Causes:

1. Heart Muscle Weakness
If the muscle of the heart is weak (cardio myopathy) which may happen if the muscle has been attacked by inflamation or affliction, or certain hereditary conditions where the muscle of the heart is abnormal and weak the heart muscle will not be able to generate enough force to eject the blood out to the body to achieve adequate flow of the blood to the body tissues.

2. Obstruction of Heart Valve
If one of the heart valves is severely obstructed (narrowed or stenotic) the heart has to work very hard to push the blood through that valve to get it out to the body. The heart muscle which is trying to push the blood will eventually get larger and larger may lead to the point where it cannot sustain the high pressure and then becomes weak.

The most commonly affected valve is the aortic valve which makes the left ventricle enlarged and the muscle become thick and work harder until that muscle simply becomes weak and sort of gives up. The blood then accumulates in the left side of the heart and backs up into the lungs where the lungs become congested with blood and the patient develops a condition called Pulmonary Edema (fluid in the lung tissue). This is usually associated with severe difficulty breathing and severe fatigue.

Causes:

3. Heart Electric Problem
a. The heart's electric system is disturbed such as with a heart block. The heart will not be able to generate enough electric impulse to stimulate the heart to contract so the heart will be unable to pump blood to the body.

b. Arrythmia such as very fast heart beats. The heart starts beating very fast because of abnormality in the electric activity such as arrythmia and the heart does not have enough time to fill with blood. If the heart does not fill with enough blood it will not have enough blood to squeeze on to push it to the body and so heart failure will result.

4. Leaking Valve
As the heart is trying to push the blood out to the body there is a leak through one major valve. The blood will therefore not go forward but go backwards through the valve into the heart.

Aortic Valve Regurgitation
A well known condition of this type is Aortic Valve Regurgitation which means that the aortic valve leading from the left ventricle to the aorta leaks backward after the heart contracts. Instead of the valve slamming tightly shut it leaves a gap allowing some of the blood to leak back into the heart. The left side of the heart then has to handle a very large amount of blood, and so it has to work harder and harder and with time it becomes weaker and weaker until heart failure occurs.

Symptoms:
A baby that has a condition that predisposes him to heart failure usually breathes fast with difficulty where the breathing is labored and frequent. The baby may also appear pale and will be sweating excessively during feedings. He will probably take breaks between feedings as if to catch his breath. A newborn with heart failure may have a large heart by chest x- ray, EKG, or echocardiogram.

The doctor may elect to do the echocardiogram which may show why the child has developed congestive heart failure.

Symptoms:
The echocardiagram, which is an ultrasound of the heart, may reveal that the child has a hole in his heart, a narrowed valve, a leaking valve, or a weak muscle.

Heart failure in a child usually tires easily, short of breath with mild activity, and may not be able to gain weight (failure to thrive). The echocardiogram may show a large heart, or some other cause of heart failure.