1. Development of new devices and catheters to treat, without surgery (non-invasively), children with heart defects. 2. Evaluate potentially useful new drugs for the treatment of heart failure and high blood pressure in the lungs (pulmonary hypertension) of the young in animal models, before consideration for clinical application. 3. Evaluate the accuracy of ultrasound measurements of cardiovascular physiology, correlating & validating them with direct blood pressure measurements in heart chambers and great vessels.