Updated December 16, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.
If you have heart failure, it is important for you to know what kinds of symptoms you can experience. By paying close attention to your symptoms, you can help your doctor optimize your therapy, both to keep your symptoms at bay and to reduce your chances of dying from heart failure.
Most symptoms caused by heart failure can be divided into three general categories: symptoms due to lung congestion, symptoms due to reduced cardiac pumping and symptoms due to heart arrhythmias.

Symptoms Due to Lung Congestion

Lung congestion commonly occurs in heart failure. Heart failure usually leads to an accumulation of fluid within the body and increased pressures within the heart, and these two factors together cause some of that "extra" fluid to accumulate in the lungs. The result is lung congestion.
This is why heart failure is often referred to as "congestive heart failure."

The lung congestion that occurs in heart failure causes shortness of breath, or dyspnea. The dyspnea is most often experienced with exertion. Dyspnea can also occur while lying flat, a condition called "orthopnea." In addition, dyspnea can occur suddenly in the middle of the night, causing one to wake up gasping for air and needing to sit up. Such an episode is called "paroxysmal nocturnal dyspnea," or PND.  Recently, "bendopnea" - dyspnea while bending over - has also been identified as a symptom of heart failure.

If heart failure worsens over time, dyspnea can gradually increase to the point of producing physical incapacity.

Severe and often sudden episodes of shortness of breath can also occur. This kind of sudden episode, called "acute pulmonary edema," is a medical emergency.

The accumulation of body fluid also leads to swelling (or edema) in the legs.

Symptoms Due to Reduced Cardiac Pumping

The main job of the heart is to pump blood to all the body's organs. In heart failure, this pumping action is usually diminished to at least some degree.
In most cases, the symptoms caused by poor cardiac pumping (also referred to as decreased cardiac output) are experienced only relatively late in the course of heart failure, when the heart muscle has become extremely weak.

When the heart muscle becomes substantially weakened, the heart can no longer pump enough blood to sufficiently supply the body's organs. The most prominent symptoms caused by this reduced pumping capability are extreme fatigue and muscle wasting. However, poor blood flow can also reduce the function of internal organs such as the brain, liver, kidneys and intestines, leading to a host of additional symptoms such as lethargy, extreme edema, abdominal distention and numerous gastrointestinal symptoms.

Doctors assess the pumping capacity of the heart by the physical examination, and by measuring the left ventricular ejection fraction (LVEF). The LVEF is the percentage of blood ejected from the left ventricle with each heart beat, so that, for instance, an LVEF of 50% indicates that the left ventricle is ejecting half its volume each time it contracts. A normal LVEF is 50% or higher. Most people who have symptoms caused by reduced cardiac pumping will have an LVEF below 30 to 35%.

Symptoms due to reduced cardiac pumping are usually limited to patients who have dilated cardiomyopathy with a very low LVEF. Hypertrophic cardiomyopathy and diastolic heart failure are both characterized by relatively well-preserved cardiac pumping action, so these kinds of symptoms are generally uncommon in these conditions.

Symptoms Due to Cardiac Arrhythmias

Heart failure is commonly associated with heart rhythm disturbances.
Atrial fibrillation is particularly common in people with heart failure. The likelihood of developing atrial fibrillation increases as the heart failure worsens. Atrial fibrillation can produce palpitations - a feeling that the heart is beating rapidly or irregularly - weakness or shortness of breath. Atrial fibrillation also tends to produce blood clots in the left atrium, which can break free and travel to the brain, producing a stroke. These clots can also produce damage to other organs in the body. Anyone with heart failure and atrial fibrillation needs to be on adequate anticoagulation (blood thinner) therapy to prevent such serious events.

Unfortunately, sudden death due to ventricular fibrillation is also disturbingly common in patients with heart failure - especially in patients with dilated cardiomyopathy and some forms of hypertrophic cardiomyopathy. Almost one out of three patients with dilated cardiomyopathy dies suddenly from ventricular arrhythmias. For this reason, many patients with significant dilated cardiomyopathy should be considered for implantable defibrillators.

Summary

Heart failure can indeed produce some very disturbing symptoms, and can significantly disrupt one's life. Fortunately, significant advances have been made during the last decade or two in treating heart failure. By paying close attention to your symptoms and working carefully with your doctor, with today's aggressive therapy odds are good that you will be able to enjoy many happy and productive years, despite this serious medical condition.

• Read more about treating heart failure.

<sub>Sources:

Hunt SA, Abraham WT, Chin MH, et al. 2009 focused update incorporated into the ACC/AHA 2005 Guidelines for the Diagnosis and Management of Heart Failure in Adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines: developed in collaboration with the International Society for Heart and Lung Transplantation. Circulation 2009; 119:e391.</sub>