Article révisé par les pairs
Résumé : The transpulmonary pressure gradient, defined by the difference between mean pulmonary artery pressure and left atrial pressure (commonly estimated by a pulmonary artery wedge pressure) has been recommended for the detection of intrinsic pulmonary vascular disease in left heart conditions associated with increased pulmonary venous pressure. In these patients, a transpulmonary pressure gradient of more than 12 mmHg would be diagnostic of an "out of proportion" pulmonary hypertension. This value is arbitrary, because the gradient is sensitive to changes in cardiac output and both recruitment and distension of the pulmonary vessels which decrease the upstream transmission of left atrial pressure. Furthermore, pulmonary blood flow is pulsatile, with systolic and mean pulmonary artery pressure determined by stroke volume and arterial compliance. It may therefore be preferable to rely on a gradient between diastolic and wedged pulmonary artery pressures. The measurement of a diastolic-to-wedge gradient combined with systemic blood pressure and cardiac output allows for a step-by-step differential diagnosis between pulmonary vascular disease, high output or high left heart filling pressure states, and sepsis. The diastolic-to-wedge gradient is superior to the transpulmonary pressure gradient for the diagnosis of "out of proportion pulmonary hypertension".