Fluid around the heart is not always terminal. Depending on where the fluid has settled in the sack around the heart, the fluid can be drained. If there is so much fluid accumulating around the heart that the heart can not expand and fill with the required amount of blood, then the person is in trouble and must get help quickly. Although I said that fluid around the heart is not always terminal, it does depend on what is causing the fluid and how much fluid is within the pericardial sack. Only a physician / surgeon can determine if this is a serious situation. Also, too much fluid compressing the heart can cause cardiac tamponade. A person with this condition can feel very short of breath, weak, lightheaded and find it difficult to sleep flat in bed. Get help ASAP.