Congestive heart failure, most commonly, refers to the process of pressure elevation in the left lower pumping chamber of the heart (the left ventricle). This then leads to increased pressure in the left upper pumping chamber of the heart. This elevation of pressure them gets transmitted to the blood vessels which are suppose to return oxygenated blood to the left side of the heart from the lungs. The end result is that body fluid starts to accumulated in the air sacks in the lungs causing shortness of breath. Presence of congestive heart failure does not necessarily imply weakening of the left lower pumping chamber of the heart. Approximately 40% of the patients with congestive heart failure have perfectly normal squeezing capacity of the left ventricle. In these patients, the primary problem is the failure of relaxation of the left ventricle (diastolic dysfunction) as the blood is returning to the left heart from the lungs. Problems with the heart valves can also cause congestive heart failure.