Measuring Electrical Resistance of Different Tissues on the Outer Surface of the Heart

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).