I have shortness of breath and chest pain when exercising; is it possible that a 21y/o man can develop chf? how can one tell? thanks.

Can't tell for sure: Shortness of breath does not always mean cardiac. It could mean something in the lungs like asthma, or deconditioning. When you get your evaluation they will be able tell.

Very unlikely: While CHF is able to occur in young people, it is uncommon. Drugs, poor health and congenital disorders may cause CHF at a young age. It is normal to have some discomfort and shortness of breath when exercising as it is stressing your body to do things you wouldn't do at rest.

No in you age: Must likely you picture is due to a respiratory disorders like asthama or acute bronchitis.

Possible: It is possible to develop congestive heart failure in a 21-year-old. Coronary artery disease is unlikely. Causes of congestive heart failure may be viral infections or high blood pressure, among others. Symptoms might not be related to heart at all. Thorough medical evaluation is required. Diagnostic studies e.g. Cxr, ekg, echocardiogram, possibly stress test may follow. See your doctor.

Very unlikely: While CHF can occur in young people, it is uncommon. Drugs, poor health and congenital disorders may cause CHF at a young age. It is normal to have some discomfort and shortness of breath when exercising as it is stressing your body to do things you wouldn't do at rest. See your physician if concerned.