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Heart rhythm and conduction disorder: symptoms and diagnosis
Last reviewed: 04.07.2025
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Symptoms of cardiac rhythm and conduction disorders
Arrhythmias and conduction disturbances may be asymptomatic or cause palpitations, hemodynamic symptoms (eg, dyspnea, chest discomfort, presyncope or syncope), or cardiac arrest. Polyuria occasionally occurs due to release of atrial natriuretic peptide during sustained supraventricular tachycardia (SVT).
Palpation of the pulse and auscultation of the heart can determine the ventricular rate and assess its regularity (or irregularity). Examination of the jugular venous pulse can help in the diagnosis of AV block or atrial tachyarrhythmias. For example, in complete AV block, the atria contract periodically during complete closure of the atrioventricular valves, resulting in a large a wave (cannon wave) in the venous jugular pulse. Other physical findings in arrhythmias are rare.
Diagnosis of cardiac rhythm and conduction disorders
Anamnesis and objective examination can identify arrhythmia and its possible causes, but for an accurate diagnosis, a 12-lead ECG or (less often) a heart rhythm recording is needed, which is used more often at the time of the onset of symptoms to identify their connection with rhythm disturbances.
ECG data are assessed comprehensively. Intervals are measured and even minimal rhythm disturbances are detected. The key diagnostic point is the atrial excitation rate, the frequency and regularity of ventricular complexes and the relationship between them. Irregular excitation signals are classified as regular-irregular or irregular (irregular). Regular-irregular rhythm is predominantly regular heartbeats, sometimes interrupted by irregular ones (e.g. premature contractions), or other variants of irregular rhythm (including repetitive related groups of contractions).
A short complex (< 0.12 s) indicates a supraventricular rhythm (above the bifurcation of the His bundle). A wide QRS complex (> 0.12 s) is a sign of a ventricular (below the bifurcation of the His bundle) or supraventricular rhythm with simultaneous conduction disturbance or premature excitation of the ventricles in Wolff-Parkinson-White syndrome (WPW syndrome).
Bradyarrhythmia
ECG diagnostics of bradyarrhythmia depends on the presence or absence of a wave, its characteristics and the connection of the wave with the complex. Bradyarrhythmia without a connection of the wave with the QRS complex indicates AV dissociation, as a result the rhythm can be nodal (with narrow ventricular complexes) or ventricular (with wide QRS complexes).
Regularity in a 1:1 ratio with the teeth indicates the absence of AV block. If the teeth precede the QRS complex, this is a sign of sinus bradycardia (if the teeth are normal) or sinus node arrest with ventricular escape rhythm and retrograde conduction of the impulse to the atria. In this case, the complex is widened.
If the rhythm is irregular, the number of teeth usually does not correspond to the number of complexes. Some teeth lead to a complex following them, and some do not (a sign of second-degree AV block). Irregularity in a 1:1 ratio with the teeth preceding them usually indicates sinus arrhythmia with a gradual increase and decrease in the sinus node frequency (if the teeth are normal).
Pauses in the rhythm, which at other times has a regular character, can occur due to a block of the teeth (an abnormal tooth can appear immediately after the preceding T tooth or disrupt the normal shape of the latter), stopping of the sinus node or blockade of the impulse exit from it, as well as second-degree AV block.
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Tachyarrhythmia
Tachyarrhythmias can be divided into four groups: by the principle of regularity and irregularity, as well as by wide and narrow complex.
Narrow irregular complex tachyarrhythmias include atrial fibrillation (AF) and flutter, or true atrial tachycardia with variable AV conduction, and polytopic atrial tachycardia. Differential diagnosis is based on the ECG pattern of atrial impulses, which are best seen in the long intercomplex intervals. Atrial impulses that appear continuous, irregular in time, and variable in shape on the electrocardiogram, and that have a very high rate (>300/min) without distinct R waves suggest atrial fibrillation (i.e., atrial fibrillation). Definite waves that vary from beat to beat and have at least three distinct shapes suggest polytopic atrial tachycardia. Regular, definite, identical in shape impulses, not interrupted by isoelectric intervals, are a sign of atrial fibrillation.
Irregular wide-complex ventricular tachyarrhythmias include the four types of atrial arrhythmias described above, combined with a block of any branch of the His bundle or ventricular preexcitation, and polymorphic ventricular tachycardia (VT). Differential diagnosis is made by atrial ECG impulses and the presence of a very rapid rhythm (> 250 per minute) in polymorphic VT.
Tachycardias with regular narrow QRS complexes include sinus tachycardia, atrial flutter or true atrial tachycardia with regular continuous conduction to the ventricles, and paroxysmal SVT (SVT from the AV node with a re-entry mechanism, orthodromic reciprocating AV tachycardia in the presence of an accessory AV pathway, and SVT from the sinus node with reentry syndrome). Vagal maneuvers or pharmacologic blockade of the AV node allow differentiation between these tachycardias. With these maneuvers, sinus tachycardia does not stop, but the heart rate decreases or AV block develops, revealing normal R waves. Atrial flutter and true atrial tachycardia are usually not changed, but AV block reveals atrial flutter waves or abnormal R waves. The most common forms of paroxysmal SVT (AB re-entry and orthodromic reciprocating tachycardia) should disappear with AV block.
Regular wide-complex ventricular tachyarrhythmia includes the same tachyarrhythmias that can be represented by a narrow complex with either bundle branch block or premature ventricular excitation, and monomorphic VT. Vagal maneuvers help to identify differences between them. If differential diagnosis is difficult, the rhythm should be considered VT, since some drugs used to treat SVT can worsen the clinical course in VT; the opposite approach is erroneous.