It refers to congestive heart failure. Here is what happens in your body: Your heart is a pumping machine as I m sure you know with four chambers. The upper chambers receive the blood and ship it to the bottom chambers that pump the blood. You have a right and left side to your heart. Usually congestive heart failure (CHF) is left sided but can be right sided as well. CHF usually results from hypertension (high blood pressure) but can also result from other mechanisms in the heart. (It s too detailed for the scope of this question). Anyway, the blood that is normally pumped to your body has a problem getting through due to narrowed vessels. Some of the blood is left in the heart at the end of the pumping cycle when it should have been pushed out. The body recognizes this as a problem and the heart beats stronger to compensate. Because all of the blood wasn t pushed out of the heart, it is added to the new volume of blood coming in. The heart muscles and chambers must stretch to compensate. Over time, the heart wears out and becomes floppy. A floppy muscle can t pump effectively and this is when you get signs and symptoms of heart failure. Think of a balloon. When you first get the balloon, it is tight and new. Now blow the balloon up and leave it sit for an hour and then let the air out. It is all wrinkled and shriveled. This is what happens to your heart. The balloon (your heart) had to compensate for the increase in air (blood) that you put into it. When it does for awhile, it gets all stretched out. There are different things that you will notice depending on which side of your heart is effected. If the left side is enlarged, you will notice the symptoms in the lungs such as difficulty breathing, crackles, and frothy sputum. If the right side of your heart is effectived, the symptoms will be in your body. You will have leg swelling/edema, the veins in your neck will stretch and get bigger, there s blood pooling in your liver and spleen, ect. You will have nausea and a bloated feeling. Hope this helps to answer your question.