Part 7.3: Management of Symptomatic Bradycardia and Tachycardia IV-73 Evidence in support of amiodarone comes from 3 obser should consider consultation with an expert in arrhythmia vational studies (LOE 5)28-30 that indicate that amiodarone effective for the termination of shock-resistant or drug Pharmacologic treatment of recurrent polymorphic VT is refractory VT. One randomized parallel study(LOE 2)31 determined by the presence or absence of a long QT during indicated that aqueous amiodarone is more effective than sinus rhythm. If a long QT interval is observed during sinus lidocaine in the treatment of shock-resistant VT. Amiodarone rhythm (ie, the VT is torsades de pointes), the first step is to administration is also supported by extrapolated evidence top medications known to prolong the QT interval. Correct (OE 7) from studies of out-of-hospital cardiac arrest with electrolyte imbalance and other acute precipitants(eg, drug shock-refractory VF/VT, which showed that amiodarone overdose or poisoning-see Part 10.2: " Toxicology in ECC) improved survival to hospital admission(but not discharge) Although magnesium is commonly used to treat torsades compared with placebo 2 or lidocaine. 3 de pointes VT(polymorphic VT associated with long QT interval), it is supported by only 2 observational studies (Loe Irregular Tachycardias 5)2.43 showing effectiveness in patients with prolonged QT Atrial fibrillation and Flutter interval. One adult case series(loe 5)44 showed that ise terenol or ventricular pacing can be effective in term Evaluation torsades de pointes associated with bradycardia and drug An irregular narrow-complex or wide-complex tachycardia is induced QT prolongation. Magnesium is unlikely to be most likely atrial fibrillation with an uncontrolled ventricular ventricular effective in terminating polymorphic VT in patients with a response. Other diagnostic possibilities include MAT. We normal QT interval (Loe 5), 43 but amiodarone may be recommend a 12-lead ECG and expert consultation if the effective (LOE 4).49 If the patient with polymorphic VT is or becomes unstable Therapy (ie, demonstrates altered level of consciousness, hypotension, Management(Box 11) should focus on control of the rapid or other signs of shock, such as severe pulmonary edema), ventricular rate(rate control) and conversion of hemodynam- provide high-energy(ie, defibrillation dose) unsynchronized cally unstable atrial fibrillation to sinus rhythm (rhy shocks. Although synchronized cardioversion is always pre- control). Patients with atrial fibrillation for >48 hours are at ferred for an organized ventricular rhythm, synchronization is increased risk for cardioembolic events and must first un not possible for some arrhythmias. The many QRS configu dergo anticoagulation before rhythm control. Electric or rations and irregular rates present in polymorphic VT make it pharmacologic cardioversion(conversion to normal sinu difficult or impossible ably synchronize rhythm)should not be attempted in these patients unless the complex. A good rule of thumb is that if your eye cannot patient is unstable or the absence of a left atrial thrombus is synchronize to each QRS complex, neither can the documented by transesophageal echocardiography. defibrillator/cardioverter Magnesium (Loe 3),34 diltiazem (LOE 2), and If there is any doubt whether monomorphic or polymorphic B-blockers(LOE 2)36.37 have been shown to be effective for VT is present in the unstable patient, do not delay shock rate control in the treatment of atrial fibrillation with a rapid delivery for detailed rhythm analysis--provide high-energy ventricular response in both the prehospital (LOE 3) and unsynchronized shocks (ie, defibrillation doses). Current research confirms that it is reasonable to use selected energies Ibutilide and amiodarone(LOE 2)39-41 have been shown to of 150 J to 200 J with a biphasic truncated exponential be effective for rhythm control in the treatment of atrial waveform or 120 J with a rectilinear biphasic waveform for fibrillation in the hospital settin the initial shock For second and subsequent biphasic shocks In summary, we recommend expert consultation and initial use the same or higher energy(Class Ila) Providers should rate control with diltiazem, B-blockers, or magnesium for use the biphasic device-specific dose; the default dose is patients with atrial fibrillation and a rapid ventricular re 200 J. If a monophasic defibrillator is used, use a dose of sponse. Amiodarone, ibutilide, propafenone, flecainide, 360 J for all unsynchronized shocks(for further informatior digoxin, clonidine, or magnesium can be considered for see Part 5:"Electrical Therapies: Automated External Defibril- rhythm control in patients with atrial fibrillation of <48 hours lators, Defibrillation, Cardioversion, and Pacing"). Lower en- duration ergy levels should not be used for these unsynchronized shocks If a pre-excitation syndrome was identified before the because low-energy shocks have a high likelihood of provoking onset of atrial fibrillation(ie, a delta wave, characteristic of VF when they are given in an unsynchronized mode. WPW, was visible during normal sinus rhythm), expert After shock delivery the healthcare provider should be consultation is advised Do not administer av nodal blocking prepared to provide immediate CPR(beginning with chest agents such as adenosine, calcium channel blockers, digoxin, compressions) and follow the ACLs Pulseless Arrest Algo- and possibly B-blockers to patients with pre-excitation atrial rithm if pulseless arrest develops. For further information see fibrillation or atrial flutter(Box 14) because these drugs can Part 7.2: "Management of Cardiac arrest." cause a paradoxical increase in the ventricular response to rapid atrial impulses of atrial fibrillation. Antiarrhythmic Drugs Ad Polymorphic (Irregular) VT (Box 14) Adenosine is an endogenous purine nucleoside that briefly Polymorphic(irregular) VT requires immediate treatment depresses AV node and sinus node activity. Adenosine is because it is likely to deteriorate to pulseless arrest. Providers recommended for the following indicationsEvidence in support of amiodarone comes from 3 