|
The cardioversion of atrial fibrillation to sinus rhythm is associated with
transient mechanical dysfunction of the left atrium and left atrial appendage and the development of spontaneous
echocardiographic contrast. This phenomenon has been termed “stunning” and is considered an important
factor for thromboembolic stroke following reversion of atrial fibrillation to sinus rhythm1-3. For this reason, it is
recommended that patients undergo 3-4 weeks of post reversion anticoagulation to reduce the risk of stroke4,5.
Atrial stunning may also occur following the electrical cardioversion of atrial flutter to sinus rhythm6-8. Although
this stunning may be less than that which occurs following reversion of atrial fibrillation, recent evidence
demonstrates that the risk of thromboembolic events in patients with chronic atrial flutter and who are
cardioverted from chronic atrial flutter is significant7,9,10.
Curative radiofrequency ablation is now considered by many to be the treatment of choice for patients with
chronic atrial flutter11,12. Despite the increasing experience with atrial flutter ablative techniques, whether these
procedures are associated with left atrial mechanical stunning is unknown and uniform recommendations for
periprocedural anticoagulation have not been adopted.
We performed a study using transesophageal echocardiography to determine whether atrial stunning occurs
following reversion of chronic atrial flutter to sinus rhythm when radiofrequency energy is the mode of reversion.
In those patients in whom left atrial mechanical dysfunction was observed following reversion to sinus rhythm,
we also investigated whether this was reversible in the short and medium term by performing repeat
transesophageal echocardiographic evaluations 30 minutes and 3 weeks following radiofrequency ablation.
The mechanism of atrial stunning following direct current cardioversion is incompletely understood. Some
evidence suggests that atrial mechanical stunning occurs as a result of the preceding atrial arrhythmia and that
atrial stunning represents a form of tachycardia-mediated atrial cardiomyopathy6,13,14. Other data implicates the
direct current shock as a significant contributor to the mechanism of stunning1,2,15,16. The present study provided
an opportunity to determine whether atrial stunning occurs in the absence of a direct current shock or acutely
administered antiarrhythmic agents, thereby gaining some insight into the mechanisms of this phenomenon.
Study patients
The study population comprised 15 male patients undergoing radiofrequency catheter ablation of chronic atrial
flutter. The patients had documented chronic atrial flutter for 17.2±13.3 months and had failed a mean of 2.4±0.6
antiarrhythmic drugs prior to radiofrequency ablation. Structural heart disease was present in 6 patients and
absent in 9 patients other than the presence of left atrial dilatation.
Radiofrequency ablation was performed under general anesthesia to facilitate performance of sequential
transesophageal echocardiographic analyses without patient discomfort. Left atrial and left atrial appendage
function were assessed at four defined time points:
1. during chronic atrial flutter immediately prior to radiofrequency ablation;
2. immediately on reversion of atrial flutter to sinus rhythm;
3. 30 minutes following reversion of atrial flutter to sinus rhythm;
4. 3 weeks following the radiofrequency ablation procedure.
Left atrial appendage flow velocities were assessed using pulse wave Doppler placing the sample volume 1 cm
into the mouth of the left atrial appendage.
Left atrial function was assessed following atrial flutter termination with transesophageal echocardiographic
pulse wave interrogation of the mitral inflow at the level of the mitral valve leaflet tips (points 2-4).
Spontaneous echo contrast was defined by the appearance of swirling clouds of echogenicity in the left atrium
and left atrial appendage distinct from white noise artifact.
|
