Pulmonary edema: Which role for echocardiography in the diagnostic workup?

Abstract

In the presence of pulmonary edema, the distinction between hydrostatic (often cardiogenic) and permeability (acute respiratory distress syndrome) edema is crucial in the hypoxemic critically-ill patient. Importantly, the absence of relevant left ventricular (LV) systolic dysfunction fails to rule outa hydrostatic pulmonary edema (e.g., acute valvular regurgitation, volume overload, severe diastolic dysfunction, mitral stenosis) and, conversely, acuterespiratory distress syndrome (ARDS) patients may present with a significant LV systolic dysfunction (e.g., septic shock) Consequently, Doppler (with elevated E/A wave ratio and shortened E wave deceleration time) combined with the measurement of mitral annulus motion with tissue Doppler (elevated E/Ea wave ratio). The evaluation of pulmonary vein pulsed-wave Doppler pattern may also help in assessing left cardiac filling pressure. LV loading conditions - hence Doppler velocity profiles - may rapidly fluctuate over time, or as a result of initial therapy. Consequently, echocardiography has a maximal diagnostic value when performed at the time of acute respiratory failure. It accurately document elevated LV filling pressures consistent with hydrostatic pulmonary edema and may help identifying the causative cardiopathy. Evaluation of LV filling pressures is best done at the mitral valve, using mitral inflow pulsed-wave Doppler (with elevated E to A waves) combined with evaluation of mitral annulus with tissue Doppler (elevated E to Ea ratio). In patients with mitral disease, evaluation of pulmonary veins pulsed-wave Doppler pattern may help to identify the consequence of valvular dysfunction on pulmonary capillary bed. Finally, it should be noted that hydrostatic pressures may fluctuate over time, and, especially, are minimized by positive respiratory pressure. It is not uncommon that hydrostatic pulmonary edema contributes to failure of weaning from mechanical ventilation, an evaluation of intravascular pressure during weaning is feasible even though sometimes difficult (rapid and/or ample respiratory movements). © 2011 Springer-Verlag Berlin Heidelberg.