A cardiac index is a system used to measure cardiac output, or the amount of blood pumped out of the left ventricle each minute. This system is useful in helping diagnose and treat a wide range of heart problems when used in combination with other tools. To calculate a patient's cardiac index, a doctor takes the amount of blood pumped per minute in liters and divides it by the patient's body surface area (BSA).
One reason to use the cardiac index to measure heart function is to better understand the effects of certain medical procedures on the heart. Measurements can be taken throughout a procedure to watch for any changes in heart rate and other factors to get a clear idea of how stressful a surgery or procedure is on the heart. This is especially helpful during cardiac surgeries, primarily bypass surgeries.
To get an accurate reading, the cardiac index score is usually taken before starting a procedure and then during or after the procedure at certain intervals. A normal heart with adequate cardiac activity pumps about 5 to 6 liters (5.28 to 6.34 quarts) of blood through the body each minute while a person is at rest. More or less than this can cause serious problems in the body. More or less cardiac output than necessary is also known as high or low blood pressure.
Professionals may also study the effects of certain medical conditions or stressors on a person's cardiac index reading. Obesity, for example, is an important topic of study because the recent epidemic in many of the world's industrialized nations is affecting the health of the general population. Unfortunately, because the problem of widespread obesity is fairly recent in development, the long-term effects of extreme weight gain have not been fully studied. Using the cardiac index in those with high BSA readings is a good way to gauge the effects of being overweight on the heart and determine how much excess weight is required to create serious problems.
The cardiac index, combined with other diagnostic equipment, is an effective way to determine the overall health of the heart. Physicians also gain better insight into the effects of surgery and other procedures on certain types of patients. These include the morbidly obese, those with certain existing heart conditions, and those with other serious ailments.