This study evaluates the usefulness of 3D echocardiography to guide pacemaker therapy in the operating room in cardiac surgical patients. Each patient will serve as his own control, following a paired design.

Cardiac surgical patients sometimes require temporary pacing wires to optimize cardiac function during weaning from cardiopulmonary bypass (CPB), and/or to treat hemodynamically significant brady-arrhythmias. The available patient series report that 8.6% to 23.9% of patient undergoing coronary artery bypass grafting (CABG) or valve surgery require temporary pacing at some time after CPB. The site of pacemaker wire placement seems to be a crucial determinant of cardiac output. In non-surgical patients isolated right ventricular (RV) pacing seems to induce electromechanical dyssynchrony of the RV and the left ventricle (LV). A normal ventricle in sinus rhythm displays a simultaneous contraction of all segments of the heart, so that regional minimal volume (i.e. maximal contraction) will occur at the same time. Isolated RV pacing seems to result in a left bundle branch type electrical activation sequence, with delayed contraction of some of the segments. The LV, but not the RV, seems to negatively affected by this state of dyssynchrony, resulting in decreased cardiac output. In surgical patients however, there is not such data available yet. Since isolated RV epicardial wire placement is still widely practiced in cardiac surgery, and in our own institution, we would like to study the effect of RV pacing on LV synchrony and LV output.

Again from studies in non-surgical patients receiving resynchronization therapy, we know that real-time three-dimensional (3D) echocardiography is very useful to pick up subtle changes in LV synchrony and thereby guide synchronization of ventricular contraction. However, to date the usefulness of real-time 3D echocardiography to guide pacemaker therapy in cardiac surgery is unknown. In the present feasibility study in cardiac surgical patients, we want to investigate the acute effects of isolated RV pacing on LV synchrony, and LV output.

Inclusion Criteria:

• Adult patient scheduled to undergo elective cardiac surgery by means of full sternotomy and use of cardiopulmonary bypass
• Preoperative moderate to good LV function, ejection fraction > 30%
• Age > 18 yrs. old
• Preoperative sinus rhythm
• Pacemaker lead inserted by cardiac surgeon during surgery
• Underlying sinus rhythm after cardiopulmonary bypass before the end of surgery
• Able to understand written and verbal patient information
• Signed informed consent

Exclusion Criteria:

• Emergency cardiac surgery
• Minimally invasive surgery
• Contraindication to TEE
• Redo surgery
• Hemodynamic instability after CPB (late exclusion criterium)
• No pacemaker lead inserted by cardiac surgeon (late exclusion criterium)
• No sinus rhythm during chest closure towards the end of surgery (late exclusion criterium)