Contrast Echocardiography During Exercise to Assess Pulmonary Blood Volume

This study is testing whether a special type of heart ultrasound (contrast echocardiography) done during exercise can measure the amount of blood in the lungs, to help diagnose the cause of shortness of breath on exertion. **You may be eligible if...** - You have been referred to a cardiac catheterization procedure to investigate why you get breathless with activity - Your doctor is open to also performing an echocardiogram (heart ultrasound) with contrast during the same session **You may NOT be eligible if...** - You are unable or unwilling to undergo an echocardiogram with contrast dye - You have had a prior bad reaction to echo contrast - In the opinion of your doctor, the echocardiogram could interfere with the clinical procedure Talk to your doctor to see if this trial is right for you.