The DefiPace Study

Who May Qualify: - Patient is scheduled to undergo elective open chest cardiac surgery (bypass and / or valve surgery) - Patient is at least 18 years old - Patient with isolated bypass surgery is at least 70 years old - Patient with valve surgery is at least 60 years old - Patient provides written willing to sign a consent form prior to the procedure - Phase B only: patient is scheduled for TMA implantation during the elective cardiac surgery and is potentially eligible for DefiPace use Who Should NOT Join This Trial: - Clinical history of either permanent, persistend or paroxysmal atrial fibrillation - Permanent pacemaker/defibrillator, other intra-cardiac active implanted electronic devices - Minimally-invasive surgery - Recent stroke within the last 3 months - A history of or current endocarditis - Pregnacy at the time of surgery Always talk to your doctor about whether this trial is right for you.