In patients who presented with recent onset atrial fibrillation (AFib) < 36h, delayed cardioversion (DC) at 48h compared to early cardioversion (EC) was non-inferior (91% vs 94%; -2.9 percentage points, 95%CI -8.2 to 2.2).
Why does this matter?
There is a significant variation in practice between how recent-onset AFib is treated in the US compared to other countries. In general, physicians in the US are more likely to utilize rate-control and have a much higher admission rate.
Better late than never?
This was a multi-center, randomized, open-label, noninferiority trial performed in the Netherlands. A total of 437 patients were randomized to either early or delayed cardioversion. EC consisted of pharmacologic conversion (flecainide was preferred) or electrical cardioversion in those who had contraindications. DC consisted of rate control with beta-blockers, non-dihydropyridine calcium channel blockers, or digoxin until HR < 110 and discharge with next-day follow-up (around 48h from onset) for re-evaluation. No TEEs were performed, and patients who had a high risk of stroke were started on anticoagulation and continued based on CHA2DS2-VASc scores. The primary outcome was sinus rhythm at the 4-week follow-up visit. Secondary outcomes included ED length of stay at the index visit, ED visits related to AFib, cardiovascular complications, and time until recurrence of Afib. A total of 335 patients had telemetric monitoring at home 3 times daily or with symptoms.
In the DC group, 91% were in sinus rhythm at the 4 week mark compared to 94% in the EC group. This resulted in a between-group difference of -2.9 percentage points (95%CI -8.2 to 2.2), which did not meet the lower 95%CI inferiority mark of 10 percentage points. In the DC group, spontaneous conversion occurred in 69% at 48h. In the EC group, 16% had spontaneous conversion (some received rate-control meds). In terms of cardiovascular complications, both groups had 1 ischemic stroke or TIA; 3 patients in both groups had unstable angina or ACS during the 4-week follow-up.
While there were similar adverse outcomes in both groups, this study was not powered to detect a difference. It seems that the majority of patients in the DC group had spontaneous conversion with rate-control and this approach is non-inferior to early cardioversion. This supports the current rate-control practice. It is also unlikely that most patients will be able to obtain follow-up so closely after being discharged. I anticipate that many of these patients will continue to get admitted in the US after rate-control.
For more on Afib, see these emDocs posts:
Early or Delayed Cardioversion in Recent-Onset Atrial Fibrillation. N Engl J Med. 2019 Apr 18;380(16):1499-1508. doi: 10.1056/NEJMoa1900353. Epub 2019 Mar 18.
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