Electrical and intravenous drug cardioversion were equally efficacious in treating acute atrial fibrillation, found a large, randomised controlled trial.
A large, randomised controlled trial looked at cardioversion, a medical procedure that quickly brings heart rhythm back to normal. Cardioversion can be done with a mild electric shock or with fast-acting drugs delivered through an IV. “These methods allow us to quickly get patients back to their normal heart rate, and send them home after four to six hours in the emergency department,” said Dr Ian Stiell, lead author and senior scientist at The Ottawa Hospital and distinguished professor at the University of Ottawa.
Acute atrial fibrillation is a rapid, irregular heartbeat that must be treated within 48 hours to avoid complications like stroke and heart failure. The study team estimates that acute atrial fibrillation accounts for 430,000 emergency department visits every year in Canada and the US.
The researchers recruited 396 patients with acute atrial fibrillation from 11 Canadian emergency departments. Cardioversion is a commonly used treatment in this country. Patients were randomly assigned to one of the two kinds. The first group received only electrical cardioversion. Patients are sedated during this procedure, so they do not feel the shock.
The second group received a drug called procainamide through an IV. 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% returned to their normal heart rhythm (176); and 95% were discharged home (183).
In the drug-then-shock group (204 patients): 96% returned to their normal heart rhythm (196); 97% were discharged home (198); and 52% recovered their normal heart rhythm with the drug alone (106).
Both kinds of cardioversion were equally good at restoring normal heart rhythm and getting patients home the same day. The drug-shock strategy was more effective for patients experiencing atrial fibrillation for the first time, and for patients younger than 70.
The two methods were equally safe -none of the patients had any serious side-effects. Two weeks after the treatment, no patients had had a stroke, 95% still had normal heart rhythm, 11% returned to the emergency department because of atrial fibrillation, three percent had an additional round of cardioversion, and two percent were admitted to hospital.
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.
“If I have a patient on a drug infusion, I can see other patients at the same time,” said Dr Jeffrey Perry, study co-author and senior scientist at The Ottawa Hospital and professor at the University of Ottawa. “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.”
The researchers note that patients often have a strong preference for one kind of cardioversion over the other, especially if they need it done regularly. “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.
While cardioversion is common in Canada, it isn’t as well known in other parts of the world.
“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 Stiell. “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.”
“Given the crowding which exists in the emergency health care setting, the Canadian Institutes of Health Research (CIHR) is proud to support this high-quality research that enhances evidence-informed clinical decisions in the transitions of care for patients with atrial fibrillation,” said Dr Brian Rowe, study co-author, scientific director of the CIHR’s Institute of Circulatory and Respiratory Health, and professor of emergency medicine at the University of Alberta.
Background: Acute atrial fibrillation is the most common arrythmia treated in the emergency department. Our primary aim was to compare conversion to sinus rhythm between pharmacological cardioversion followed by electrical cardioversion (drug–shock), and electrical cardioversion alone (shock-only). Our secondary aim was to compare the effectiveness of two pad positions for electrical cardioversion.
Methods: We did a partial factorial trial of two protocols for patients with acute atrial fibrillation at 11 academic hospital emergency departments in Canada. We enrolled adult patients with acute atrial fibrillation. Protocol 1 was a randomised, blinded, placebo-controlled comparison of attempted pharmacological cardioversion with intravenous procainamide (15 mg/kg over 30 min) followed by electrical cardioversion if necessary (up to three shocks, each of ≥200 J), and placebo infusion followed by electrical cardioversion. For patients having electrical cardioversion, we used Protocol 2, a randomised, open-label, nested comparison of anteroposterior versus anterolateral pad positions. Patients were randomly assigned (1:1, stratified by study site) for Protocol 1 by on-site research personnel using an online electronic data capture system. Randomisation for Protocol 2 occurred 30 min after drug infusion for patients who had not converted and was stratified by site and Protocol 1 allocation. Patients and all research and emergency department staff were masked to treatment allocation for Protocol 1. The primary outcome was conversion to normal sinus rhythm for at least 30 min at any time after randomisation and up to a point immediately after three shocks. Protocol 1 was analysed by intention to treat and Protocol 2 excluded patients who did not receive electrical cardioversion. This study is registered at ClinicalTrials.gov, number NCT01891058.
Findings: Between July 18, 2013, and Oct 17, 2018, we enrolled 396 patients, and none were lost to follow-up. In the drug–shock group (n=204), conversion to sinus rhythm occurred in 196 (96%) patients and in the shock-only group (n=192), conversion occurred in 176 (92%) patients (absolute difference 4%; 95% CI 0–9; p=0·07). The proportion of patients discharged home was 97% (n=198) versus 95% (n=183; p=0·60). 106 (52%) patients in the drug–shock group converted after drug infusion only. No patients had serious adverse events in follow-up. The different pad positions in Protocol 2 (n=244), had similar conversions to sinus rhythm (119 [94%] of 127 in anterolateral group vs 108 [92%] of 117 in anteroposterior group; p=0·68).
Interpretation: Both the drug–shock and shock-only strategies were highly effective, rapid, and safe in restoring sinus rhythm for patients in the emergency department with acute atrial fibrillation, avoiding the need for return to hospital. The drug infusion worked for about half of patients and avoided the resource intensive procedural sedation required for electrical cardioversion. We also found no significant difference between the anterolateral and anteroposterior pad positions for electrical cardioversion. Immediate rhythm control for patients in the emergency department with acute atrial fibrillation leads to excellent outcomes.
Funding: Heart and Stroke Foundation of Canada and the Canadian Institutes of Health Research.
Ian G Stiell, Marco L A Sivilotti, Monica Taljaard, David Birnie, Alain Vadeboncoeur, Corinne M Hohl, Andrew D McRae, Brian H Rowe, Robert J Brison, Venkatesh Thiruganasambandamoorthy, Laurent Macle, Bjug Borgundvaag, Judy Morris, Eric Mercier, Catherine M Clement, Jennifer Brinkhurst, Connor Sheehan, Erica Brown, Marie-Joe Nemnom, George A Wells, Jeffrey J Perry