Measurement of stroke volume and cardiac output using echocardiography and doppler

Abstract

Cardiac output measurement is of prime importance in the hemodynamic assessment of patients with circulatory failure. It helps distinguish the different types of shock and, more importantly, is crucial in discriminating between cardiac dysfunction and failure and also in evaluating the impact of various interventions. Different methods can be used to measure cardiac output or, more precisely, stroke volume since cardiac output is the product of stroke volume and heart rate. Stroke volume is probably more important as changes in heart rate (adaptive or in response to drugs) may occur. For example, it is important to establish whether the increase in cardiac output during dobutamine administration is related to an increase in stroke volume (and thus contractility) or to a change in heart rate since the implications for the benefits of the intervention may differ. In practice, measurement of left ventricular outflow tract diameter with two-dimensional imaging (parasternal, long-axis) and flow with pulsed Doppler (apical five-chamber view) is the best-validated technique. It can verify where there is any significant aortic regurgitation or stenosis. When these techniques cannot be implemented, others can be used, though they may be less reliable or more difficult to conduct in critically ill patients. © 2011 Springer-Verlag Berlin Heidelberg.