Shortness of breath can occur because of heart muscle failure. This is called a cardiomyopathy. The heart is a muscle, a pump, that circulates fluid through the body. If the heart muscle is damaged by repeated heart attacks, or by inflammation, or by drugs such as alcohol, the pump fails and fluid, edema, accumulates in the lungs. This is called peri-carditis.
Shortness of breath can occur because of an altered heart rhythm.
This is called an arrhythmia. In an arrhythmia the heart beats so fast it doesn't have time to fill properly. This improper filling results in a decreased force of contraction and fluid accumulates in the lungs. The interference can be caused by inflammation, infection, or obstruction of the nose or airways. Shortness of breath occurs because of interference with the exchange of oxygen from the air to the lungs.