Cardiovascular dysfunction. A rationale for characterization and a guide to therapy.

Traditional clinical assessment of cardiac function has relied on the indirect measurement of systemic blood pressure, heart rate and rhythm, and central venous pressure. However, because the circulation comprises complex interactions between flow and impedance in two hydraulic systems coupled in series, the usual assumptions drawn from the measurement of only a representative sample of this system can lead to serious errors in interpretation. This is particularly significant in conditions leading to physiologic distortions. Patients undergoing major surgery, or with suspected cardiac dysfunction, can only be adequately managed with a knowledge of both right and left heart pressures, together with the measurement of cardiac output. This report presents a rationale for the use of a simple method for interpreting these data and a guide to optimizing management. For those patients with heart failure who are unable to be sustained with conventional pharmacology, criteria are suggested that may help the clinician decide when more aggressive intervention, such as mechanical assist, is required.