I-72 Circulation December 13. 2005 Adenosine. If reentry SVT does not respond to vagal maneu- 20 to 25 mg(0.35 mg/kg). The maintenance infusion dose is vers, give 6 mg of IV adenosine as a rapid IV push( Class I). 5 to 15 mg/h, titrated to heart rate Give adenosine rapidly over I to 3 seconds through a large A wide variety of B-blockers may be given for treatment of (eg, antecubital) vein followed by a 20-mL saline flu supraventricular tachyarrhythmias. More detailed information elevation of the arm. If the rate does not convert witl 2 minutes, give a 12-mg bolus Give a second 12-mg is provided below. Side effects of B-blockers can include the rate fails to convert within I to 2 minutes after the first bradycardias, AV conduction delays, and hypotension 12-mg bolus Five prospective controlled nonrandomized cohort studies Wide-Broad-) Complex Tachycardia(Boxes 12 (LOE 216, LOE 317-20)showed that adenosine is safe and 13,14) effective in converting SVT in both the in-hospital and Evaluation out-of-hospital settings. Although 2 randomized clinical trials The first step in the management of any tachycardia is to (LOE 3)72 documented a similar SVT conversion rate determine if the patients condition is stable or unstable( Box between adenosine and calcium channel blockers adenosine was more rapid with fewer severe side effects than verapamil. presumed to have VT, and immediate cardioversion is per tion of induced sustained reentrant SVT(LOE 6) formed (Box 4 and see above) If the patient is stable, the second step in management is to Adenosine is safe and effective in pregnancy. 2 Adenosine, obtain a 12-lead ECG(Box 5)to evaluate the QRS duration however, does have several important drug interactions Larger doses may be required for patients with a significant (ie, narrow or wide). At this point the provider should blood level of theophylline, caffeine, or theobromine. The consider the need to obtain expert consultation. If the patient initial dose should be reduced to 3 mg in patients taking becomes unstable at any time, proceed with synchronized dipyridamole or carbamazepine, those with transplanted cardioversion. If the patient develops pulseless arrest or is hearts, or if given by central venous access. Side effects with unstable with polymorphic VT, treat as VF and deliver adenosine are common but transient; flushing, dyspnea, and high-energy unsynchronized shocks (ie, defibrillation doses) chest pain are the most frequently observed. 24 Wide-complex tachycardias are defined as those with a If the rhythm does convert(Box 9), it was probably reentry QRS 20.12 second. The most common forms of wide VT. Monitor the patient for recurrence and treat any complex tachycardia are recurrence with adenosine or control the rate with a longer acting AV nodal blocking agent(eg, diltiazem or B-blocker · SVT with aberrancy Calcium Channel Blockers and B-Blockers. If adenosine fails Pre-excited tachycardias(associated with or mediated by to convert reentry SVT (Box 10), attempt rate control with a an accessory pathway) ondihydropyridine calcium channel blocker(ie, verapami or diltiazem) or B-blocker as a second-line agent(Class The third step in management of a tachycardia is to determin Ila).25-27 These drugs act primarily on nodal tissue either if the rhythm is regular or irregular(Box 12). A regular slow the ventricular response to atrial arrhythmias by bloc wide-complex tachycardia is likely to be vT or SVT with ing conduction through the AV node or to terminate the berrancy. An irregular wide-complex tachycardia may be atrial reentry SVT that depends on conduction through the Av fibrillation with aberrancy, pre-excited atrial fibrillation(ie, atrial fibrillation with WPW syndrome), or polymorphic VT. Poly Verapamil and, to a lesser extent, diltiazem may e morphic VT may represent torsades de pointes(see below) myocardial contractility and critically reduce cardiac Providers should consider the need for expert consultation when in patients with severe left ventricular dysfunction m treating wide-complex tachycardia pamil and diltiazem)are considered harmful when given Therapy for Regular Wide-Complex tachycardias channel blockers that affect the av node (including ve (Box 13) patients with atrial fibrillation or atrial flutter associated with If the wide-complex regular tachycardia is thought to be SVT, known pre-excitation(Wolff-Parkinson-White [WPW] syn- adenosine is recommended. The dose used(6 mg rapid IV drome. B-Blockers should be used with caution in patients push; providers may follow the first dose with a 12-mg bolus with pulmonary disease or congestive heart failure and a second 12-mg bolus if the rate fails to convert)is the For verapamil, give a 2.5 to 5 mg Iv bolus over 2 minutes ame as that for reentry svt(see above for more (over 3 minutes in older patients). If there is no therapeut response and no drug-induced adverse event, repeated doses Synchronized cardioversion is appropriate for treatment of of 5 to 10 mg may be administered every 15 to 30 minutes to monomorphic(regular) wide-complex tachycardia, particu- a total dose of 20 mg. An alternative dosing regimen is to give larly if the patient is symptomatic(eg, signs of altered level of a 5-mg bolus every 15 minutes to a total dose of 30 mg. consciousness). If the rhythm is identified as likely VT in a Verapamil should be given only to patients with narrow- stable patient, IV antiarrhythmic drugs may be effective. If complex reentry SVT or arrhythmias known with certainty to antiarrhythmics are administered, we recommend amiodarone be of supraventricular origin. It should not be given to ( Class Ila). Give 150 mg IV over 10 minutes; repeat as patients with impaired ventricular function or heart failure. needed to a maximum dose of 2.2 g Iv per 24 hours For diltiazem, give a dose of 15 to 20 mg(0. 