What is the difference between heart attack and heart failure?

Blocked artery: Heart attacks are almost always caused by a blockage in one of the arteries that supplies the heart. This stops the flow of blood (and oxygen) to that area of the heart and eventually the involved area of muscle dies. Heart failure is most often the result of several small or one large heart attack that affects enough muscle to keep the heart from being able to pump blood effectively.

MI and CHF: Heart attack is basically a lack of blood flow to the heart muscle which if prolonged results in death of the heart muscle. Heart failure is an abnormal pump funtion of the heart. Where the heart in general doesn't pump blood out of the main chamber to the rest of the body, therefore the name heart failure.