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16-September-2008 16:15:12 - AV nodal reentrant tachycardia May 2008 AV nodal reentrant tachycardia Classification and external resources ICD-10 I47.1 ICD-9 426.89, 427.0 eMedicine med/2955 ped/2535 MeSH D013611 AV nodal reentrant tachycardia AVNRT is a type of tachycardia fast rhythm of the heart. It is a type of supraventricular tachycardia SVT, meaning that it originates from a location within the heart above the bundle of His. AV nodal reentrant tachycardia is the most common regular supraventricular tachycardia. It is more common in women than men approximately 75% of cases occurring in females. The main symptom is palpitations. Treatment may be with specific physical maneuvers, medication, or rarely DC cardioversion. Frequent attacks may require radiofrequency ablation, in which the abnormally conducting tissue in the heart is destroyed. Contents 1 Signs and symptoms 2 Diagnosis 3 Classification 3.1 Common AVNRT 3.2 Uncommon AVNRT 4 Pathophysiology 5 Treatment 5.1 Vagal maneuvers 5.2 Medication 5.3 Cardioversion 5.4 Electrophysiology 6 See also Signs and symptoms The main symptom is the sudden development of rapid regular palpitations. Often, no precipitant is present, although some report development of symptoms in stressful situations, consumption of alcohol or caffeine, or other factors. In some cases, the onset of the tachycardia is associated with a brief drop in blood pressure. When this happens, the patient may experience dizziness or rarely syncope fainting. If the heart rate is very fast, and the patient has underlying coronary artery disease obstruction of the arteries of the heart by atherosclerosis, chest pain similar to angina may be experienced; this pain is band- or pressure-like around the chest and often radiates to the left arm and angle of the left jaw. AVNRT is rarely life-threatening. Diagnosis If the symptoms are present while the patient is attending medical care e.g. emergency department, an electrocardiogram ECG/EKG may show typical changes that confirm the diagnosis. If the palpitations are recurrent, a doctor may request a Holter monitor 24 hour or longer portable ECG recording. Again, this will show the diagnosis if the recorder is attached at the time of the symptoms. Rarely, disabling but infrequent episodes of palpitations may require the insertion of a small microchip-based device e.g. Reveal Plus under the skin that continuously record heart activity, and can be read through the skin after an episode. All these ECG-based technologies also enable the distinction between AVNRT and other tachycardias such as atrial fibrillation, atrial flutter, sinus tachycardia, ventricular tachycardia and Wolff-Parkinson-White syndrome, all of which may have symptoms that are similar to AVNRT. Blood tests commonly performed in people with palpitations are: thyroid function tests TFTs - an overactive thyroid increases the risk of AVNRT electrolytes - disturbances in potassium, calcium and magnesium may predispose to AVNRT cardiac markers - if there is a concern that myocardial infarction heart attack has occurred either as a cause or as a result of the AVNRT; this is usually only the case if the patient has experienced chest pain Classification There are several types of AVNRT. The common form or usual AVNRT utilizes the slow AV nodal pathway as the anterograde limb of the circuit and the fast AV nodal pathway as the retrograde limb. The reentry circuit can be reversed such that the fast AV nodal pathway is the anterograde limb and the slow AV nodal pathway is the retrograde limb. This, not surprisingly is referred to as the uncommon form of AVNRT. However, there is also a third type of AVNRT that utilizes the slow AV nodal pathway as the anterograde limb and left atrial fibers that approach the AV node from the left side of the inter-atrial septum as the retrograde limb. This is known as atypical, or Slow-Slow AVNRT. Common AVNRT In common AVNRT, the anterograde conduction is via the slow pathway and the retrograde conduction is via the fast pathway slow-fast AVNRT. Because the retrograde conduction is via the fast pathway, stimulation of the atria which produces the inverted P wave will occur at the same time as stimulation of the ventricles which causes the QRS complex. As a result, the inverted P waves may not be seen on the surface ECG since they are buried with the QRS complexes. Often the retrograde p-wave is visible, but also in continuity with the QRS complex, appearing as a pseudo R prime wave in lead V1 or a pseudo S wave in the inferior leads. Uncommon AVNRT In uncommon AVNRT, the anterograde conduction is via the fast pathway and the retrograde conduction is via the slow pathway fast-slow AVNRT. Multiple slow pathways can exist so that both anterograde and retrograde conduction are over slow pathways. slow-slow AVNRT. Because the retrograde conduction is via the slow pathway, stimulation of the atria will be delayed by the slow conduction tissue and will typically produce an inverted P wave that falls after the QRS complex on the surface ECG. Pathophysiology AVNRT occurs when a reentry circuit forms within or just next to the atrioventricular