As heart failure worsens, shortness of breath occurs with less and less activity, until it occurs at rest. People are short of breath mostly when they lie down because fluid seeps throughout the lung tissue. When they sit up, gravity causes fluid to collect at the base of the lungs, which is less of a problem. Any disorder that upsets the normal, delicate balance between oxygen supply and oxygen requirement, such as inadequate oxygen-carrying capacity of the blood from anemia or increased overall metabolism in the body from an overactive thyroid, can make a person short of breath. When the heart pumps inefficiently, blood flow to the muscles may be inadequate during exercise, causing the person to feel weak and tired.
Symptoms are often subtle.
People compensate by gradually diminishing activity, or they may blame the symptoms on increasing age. Palpitations Ordinarily, people don't notice the beating of their heart. They may feel the heart beating very forcefully or rapidly or sense an irregular heartbeat. A doctor can confirm these symptoms by checking the pulse and listening to the heartbeat through a stethoscope placed on the chest. Palpitations that occur together with other symptoms such as shortness of breath, pain, weakness and fatigue, or fainting are more likely to result from an abnormal heart rhythm or a serious underlying disease.