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Violation of the rhythm and conduction of the heart: symptoms and diagnosis
Last reviewed: 23.04.2024
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Symptoms of rhythm and conduction of the heart
Arrhythmias and conduction abnormalities may occur asymptomatically or cause a palpitations, symptoms of hemodynamic disorders (eg, dyspnea, chest discomfort, pre-syncope or fainting) or cardiac arrest. Sometimes polyuria occurs due to the release of the atrial natriuretic peptide during prolonged supraventricular tachycardia (CBT).
Palpation of the pulse and auscultation of the heart can determine the frequency of the ventricular rhythm and evaluate the regularity (or irregularity). A study of the pulse on the jugular veins can help in the diagnosis of AB-blockade or atrial tachyarrhythmias. For example, with complete AV block, the atria are periodically contracted during the complete closure of the atrioventricular valves, which leads to the appearance of a large wave a (gun wave) in the venous jugular pulse. Other physical findings in arrhythmias are rare.
Diagnosis of rhythm disturbance and conduction of the heart
With an anamnesis and an objective examination, you can identify arrhythmia and its possible causes, but for accurate diagnosis you need an ECG in 12 leads or (more rarely) a heart rate record that is used more often at the time of symptoms to identify their relationship to rhythm disturbances.
ECG data are evaluated in a complex manner. Measure intervals and detect even minimal disturbances in rhythm. The key diagnostic moment is the frequency of atrial excitation, the frequency and regularity of the ventricular complexes and the relationship between them. Irregular excitation signals are classified as regularly-irregular or irregular (incorrect). The irregularly irregular rhythm is predominantly regular cardiac contractions, sometimes interrupted by irregular (eg, premature contractions), or other irregular rhythm patterns (including recurring associated abbreviations).
The truncated complex (<0.12 s) indicates a supraventricular rhythm (above the bifurcation of the bundle of His). A wide QRS complex (> 0.12 s) is a sign of ventricular (below the bundle bifurcation) or supraventricular rhythm with simultaneous disruption of premature ventricular excitation in Wolff-Parkinson-White syndrome (WPW syndrome).
Bradyarrhythmias
ECG diagnosis of bradyarrhythmias depends on the presence or absence of the tooth, its characteristics and the connection of the tooth with the complex. Bradyarrhythmia without the connection of the tooth with the QRS complex indicates AV-dissociation, as a result, the rhythm may be nodal (in narrow parasitic complexes) or ventricular (with wide QRS complexes ) .
Regularity in a ratio of 1: 1 with prongs indicates the absence of AV blockade. If the prongs precede the QRS complex, this is a sign of sinus bradycardia (if the teeth are normal) or stopping the sinus node with a replacement ventricular rhythm and retrograde delivery of the pulse to the atria. In this case the complex is extended.
If the rhythm is incorrect, the number of teeth usually does not correspond to the number of complexes. Some of the teeth lead to the appearance of a complex behind them, and some do not (a sign of the AV blockade of the 2nd degree). Irregularity in a ratio of 1: 1 with the preceding teeth usually indicates a sinus arrhythmia with a gradual increase and decrease in the frequency of the sinus node (if the teeth are normal).
Pauses in a rhythm that at other times have the correct character can occur due to blockage of the teeth (an abnormal tooth can appear immediately after the preceding T wave or disrupt the normal shape of the latter), stop the sinus node or blockade the output of the pulse from it, and also the AV blockade II degree.
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Tachyarrhythmias
Tachyarrhythmias can be divided into four groups: according to the principle of regularity and irregularity, as well as a wide and narrow complex
Tachyarrhythmias with a narrow irregular complex include fibrillation (AF) and atrial flutter or a true atrial tachycardia with variable AB-carrying and polytopic atrial tachycardia. Differential diagnosis is based on the evaluation of ECG-pulses of the atria, which are best seen in the long intervals between the complexes. The atrial pulses, which appear continuous on the electro-caryogram, irregular in time and having different shapes, and also have a very high frequency (> 300 per minute) without certain R teeth, suggest atrial fibrillation (i.e., atrial fibrillation). Certain teeth that differ from contraction to contraction and have at least three different forms indicate a polytopic atrial tachycardia. Regular, definite, uniform in form impulses, not interrupted by isoelectric gaps, is a sign of atrial flutter.
Irregular tachyarrhythmias with a wide ventricular complex include the four types of atrial arrhythmias described above, combined with the blockade of any bundle branch or ventricular pre-excitation, and polymorphic ventricular tachycardia (VT). Differential diagnostics is performed on the ECG pulses of the atria and the presence of a very frequent rhythm (> 250 per minute) at the polymorphic VT.
Tachycardia with regular narrow QRS complexes includes sinus tachycardia, atrial flutter or a true atrial tachycardia with a correct permanent presentation to the ventricles, as well as paroxysmal CBT (CBT from the AV compound with the re-entry mechanism, ortodromic reciprocal AV tachycardia in the presence of an additional AV pathway and SVT from the sinus node with the syndrome reentry). Vagal assays or pharmacological blockade of the AV node allow differentiation between these tachycardias. When these procedures are performed, the sinus tachycardia does not stop, but the heart rate decreases or the AV blockade develops, which makes it possible to identify normal R waves. Atrial flutter and true atrial tachycardia usually do not change, but the AV blockade reveals atrial flutter waves or altered R wave. The most frequent forms paroxysmal CBT (AB-re-entry and orthodromic reciprocal tachycardia) should disappear with AB-blockade.
Regular tachyarrhythmias with a wide ventricular complex include the same tachyarrhythmias, which can be represented by a narrow complex both with the blockade of any leg of the fasciculus, and with premature ventricular excitation, and monomorphic VT. Vagal tests help to identify the differences between them. If there is a difficulty in differential diagnosis, the rhythm should be regarded as VT, since some drugs used in the treatment of SVT may worsen the clinical course with VT; the reverse approach is erroneous.