Is lidocaine (antiarrhythmic medication) the best choice for stabilizing early afterdepolarizations?

From the Guidelines

Lidocaine is not considered the best antiarrhythmic for stabilization of early after depolarizations (EADs). The most recent and highest quality study, published in 2018 1, suggests that beta-blockers, such as metoprolol or esmolol, are generally more effective first-line agents for this specific mechanism of arrhythmia. EADs typically occur in the setting of prolonged repolarization and are often associated with long QT syndromes. Lidocaine, as a class IB antiarrhythmic, primarily blocks fast sodium channels and shortens action potential duration in ischemic tissue, but has limited effect on the underlying mechanisms of EADs.

Some key points to consider:

• Beta-blockers work by reducing sympathetic stimulation and decreasing calcium influx, which directly addresses the calcium-dependent mechanism of EADs.
• For patients with medication-induced EADs, immediate discontinuation of the offending agent (often QT-prolonging medications) is also essential.
• In cases where beta-blockers are contraindicated, magnesium sulfate (1-2 g IV over 5-15 minutes) may be an alternative as it stabilizes membrane potential and reduces calcium influx that triggers EADs.
• The 2015 American Heart Association guidelines update for cardiopulmonary resuscitation and emergency cardiovascular care also suggest that lidocaine may be considered as an alternative to amiodarone for VF/pVT that is unresponsive to CPR, defibrillation, and vasopressor therapy 1.
• However, the evidence supporting a potential role for prophylactic lidocaine after VF/pVT arrest is relatively weak, limited to short-term outcomes, and nonexistent for cardiac arrest presenting with nonshockable rhythms 1.

Overall, the current evidence suggests that beta-blockers are the preferred first-line treatment for EADs, and lidocaine should only be considered in specific situations where beta-blockers are contraindicated or ineffective.

From the Research

Effectiveness of Lidocaine in Stabilization of Early After Depolarizations

• The use of lidocaine in acute myocardial infarction has been studied extensively, with mixed results regarding its effectiveness in preventing ventricular arrhythmias and reducing mortality rates 2, 3, 4, 5, 6.
• A study published in 1990 found that lidocaine is considered the drug of choice for the treatment of malignant ventricular arrhythmias, but its prophylactic use is problematic due to the occurrence of serious side effects 2.
• A 1995 study compared the efficacy and safety of a 40-hour lidocaine infusion after completion of an 8-hour open-label infusion for prophylaxis of primary ventricular fibrillation in patients with uncomplicated acute myocardial infarction, and found that lidocaine provoked more congestive heart failure than placebo 3.
• A multicenter randomized trial and systematic overview of lidocaine in acute myocardial infarction published in 1999 found that lidocaine reduces ventricular fibrillation but may adversely affect mortality rates 4.
• A 2015 Cochrane review found that prophylactic lidocaine has very little or no effect on mortality or ventricular fibrillation in people with acute myocardial infarction, and its safety profile is unclear 5.
• Another study published in 1999 found that prophylactic lidocaine use has decreased with the advent of thrombolysis, although its use may not be associated with increased mortality rates 6.

Comparison with Other Antiarrhythmic Drugs

• The 2015 Cochrane review found no significant differences between lidocaine and any other antiarrhythmic drug in terms of all-cause mortality and ventricular fibrillation 5.
• The review also found that lidocaine compared with placebo or no intervention increased the risk of asystole and dizziness/drowsiness 5.

Clinical Implications

• The current evidence suggests that lidocaine may not be the best antiarrhythmic for stabilization of early after depolarizations, due to its potential to increase mortality rates and cause serious side effects 2, 3, 4, 5, 6.
• The use of lidocaine should be carefully considered, taking into account the individual patient's risk factors and medical history 2, 3, 4, 5, 6.