Safety of electrical cardioversion

VANCOUVER, CANADA. A study carried out by physicians at St. Paul’s Hospital in Vancouver concludes that electrical cardioversion of patients with atrial fibrillation or atrial flutter has a very low rate of long-term complications. During the period January 1, 2000 until September 2007, 1233 such patients made 1820 visits to the emergency departments at St. Paul’s and Mt. St. Joseph’s hospitals. Of these, 400 underwent electrical cardioversion. Most (72%) needed only one shock to revert to normal sinus rhythm (NSR) and 68% needed only 100 joule energy or less to convert. A formal chart review was done for 141 of the 400 patients yielding the following patient characteristics:

  • Average age – 57 years
  • Male sex – 75%
  • Lone atrial fibrillation – 74%
  • Admitted with atrial fibrillation – 87%
  • Admitted with atrial flutter – 13%
  • Average heart rate at admission – 122 bpm
  • Average blood pressure at admission – 127/80
  • Percent having a CHADS2 score of 0 – 61%
  • Percent having a CHADS2 score of 1 – 37%

Most patients (94%) were cardioverted within 24 hours of the onset of their symptomatic episode with only 3.5% failing to regain NSR. The length of stay in the emergency department ranged from 1.4 to 22.8 hours with a median time of 4 hours. All 400 patients were followed for 30 days after their cardioversion. During this time no patients died, experienced a stroke, or had a thromboembolic event. Only 22 patients (5.5%) made a follow-up visit to an emergency department and of these, six (1.5%) required a repeat cardioversion.

The emergency physicians conclude that electrical cardioversion is safe for up to 30 days for both atrial fibrillation and atrial flutter. However, they do point out that the patient population involved in the study were relatively young, had mostly lone AF, had a low risk of stroke (low CHADS2 score), and had been in AF or flutter for only a short time. Thus their findings may not apply to sicker patients.
Scheuermeyer, FX, et al. Thirty-day outcomes of emergency department patients undergoing electrical cardioversion for atrial fibrillation or flutter. Academic Emergency Medicine, Vol. 17, April 2010, pp. 408-15

Editor’s comment: The majority (94%) of patients involved in the study had been in afib or atrial flutter for less than 24 hours. Thus it is difficult to extrapolate the results to the cardioversion of persistent afibbers who often have been in afib for 7 days or more. It is interesting that a recent study concluded that electrical cardioversion was most effective if carried out between 24 and 36 hours following the onset of an afib episode.