I have heart disease. lately i am short of breath climbing the stairs. all the heart and lung test have been normal. what else could be the cause?

What kind of: Heart disease do you have? Still you mention heart and lung test are negative. It could be lack of physical conditioning.

Workup and Mgt: The difficulty that you are having with climbing stairs may be caused by a number of conditions, including pulmonary hypertension, asthma, cardiac disease. I would suggest reviewing your cardiac stress test with your physician, asking about pulmonary arterial hypertension, and ruling out a possible clot in your lungs. Pulmonary function testing, a V/Q scan and Doppler of your lower extremities.