Characterization of pulmonary hypertension in heart failure using the diastolic pressure gradient: limitations of a solitary measurement.

SEE PAGE 9 W hen pulmonary hypertension (PH), defined by mean pulmonary artery pressure (mPAP) $25 mm Hg, is associated with an abnormally elevated pulmonary capillary wedge pressure (PCWP) >15 mm Hg or left ventricular end-diastolic pressure (LVEDP) >18 mm Hg (1), it has been variably termed World Health Organization Group 2 PH (1), pulmonary venous hypertension (2), “post-capillary PH” (3), or “passive PH” (4). This type of PH is distinct from primary pulmonary arterial hypertension where there is no increase in left ventricular filling pressure (i.e., pre-capillary PH). Patients with left ventricular dysfunction (LVD) may develop a pre-capillary pulmonary arterial contribution to PH, reflected by an increased transpulmonary gradient (TPG), defined as mPAP-PCWP that exceeds 12 to 15 mm Hg, or an elevated pulmonary vascular resistance (PVR), defined as TPG/ cardiac output that exceeds 2.5 to 3 Wood units (5,6). This type of PH, which is “out of proportion” to underlying left-sided disease in the setting of normalized volume status, has been termed “mixed PH,” given both pre-capillary and post-capillary contributions to elevated PAP. In patients with LVD,