The purpose of this study is to evaluate the exercise capacity of patients with complete heart block who are chronically being paced from the right ventricle. Also, we hope to correlate the level of uncoordinated contraction with the patients exercise capacity. We will enroll patients with complete heart block as diagnosed by standard electrocardiographic means and now have a permanent pacemaker. All patients we approach for this study will receive an echocardiogram to assess their heart function. As part of the echocardiogram, they will also receive a Tissue Synchronization Imaging (TSI) evaluation to assess the level of uncoordinated contraction they have. The patients will then be subjected to a cardiac exercise stress test which will involve them running on a treadmill until they cannot continue while data is collected regarding their heart's response to exercise. All portions of the study are noninvasive, which means they work from probes and monitors outside the body.