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Cardiovascular Medicine Su p raventricu Ia r Tachyca rd ia Diagnosis SVTs are a group of arrhythmias that arise in atrial tissue or the AV node. The most common SVTs, exclusive of AF and atrial flut- ter, are AVNRI, AVRI, and atrial tachycardia. The ECG usually reveals a narrow-complex tachycardia, although the QRS complexes can be wide in the presence ofbundle branch block, aberrancy, pacing, or anterograde accessory pathway conduction' The most common paroxysmal SVT is AVNRT. Typical AVNRT often has an RP interval so short that the P wave is buried within the QRS complex, but it may be seen as a pseudo R in lead V, and a pseudo S wave in the inferior leads. AVRT is a reentrant circuit that includes a bypass pathway and the AV node. Ifa bypass pathway conducts antegrade, a preexcita- tion pattern may be seen on the ECG. When this pattern is accompanied by a symptomatic tachycardia, it is termed WPW syndrome (see Wolff Parkinson White Syndrome). MAT is an irregular SVT that demonstrates three or more P waves of different morphologies and is often seen in end-stage COPD. Narrow-complex tachycardia Regular rhythm lrregular rhythm

AVRT is a reentrant circuit that includes a bypass pathway and the AV node. Ifa bypass pathway conducts antegrade, a preexcita- tion pattern may be seen on the ECG. When this pattern is accompanied by a symptomatic tachycardia, it is termed WPW syndrome (see Wolff Parkinson White Syndrome). MAT is an irregular SVT that demonstrates three or more P waves of different morphologies and is often seen in end-stage COPD. Narrow-complex tachycardia Regular rhythm lrregular rhythm P wave P wave P wave P wave Short RP Long RP Morphology same Just after ORS as sinus. Seen (pseudo R'in interual interval P wave P wave P wave before every lead Vt)or ORS complex. buried in QRS Flutter waves lrregular baseline, At least three in leads ll, lll, no P waves morphologies aVE and Vt of P wave Sinus AVNRT AVRT Atrial tachycardia tachycardia Atrial flutter Atrial Multifocal atrial fibrillation tachycardia Classification of l{arrow-Complex Tachycardia: AVN RT : atrioventricu la r nodal reentrant tachyca rd ia; AVRT : atrioventricu lar reciprocati ng tachyca rd ia Treatment Episodes of SVT can often be terminated with Valsalva maneuvers, carotid sinus massage, or facial immersion in cold water.

Sinus AVNRT AVRT Atrial tachycardia tachycardia Atrial flutter Atrial Multifocal atrial fibrillation tachycardia Classification of l{arrow-Complex Tachycardia: AVN RT : atrioventricu la r nodal reentrant tachyca rd ia; AVRT : atrioventricu lar reciprocati ng tachyca rd ia Treatment Episodes of SVT can often be terminated with Valsalva maneuvers, carotid sinus massage, or facial immersion in cold water. Adenosine can be used to terminate SVT and to help diagnose the cause. Termination with adenosine often suggests AV node dependence (AVNRT and AVRI), whereas continued P waves during AV block can help identiflz atrial flutter and atrial tachycar- dia. Rate control for atrial tachycardia can be achieved with p blockers or calcium channel blockers. Use oral calcium channel blockers and B-blockers to prevent recurrent AVNRT. For recurrent AVNRT despite drug therapy or intolerance of drug therapy, select catheter ablation therapy. Treatment of MAT is directed at correcting associated pulmonary and cardiac disease, hypokalemia, and hypomagnesemia. Drug therapy is indicated for patients who are symptomatic or experience complications such as HF or chest pain secondary to cardiac ischemia. Metoprolol is the drug of choice followed by verapamil in patients with bronchospastic disease. 20

Cardiovascular Medicinc DO]I'T BETRICKED o Do not treat irregular wide-complex tachycardia or polymorphic tachycardia with adenosine. TE TYOURSELF A 32-year-old wornan has a 4-hour history of palpitations. BP is 80/50 mm Hg. An ECG shows regular, narrow-complex tachycar- dia of 180/min and normal QRS complex morpholory. No P waves are seen. ANSWER: The diagnosis is AVNRL Choose the Valsalva maneuver, carotid sinus massage, verapamil, or IV adenosine. AY-llodal ReentnntTachyodla:The ECG shows a nanow-complex tachycardia at 144/min and no visible P waves. AV Rcdprocatlng lachyodia: The ECG shows a narrow'complex tachycardia with the P wave buried in the ST segment. 21