant and leads to a decrease in cerebral blood flow, weakness, dizziness, and syncopal states (fainting) occur.
Premorbid background and physical examination
Taking an anamnesis in patients often reveals a burdened premorbid background: an unfavorable course of the perinatal period, a family history of cardiovascular diseases, frequent respiratory and chronic infections. During examination, concomitant stigmata may be found: signs of hypertension-hydrocephalus syndrome, manifestations of connective tissue dysplasia (CTD), and delayed pubertal development.
Physical examination is aimed at identifying rhythm disturbances and assessing the state of the heart:
- Pulse palpation: allows recording acceleration or deceleration, irregular rhythm, skipped beats, weakened pulse wave, and compensatory pauses.
- Assessment of basic parameters: blood pressure measurement, determination of heart dimensions, auscultation (soundness of heart sounds, murmurs) to exclude primary organic pathology.
Instrumental verification
Instrumental verification necessarily includes ECG and EchoCG. ECG is the main method for diagnosing blocks. Echocardiography, in turn, serves as the main visualization method allowing the identification of the structural substrate. For example, in persistent atrial arrhythmias (such as atrial fibrillation), EchoCG often visualizes pronounced left atrial dilatation (indexed volume >40 ml/m²), which serves as the anatomical basis of the pathology, and signs of myocardial hypertrophy and left ventricular diastolic dysfunction may also be detected.
To memorize the classification of conduction disorders by levels, use the rule of impulse movement «from top to bottom»: sinoatrial (sinus node) → intraatrial (through the atria) → atrioventricular (AV node) → intraventricular (bundle branch blocks).
Class and exam questions
Which group of arrhythmias does intraatrial block belong to?
It is classified as a cardiac conduction disorder, along with sinoatrial, atrioventricular, and intraventricular blocks.
How to differentiate isolated myocarditis from pericarditis?
The key tool is the ECG. In myocarditis, rhythm disturbances as well as intraatrial and intraventricular blocks are specific, which is not observed in isolated pericarditis.
How often do rhythm disorders in children occur asymptomatically?
About 40% of cases have a latent course and are an incidental finding during screening ECG studies or upon examination after a suffered ARVI.
What else to study on this topic
- Sick sinus syndrome (SSS) and combined arrhythmias
- Differential diagnosis of acute and chronic pericarditis
- Hemodynamically significant symptoms of rhythm disorders (syncopal states)
- Criteria for heart failure with preserved ejection fraction (HFpEF)
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