node. The circuit usually involves two anatomical pathways: the fast pathway and the slow pathway, which are both in the right atrium. The slow pathway which is usually targeted for ablation is located inferiorly and slightly posterior to the AV node, often following the anterior margin of the coronary sinus. The fast pathway is usually located just superior and posterior to the AV node. These pathways are formed from tissue that behaves very much like the AV node, and some authors regard them as part of the AV node. The fast and slow pathways should not be confused with the accessory pathways that give rise to Wolff-Parkinson-White syndrome WPW syndrome or atrioventricular re-entrant tachycardia AVRT. In AVNRT, the fast and slow pathways are located within the right atrium in close proximity to or within the AV node and exhibit electrophysiologic properties similar to AV nodal tissue. Accessory pathways that give rise to WPW syndrome and AVRT are located in the atrioventricular valvular rings, they provide a direct connection between the atria and ventricles, and have electrophysiologic properties similar to ventricular myocardium. Treatment An episode of supraventricular tachycardia SVT due to AVNRT can be terminated by any action that transiently blocks the AV node. Various methods are possible. Vagal maneuvers Some people with known AVNRT may be able to stop their attack by using various tricks to activate the vagus nerve. This includes carotid sinus massage pressure on the carotid sinus in the neck or the Valsalva maneuver increasing the pressure in the chest by attempting to exhale against a closed airway. Medication Medical therapy can be initiated with AV nodal slowing drugs such as adenosine which is a pharmacologic cardioversion, beta blockers or calcium channel blockers such as verapamil. Numerous other antiarrhythmic drugs may be effective if the more commonly used medications have not worked; these include flecainide or amiodarone. Both adenosine and beta blockers may cause tightening of the airways, and are therefore used with caution in people who are known to have asthma. Cardioversion In very rare instances, cardioversion the electrical restoration of a normal heart rhythm is needed in the treatment of AVNRT. This would normally only happen if all other treatments have been ineffective, or if the fast heart rate is poorly tolerated e.g. the development of heart failure symptoms, low blood pressure or coma. Electrophysiology After being diagnosed with AVNRT, patients can also undergo an electrophysiology EP study to confirm the diagnosis. Catheter ablation of the slow pathway, if successfully carried out, can potentially cure the patient of AVNRT. See also Wolff-Parkinson-White syndrome Supraventricular tachycardia Cardiac electrophysiology Clinical cardiac electrophysiology v d e Cardiovascular disease: heart disease - Circulatory system pathology I00-I52, 390-429 Ischaemic/ Acute coronary CHD: CAD - Coronary thrombosis - Coronary vasospasm - Coronary artery aneurysm Angina pectoris Prinzmetal's angina - Myocardial infarction heart attack Myocardial rupture - Dressler's syndrome Layers Pericardium Pericarditis Acute, Constrictive - Pericardial effusion - Cardiac tamponade - Hemopericardium Myocardium Myocarditis Cardiomyopathy: Dilated Alcoholic - Hypertrophic - Restrictive Loeffler endocarditis, Cardiac amyloidosis Arrhythmogenic right ventricular dysplasia Endocardium/ valves Endocarditis Subacute bacterial endocarditis, Libman-Sacks endocarditis, Nonbacterial thrombotic endocarditis mitral regurgitation, prolapse, stenosis - aortic stenosis, insufficiency - tricuspid stenosis, insufficiency - pulmonary stenosis, insufficiency Conduction/ arrhythmia Heart block AV 1°, 2°, 3° - Bundle branch Left, Right - Bifascicular/Trifascicular - Sinoatrial - Sick sinus syndrome - Adams-Stokes syndrome Pre-excitation syndrome Wolff-Parkinson-White - Lown-Ganong-Levine Tachycardia Paroxysmal - Supraventricular AV nodal reentrant, Accelerated idioventricular rhythm, Sinus - Ventricular Torsades de pointes, Catecholaminergic polymorphic Premature contraction Atrial - Ventricular Flutter/fibrillation Atrial flutter - Ventricular flutter - Atrial fibrillation Familial - Ventricular fibrillation Pacemaker Wandering pacemaker - Ectopic pacemaker - Parasystole Long QT syndrome Romano-Ward syndrome - Andersen-Tawil syndrome - Jervell and Lange-Nielsen syndrome Cardiac arrest Sudden cardiac death - Asystole Other Cardiomegaly - Ventricular hypertrophy Left, Right/Cor pulmonale Heart failure Cardiac asthma - Rheumatic fever See also congenital, neoplasia Retrieved from http://en..org/wiki/AV_nodal_reentrant_tachycardia Categories: Cardiac electrophysiologyHidden categories: Articles lacking sources from May 2008 | All articles lacking sources Views Article Discussion this page History Personal tools Log in / create account Navigation Main page Contents Featured content Current events Random article Search Go Search Interaction Community portal Recent changes Contact Donate to Help Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page This page was last modified on 14 May 2008, at 22:52
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