Isolation of the entire posterior left atrium improves the outcomes
of patients who undergo the Cox maze procedure, the gold standard
surgical treatment for atrial fibrillation, according to a report in
The Journal of Thoracic and Cardiovascular Surgery for April.

The Cox maze procedure, which was first used clinically in 1987,
involves the creation of incisions on the right and left atria in an
effort to disrupt the reentrant circuits thought to be necessary for
sustaining atrial fibrillation.

Since its introduction, a number of changes in the Cox maze
procedure have taken place. In the present study, Dr. Ralph J.
Damiano Jr. and colleagues investigated the clinical impact of one
of the most recent changes: using two ablations lines rather than
just one to connect ablation areas near the pulmonary veins. The new
modification results in a "box lesion" that fully isolates the
posterior left atrium.

The study involved 137 patients who underwent the Cox maze procedure
at the Barnes-Jewish Hospital in St. Louis. Fifty-six of the
patients were treated prior to May 2004 when the single ablation
line technique was used, and 81 were treated after this point, when
the box lesion was routinely performed.

The rate of early atrial tachyarrhythmia was 37% in the box lesion
group, versus 71% in the single lesion group (p < 0.001).

Among box lesion-treated patients, 87% and 96% were free from atrial
fibrillation recurrence at 1 and 3 months, respectively. The
corresponding percentages in the single lesion group were
significantly lower-69% and 85%.

At 6 months after surgery, 44% of single lesion-treated patients
were using antiarrhythmic agents compared with just 15% of patients
treated with the box lesion.

Creation of the box lesion did not increase operative time or
postoperative morbidity or mortality, the findings indicate.

In light of these results, the authors conclude, "A complete box
lesion should be included in all patients undergoing the Cox maze
procedure."

J Thorac Cardiovasc Surg 2008;135:870-877.