obser￾vational studies (LOE 5)28 –30 that indicate that amiodarone is effective for the termination of shock-resistant or drug￾refractory VT. One randomized parallel study (LOE 2)31 indicated that aqueous amiodarone is more effective than lidocaine in the treatment of shock-resistant VT. Amiodarone administration is also supported by extrapolated evidence (LOE 7) from studies of out-of-hospital cardiac arrest with shock-refractory VF/VT, which showed that amiodarone improved survival to hospital admission (but not discharge) compared with placebo32 or lidocaine.33 Irregular Tachycardias Atrial Fibrillation and Flutter Evaluation An irregular narrow-complex or wide-complex tachycardia is most likely atrial fibrillation with an uncontrolled ventricular response. Other diagnostic possibilities include MAT. We recommend a 12-lead ECG and expert consultation if the patient is stable. Therapy Management (Box 11) should focus on control of the rapid ventricular rate (rate control) and conversion of hemodynam￾ically unstable atrial fibrillation to sinus rhythm (rhythm control). Patients with atrial fibrillation for 48 hours are at increased risk for cardioembolic events and must first un￾dergo anticoagulation before rhythm control. Electric or pharmacologic cardioversion (conversion to normal sinus rhythm) should not be attempted in these patients unless the patient is unstable or the absence of a left atrial thrombus is documented by transesophageal echocardiography. Magnesium (LOE 3),34 diltiazem (LOE 2),35 and -blockers (LOE 2)36,37 have been shown to be effective for rate control in the treatment of atrial fibrillation with a rapid ventricular response in both the prehospital (LOE 3)38 and hospital settings. Ibutilide and amiodarone (LOE 2)39 – 41 have been shown to be effective for rhythm control in the treatment of atrial fibrillation in the hospital setting. In summary, we recommend expert consultation and initial rate control with diltiazem, -blockers, or magnesium for patients with atrial fibrillation and a rapid ventricular re￾sponse. Amiodarone, ibutilide, propafenone, flecainide, digoxin, clonidine, or magnesium can be considered for rhythm control in patients with atrial fibrillation of 48 hours duration. If a pre-excitation syndrome was identified before the onset of atrial fibrillation (ie, a delta wave, characteristic of WPW, was visible during normal sinus rhythm), expert consultation is advised. Do not administer AV nodal blocking agents such as adenosine, calcium channel blockers, digoxin, and possibly -blockers to patients with pre-excitation atrial fibrillation or atrial flutter (Box 14) because these drugs can cause a paradoxical increase in the ventricular response to the rapid atrial impulses of atrial fibrillation. Polymorphic (Irregular) VT (Box 14) Polymorphic (irregular) VT requires immediate treatment because it is likely to deteriorate to pulseless arrest. Providers should consider consultation with an expert in arrhythmia management. Pharmacologic treatment of recurrent polymorphic VT is determined by the presence or absence of a long QT during sinus rhythm. If a long QT interval is observed during sinus rhythm (ie, the VT is torsades de pointes), the first step is to stop medications known to prolong the QT interval. Correct electrolyte imbalance and other acute precipitants (eg, drug overdose or poisoning—see Part 10.2: “Toxicology in ECC”). Although magnesium is commonly used to treat torsades de pointes VT (polymorphic VT associated with long QT interval), it is supported by only 2 observational studies (LOE 5)42,43 showing effectiveness in patients with prolonged QT interval. One adult case series (LOE 5)44 showed that isopro￾terenol or ventricular pacing can be effective in terminating torsades de pointes associated with bradycardia and drug￾induced QT prolongation. Magnesium is unlikely to be effective in terminating polymorphic VT in patients with a normal QT interval (LOE 5),43 but amiodarone may be effective (LOE 4).45 If the patient with polymorphic VT is or becomes unstable (ie, demonstrates altered level of consciousness, hypotension, or other signs of shock, such as severe pulmonary edema), provide high-energy (ie, defibrillation dose) unsynchronized shocks. Although synchronized cardioversion is always pre￾ferred for an organized ventricular rhythm, synchronization is not possible for some arrhythmias. The many QRS configu￾rations and irregular rates present in polymorphic VT make it difficult or impossible to reliably synchronize to a QRS complex. A good rule of thumb is that if your eye cannot synchronize to each QRS complex, neither can the defibrillator/cardioverter. If there is any doubt whether monomorphic or polymorphic VT is present in the unstable patient, do not delay shock delivery for detailed rhythm analysis—provide high-energy unsynchronized shocks (ie, defibrillation doses). Current research confirms that it is reasonable to use selected energies of 150 J to 200 J with a biphasic truncated exponential waveform or 120 J with a rectilinear biphasic waveform for the initial shock. For second and subsequent biphasic shocks use the same or higher energy (Class IIa). Providers should use the biphasic device-specific dose; the default dose is 200 J. If a monophasic defibrillator is used, use a dose of 360 J for all unsynchronized shocks (for further information see Part 5: “Electrical Therapies: Automated External Defibril￾lators, Defibrillation, Cardioversion, and Pacing”). Lower en￾ergy levels should not be used for these unsynchronized shocks because low-energy shocks have a high likelihood of provoking VF when they are given in an unsynchronized mode. After shock delivery the healthcare provider should be prepared to provide immediate CPR (beginning with chest compressions) and follow the ACLS Pulseless Arrest Algo￾rithm if pulseless arrest develops. For further information see Part 7.2: “Management of Cardiac Arrest.” Antiarrhythmic Drugs Adenosine Adenosine is an endogenous purine nucleoside that briefly depresses AV node and sinus node activity. Adenosine is recommended for the following indications: Part 7.3: Management of Symptomatic Bradycardia and Tachycardia IV-73