European Journal of Cardiovascular Medicine

Pulmonary hypertension (PH) is a progressive disorder characterized by elevated pulmonary arterial pressure. It is caused by a multitude of intrinsic and extrinsic pulmonary vascular disease processes that cause hemodynamic alterations which overcome the normal pulmonary vasoregulatory mechanisms. PH is diagnosed when the mean pulmonary artery pressure (mPAP) is 25 mmHg at rest in right heart catheterization (RHC) ⁽¹⁾ Pulmonary hypertension (PH) in patients with interstitial lung diseases (ILDs) is not well recognized and can occur in the absence of advanced pulmonary dysfunction or hypoxemia. Connective tissue disease-related ILD, sarcoidosis, idiopathic pulmonary fibrosis and pulmonary Langerhans cell histiocytosis are the ILDs most commonly associated with PH. Pulmonary hypertension is an under recognized complication in patients with ILDs and can adversely affect symptoms, functional capacity, and survival ^(2-3). Pulmonary hypertension can arise in patients with ILDs through various mechanisms, including pulmonary vasoconstriction and vascular remodeling, vascular destruction associated with progressive parenchymal fibrosis, vascular inflammation, perivascular fibrosis, and thrombotic angiopathy. The presence of PH is generally associated with a worse prognosis in patients with ILDs ^(3-4).

Several retrospective analyses indicate that PH in IPF may be frequent ^{(5, 6, 7)}. In patients with IPF a pulmonary arterial enlargement on computed tomography (CT) may occur even in the absence of PH, due to presence of fibrosis; therefore, it is an unreliable sign of PH in IPF patients.

Shorr et al.⁽⁸⁾ confirmed that PH was common in IPF patients who were candidates for lung transplantation and was present in about 45% of these subjects; however, severe PH (mean PAP >35 mmHg) was relatively infrequent. In a prospective analysis of consecutive patients with early stage IPF undergoing initial workup with RHC and pulmonary function testing, Hamada et al. ⁽⁹⁾ 

Study place- The study was conducted in the department of radiology at a tertiary care hospital for period of 18 months.

Study design- Prospective cross-sectional study.

Inclusion Criteria-Patients undergoing HRCT (chest) and diagnosed case of Interstitial Lung Disease.

Exclusion Criteria-Patients having hypertension, heart disease, history of TB, COPD,

Sample size- 130 patients.

Data analysis- The data was collected, analyzed and entered into Microsoft Excel using SPSS 27. version.

Ethical considerations-All the necessary permissions were obtained from the Institutional Ethical Committee before the commencement of the study. Written valid consent was obtained from the patients in their local language.

HRCT was performed on a 64-slice DUAL source multi-detector CT (MDCT) scanner (GE 750 HD). All patients were scanned from lung apices to lung bases at full suspended inspiration using standard exposure parameters (90 mA and 120kVp) in a single breath hold. As Tan et al. ⁽¹⁶⁾ reported, vascular measurements were preceded on the mediastinal window images of chest CT. The contents included: 1) MPA diameter: the widest part of MPA before MPA bifurcation (fig 1,2) right pulmonary artery (RPA) and left pulmonary artery (LPA) diameters: the widest part of RPA and LPA after MPA bifurcation (fig.2,3 ) Widest part of Ascending aorta diameter at the same level of MPA (fig.1). Then, the ratio of MPA/Aorta was calculated. Two senior radiologists accomplished all measurements respectively, without clinical data or echocardiography results of the subjects. If there was a big difference (≥5%), they consulted each other and repeated until a consensus was reached.

1.CORRELATION BETWEEN MAIN PULMONARY ARTERY DIAMETER AND INTERSTITIAL LUNG DISEASE

Table 1: Comparison of MPA with the HRCT diagnosed ILD in our study

Figure 1: Graph showing distribution of mean Dpa and ILD

In above study the Main pulmonary artery diameter in HRCT diagnosed interstitial lung disease, MPA is more dilated in female as compared to male and mean MPA diameter is more in Smoking related ILD than rest of the ILD.

