Resting mean pulmonary artery pressure (mPAP) values between 20 and 25 mm Hg are above normal but do not fulfill the criteria for pulmonary hypertension (PH). The clinical relevance of such borderline hemodynamics is a matter of discussion.
We focused on patients who underwent right-sided heart catheterization during rest and exercise for symptoms indicative of PH or due to underlying disease associated with an increased risk for pulmonary arterial hypertension and characterized the patients according to their resting mPAP. Patients with manifest PH (mPAP ≥ 25 mm Hg) were excluded.
We included 141 patients, 32 of whom presented with borderline hemodynamics (20 < mPAP < 25 mm Hg). Borderline patients were older (65.8 ± 12.5 years vs 57.3 ± 12.5 years, P = .001) and more often had cardiac comorbidities (53% vs 15%, P < .001) or decreased lung function (47% vs 16%, P < .001) as compared with patients with resting mPAP < 21 mm Hg. After correction for age, borderline patients had significantly increased pulmonary vascular resistance (2.7 ± 0.7 Wood units vs 1.8 ± 0.8 Wood units, P < .001) and mPAP/cardiac output (CO) and transpulmonary gradient/CO slopes (both P < .001) as well as lower peak oxygen uptake (16.9 ± 4.6 mL/min/kg vs 20.9 ± 4.7 mL/min/kg, P = .009) and 6-min walk distance (383 ± 120 m vs 448 ± 92 m, P = .001). During follow-up (4.4 ± 1.4 years), the mortality rate of borderline patients vs patients with resting mPAP < 21 mm Hg was 19% vs 4%.
In patients undergoing right-sided heart catheterization with exclusion of manifest PH, borderline elevation of pulmonary arterial pressure is associated with cardiac and pulmonary comorbidities, decreased exercise capacity, and a poor prognosis.