New ACLS Guidelines
Abstract & Commentary
Synopsis: The new AHA guidelines make appropriate changes in recommendations for acute therapy of several arrhythmias.
Source: No authors listed. Circulation 2000;102:I112-I128.
The revised guidelines for advanced cardiovascular life support (ACLS) have reevaluated the role of antiarrhythmic drugs in the acute management of tachycardias.
The guidelines begin by stating that accurate electocardiogram (ECG) diagnosis is the key to the appropriate pharmacologic management of patients with sustained arrhythmias; however, it should be recognized that overly complex ECG diagnostic algorithms are difficult to teach, learn, remember, and apply. Recognition of atrioventricular (AV) dissociation when possible, is very useful but a 12-lead ECG is usually required. In many emergency medical systems (EMS), a 12-lead ECG is not readily obtainable. Therefore, for those who are not cardiovascular specialists, ECG analysis should stress simplicity (e.g., rate, regularity, wide or narrow) rather than complex features. It is safer to misdiagnose supraventricular tachycardia (SVT) as ventricular tachycardia (VT) than the converse.
Lidocaine has traditionally been the first-line agent chosen for treating a patient with a wide complex tachycardia. The new guidelines cite studies showing that lidocaine is less effective than other drugs (e.g., IV procainamide, sotalol, or amiodarone) in patients with VT, and lidocaine is now relegated to second-tier therapy in the new tachyarrhythmia management algorithms.
Adenosine retains its place in the management of paroxysmal SVT, but cautions are now given concerning potential toxicity when adenosine is used in wide complex tachycardias not known to be supraventricular in origin. Rare cases of angina, hypotension, and proarrhythmia have been reported, and it is now recognized that adenosine should not be used indiscriminately for diagnostic purposes.
Amiodarone has been added to the new tachyarrhythmia management algorithms. It is particularly useful in patients with severely compromised ventricular function. Use of IV amiodarone is now recommended for patients with hemodynamically stable and unstable VT and for wide complex tachycardias of uncertain origin. Amiodarone is now also recommended in ventricular fibrillation (VF)/pulseless VT when initial attempts at electrical defibrillation have been unsuccessful.
Bretylium was formerly included in ACLS algorithms for unstable VT and VF. After review of available data on the use of bretylium, the new guidelines no longer include use of bretylium since there are limited data showing it is effective while its use is frequently associated with toxicity.
Comment by John P. DiMarco, MD, PhD
The new AHA guidelines make appropriate changes in recommendations for acute therapy of several arrhythmias. Within the last 15 years, we have learned much about the electrophysiologic substrates and mechanisms responsible for arrhythmias. Clinical trial data are now available on which to base recommendations. The goal is now to use drugs with actions specific for the arrhythmia and patient being treated. For supraventricular tachyarrhythmias, adenosine and calcium channel blockers are the drugs of choice for effective manipulation of AV nodal conduction leading to either termination or effective rate control. Treatment of ventricular arrhythmias has been a more difficult topic to study since the patients are frequently unstable and/or unable to give consent. In hemodynamically tolerated patients, misdiagnosis of VT as SVT often led to the inappropriate administration of adenosine or a calcium channel blocker, occasionally with severe adverse consequences. The guidelines now appropriately caution against this practice. Since these arrhythmias most frequently arise in scarred muscle, the guidelines now recognize that use of IV procainamide, sotalol and amiodarone are likely to be more effective and these agents should be the drugs of choice.
Finally, the removal of bretylium for the ACLS guidelines is certainly appropriate and long overdue. The data supporting bretylium as an antiarrhythmic drug were old and clearly flawed. In view of the lack of evidence documenting efficacy, the high occurrence of toxicity means that bretylium should have no role in arrhythmia management.
Reference
- Kudenchuk PJ, et al. N Engl J Med 1999;341:871-878.
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