The added value of cardiopulmonary exercise testing in the follow-up of pulmonary arterial hypertension

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BACKGROUND

The added value of cardiopulmonary exercise testing (CPET) in the follow-up of patients with stable pulmonary arterial hypertension (PAH) remains undefined.

METHODS

Idiopathic, heritable, and drug-induced PAH patients free from clinical worsening (CW) after 1 year of treatment were enrolled in derivation (n = 80) and validation (n = 80) cohorts at an interval of 6 years and followed for 3 years. Prognostic models were constructed and validated in low-risk patients in World Health Organization (WHO) Functional Class I or II with cardiac index (CI) ≥2.5 liters/min/m2 and right atrial pressure (RAP) <8 mm Hg. Discrimination and calibration were assessed.

RESULTS

Forty-one derivation cohort patients had CW (51.2%) during 722 ± 349 days. Changes (∆) in WHO classification and CI and absolute value of RAP were independent predictors of CW. With addition of CPET variables, peak oxygen uptake (VO2 peak) and ∆CI independently improved the power of the prognostic model. Receiver operating characteristic (ROC)-derived cut-off values for ∆CI and VO2 peak were 0.40 liter/min/m2 and 15.7 ml/kg/min (≥60% predicted value), respectively. Twenty-nine validation cohort patients had CW (36.2%) during 710 ± 282 days. Different combinations of cut-off values of VO2 peak and ∆CI defined 4 groups. The event-free survival rates at 1, 2, and 3 years were 100%, 100%, and 100%, respectively, for the high ∆CI with high VO2 peak combination; 100%, 88%, and 71% for low ∆CI/high VO2 peak; 80%, 54%, and 40% for high ∆CI/low VO2 peak; and 72%, 54%, and 33% for low ∆CI/low VO2 peak.

CONCLUSIONS

The combinations of baseline VO2 peak and change in CI during follow-up is important in prognostication of low-risk patients with idiopathic, heritable, and drug-induced PAH.

Section snippets

Derivation cohort

A derivation cohort was constituted based on 80 consecutive idiopathic, heritable, and drug-induced PAH cases evaluated at our institution between June 2006 and December 2009. Patients were enrolled if they had been without clinical worsening (CW) for 1 year after diagnosis and institution of treatment, to avoid the influence of add-on therapies, and prospectively followed.

Initial diagnosis relied on a right heart catheterization showing pre-capillary PH (mean pulmonary artery pressure [mPAP]

Derivation cohort and prognostic modeling

Anthropometric, clinical, hemodynamic, and CPET data of the patients in the derivation cohort are summarized in Table 1. Age and sex distributions were typical. Diabetes (4 patients, 5%), hypercholesterolemia (8 patients, 10%), thyroid disease (5 patients, 6%), and clinical depression (4 patients, 5%) were the most frequent comorbidities. Most of the patients were in WHO FC II with a satisfactory 6MWD (>400 meters). Twenty-six (32%) patients had <3 low-risk criteria, according to ESC/ERS

Discussion

The present results show that CPET is a relevant addition to right heart catheterization to assess PAH patients who are clinically improved and stabilized 1 year after institution of targeted therapies.

Treatment options for PAH patients have expanded in recent years, so that physicians now can choose between various combinations of drugs and modes of administration.1 To facilitate decision-making, European PH guidelines have proposed a dynamic risk strategy based on repetitive assessments every

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These authors have contributed equally to this work.

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