What is the best treatment for a congested heart?

It depends: I am assuming you mean congestive heart failure. This can be caused by several things. Treatment will depend on what is the cause of the heart failure. For ex. Valve disease, blocked arteries, high blood pressure, infections can all be a source. If the problem is treated it will often help. Certain medications like diuretics, blood pressure meds, limiting salt in diet are often used too.

CHF: Treatment depends on what the cause of the CHF is. Could be surgical, could be medical. Systolic CHF is different from diastolic CHF and valvar stenosis CHF is different from valvar insufficiency chf. Virtually all kinds have diuretic as part of the treatment.