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Shock Only or Drug-Shock? 2 Different Cardioversion Techniques Equally Effective, Study Says


The drug-shock strategy was more effective for patients experiencing atrial fibrillation for the first time and for patients younger than 70 years, the researchers said.

Both the anti-arrhythmia drug procainamide as well as a technique called cardioversion have equal safety and effectiveness in rapidly restoring normal heart rhythm in patients with acute atrial fibrillation (AF) in the emergency department (ED), according to a study published Thursday.

The study, published in The Lancet, examined 396 patients with acute AF recruited from 11 EDs in Canada. Cardioversion, delivered through a mild electric shock or with fast-acting intravenous (IV) medications, is common in Canada, but isn’t as well known in other parts of the world, according to the authors, who said this was the first study to compare the 2 techniques.

The study team estimates that acute AF accounts for 430,000 ED visits every year in Canada and the United States.

Patients were randomly assigned to 1 of the 2 techniques. The first group received only electrical cardioversion. Patients are sedated during this procedure, so they do not feel the shock.

The second group received procainamide. If the drug did not reset the patient's heart rhythm within 30 minutes, they received electrical cardioversion.

In the shock-only group (192 patients):

  • 92%, or 176, returned to their normal heart rhythm
  • 95%, or 183, were discharged home

In the drug-then-shock group (204 patients):

  • 96%, or 196, returned to their normal heart rhythm
  • 97%, or 198, were discharged home
  • 52%, or 106, recovered their normal heart rhythm with the drug alone

The drug-shock strategy was more effective for patients experiencing AF for the first time and for patients younger than 70 years. But both kinds of cardioversion were equally good at restoring normal heart rhythm and getting patients home the same day, and none of the patients had any serious adverse effects.

Two weeks after the treatment, 95% still had normal heart rhythm, 11% returned to the ED because of AF, 3% had an additional round of cardioversion, and 2% were admitted to hospital. No strokes occured after the treatment.

The researchers were interested to see that over half of the patients who received the drug did not need a shock to restore their regular heart rhythm. They recommend that physicians try the drug cardioversion first, to avoid unnecessary sedation.

Patients often have a strong preference for one kind of cardioversion over the other, especially if they need it done regularly, the authors said.

There appear to be benefits for doctors as well when they perform cardioversions with drugs.

“If I have a patient on a drug infusion, I can see other patients at the same time,” said Jeffrey Perry, MD, study co-author and senior scientist at The Ottawa Hospital and professor at the University of Ottawa, in a statement. “To do an electrical cardioversion, I need to find another doctor, a nurse and a respiratory therapist, and it takes time to assemble those people.”

In addition, cardioversion may help alleviate crowding in the ED, according to Brian Rowe, MD, co-author and scientific director of the Canadian Institutes of Health Research Institute of Circulatory and Respiratory Health, and professor of emergency medicine at the University of Alberta.

However, the decision of which technique to try is an example of shared decision making, according to Perry.

“While we believe that there are advantages to trying the drug infusion before the shock, the treatment choice is ultimately a shared decision between the patient and physician,” said Perry.

“In some countries, patients with acute atrial fibrillation are sent home with pills to slow their heart rate, while others are admitted to hospital,” said Ian Stiell, MD, lead author and senior scientist at The Ottawa Hospital and distinguished professor at the University of Ottawa. “Our study showed that cardioversion in the emergency department is safe and effective. We hope our results convince more physicians around the world to adopt these methods.”

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