Heart Rhythm Stabilizing Drugs Marginally Improve Survival Rates

Heart stabilizing drugs administered after a cardiac arrest may not be as effective as previously thought.

It has been established that worldwide cardiac arrests are a significant killer of both men and women. In the United States each year, 326,000 people have a cardiac arrest outside of the hospital and a staggering 10% survive.

In a study presented at the American College of Cardiology's 65th Annual Scientific Session, researchers explained that the administration of heart stabilizing drugs after an out-of-hospital cardiac arrest may not make much a difference in the patient’s survival.

Heart stabilizing drugs such as amiodarone or lidocaine are administered if a patient is unresponsive to a defibrillator. These 2 drugs are commonly thought to return the heart’s electrical signals to normal levels.

Researchers studied patients whose cardiac arrest was caused by ventricular fibrillation or pulseless ventricular tachycardia. In all cases studied, the paramedics were unable to return the patient’s heart to a normal rhythm with a defibrillator alone.

The randomized, double-blind, and placebo-controlled study enrolled 3026 participants, who received up to 450 milligrams of amiodarone, up to 180 milligrams of lidocaine, or a saline placebo.

Of the patients enrolled in the study, 974 received amiodarone, 993 received lidocaine, and 1059 received the placebo.

Patients whose cardiac arrest was witnessed by another person, and received the placebo, had a survival rate of about 23%.

Among these patients who were administered either amiodarone or lidocaine, there was an improved survival rate of about 28%.

This patient group was previously believed to have an improved chance of surviving a cardiac arrest because the emergency is recognized soon after it begins, which makes them less likely to sustain fatal organ damage at the time they receive medical attention, according to the study.

In addition to this, patients who received either 1 of amiodarone or lidocaine needed fewer shocks with a defibrillator to achieve a stable heart rhythm. No patient in this study experienced any adverse side effects from the drugs. The researchers said there was no neurological differences between the the placebo group and the group who received the drugs.

With a survival rate improvement of only 5%, the results were deemed statistically insignificant. However, researchers said that any improvement in survival is significant in a clinical sense.

"If you assume these drugs might improve survival rates by just 3%overall or by 5%in witnessed cardiac arrest events, this means they could save 1800 additional patients every year in the United States alone from out-of-hospital cardiac arrest,” said the study’s lead author, Peter Kudenchuk, MD. “That's a huge potential impact on the single greatest killer of men and women with heart disease.”

Kudenchuck added that a possible limitation of this study was that the drugs may have been administered late, perhaps making them less effective once administered.

Additional studies will be needed to show how different doses of the drugs, and even a combination of the drugs, could improve the survival rate of patients.