Postoperative atrial fibrillation after coronary artery bypass grafting will be monitored up to 1 year after the procedure by implanting a Reveal XT internal loop recorder two weeks before the surgery. Frequency, burden, and possible risk factors will be described.

During the operation direct contact epicardial mapping will be performed and tissue samples will be collected to identify an electrophysiological and a structural substrate for development of AF.

Background of the study:

Postoperative atrial fibrillation (POAF) after cardiac surgery is a common (1 in 4) complication and associated with morbidity and mortality. Not all episodes of AF are noticed and detected, especially after discharge. several studies have shown high mortality in POAF patients, suggesting a progression in AF frequency.

Objective of the study:

To investigate the real incidence and burden of POAF. Afterwards a risk stratification of POAF is made. To identify a structural and electrophysiological substrate for the development of POAF and new onset AF during follow up.

Study design:

140 patients will receive a Reveal device. After 3 and 12 months data will be subtracted from the device. 100 of these patient will undergo additional mapping and tissue biopsies during operation.

Study population:

All patients undergoing cardiac surgery without a history of AF and without a pacemaker will be invited to participate in the study.

Primary study parameters/outcome of the study:

Incidence of POAF until 3 months after CABG.

Secondary study parameters/outcome of the study:

Incidence of POAF until 12 months after CABG. Determine risk factors for early and late POAF. Detect pre-operative (unnoticed) episodes of AF.

Determine a substrate for development of AF.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness:

There is a small risk of minor complications (hemorrhage and infection of the pocket).The device can be explanted easily if necessary. Ther is a burden of the im- and explantation of the device (local anesthesia, approx. 20 minutes). Patient will have to visit the out-hospital clinic twice.

The operation will be prolonged by 30 minutes due to mapping.

Inclusion Criteria:

• Undergoing non emergency surgery
• Sinus rhythm on initial visit

Exclusion Criteria:

• History of atrial fibrillation
• Internal pacemaker

those patients undergoing cardiac surgery.