Mean pulmonary artery pressure (MPAP) appears to be an independent predictor of mortality in connective tissue disease-associated interstitial lung disease (CTD-ILD), according to a retrospective cohort study of patients with CTD in Japan.1 

It has long been recognized that patients with ILD-associated pulmonary hypertension (PH) have increased rates of mortality when compared to those with ILD alone.  Fewer research has assessed survival outcomes of patients with ILD and various types underlying CTD.  To evaluate if pulmonary arterial pressure (PAP) is prognostic of survival in CTD-ILD, researchers at Tosei General Hospital, Aichi, Japan retrospectively reviewed disease backgrounds, pulmonary function tests, and right heart catheterization (RHC) data from patients with CTD-ILD seen at their hospital.  

In this cohort of patients, ILD diagnosis was confirmed by high-resolution CT (HRCT). Patients included in the study also underwent spirometry, with determination of single breath diffusing lung capacity of carbon monoxide (DLCO). RHC was used to quantify PH, defined as PAP ≥ 25 mmHg. MPAP was measured via Swan Ganz catheter with the catheter tip placed within the right main trunk of the pulmonary artery. MPAP ≥ 20 mmHg was used as the cut-off for predicting the prognosis, based on findings from a previous study.  Cardiac output was measured via the thermodilution method.


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Underlying clinical diagnoses were made according to established criteria, and included systemic sclerosis (SSc), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), polymyositis/dermatomyositis (PM/DM), mixed connective tissue disease (MCTD), and Sjögren’s syndrome (SjS).

A total of 74 patients were retrospectively analyzed, including 33 men and 41 women with a mean age 62.8 ± 9.6. Of these patients, 24 were diagnosed with with RA, 14 with SSc, 14 with PD/DM, 11 with primary SjS, and 11 with other diagnoses.  PH was diagnosed in 6 patients. DLCO was reduced in 47 patients. After RHC evaluation, 27 patients (36.5 %) were started on medication for CTD or ILD.  Oral corticosteroids were taken by 23 patients (31.1%).  An additional 10 patients were treated with immunosuppresive pharmacotherapy (cyclosporin, tacrolimus, cyclophosphamide, methotrexate). Four patients (5.4 %) were taking beraprost sodium for Raynaud’s phenomenon.

Overall, study participants had a mean MPAP of 17.2 mmHg (±5.5 mmHg). No differences in MPAPs were found among the various types of underlying CTD.

Over the mean study observation period of 44.4 months (± 2.2 months), 15 patients died, of which 6 deaths were attributed to respiratory failure, 4 due to acute disease exacerbation, 3 due to malignancy, 1 due to multiple organ failure, and 1 due to neuromuscular disease.  

No association was found between CTD background disease and survival in this cohort of patients (SSc, MCTD vs other CTD hazard ratio [HR] = 1.186; 95 % confidence interval [CI] 0.333–4.223, P = .792, RA vs other CTD: HR = 0.530; 95 % CI 0.192–1.465, P = .221, and PM/DM vs other CTD: HR = 1.739; 95 % CI 0.392–7.714, P = .467). 

MPAP, on the other hand, had significant impact on survival after univariate Cox proportional hazard analysis. MPAP remained independently associated with survival after multivariate Cox proportional hazard analysis (HR = 1.087; 95 % CI 1.008–1.172; P = .030).

Summary and Clinical Applicability

Mild elevation in MPAP is commonly found in newly diagnosed CTD-ILD, regardless of the background CTD. Higher MPAPs at time of initial patient evaluation is independently associated with increased mortality.

“This result suggests the importance of evaluating MPAP at an early stage in patients with CTD-ILD, and not limiting it to patients with advanced disease,” the authors concluded.

Limitations and Disclosures

This study was retrospectively designed and only included patients from a single hospital center. Study participants were limited to those without severe hypoxemia, thus prognostic conclusions may not be applicable to this particular group of patients. Vasoreactivity and nocturnal hypoxemia were not evaluated in this study.  

Reference

1. Takahashi K, Taniguchi H, Ando M, et al. Mean pulmonary arterial pressure as a prognostic indicator in connective tissue disease associated with interstitial lung disease: a retrospective cohort study. BMC Pulm Med. 2016;16(1):55.