I-74 Circulation December 13. 2005 For defined, stable, narrow-complex AV nodal or sinus For stable, narrow-complex, reentry mechanism nodal reentry tachycardias. 16-2 The most frequent example tachycardias (reentry SVT) if rhythm remains uncontrolled of these is reentry SVT(Class I). Adenosine will not or unconverted by adenosine or vagal maneuvers(Class terminate arrhythmias such as atrial flutter, atrial fibrilla- Ila)25- tion, or atrial or ventricular tachycardias, because these For stable, narrow-complex, automaticity mechanism arrhythmias are not due to reentry involving the AV or tachycardias junctional, ectopic, multifocal) if the rhythm sinus node. Adenosine will not terminate the arrhythmia is not controlled or converted by adenosine or vagal but may produce transient AV or retrograde(ventricu maneuver loatrial) block clarifying the underlying rhyth To control rate of ventricular response in patients with or unstable reentry SVT while tions are ma atrial fibrillation or atrial flutter( Class IIa)5.38 cardioversion(Class Ilb) For undefined, stable, narrow-complex SVT as a combina- IV verapamil is effective for terminating narrow-complex tion therapeutic and diagnostic maneuver. reentry SVT, and it may also be used for rate control in atrial For stable, wide-complex tachycardias in patients with a fibrillation. The initial dose of verapamil is 2.5 to 5 mg I\ recurrence of a known reentry pathway that has been given over 2 minutes. In the absence of a therapeutic respo previously defined. or a drug-induced adverse event, repeat doses of 5 to 10 mg may be administered every 15 to 30 minutes to a total dose of Amiodarone Iv 20 mg. An alternative dosing regimen is to give a 5-mg bolus IV amiodarone is a complex drug with effects on sodium, every 15 minutes to a total dose of 30 mg. Verapamil should potassium, and calcium channels as well as a-and be given only to patients with narrow-complex reentry SVT B-adrenergic blocking properties. Amiodarone or arrhythmias known with certainty to be of supraventricular mended for tachyarrhythmias, with the following indications: ongin. It should not be given to patients with impaired ventricular function or heart failure For narrow-complex tachycardias that originated from a Diltiazem at a dose of 0.25 mg/kg, followed by a second reentry mechanism(reentry SVT) if the rhythm remains dose of 0.35 mg/kg, seems to be equivalent in efficacy to uncontrolled by adenosine, vagal maneuvers, and AV verapamil 25-27 Verapamil and, to a lesser extent, diltiazem nodal blockade in patients with preserved or impaired may decrease myocardial contractility and critically reduce ventricular function(Class Ilb )22 Control of hemodynamically stable VT, polymorphic VT tion. Calcium channel blockers that affect the av node(eg. with a normal QT interval, and wide-complex tachycardia verapamil and diltiazem) are considered harmful when given of uncertain origin(Class Ilb)28-31 to patients with atrial fibrillation or atrial flutter associated To control rapid ventricular rate due to accessory pathway with known pre-excitation(WPW) syndrom conduction in pre-excited atrial arrhythmias( Class IIb)22 B-Adrenergic Blockers Administer 150 mg of IV amiodarone over 10 minutes, B-Blocking agents(atenolol, metoprolol, labetalol, propran followed by a I mg/min infusion for 6 hours and then a 0.5 olol, esmolol) reduce the effects of circulating catechol- mg/min maintenance infusion over 18 hours. Supplementary amines and decrease heart rate and blood pressure. They also infusions of 150 an be repeated every 10 minutes as have various cardioprotective effects for patients with acute necessary for recurrent or resistant arrhythmias to a maxi- coronary syndromes. For acute tachyarrhythmias, these mum manufacturer-recommended total daily Iv dose of agents are indicated for rate control in the following 2.2 g. One study found amiodarone to be effective in patients situations: with atrial fibrillation when administered at relatively high doses of 125 mg/h for 24 hours(total dose 3 g).4I In patients For narrow-complex tachycardias that originate from either known to have severely impaired heart function, IV amid- a reentry mechanism(reentry SVT)or an automatic focus arone is preferable to other antiarrhythmic agents for atrial trolled by vagal maneuvers and adenosine in the patient and ventricular arrhythmias with preserved ventricular function(Class Ila) The major adverse effects of amiodarone are hypotension To control rate in atrial fibrillation and atrial flutter in the and bradycardia, which can be prevented by slowing the rate patient with preserved ventricular function6,37 The recommended dose of atenolol (B1) is 5 mg slow I Calcium Channel Blockers: Verapamil (over 5 minutes). If the arrhythmia persists 10 minutes after and Diltiazem that dose and the first dose was well tolerated, give a second Verapamil and diltiazem are nondihydropyridine calcium dose of 5 mg slow IV(over 5 minutes). hannel blocking agents that slow conduction and increase Metoprolol(B1)is given in doses of 5 mg by slow IV/O refractoriness in the AV node. These actions may terminate push at 5-minute intervals to a total of 15 mg It arrhythmias and control ventricular response rate in An alternative agent is propranolol(B, and B, effects)O. with a variety of atrial tachycardias. These medica- mg/kg by slow Iv push divided into 3 equal doses at 2-to tions are indicated in the following circumstances 