Pulmonary artery diameter to predict pulmonary hypertension in pulmonary sarcoidosis

Abstract

Pulmonary hypertension (PH) is a known complication of pulmonary sarcoidosis with a prevalence ranging from 5% to 74% [1]. The aetiology of PH in sarcoidosis is not fully understood. Usually, it is attributed to the destruction of the distal capillary bed by lung fibrosis and/or chronic hypoxaemia. However, the severity of PH does not correlate consistently with the degree of pulmonary fibrosis, and PH exists in sarcoidosis patients without fibrosis, suggesting a multifactorial mechanism. The presence of PH is associated with a poor prognosis, and early diagnosis and treatment might improve outcome [1]. Echocardiography should always be performed when PH is suspected [2]. However, the accuracy of echocardiography in patients with interstitial lung diseases is often limited due to poor image quality and unreliable tricuspid regurgitation signal to measure the right ventricular systolic pressure (RVSP) [3]. Further invasive investigation with the gold standard, right heart catheterisation (RHC), is often required. In order to optimise the noninvasive diagnostic approach, there is a need for more accurate predictors of PH. Computed tomography (CT) may raise suspicion of PH in symptomatic patients or those examined for unrelated indications by showing an increased pulmonary artery (PA) diameter (⩾29 mm) and PA diameter/ascending aorta diameter (AAD) ratio (⩾1.0) [2]. Similarly, PA diameter indexed to body surface area (BSA) has been suggested as possible predictor of PH. However, these parameters have never been investigated in pulmonary sarcoidosis specifically.In this study, PA diameter measurements on chest CT were retrospectively evaluated as predictors of PH. Patients suspected of PH and referred for analysis between November 2007 and May 2014 were included in cases with a consensus diagnosis of pulmonary sarcoidosis, aged ⩾18 years, with availability of chest CT within 1 year of PH analysis. The analysis protocol was based on the European PH guideline [2], and consisted of an ECG, laboratory testing, and echocardiographic assessment of RVSP and secondary parameters. Subsequently, patients were classified as "PH likely" (RVSP >50 mmHg), "PH possible" (RVSP of 36-50 mmHg or presence of secondary signs with normal/absent RVSP signal) or "PH unlikely" (RVSP <36 mmHg or absence of signal without secondary signs). RHC was performed if PH was possible or likely. PH was defined as an invasively measured mean PA pressure (mPAP) ⩾25 mmHg. Patients were divided into three groups: "PH confirmed by RHC", "no PH confirmed by RHC" and "no PH based on echocardiography".

Sarcoidosis-Associated Pulmonary Hypertension

“…Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and DLCO are generally lower in SAPH compared with sarcoidosis patients without PH. 6,7,11,18,21,60 DLCO seems to be the strongest independent predictor. 18,21 As mentioned earlier, destruction of the alveoli and loss of pulmonary capillary volume due to fibrosis and muscle cell proliferation are believed to cause reduction of the DLCO.…”

“…Positive correlation with mean PAP has been described in patients with lung disease [66][67][68] ; however, the presence of fibrotic lung disease complicates the accuracy of these measurements. 60,69,70 Huitema et al studied sarcoidosis patients only, and found a good correlation between the pulmonary artery diameter indexed for body surface area and presence of PH. 60 Other chest CT parameters can be indicative for the presence of PH, such as segmental artery to bronchus ratio >1 or right ventricular enlargement, but they have not shown any valuable correlation for clinical practice.…”

“…60,69,70 Huitema et al studied sarcoidosis patients only, and found a good correlation between the pulmonary artery diameter indexed for body surface area and presence of PH. 60 Other chest CT parameters can be indicative for the presence of PH, such as segmental artery to bronchus ratio >1 or right ventricular enlargement, but they have not shown any valuable correlation for clinical practice. 68…”

Advanced Pulmonary Sarcoidosis

“…99 Correcting for body mass index may improve the predictability of this ratio. 100 However, not all groups have found the ratio as reliable in SAPH. 101 Transthoracic echocardiogram (TTE) is one of the most widely used tests to assess for pulmonary hypertension.…”

In Rotterdam, size really does matter: implications of pulmonary artery enlargement on mortality

“…Recently, there has been significant interest in the use of CT in COPD, with several studies evaluating the utility of the ratio of the pulmonary artery to ascending aortic diameter (PA:A ratio) and pulmonary arterial enlargement [15–19]. The PA:A has been calculated in several cohorts of healthy patients and those with different chronic respiratory conditions, and correlates with PA pressures as measured by RHC [9, 15–17, 20–22] and worsening clinical outcomes [15, 17, 18, 20, 21, 23–25]. In a cohort of very severe COPD patients, the PA:A correlated with invasive haemodynamics, and a PA:A >1 independently predicted PH defined as a mean PA pressure >25 mmHg at right heart catheterisation with a sensitivity of 73% and a specificity of 84% [16].…”