2. CORRELATION BETWEEN MPA/AORTA DIAMETER AND ILD

Table

Table 3

On comparison with ratio between main pulmonary artery and ascending aorta diameter with HRCT diagnosed interstitial lung disease in our study population of 135 patients, the rPA is found to be more than one in female 57% than male 43% and mean rPA is more than 1 in Fibrotic NSIP and Smoking related ILD.

In the above study it was observed that the main pulmonary artery is dilated more in smoking related ILD (RB ILD and DIP) with the mean dPA = 30.4mm than the rest of the ILDs. Mean dPA in UIP (27.3mm) was less than the NSIP pattern. In NSIP, Fibrotic type has more mean dPA (29.4mm) than the cellular type. From our study, PAH is more common in NSIP pattern than UIP. Whereas in NSIP, PAH is more common in fibrotic NSIP then the cellular NSIP. Fibrotic NSIP, COP and Smoking related ILD patients got the maximum mean rPA greater than 1.03   compared to the other ILDs. We also found that the mean dPA of patients with Collagen Vascular Diseases like Scleroderma, SLE and rheumatoid arthritis which is < 0.85is less compared to other ILDs as these patients have more mean Aortic diameter (31mm) equally affected between both genders in the 6^th decade

Likewise, we observed that the mean right pulmonary artery out of all ILD patients being 19.62±3.02, it is dilated more in fibrotic NSIP (20.81mm). Whereas, the mean left pulmonary artery in our study being 18.77±3.63 which is maximum in Smoking related ILD (21.4 mm) than that of fibrotic NSIP (20.2mm) and other ILDs. Based on the observation we found that the dPA and rPA is increased more commonly in Smoking Related ILD than the fibrotic NSIP. Thus, the prevalence of PAH will be more common in smoking related ILD. The incidence of PAH is least in collagen vascular disease among all ILDs.

Devaraj et al. in 2008⁽¹⁴⁾ demonstrated a poor correlation of baseline mPAP and pulmonary vascular resistance index with MPA in patients with a mixed group of interstitial lung disease (ILD), compared to those without ILD, although the use of the rPA in the ILD group significantly improved the correlation. Importantly, patients with fibrosis and no PH or very low levels of PH still had evidence of increased MPA. The authors concluded that MPA alone is an unreliable sign of PH in patients with ILD and that rPA was better

Grubstein A, Benjaminov O, Dayan DB, et al. in 2008⁽¹⁷⁾ concluded that the size of the main pulmonary artery on CT angiography has a good predictive value regarding the severity of PH. Nathan et al.⁽¹⁸⁾ in 2008 demonstrated the change in measured parameters such as MPA and rPA over time, and the relationship of change with outcome. A subset of patients with IPF develop rapidly progressive PH and have a particularly bad prognosis. Perhaps change in MPA or rPA may help to identify these “rapid progressors”.

Boerrigter et al. in 2008⁽¹⁹⁾ examined the relationship between MPA, intraluminal PA pressure and duration of the disease in patients with PAH (i.e. without lung fibrosis). The authors demonstrated an inverse correlation of dPA with age, which was thought to probably reflect age-related fibrosis of the PA wall, making it less prone to dilatation over time. This is a novel finding in the PH literature that has not been examined in patients with ILD, and may contribute to the complex relationship of MPA and rPA with outcome. Further studies of serial change in these parameters are clearly warranted.

In the above study, mean size of main or central pulmonary arterial diameter(dPA) was 27.16±3.96, ratio between main pulmonary and aorta diameter(rPA) was 9.53±1.43, right pulmonary arterial diameter (RPAD) 19.62±3.02 and left pulmonary arterial diameter (LPAD) was 18.77±3.63. Main pulmonary artery is dilated more in smoking related lung disease than the rest of the Interstitial Lung disease

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