/v-42 Circulation December 13, 2005 organized QRS complex and a perfusing rhythm(pulses). The Ventricular Tachycardia unstable patient demonstrates signs of poor perfusion, includ- The amount of energy and timing of shocks for treatment of ing altered mental status, ongoing chest pain, hypotension, or VT with pulses are determined by the patients condition and other signs of shock(eg, pulmonary edema) the morphologic characteristics of the VT 139 Pulseless VT is Synchronized cardioversion is recommended to treat un- treated as VF ( see Part 7.2: "Management of Cardiac Ar- stable supraventricular tachycardia due to reentry, atrial rest"). Management of stable VT is summarized in Part 7.3 fibrillation, and atrial flutter. These arrhythmias are all caused Management of Symptomatic Bradycardia and by reentry, an abnormal rhythm circuit that allows a wave of Tachycardia. Unstable morphic (regular) VT with depolarization to travel in a circle. The delivery of a shock pulses is treated with synchronized cardioversion. Unstable can stop these rhythms because it interrupts the circulating polymorphic(irregular)VT with or without pulses is treated (reentry) pattern. Synchronized cardioversion is also recom- S VF using unsynchronized high-energy shocks(ie, defibriN- mended to treat unstable monomorphic VT. For additional information see Part 7.3:"Management of Symptomatic Monomorphic VT(regular form and rate) with a pulse Bradycardia and Tachycardia. responds well to monophasic waveform cardioversion(syn Cardioversion will not be effective for treatment of junc- chronized) shocks at initial energies of 100 J. If there is no tional tachycardia or ectopic or multifocal atrial tachycardia response to the first shock, increase the dose in a stepwise because these rhythms have an automatic focus. Automatic fashion(eg, 100 J, 200 J, 300 J, 360 J). These recommenda- rhythms are created when local cells are stimulated to tions are consistent with the recommendations in the ECC spontaneously depolarize at a rapid rate. Sinus tachycardia is Guidelines 2000. 50 a good example of an automatic rhythm. It results when the Although synchronized cardioversion is preferred for treat cells in the sinus node are stimulated (eg, by catecholamines) ment of an organized ventricular rhythm, for some arrhyth- to depolarize at a rapid rate. Junctional tachycardia and mias synchronization is not possible. The many QRS config- ectopic or multifocal atrial tachycardia also result when cells urations and irregular rates that comprise polymorph are stimulated to depolarize at a rapid rate. Delivery of a ventricular tachycardia make it difficult or impossible to shock cannot stop these rhythms. In fact, shock delivery to reliably synchronize to a QRs complex. In addition, the heart with a rapid automatic focus may increase the rate of the Patient with persistent polymorphic VT will probably no maintain perfusion/pulses for very long, so any attempt to Synchronized cardioversion is not used for treatment of distinguish between polymorphic vT with or without pulses VE, pulseless VT, or unstable polymorphic (irregular)VT. quickly becomes moot. A good rule of thumb is that if your These rhythms require delivery of high-energy unsynchro- eye cannot synchronize to each QRS complex, neither can the defibrillator/cardioverter. If there is any doubt whether mono- nized shocks(ie, defibrillation doses). Electrical therapy for morphic or polymorphic VT is present in the unstable patient, Vt is discussed further below For additional information see Part 7.2: " Management of Cardiac Arrest do not delay shock delivery to perform detailed rhythm analysis--provide high energy unsynchronized shocks (ie, Supraventricular Tachycardias(Reentry SVT) defibrillation doses ). The recommended initial monophasic energy dose for car- The recommended shock doses for high-energy, unsyn dioversion of atrial fibrillation is 100J to 200 J. Cardiover- chronized shocks(defibrillation) with a biphasic or monopha- sic device are those presented earlier in this section(see sion of atrial flutter and other supraventricular tachycardias "Manual Defibrillation, Shock Energies"). After shock deliv- generally requires less energy; an initial energy of 50 J to 100J ery the healthcare provider should be prepared to provide MDS waveform is often sufficient. If the initial 50-J shock immediate CPR(beginning with chest compressi fails, providers should increase the dose in a stepwise follow the ACLs Pulseless Arrest Algorithm if fashion. 3 These recommendations are consistent with those contained in the ECC Guidelines 2000. 50 Cardioversion with arrest develops(for further information see Part 7 agement of Cardiac Arrest") biphasic waveforms is now available, 32 but the optimal doses There is limited data about the treatment of polymorphic for cardioversion with biphasic waveforms have not been established with certainty. Extrapolation from published ex (irregular) VT. Providers should consider consultation with an expert in arrhythmia management. Treatment of the patient perience with elective cardioversion of atrial fibrillation using with polymorphic VT is presented in section 7.3: " Manage rectilinear and truncated exponential waveforms supports an ment of Symptomatic Bradycardia and Tachycardia. initial dose of 100 J to 120 J with escalation as needed. 33 This initial dose has been shown to be 80% to 85% effective Pacing in terminating atrial fibrillation. Until further evidence be- Pacing is not recommended for patients in asystolic cardiac comes available, this information can be used to extrapolate arrest. Pacing can be considered in patients with symptomatic biphasic cardioversion doses to other tachyarrhythmias. 35-l38 bradycardia A recent prospective randomized study that compared the Three randomized controlled trials (loE 2)140-142 of fair ctilinear biphasic waveform (200 J maximum selected energy quality and additional studies (oe 3 to 7)43-149 indicate no with a biphasic truncated exponential waveform(360 J maxi- improvement in the rate of admission to hospital or survival mum energy) for elective cardioversion found no significant to hospital discharge when paramedics or physicians at- differences in efficacy between the 2 waveforms. 