3-minute intervals. The rate of administration should not● For defined, stable, narrow-complex AV nodal or sinus nodal reentry tachycardias.16 –21 The most frequent example of these is reentry SVT (Class I). Adenosine will not terminate arrhythmias such as atrial flutter, atrial fibrilla￾tion, or atrial or ventricular tachycardias, because these arrhythmias are not due to reentry involving the AV or sinus node. Adenosine will not terminate the arrhythmia but may produce transient AV or retrograde (ventricu￾loatrial) block clarifying the underlying rhythm. ● For unstable reentry SVT while preparations are made for cardioversion (Class IIb). ● For undefined, stable, narrow-complex SVT as a combina￾tion therapeutic and diagnostic maneuver. ● For stable, wide-complex tachycardias in patients with a recurrence of a known reentry pathway that has been previously defined. Amiodarone IV IV amiodarone is a complex drug with effects on sodium, potassium, and calcium channels as well as - and -adrenergic blocking properties. Amiodarone is recom￾mended for tachyarrhythmias, with the following indications: ● For narrow-complex tachycardias that originated from a reentry mechanism (reentry SVT) if the rhythm remains uncontrolled by adenosine, vagal maneuvers, and AV nodal blockade in patients with preserved or impaired ventricular function (Class IIb)22 ● Control of hemodynamically stable VT, polymorphic VT with a normal QT interval, and wide-complex tachycardia of uncertain origin (Class IIb)28 –31 ● To control rapid ventricular rate due to accessory pathway conduction in pre-excited atrial arrhythmias (Class IIb)22 Administer 150 mg of IV amiodarone over 10 minutes, followed by a 1 mg/min infusion for 6 hours and then a 0.5 mg/min maintenance infusion over 18 hours. Supplementary infusions of 150 mg can be repeated every 10 minutes as necessary for recurrent or resistant arrhythmias to a maxi￾mum manufacturer-recommended total daily IV dose of 2.2 g. One study found amiodarone to be effective in patients with atrial fibrillation when administered at relatively high doses of 125 mg/h for 24 hours (total dose 3 g).41 In patients known to have severely impaired heart function, IV amiod￾arone is preferable to other antiarrhythmic agents for atrial and ventricular arrhythmias. The major adverse effects of amiodarone are hypotension and bradycardia, which can be prevented by slowing the rate of drug infusion. Calcium Channel Blockers: Verapamil and Diltiazem Verapamil and diltiazem are nondihydropyridine calcium channel blocking agents that slow conduction and increase refractoriness in the AV node. These actions may terminate reentrant arrhythmias and control ventricular response rate in patients with a variety of atrial tachycardias. These medica￾tions are indicated in the following circumstances: ● For stable, narrow-complex, reentry mechanism tachycardias (reentry SVT) if rhythm remains uncontrolled or unconverted by adenosine or vagal maneuvers (Class IIa)25–27 ● For stable, narrow-complex, automaticity mechanism tachycardias (junctional, ectopic, multifocal) if the rhythm is not controlled or converted by adenosine or vagal maneuvers ● To control rate of ventricular response in patients with atrial fibrillation or atrial flutter (Class IIa)35,38 IV verapamil is effective for terminating narrow-complex reentry SVT, and it may also be used for rate control in atrial fibrillation. The initial dose of verapamil is 2.5 to 5 mg IV given over 2 minutes. In the absence of a therapeutic response or a drug-induced adverse event, repeat 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. Diltiazem at a dose of 0.25 mg/kg, followed by a second dose of 0.35 mg/kg, seems to be equivalent in efficacy to verapamil.25–27 Verapamil and, to a lesser extent, diltiazem may decrease myocardial contractility and critically reduce cardiac output in patients with severe left ventricular dysfunc￾tion. Calcium channel blockers that affect the AV node (eg, verapamil and diltiazem) are considered harmful when given to patients with atrial fibrillation or atrial flutter associated with known pre-excitation (WPW) syndrome.
-Adrenergic Blockers -Blocking agents (atenolol, metoprolol, labetalol, propran￾olol, esmolol) reduce the effects of circulating catechol￾amines and decrease heart rate and blood pressure. They also have various cardioprotective effects for patients with acute coronary syndromes. For acute tachyarrhythmias, these agents are indicated for rate control in the following situations: ● For narrow-complex tachycardias that originate from either a reentry mechanism (reentry SVT) or an automatic focus (junctional, ectopic, or multifocal tachycardia) uncon￾trolled by vagal maneuvers and adenosine in the patient with preserved ventricular function (Class IIa) ● To control rate in atrial fibrillation and atrial flutter in the patient with preserved ventricular function36,37 The recommended dose of atenolol (1) is 5 mg slow IV (over 5 minutes). If the arrhythmia persists 10 minutes after that dose and the first dose was well tolerated, give a second dose of 5 mg slow IV (over 5 minutes). Metoprolol (1) is given in doses of 5 mg by slow IV/IO push at 5-minute intervals to a total of 15 mg. An alternative agent is propranolol (1 and 2 effects) 0.1 mg/kg by slow IV push divided into 3 equal doses at 2- to 3-minute intervals. The rate of administration should not IV-74 Circulation December 13, 2005