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Back to Cardiovascular Diseases
AV nodal reentrant tachycardia (AVNRT)
Atrioventricular (AV) nodal reentrant tachycardia is the
most common type (excluding atrial fibrillation) of supraventricular
tachycardia. It accounts for about 60% of all fast heart rates that
start in the upper part of the heart (excluding atrial fibrillation).
AV nodal reentrant tachycardia (AVNRT)
occurs in the presence of a reentrant circuit (an abnormal or extra
electrical pathway in the heart, a kind of "short circuit.") involving two anatomically
and physiologically distinct pathways (fast
and slow pathways) linking the right atrium to the AV node. AVNRT is the
most common paroxysmal supraventricular tachycardia (PSVT).
Symptoms and signs
These includes attacks of palpitations, dizziness and syncope,
dyspnea, chest pain as well as anxiety. These attacks start and
terminate abruptly (i.e. paroxysmal).
ECG readings
In typical (slow-fast)
AVNRT, activation spreads from the atrium to the AV node via the slow
pathway and returns to the atrium via the fast pathway. The ECG reveals
a rate usually between l50-250 bpm-with a P
wave obscured by the nearly synchronous atrial and ventricular
depolarization-and a QRS complex that is either normal (base-line)
or broadened, owing to rate-related aberrancy
In atypical (fast-slow) AVNRT, the activation
pathway is reversed, the rate is similar to that for typical AVNRT but
an inverted P wave usually is readily apparent in the T wave, resulting
in a normal or minimally prolonged PR interval.
Treatment
Initial therapy of acute episodes of narrow-complex
tachycardias, particularly AVNRT includes vagal maneuvers (e.g. carotid
massage, Valsalva maneuver) and, if unsuccessful, bolus administration
of short-acting agents that slow or block AV nodal conduction, such as
adenosine, verapamil, or diltiazem.
Chronic drug therapy may include calcium
channel antagonists, beta-adrenergic antagonists, or digoxin. Radiofrequency
catheter ablation now can obviate the need for such therapy in most patients.
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