25 mg/kg) Iv Alternative drugs for wide-complex regular tachycardias are over 2 minutes; if needed, in 15 minutes give an Iv dose of procainamide and sotalol(sAdenosine. If reentry SVT does not respond to vagal maneu￾vers, give 6 mg of IV adenosine as a rapid IV push (Class I). Give adenosine rapidly over 1 to 3 seconds through a large (eg, antecubital) vein followed by a 20-mL saline flush and elevation of the arm. If the rate does not convert within 1 to 2 minutes, give a 12-mg bolus. Give a second 12-mg bolus if the rate fails to convert within 1 to 2 minutes after the first 12-mg bolus. Five prospective controlled nonrandomized cohort studies (LOE 216; LOE 317–20) showed that adenosine is safe and effective in converting SVT in both the in-hospital and out-of-hospital settings. Although 2 randomized clinical trials (LOE 3)17,21 documented a similar SVT conversion rate between adenosine and calcium channel blockers, adenosine was more rapid with fewer severe side effects than verapamil. Amiodarone can achieve nearly 100% efficacy in the inhibi￾tion of induced sustained reentrant SVT (LOE 6).22 Adenosine is safe and effective in pregnancy.23 Adenosine, however, does have several important drug interactions. Larger doses may be required for patients with a significant blood level of theophylline, caffeine, or theobromine. The initial dose should be reduced to 3 mg in patients taking dipyridamole or carbamazepine, those with transplanted hearts, or if given by central venous access. Side effects with adenosine are common but transient; flushing, dyspnea, and chest pain are the most frequently observed.24 If the rhythm does convert (Box 9), it was probably reentry SVT. Monitor the patient for recurrence and treat any recurrence with adenosine or control the rate with a longer￾acting AV nodal blocking agent (eg, diltiazem or -blocker). Calcium Channel Blockers and -Blockers. If adenosine fails to convert reentry SVT (Box 10), attempt rate control with a nondihydropyridine calcium channel blocker (ie, verapamil or diltiazem) or -blocker as a second-line agent (Class IIa).25–27 These drugs act primarily on nodal tissue either to slow the ventricular response to atrial arrhythmias by block￾ing conduction through the AV node or to terminate the reentry SVT that depends on conduction through the AV node. Verapamil and, to a lesser extent, diltiazem may decrease myocardial contractility and critically reduce cardiac output in patients with severe left ventricular dysfunction. Calcium channel blockers that affect the AV node (including vera￾pamil and diltiazem) are considered harmful when given to patients with atrial fibrillation or atrial flutter associated with known pre-excitation (Wolff-Parkinson-White [WPW]) syn￾drome. -Blockers should be used with caution in patients with pulmonary disease or congestive heart failure. For verapamil, give a 2.5 to 5 mg IV bolus over 2 minutes (over 3 minutes in older patients). If there is no therapeutic response and no drug-induced adverse event, repeated doses of 5 to 10 mg may be administered every 15 to 30 minutes to a total dose of 20 mg. An alternative dosing regimen is to give a 5-mg bolus every 15 minutes to a total dose of 30 mg. Verapamil should be given only to patients with narrow￾complex reentry SVT or arrhythmias known with certainty to be of supraventricular origin. It should not be given to patients with impaired ventricular function or heart failure. For diltiazem, give a dose of 15 to 20 mg (0.25 mg/kg) IV over 2 minutes; if needed, in 15 minutes give an IV dose of 20 to 25 mg (0.35 mg/kg). The maintenance infusion dose is 5 to 15 mg/h, titrated to heart rate. A wide variety of -blockers may be given for treatment of supraventricular tachyarrhythmias. More detailed information is provided below. Side effects of -blockers can include bradycardias, AV conduction delays, and hypotension. Wide- (Broad-) Complex Tachycardia (Boxes 12, 13, 14) Evaluation The first step in the management of any tachycardia is to determine if the patient’s condition is stable or unstable (Box 3). An unstable patient with wide-complex tachycardia is presumed to have VT, and immediate cardioversion is per￾formed (Box 4 and see above). If the patient is stable, the second step in management is to obtain a 12-lead ECG (Box 5) to evaluate the QRS duration (ie, narrow or wide). At this point the provider should consider the need to obtain expert consultation. If the patient becomes unstable at any time, proceed with synchronized cardioversion. If the patient develops pulseless arrest or is unstable with polymorphic VT, treat as VF and deliver high-energy unsynchronized shocks (ie, defibrillation doses). Wide-complex tachycardias are defined as those with a QRS 0.12 second. The most common forms of wide￾complex tachycardia are ● VT ● SVT with aberrancy ● Pre-excited tachycardias (associated with or mediated by an accessory pathway) The third step in management of a tachycardia is to determine if the rhythm is regular or irregular (Box 12). A regular wide-complex tachycardia is likely to be VT or SVT with aberrancy. An irregular wide-complex tachycardia may be atrial fibrillation with aberrancy, pre-excited atrial fibrillation (ie, atrial fibrillation with WPW syndrome), or polymorphic VT. Poly￾morphic VT may represent torsades de pointes (see below). Providers should consider the need for expert consultation when treating wide-complex tachycardias. Therapy for Regular Wide-Complex Tachycardias (Box 13) If the wide-complex regular tachycardia is thought to be SVT, adenosine is recommended. The dose used (6 mg rapid IV push; providers may follow the first dose with a 12-mg bolus and a second 12-mg bolus if the rate fails to convert) is the same as that for reentry SVT (see above for more information). Synchronized cardioversion is appropriate for treatment of monomorphic (regular) wide-complex tachycardia, particu￾larly if the patient is symptomatic (eg, signs of altered level of consciousness). If the rhythm is identified as likely VT in a stable patient, IV antiarrhythmic drugs may be effective. If antiarrhythmics are administered, we recommend amiodarone (Class IIa). Give 150 mg IV over 10 minutes; repeat as needed to a maximum dose of 2.2 g IV per 24 hours. Alternative drugs for wide-complex regular tachycardias are procainamide and sotalol (see below). IV-72 Circulation December 13, 2005