Unforeseen difficulty identifying and enrolling eligible subjects

This is a research study to evaluate the electrical properties of heart tissue. The purpose of this study is to determine the impedance (electrical resistance) of different tissues on the outer surface of the heart. This may be important for distinguishing scarred heart muscle from fat that can be seen on the surface of the heart. This information may eventually be utilized in patients that undergo a procedure (called catheter ablation) for the treatment of life-threatening heart rhythms. Investigators expect a detectable difference between the impedance of normal and infarcted myocardium (approximately 50 ohms).

The treatment of cardiac arrhythmias with endocardial catheter ablation has evolved rapidly over the past few decades. At the time of this writing, the ablation of almost all atrial and ventricular arrhythmias has been described in the literature. Multiple energy modalities (e.g. radiofrequency, cryotherapy) and approaches (e.g. retrograde aortic, transseptal puncture) have been described, yet ablation of some rhythms is not as successful as others.

The realization that ventricular tachycardia (VT) in the setting of Chagas Disease can originate in the epicardium has lead to the development of a percutaneous, transthoracic epicardial approach to mapping and ablation of this arrhythmia. This approach has now been applied to patients with VT in the setting of ischemic and nonischemic heart disease at many centers throughout the world. Traditional mapping technologies are utilized on the epicardium to define scarred heart tissue and locate the VT circuit.

It is well known that human hearts display a variable amount of fat overlying the epicardium. Not only is the coronary vasculature embedded in a layer of adipose tissue, but the rest of the heart may have areas of epicardial fat. As fat is an insulator and does not generate or easily conduct electrical activity, current mapping techniques may classify epicardial fat incorrectly as myocardial scar. This may have important effects on the ability to diagnose and treat arrhythmias with epicardial ablation.

Inclusion Criteria:

• All adult patients undergoing elective cardiac surgery for coronary artery disease (with or without normal heart function) or valvular disease (with normal heart function) at the Hospital of the University of Pennsylvania under the direction of Y. Joseph Woo MD will be eligible.

Exclusion Criteria:

• Patients undergoing emergent surgery and patients with idiopathic cardiomyopathy, infiltrative cardiomyopathies and hypertrophic cardiomyopathies will be excluded.

Adult patients undergoing elective cardiac surgery for coronary artery disease