AV nodal reentrant tachycardia
The AV nodal reentrant tachycardia ( Syn: AV nodal reentrant tachycardia ( AVNRT ) ) is a benign heart rhythm disorder that is characterized by sudden onset and ending fast, regular heartbeat.
Dissemination
The AVNRT is the most common supraventricular tachycardia in adults, accounting for 60-70 % of all paroxysmal arrhythmias from.
Basics
In one part of the conduction system of the heart, the AV node, exist in these patients two areas adjacent, sg Railways ( engl. pathway ) through which the excitation is transferred from the atria to the ventricles. These orbits differ to conduct an electric pulse in their ability. One speaks of a dual AV nodal physiology or dual AV node.
Almost pathway begins at the anterior input of the AV node and can quickly passes in both directions, ie antegrade ( from the auricle to ventricle ) and retrograde conduct (of the chamber to the atrium). The slow- pathway begins at the posterior input, passes more slowly and has a shorter refractory period.
Pathogenesis
In the typical case ( typical slow / fast AVNRT, 95%) occurs by an early incident atrial extrasystole in the region to a block in the fast- pathway. The excitement now runs on the slow- pathway to the ventricle, where it meets the chamber end of the fast- pathway, running in a circle back to the court to again run via slow- pathway towards chamber.
In the atypical fast / slow AVNRT ( Syn: reverse AVNRT ) is to conduct retrogradely the excitement in the location and the slow- pathway to it. This results in an ectopic the chamber to block the fast- pathway, the excitement runs through the slow- pathway to the atria and in the circle back via fast- pathway to the chamber.
Clinical manifestations
The rhythm disorder manifests itself in sudden onset, rapid, regular heart beat with a frequency of 140-250 beats per minute. Most often this is well tolerated, syncope but come before. In addition to strong urge to urinate ( undistributed by atrial stretch ANP) reported shortness of breath and dizziness. The arrhythmia ends as suddenly as it began.
Methods of investigation
ECG
In the resting ECG is a shortened PQ distance ( <110 ms) are occasionally found during sinus rhythm as a sign of the fast- pathway. In contrast to the WPW syndrome, however, no delta wave is an expression of pre-excitation.
In typical AVNRT can be found in the seizure ECG a narrow complex tachycardia without regular P waves ( hidden in the QRS complex ). Changes in the ST segment may occur. In the form of the atypical frequency likely slowly between 120 and 160 beats per minute. There is a negative, since retrograde conducted P wave in II, III, aVF with a very short distance PQ (RP > PR ).
The induction of tachycardia by supraventricular extrasystole in the typical AVNRT and ventricular extrasystole in atypical can be seen in long-term ECG.
The spontaneous termination of typical AVNRT is caused by a block of the fast- pathway. Usually one can observe a negative P wave after the last chamber complex of the tachycardia. The spontaneous end of the atypical form comes about through a block of the slow- pathway, is still missing after the termination of the tachycardia, the retrograde P wave.
Electrophysiological study
The diagnosis of AVNRT is usually secured by non- invasively acquired parameters when performing an EPC. In 70 % of cases, a dual AV nodal physiology demonstrated. However, no AVNRT can at 50 % of patients in which a double AV node is also found in other studies to be triggered.
Treatment and cure views
In the acute attack, adenosine is the diagnosis and treatment of choice. It causes a few seconds ongoing total AV block and ends about the arrhythmia. In other other rhythm disturbances (eg, clockwise typical atrial flutter ) can make a similar ECG pattern, are unmasked. If the arrhythmia start up again in the short term, calcium channel blockers may be given the diltiazem or verapamil type.
Pharmacological long-term treatment is possible in principle with beta-blockers or calcium channel blockers, however, suffer from a high rate of relapse.
The treatment of choice for multiple episodes occurred AVNRT is catheter ablation. Here, with much success (> 95 %) of slow- pathway ablated. The ablation of the fast- pathway is a reserve engineering. The most dangerous risk of causing a third -degree AV block with a permanent need for a pacemaker, is 0.5-2 %.
Literature and sources
- Mewis, Riessen, Spyridopoulos (eds): Cardiology compact - Everything for station and board examination. 2 edition. Thieme, Stuttgart, New York 2006, ISBN 3-13-130742-0, pp. 572-577.
- Disease in cardiology