A fluid challenge may help to the differential diagnosis between pre- and post-capillary pulmonary hypertension (PH). However the test is still in need of standardization and better defined clinical relevance.
Methods and Results
Two-hundred-twelve patients referred for PH underwent a right heart catheterization with measurements before and after rapid infusion of 7 ml/kg of saline. PH was defined by a mean pulmonary artery pressure (mPAP) ≥ 25 mmHg and post-capillary PH by a wedged PAP (PAWP) > 15 mmHg. An increase in PAWP ≥ 18 mmHg was considered diagnostic for post-capillary PH. At baseline, 66 patients were diagnosed with no PH, 22 with post-capillary PH and 124 with pre-capillary PH (mostly pulmonary arterial hypertension, PAH). After fluid challenge 5/66 patients with no PH (8%) and 8/124 with pre-capillary PH (6%) were reclassified as post-capillary PH. Fluid challenge was associated with an increase in PAWP by 7±2 mmHg in post-capillary PH, and 3±1 mmHg in both pre-capillary PH and no-PH patients. Between group differences were significant, but there was overlap. There were no adverse events related to fluid challenge. Prediction bands calculated from quadratic fits of the PAWP responses in pooled no-PH control and pre-capillary PH patients confirmed 18 mmHg as cut-off for the diagnosis of post-capillary PH.
Fluid challenge with 7 ml/kg saline increases PAWP, more in post-capillary PH than in pre-capillary PH or no-PH controls. A cut-off value of 18 mmHg allows to re-classify 6-8% of patients with pre-capillary PH or normal hemodynamics at baseline.