Renewed impact of lidocaine on refractory ventricular arrhythmias in the amiodarone era

Lidocaine as an anti-arrhythmic drug: Are there any indications left?

Lidocaine is classified as a class Ib anti-arrhythmic that blocks voltage- and pH-dependent sodium channels. It exhibits well investigated anti-arrhythmic effects and has been the anti-arrhythmic of choice for the treatment of ventricular arrhythmias for several decades. Lidocaine binds primarily to inactivated sodium channels, decreases the action potential duration, and increases the refractory period. It increases the ventricular fibrillatory threshold and can interrupt life-threatening tachycardias caused by re-entrant mechanisms, especially in ischemic tissue. Its use was pushed into the background in the era of amiodarone and modern electric device therapy. Recently, lidocaine has come back into focus for the treatment of acute sustained ventricular tachyarrhythmias. In this brief overview, we review the clinical pharmacology including possible side effects, the historical course, possible indications, and current Guideline recommendations for the use of lidocaine.

Combination Formulation of Tetrodotoxin and Lidocaine as a Potential Therapy for Severe Arrhythmias

Severe arrhythmias-such as ventricular arrhythmias-can be fatal, but treatment options are limited. The effects of a combined formulation of tetrodotoxin (TTX) and lidocaine (LID) on severe arrhythmias were studied. Patch clamp recording data showed that the combination of LID and TTX had a stronger inhibitory effect on voltage-gated sodium channel 1.5 (Nav1.5) than that of either TTX or LID alone. LID + TTX formulations were prepared with optimal stability containing 1 μg of TTX, 5 mg of LID, 6 mg of mannitol, and 4 mg of dextran-40 and then freeze dried. This formulation significantly delayed the onset and shortened the duration of arrhythmia induced by aconitine in rats. Arrhythmia-originated death was avoided by the combined formulation, with a decrease in the mortality rate from 64% to 0%. The data also suggests that the anti-arrhythmic effect of the combination was greater than that of either TTX or LID alone. This paper offers new approaches to develop effective medications against arrhythmias.

Management of monomorphic ventricular tachycardia electrical storm in structural heart disease

Electrical storm (ES) is a life-threatening condition that is defined by three or more episodes of sustained ventricular tachycardia (VT), ventricular fibrillation (VF), or appropriate shocks from an implantable cardioverter defibrillator (ICD) within 24 hours. The most common form of ES is monomorphic VT. It carries poor outcome despite all available intervention therapies. The therapies include rapid recognition of the condition, treatment of the reversible causes, ICD-reprogramming, antiarrhythmic drugs, sedation, and catheter ablation (CA). The first line antiarrhythmic drugs are amiodarone and β-blockers with superiority of propranolol over the others. The long-term use of the antiarrhythmic drugs is limited due to their adverse effects and drug-related proarrhythmic effect. The basic mechanism of monomorphic VT is re-entry pathway which can be targeted by CA. CA should be considered in drug refractory ES and patients should be referred in early course of disease. There are reported studies which showed the superiority of CA over the medical treatment in reducing the arrythmia burden and ICD appropriate shock. The survival benefit has been reported after successful ablation of ES in case series but to date no randomized control trial shows mortality benefit.

Acute hospital administration of amiodarone and/or lidocaine in shockable patients presenting with out-of-hospital cardiac arrest: A nationwide cohort study

BACKGROUND

Terminating ventricular fibrillation (VF) or pulseless ventricular tachyarrhythmia (VT) is critical for successful resuscitation of patients with shockable cardiac arrest. In the event of shock-refractory VF, applicable guidelines suggest use of anti-arrhythmic agents. However, subsequent long-term outcomes remain unclear. A nationwide cohort study was therefore launched, examining 1-year survival rates in patients given amiodarone and/or lidocaine for cardiac arrest.

METHODS

Medical records accruing between years 2004 and 2011 were retrieved from the Taiwan National Health Insurance Research Database (NHIRD) for review. This repository houses all insurance claims data for nearly the entire populace (>99%). Candidates for study included all non-traumatized adults receiving DC shock and cardiopulmonary resuscitation immediately or within 6h of emergency room arrival. Analysis was based on data from emergency rooms and hospitalization.

RESULTS

One-year survival rates by treatment group were 8.27% (534/6459) for amiodarone, 7.15% (77/1077) for lidocaine, 11.10% (165/1487) for combined amiodarone/lidocaine use, and 3.26% (602/18,440) for use of neither amiodarone nor lidocaine (all, p<0.0001). Relative to those given neither medication, odds ratios for 1-year survival via multiple regression analysis were 1.84 (95% CI: 1.58-2.13; p<0.0001) for amiodarone, 1.88 (95% CI: 1.40-2.53; p<0.0001) for lidocaine, and 2.18 (95% CI: 1.71-2.77; p<0.0001) for dual agent use.

CONCLUSIONS

In patients with shockable cardiac arrest, 1-year survival rates were improved with association of using amiodarone and/or lidocaine, as opposed to non-treatment. However, outcomes of patients given one or both medications did not differ significantly in intergroup comparisons.