Part 7.3: Management of Symptomatic Bradycardia and Tachycardia V ister adenosine while preparations are made for synchronized and rate) is unstable but has a pulse, treat with synchronized cardioversion(Class Ilb), but do not delay cardioversion to cardioversion. To treat monomorphic VT using a monophasic administer the drug or to establish IV access waveform, provide an initial shock of 100 J. If there is no o. If the patient with tachycardia is stable(ie, no serious signs response to the first shock, increase the dose in a stepwise or symptoms related to the tachycardia), the provider has time to obtain a 12-lead ECG and evaluate the rhythm(Box 5)and tions are consistent with the recommendations in the ecc determine treatment options. Stable patients may await exper Guidelines 2000.2 There is insufficient data to recommend consultation because treatment has the potential for harm. specific biphasic energy doses for treatment of VT. If a patient has polymorphic VT and is unstable, treat the Synchronized Cardioversion and Unsynchronized rhythm as VF and deliver high-energy unsynchronized shocks Shocks(Box 4) (ie, defibrillation doses). Although synchronized cardiover- Synchronized cardioversion is shock delivery that is timed sion is preferred for treatment of an organized ventricular (synchronized)with the QRS complex. This synchronization rhythm, for some irregular rhythms, such as polymorphic VT, avoids shock delivery during the relative refractory period of synchronization is not possible. If there is any doubt whether the cardiac cycle(some call it the"vulnerable period"), when monomorphic or polymorphic VT is present in the unstable a shock could produce VE. The energy(shock dose)used patient, do not delay shock delivery to perform detailed for synchronized cardioversion is lower than the doses used rhythm analysis--provide high-energy unsynchronized for unsynchronized shocks (ie, doses for attempted defibril- shocks (ie, defibrillation doses). Use the ACLS Pulseless lation).Low-energy shocks should always be delivered as Arrest Algorithm(see Part 7.2:"Management of Cardiac synchronized shocks because delivery of low energy unsyn- Arrest") chronized shocks is likely to induce VF. If cardioversion is needed and it is impossible to synchronize a shock(eg, the Regular Narrow-Complex Tachycardia(Boxes 7, patient's rhythm is irregular), use high-energy unsynchro- 8, 9, 10) nized shocks(defibrillation doses ). Sinus tachycardia Synchronized cardioversion is recommended to treat (n) unstable Svt due to reentry, (2)unstable atrial fibrillation, Sinus tachycardia is common and usually results from physiologic stimulus, such as fever, anemia, or shock. Sinus and (3) unstable atrial flutter. These arrhythmias are caused tachycardia occurs when the sinus node discharge rate is by reentry, an abnormal rhythm circuit that allows a wave depolarization to travel in a circle. Delivery of a shock >100 times per minute in response to a variety of stimuli or sympathomimetic agents. No specific drug treatment is re stop these rhythms because it interrupts the circulating quired. Therapy is directed toward identification and (reentry) pattern. Synchronized cardioversion is also recom- ment of the underlying cause. When cardiac function is poor. mended to treat unstable monomorphic (regular)VT. If possible, establish IV access before cardioversion and cardiac output can be dependent on a rapid heart rate. In such compensatory tachycardias, stroke volume is limited,so administer sedation if the patient is conscious. But do not normalizing "the heart rate can be detrimental delay cardioversion. Consider expert consultation. For further information about defibrillation and cardioversion see part 5 Supraventricular Tachycardia(Reentry SVT) Electrical Therapies The recommended initial dose for cardioversion of atrial valuation fibrillation is 100 J to 200 J with a monophasic waveform. A entry SVT is a regular tachycardia that is caused by dose of 100 J to 120 J is reasonable with a biphasic reentry, an abnormal rhythm circuit that allows a wave of depolarization to travel in a circle. The often abrupt onset and waveform Escalate the second and subsequent shock doses termination of this tachyarrhythmia led to its original name as needed Cardioversion of atrial flutter and other SVTs generally paroxysmal supraventricular tachycardia(PSVT). The rate of requires less energy. An initial energy of 50 J to 100 J reentry SVT exceeds the typical upper limits of sinus monophasic damped sine(MDS) waveform is often suffi- tachycardia at rest(120 beats per minute) with or without discernible P waves. The rhythm is considered to be of cient. If the initial 50-J shock fails, increase the dose in a supraventricular origin if the QRS complex is narrow(<120 stepwise fashion. 2 More data is needed before detailed milliseconds or <0.12 second)or if the QRS complex is wide comparative dosing recommendations for cardioversion with broad) and bundle branch aberrancy is known to be present Reentry SVT may include AV nodal reentrant tachycardia o Cardioversion is not likely to be effective for treatment of junctional tachycardia or ectopic or multifocal atrial AV reentry tachycardia tachycardia because these rhythms have an automatic focus, Therapy rapid rate. Delivery of a shock generally cannot stop these Vagal mo initial therapeutic choices for the termination of rhythms. In fact, shock delivery to a heart with a rapid preferred stable reentry SVT(Box 7). Vagal maneuvers alone (Valsalva automatic focus may increase the rate of the tachyarrhythmia. maneuver or carotid sinus massage)will terminate about 20% The amount of energy required for cardioversion of VT is to 25% of reentry SVT14: adenosine treatment is required for determined by the morphologic characteristics and the rate of the remainder In I study (LoE 4)is of stable reentry SVT in the VT. 3 If the patient with