The cardiovascular system serves the body by supplying nutrients and removing wastes. The function of the heart and circulation can be measured by a great variety of methods, but it is essential to understand the physiologic basis of the measurements for proper interpretation. Furthermore, the entire clinical condition must be always considered in the combination with the wealth of numerical data available in today’s patients (Table II). Since all pharmacologic interventions have risks, interventions to correct a single numerical aberrancy should be undertaken only if the overall clinical picture is compatible with the value and/or if there is other corroborating data.