Are patients with atrial flutter at risk of embolisation when cardioverted? Do they need anticoagulation to cover the procedure?

Although common clinical practice and guidelines do not advocate routine anticoagulation of patients with atrial flutter undergoing cardioversion, there are no data to support this practice. Rather, recent studies suggest the prevalence of intraatrial thrombus in unselected patients with atrial flutter is significant and of the order of 30–35% (compared with 3% prevalence in a control population in sinus rhythm). The atrial standstill (or stunning) that has been described post-cardioversion of atrial fibrillation and is thought to be a factor in the associated thromboembolic risk has also now been described immediately post-cardioversion of patients with atrial flutter. Although some authors argue that the stunning post-cardioversion of atrial flutter is “attenuated” compared with the response in atrial fibrillation, the thromboembolic rate associated with cardioversion of atrial flutter in the absence of anticoagulation argues against this. Indeed, the thromboembolic rate appears to be comparable with the early experience of cardioverting atrial fibrillation. Furthermore, atrial flutter is an intrinsically unstable rhythm which may degenerate into atrial fibrillation and certain patients alternate between atrial fibrillation and atrial flutter.

Like atrial fibrillation, atrial flutter may be the first manifestation of underlying heart disease and it is likely, though not yet proven, that the thromboembolic risks associated with both chronic atrial flutter and with cardioversion of atrial flutter vary with the extent of underlying cardiovascular pathology. Although existing data are limited, on current evidence we advise that patients with atrial flutter should be anticoagulated prior to, during and postcardioversion, in the same way as patients with atrial fibrillation.