monomorphic VT(regular form younger patients, vagal maneuvers were often unsuccessful.ister adenosine while preparations are made for synchronized cardioversion (Class IIb), but do not delay cardioversion to administer the drug or to establish IV access. If the patient with tachycardia is stable (ie, no serious signs or symptoms related to the tachycardia), the provider has time to obtain a 12-lead ECG and evaluate the rhythm (Box 5) and determine treatment options. Stable patients may await expert consultation because treatment has the potential for harm. Synchronized Cardioversion and Unsynchronized Shocks (Box 4) Synchronized cardioversion is shock delivery that is timed (synchronized) with the QRS complex. This synchronization avoids shock delivery during the relative refractory period of the cardiac cycle (some call it the “vulnerable period”), when a shock could produce VF.11 The energy (shock dose) used for synchronized cardioversion is lower than the doses used for unsynchronized shocks (ie, doses for attempted defibril￾lation). Low-energy shocks should always be delivered as synchronized shocks because delivery of low energy unsyn￾chronized shocks is likely to induce VF. If cardioversion is needed and it is impossible to synchronize a shock (eg, the patient’s rhythm is irregular), use high-energy unsynchro￾nized shocks (defibrillation doses). Synchronized cardioversion is recommended to treat (1) unstable SVT due to reentry, (2) unstable atrial fibrillation, and (3) unstable atrial flutter. These arrhythmias are caused by reentry, an abnormal rhythm circuit that allows a wave of depolarization to travel in a circle. 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 (regular) VT. If possible, establish IV access before cardioversion and administer sedation if the patient is conscious. But do not delay cardioversion. Consider expert consultation. For further information about defibrillation and cardioversion, see Part 5: “Electrical Therapies.” The recommended initial dose for cardioversion of atrial fibrillation is 100 J to 200 J with a monophasic waveform. A dose of 100 J to 120 J is reasonable with a biphasic waveform. Escalate the second and subsequent shock doses as needed. Cardioversion of atrial flutter and other SVTs generally requires less energy. An initial energy of 50 J to 100 J monophasic damped sine (MDS) waveform is often suffi￾cient. If the initial 50-J shock fails, increase the dose in a stepwise fashion.12 More data is needed before detailed comparative dosing recommendations for cardioversion with biphasic waveforms can be made. Cardioversion is not likely to be effective for treatment of junctional tachycardia or ectopic or multifocal atrial tachycardia because these rhythms have an automatic focus, arising from cells that are spontaneously depolarizing at a rapid rate. Delivery of a shock generally cannot stop these rhythms. In fact, shock delivery to a heart with a rapid automatic focus may increase the rate of the tachyarrhythmia. The amount of energy required for cardioversion of VT is determined by the morphologic characteristics and the rate of the VT.13 If the patient with monomorphic VT (regular form and rate) is unstable but has a pulse, treat with synchronized cardioversion. To treat monomorphic VT using a monophasic waveform, provide an initial shock 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. 2 There is insufficient data to recommend specific biphasic energy doses for treatment of VT. If a patient has polymorphic VT and is unstable, treat the rhythm as VF and deliver high-energy unsynchronized shocks (ie, defibrillation doses). Although synchronized cardiover￾sion is preferred for treatment of an organized ventricular rhythm, for some irregular rhythms, such as polymorphic VT, synchronization is not possible. If there is any doubt whether monomorphic 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). Use the ACLS Pulseless Arrest Algorithm (see Part 7.2: “Management of Cardiac Arrest”). Regular Narrow-Complex Tachycardia (Boxes 7, 8, 9, 10) Sinus Tachycardia Sinus tachycardia is common and usually results from a physiologic stimulus, such as fever, anemia, or shock. Sinus tachycardia occurs when the sinus node discharge rate is 100 times per minute in response to a variety of stimuli or sympathomimetic agents. No specific drug treatment is re￾quired. Therapy is directed toward identification and treat￾ment of the underlying cause. When cardiac function is poor, cardiac output can be dependent on a rapid heart rate. In such compensatory tachycardias, stroke volume is limited, so “normalizing” the heart rate can be detrimental. Supraventricular Tachycardia (Reentry SVT) Evaluation Reentry SVT is a regular tachycardia that is caused by reentry, an abnormal rhythm circuit that allows a wave of depolarization to travel in a circle. The often abrupt onset and termination of this tachyarrhythmia led to its original name, paroxysmal supraventricular tachycardia (PSVT). The rate of reentry SVT exceeds the typical upper limits of sinus tachycardia at rest (120 beats per minute) with or without discernible P waves. The rhythm is considered to be of supraventricular origin if the QRS complex is narrow (
120 milliseconds or
0.12 second) or if the QRS complex is wide (broad) and bundle branch aberrancy is known to be present. Reentry SVT may include AV nodal reentrant tachycardia or AV reentry tachycardia. Therapy Vagal Maneuvers. Vagal maneuvers and adenosine are the preferred initial therapeutic choices for the termination of stable reentry SVT (Box 7). Vagal maneuvers alone (Valsalva maneuver or carotid sinus massage) will terminate about 20% to 25% of reentry SVT14; adenosine treatment is required for the remainder. In 1 study (LOE 4)15 of stable reentry SVT in younger patients, vagal maneuvers were often unsuccessful. Part 7.3: Management of Symptomatic Bradycardia and Tachycardia IV-71