Oxygen Uptake Efficiency Slope Predicts Poor Outcome in Patients With Idiopathic Pulmonary Arterial Hypertension

Tang Y, Luo Q, Liu Z, Ma X, Zhao Z, Huang Z, Gao L, Jin
Q, Xiong C, Ni X.

J Am Heart Assoc. 2017 Jun 30;6(7).

BACKGROUND: Few published studies have evaluated the power of the oxygen uptake
efficiency slope (OUES) to predict outcomes in patients with idiopathic pulmonary
arterial hypertension (IPAH), who typically die of right-sided heart failure. Our
study sought to evaluate the power of OUES to predict clinical worsening and
mortality in patients with IPAH.
METHODS AND RESULTS: Patients with newly diagnosed IPAH who underwent
symptom-limited cardiopulmonary exercise testing from November 11, 2010, to June
25, 2015, in our hospital were prospectively enrolled and followed for up to
66 months. Clinical worsening and mortality were recorded. A total of 210
patients with IPAH (159 women; mean age, 32±10 years) were studied with a median
follow-up of 41 months. Thirty-one patients died, 1 patient underwent lung
transplantation, and 85 patients presented with clinical worsening. The
univariate analysis revealed that OUES, OUESI (OUESI=OUES/body surface area),
peak oxygen uptake (V˙O2), peak V˙O2/kg, ventilation (V˙E)/carbon dioxide output
(V˙CO2) slope, peak systolic blood pressure, heart rate recovery, pulmonary
vascular resistance, cardiac index, N-terminal prohormone brain natriuretic
peptide, and World Health Organization functional class were all predictive of
clinical worsening and mortality (all P<0.05). Multivariate analysis demonstrated
that OUESI and cardiac index were independently predictive of clinical worsening,
and OUESI and N-terminal prohormone brain natriuretic peptide were independently
predictive of mortality. Patients with OUESI ≤0.52 m-2 had a worse 5-year
survival rate than patients with OUESI >0.52 m-2 (41.9% versus 89.8%, P<0.0001).
CONCLUSIONS: The OUES, a submaximal parameter obtained from cardiopulmonary
exercise testing, provides prognostic information for predicting clinical
worsening and mortality in patients with IPAH.