34 tempted to provide pacing in asystolic patients in the prelorganized QRS complex and a perfusing rhythm (pulses). The unstable patient demonstrates signs of poor perfusion, includ￾ing altered mental status, ongoing chest pain, hypotension, or other signs of shock (eg, pulmonary edema). Synchronized cardioversion is recommended to treat un￾stable supraventricular tachycardia due to reentry, atrial fibrillation, and atrial flutter. These arrhythmias are all caused by reentry, an abnormal rhythm circuit that allows a wave of depolarization to travel in a circle. The delivery of a shock can stop these rhythms because it interrupts the circulating (reentry) pattern. Synchronized cardioversion is also recom￾mended to treat unstable monomorphic VT. For additional information see Part 7.3: “Management of Symptomatic Bradycardia and Tachycardia.” Cardioversion will not be effective for treatment of junc￾tional tachycardia or ectopic or multifocal atrial tachycardia because these rhythms have an automatic focus. Automatic rhythms are created when local cells are stimulated to spontaneously depolarize at a rapid rate. Sinus tachycardia is a good example of an automatic rhythm. It results when the cells in the sinus node are stimulated (eg, by catecholamines) to depolarize at a rapid rate. Junctional tachycardia and ectopic or multifocal atrial tachycardia also result when cells are stimulated to depolarize at a rapid rate. Delivery of a shock cannot stop these rhythms. In fact, shock delivery to a heart with a rapid automatic focus may increase the rate of the tachyarrhythmia. Synchronized cardioversion is not used for treatment of VF, pulseless VT, or unstable polymorphic (irregular) VT. These rhythms require delivery of high-energy unsynchro￾nized shocks (ie, defibrillation doses). Electrical therapy for VT is discussed further below. For additional information see Part 7.2: “Management of Cardiac Arrest.” Supraventricular Tachycardias (Reentry SVT) The recommended initial monophasic energy dose for car￾dioversion of atrial fibrillation is 100 J to 200 J. Cardiover￾sion of atrial flutter and other supraventricular tachycardias generally requires less energy; an initial energy of 50 J to 100 J MDS waveform is often sufficient. If the initial 50-J shock fails, providers should increase the dose in a stepwise fashion.93 These recommendations are consistent with those contained in the ECC Guidelines 2000.50 Cardioversion with biphasic waveforms is now available,132 but the optimal doses for cardioversion with biphasic waveforms have not been established with certainty. Extrapolation from published ex￾perience with elective cardioversion of atrial fibrillation using rectilinear and truncated exponential waveforms supports an initial dose of 100 J to 120 J with escalation as needed.133,134 This initial dose has been shown to be 80% to 85% effective in terminating atrial fibrillation. Until further evidence be￾comes available, this information can be used to extrapolate biphasic cardioversion doses to other tachyarrhythmias.135–138 A recent prospective randomized study that compared the rectilinear biphasic waveform (200 J maximum selected energy) with a biphasic truncated exponential waveform (360 J maxi￾mum energy) for elective cardioversion found no significant differences in efficacy between the 2 waveforms.134 Ventricular Tachycardia The amount of energy and timing of shocks for treatment of VT with pulses are determined by the patient’s condition and the morphologic characteristics of the VT.139 Pulseless VT is treated as VF (see Part 7.2: “Management of Cardiac Ar￾rest”). Management of stable VT is summarized in Part 7.3: “Management of Symptomatic Bradycardia and Tachycardia.” Unstable monomorphic (regular) VT with pulses is treated with synchronized cardioversion. Unstable polymorphic (irregular) VT with or without pulses is treated as VF using unsynchronized high-energy shocks (ie, defibril￾lation doses). Monomorphic VT (regular form and rate) with a pulse responds well to monophasic waveform cardioversion (syn￾chronized) shocks at initial energies of 100 J. If there is no response to the first shock, increase the dose in a stepwise fashion (eg, 100 J, 200 J, 300 J, 360 J). These recommenda￾tions are consistent with the recommendations in the ECC Guidelines 2000. 50 Although synchronized cardioversion is preferred for treat￾ment of an organized ventricular rhythm, for some arrhyth￾mias synchronization is not possible. The many QRS config￾urations and irregular rates that comprise polymorphic ventricular tachycardia make it difficult or impossible to reliably synchronize to a QRS complex. In addition, the patient with persistent polymorphic VT will probably not maintain perfusion/pulses for very long, so any attempt to distinguish between polymorphic VT with or without pulses quickly becomes moot. 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 mono￾morphic or polymorphic VT is present in the unstable patient, do not delay shock delivery to perform detailed rhythm analysis—provide high energy unsynchronized shocks (ie, defibrillation doses). The recommended shock doses for high-energy, unsyn￾chronized shocks (defibrillation) with a biphasic or monopha￾sic device are those presented earlier in this section (see “Manual Defibrillation, Shock Energies”). After shock deliv￾ery the healthcare provider should be prepared to provide immediate CPR (beginning with chest compressions) and follow the ACLS Pulseless Arrest Algorithm if pulseless arrest develops (for further information see Part 7.2: “Man￾agement of Cardiac Arrest”). There is limited data about the treatment of polymorphic (irregular) VT. Providers should consider consultation with an expert in arrhythmia management. Treatment of the patient with polymorphic VT is presented in section 7.3: “Manage￾ment of Symptomatic Bradycardia and Tachycardia.” Pacing Pacing is not recommended for patients in asystolic cardiac arrest. Pacing can be considered in patients with symptomatic bradycardia. Three randomized controlled trials (LOE 2)140–142 of fair quality and additional studies (LOE 3 to 7)143–149 indicate no improvement in the rate of admission to hospital or survival to hospital discharge when paramedics or physicians at￾tempted to provide pacing in asystolic patients in the prehos￾IV-42 Circulation December 13, 2005