Tachycardia reentrant

AV nodal reentrant tachycardia Reentrant circuit within or near AV Adenosine AV nodal block... 

Reentry mechanism Intranodal (AV node) reentry Extranodal reentry Reentrant tachyarrhythmia Atrial flutter Atrial fibrillation Ventricular tachycardia Ventricular fibrillation Conduction B/ocks ... 

Supraventricular bradycardia is treated by implantation of a pacemaker device or has been treated pharmacologically with atropine. Supraventricular paroxysmal tachycardia is treated with aj marine or praj marine. Supraventricular tachyarrhythmias or AV reentrant arrhythmia typically can be terminated using adenosine. 

O Paroxysmal supraventricular tachycardia is caused by reentry that includes the AV node as a part of the reentrant circuit. Typically, electrical impulses travel forward (antegrade) down the AV node and then travel back up the AV node (retrograde) in a repetitive circuit. In some patients, the retrograde conduction pathway of the reentrant circuit may exist in extra-AV nodal tissue adjacent to the AV node. One of these pathways usually conducts impulses rapidly, while the other usually conducts impulses slowly. Most commonly, during PSVT the impulse conducts antegrade through the slow... 

The first-line drug for treating an acute attack of reentrant supraventricular tachycardia (SVT) is... 

Type II drugs include /Tadrenergic antagonists clinically relevant mechanisms result from their antiadrenergic actions. /3- Blockers are most useful in tachycardias in which nodal tissues are abnormally automatic or are a portion of a reentrant loop. These agents are also helpful in slowing ventricular response in atrial tachycardias (e.g., AF) by their effects on the AV node. 

Type IV drugs inhibit calcium entry into the cell, which slows conduction, prolongs refractoriness, and decreases SA and AV nodal automaticity. Calcium channel antagonists are effective for automatic or reentrant tachycardias that arise from or use the SA or AV nodes. 

FIGURE 6-2. Algorithm for the treatment of acute (top portion) paroxysmal supraventricular tachycardia and chronic prevention of recurrences (bottom portion). Note For empiric bridge therapy prior to radiofrequency ablation procedures, calcium channel blockers (or other atrioventricular [AV] nodal blockers) should not be used if the patient has AV reentry with an accessory pathway. (AAD, antiarrhythmic drugs AF, atrial fibrillation AP, accessory pathway AVN, atrioventricular nodal AVNRT, atrioventricular nodal reentrant tachycardia AVRT, atrioventricular reentrant tachycardia DCC, direct-current cardioversion ECG, electrocardiographic monitoring EPS, electrophysiologic studies PRN, as needed VT, ventricular tachycardia.)... 

Atrial fibrillation For the prevention of paroxysmal atrial fibrillation/flutter (PAF) associated with disabling symptoms and paroxysmal supraventricular tachycardias (PSVT), including atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia, and other supraventricular tachycardias of unspecified mechanism associated with disabling symptoms in patients without structural heart disease. 

Stable monomorphic VT, HR control in a fib, A/ reentrant narrow complex tachycardia 20 mg/min IV until one of these ar hythmia stopped, hypotension, QRS... 

Supravantricular tachycardia is classified into several types depending on the localization of the reentrant circuit. The most common type is AV reentrant tachycardia via an accessory pathway (i.e., the bundle of Kent). The main objective of therapy is... 

Lidocaine (Xylocaine) was introduced as a local anesthetic and is still used extensively for that purpose (see Chapter 27). Lidocaine is an effective sodium channel blocker, binding to channels in the inactivated state. Lidocaine, like other IB agents, acts preferentially in diseased (ischemic) tissue, causing conduction block and interrupting reentrant tachycardias. 

Flecainide slows conduction in the His-Purkinje system and ventricular muscle to a greater degree than in the atrium. Flecainide may also cause block in accessory A-V connections, which is the principal mechanism for its effectiveness in treating A-V reentrant tachycardia. 

Amiodarone is effective in maintaining sinus rhythm in most patients with paroxysmal atrial hbrillation and in many patients with persistent atrial hbrillation. It is also effective in preventing recurrences of A-V nodal reentry and atrial tachyarrhythmias and in the prevention of reentrant rhythms and atrial hbrillation in patients with Wohf-Parkinson-White syndrome. Also, it is the most efficacious therapy for postoperative junctional ectopic tachycardia. 

The effects on the A-V node may result in a conduction block and the termination of tachycardias that use the A-V node as a Umb of a reentrant circuit. Adenosine does not affect the action potential of ventricular myocytes because the adenosine-stimulated potassium channel is absent in ventricular myocardium. 

Biondi B, Fazio S, Coltorti F, Palmieri EA, Carella C, Lombardi G, Sacca L. Clinical case seminar. Reentrant atrioventricular nodal tachycardia induced by levothyroxine. J Clin Endocrinol Metab 1998 83(8) 2643-5. 

Sidhu, J. S., Rajawat, Y. S., Rami, T. G., Gollob, M. H., Wang, Z., Yuan, R., Marian, A. J., DeMayo, F. J., Weilbacher, D., Taffet, G. E., Davies, J. K., Carling, D., Khoury, D. S., and Roberts, R. 2005. Transgenic mouse model of ventricular preexcitation and atrioventricular reentrant tachycardia induced by an AMP-activated protein kinase loss-of-function mutation responsible for Wolff-Parkinson-White syndrome. Circulation 111 21-29. 

Therapeutic uses Verapamil and diltiazem are more effective against atrial than ventricular dysrhythmias. They are useful in treating reentrant supraventricular tachycardia and reducing ventricular rate in atrial flutter and fibrillation. In addition, these drugs are used to treat hypertension (see p. 187) and angina (see p. 177). 

Arruodarone is used in chronic ventricular arrhythmias in atrial fibrillation it both slows the ventricular response and may restore sinus rhythm it may be used to maintain sinus rhythm after cardioversion for atrial fibrillation or flutter. Amiodarone should no longer be used for the management of reentrant supraventricular tachycardias associated with the Wolff-Parkinson-White syndrome as radiofrequency ablation is preferable. 

Rowland E, McKenna WJ, Krikler DM. Electrophysiologic and antiarrhythmic actions of bepridil. Comparison with verapamil and ajmaline for atrioventricular reentrant tachycardia. Am J Cardiol 1985 55(13 Pt 1) 1513-19. 

Obel IW, Jardine R, Haitus B, Millar RN. Efficacy of oral sotalol in reentrant ventricular tachycardia. Cardiovasc Drugs Ther 1990 4(Suppl 3) 613-18. 

Naccarelli GV, Jackman WM, Akhtar M, Rinkenberger RL, Friday KJ, Dougherty AH, Tchou P, Yeung-Lai-Wah JA. Efficacy and electrophysiologic effects of encainide for atrioventricular nodal reentrant tachycardia. Am J Cardiol 1988 62(19) L31-6. 

Saoudi N, Galtier M, Hidden F, Gerber L, Letac B. Bundle-branch reentrant ventricular tachycardia a possible mechanism of flecainide proarrhythmic effect. J Electrophysiol 1988 2 365-71. 

Amiodarone is indicated for the suppression and prevention of documented life-threatening, recurrent, ventricular tachycardia or fibrillation when other agents have failed. Amiodarone is also used in the management of supraventricular tachyarrhythmias including paroxysmal atrial fibrillation and atrial flutter, ectopic or multifocal atrial tachycardia, junctional tachycardia, and paroxysmal reentrant supraventricular tachycardia when other agents have failed to suppress or prevent their recurrence. Amiodarone has also been used to treat wide-complex tachycardia of uncertain mechanism. 

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