Pulmonary Artery Hypertension (PAH), defined as a resting Mean Pulmonary Artery Pressure (MPAP) ≥25 mmHg, is an important complication of several Interstitial Lung Diseases (ILDs) and can adversely affect patient outcomes.PH is a common complication of ILDs, particularly in idiopathic pulmonary fibrosis (IPF) [1].

Interstitial Lung Diseases (ILDs) comprise a broad and heterogeneous group of more than two hundred diseases with common functional characteristics. Their diagnosis and management require a multidisciplinary approach. This multidisciplinary approach involves the assessment of comorbid conditions including Pulmonary Hypertension (PH) that exerts a dramatic impact on survival [2].

Interstitial Lung Diseases (ILDs) comprise a broad and heterogeneous group of more than two hundred diseases with common functional characteristics. Their diagnosis and management require a multidisciplinary approach. This multidisciplinary approach involves the assessment of comorbid conditions including Pulmonary Hypertension (PH) that exerts a dramatic impact on survival [2].

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 underrecognized complication in patients with ILDs and can adversely affect symptoms, functional capacity and survival. 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. Diagnosis of PH in these patients requires a high index of suspicion because the clinical presentation tends to be nonspecific, particularly in the presence of an underlying parenchymal lung disease [3].

There is paucity of studies on the Pulmonary Artery Hypertension (PAH) and it’s Association with socio-demographic variables among patients diagnosed with Interstitial Lung Diseases (ILD), in this hilly area of northern India. The present study was done to evaluate the prevalence of Pulmonary Artery Hypertension (PAH) and it’s Association with socio-demographic variables among Interstitial Lung Diseases (ILDs) patients.

Aims and Objectives

To study the Pulmonary artery hypertension (PAH) & its Association with socio-demographic variables among Interstitial Lung Diseases (ILDs) patients.

The present study was conducted at Indira Gandhi Medical College, Shimla which is a tertiary care center of Himachal Pradesh, located in North India in Asian Continent and covers the majority of the population of this state. All consecutive patients of Interstitial Lung Diseases (ILDs), attending the outpatient services of the Department of Pulmonary Medicine, IGMC Shimla from July 2018 to June 2019 were screened for enrolment in the study. All types of ILDs were enrolled in the study.

Inclusion Criteria

• Stable ILD patients: diagnosis of ILD according to ATS/ERS guidelines based on an overall assessment of High-Resolution Computed Tomography (HRCT) scan, lung function tests, (bronchoscopy and biopsy, if available) 

• Age >18 years, written consent

Exclusion Criteria

• Subjects with evidence of left heart disease, Chronic kidney disease, Liver disease

• Chronic lung diseases other than ILDs

• Patients with HIV

• Pregnant

Patients presenting with respiratory symptoms such as cough, shortness of breath and diagnosed cases of ILD were evaluated. 

All consecutive ILD patients were subjected to focused history and physical examination as structured questionnaire record information related to; Demographics, Duration of ILD, Pulmonary Artery Hypertension (PAH) and its Association with socio-demographic variables etc.

The data was collected, entered in the MS Excel sheet and analyzed using Epi info V7 software. Continuous variables were reported as mean ± SD or median and interquartile range depending on the distribution of the variables. Categorical variables were recorded as counts and percentages. Differences between means of continuous variables were compared using the unpaired student’s’ test. A p-value of <0.05 was considered as statistically significant.

Among the study population, 50 patients 27 (54%) were female and 23 (46%) were male. The mean age of the study population was 57.821+5.03years. The mean age of males and females was 62.561+3.84 years and 53.771+5.07 years respectively. The mean duration of symptoms of ILD was 3.034+2.62 years. There was no significant difference between males and females regarding the duration of illness (2.76+2.46 years versus 3.39+2.77 years, p=0.40) (Table 1).

Pulmonary Artery Hypertension (PAH) was by derived Pulmonary Flow Acceleration Time Formula (PFAT). Those who had Mean pulmonary artery pressure (MPAP) >25 mmHG was diagnosed as PAH case. Out of 50 patients, 44 (88%) had PAH.

In the study population, the mean age was 57.82+15.02 years with the mean age in population with PAH group and without PAH group was 60.07+13.15 years and 41.33+18.90 years respectively and the difference in mean age between the groups was statically significant with a p- value of 0.003. 

Among 50 patients, males were 23 ((46%) and female were 27 (54%), with a p-value of 0.13. In patients, those who had PH had an equal distribution of male and female with 22 (50%) each, with a p-value of 0.13.

The majority of patients were from the rural background of 44 (88%), with 38 (86.36%) patients had a PH with a p-value of 0.44. Among 50 patients, majority belong to the lower class of socioeconomic status. The majority patients who had PH belong to lower class i.e. sixteen (36.36%), eleven (25%) to upper class, four (9.09%) to upper-middle class, twelve (27.27%) to lower upper class and one (2.27%) to lower middle class with a p-value of 0.19.

Among 50 patients, 31(62%) of patients were never smoked, seventeen 17 (34%) were ex-smoker and two patients were active smokers. Out of 50 patients, 26 (59.09%) patients had PH, who never smoked, 16 (36.36%) and 2(4.4%) - with a history of ex-smoker and active smoker respectively, with a p-value of 0.5 (Table 2).

Table 1: Age and Gender Distribution of the Study Population (N=50)

Table 2: Association of Socio-Demographic Variables with PAH (N=50)

Among 50 patients the mean duration of ILD was 3.04+ 2.60 years. In patients who had PH the mean duration of ILD was 3.29+ 2.66 year, with a P value of 0.07.

Among 50 patients, the most common type of ILD was IPF (48%). Majority of patients of ILD were in PH group. IPF-23 (52.27%), sarcoidosis-9 (20.45%), SSc-6 (13.64%), SLE-ILD-2 (4.45%), CPFE-1 (2.27%) and HP -3 (6.82%) respectively, with a p-value of 0.4.

Among 50 patients 8 (16%) had a history of ATT, among them 7 (15.91%) had PH, with a p-value of 0.66. Out of 50 patients, 10 (20%) had a history of oxygen therapy, among them 9(20.45%) patients had PH with a p-value of 0.44.

The association with sociodemographic characteristics, duration of ILD and underlying etiology of ILD and use of domiciliary oxygen therapy was analyzed to determine the risk determinants of PAH.

The mean age of the study population was 57.821+5.03 with male and female mean age 62.561+3.84 and 53.77+15.07 respectively. Females were more than male and younger with a mean duration of ILD of 3.034±2.62 years. A similar finding was also reported in the study conducted by Agarwal et al. [4], In the ILD registry of Indian data, it was reported that ILDs occur at a younger age compared to the western countries and females are affected more [5].

In our study variables like a sociodemographic, clinical, laboratory and were analyzed by univariate analysis and correlates with pulmonary hypertension calculated by pulmonary artery acceleration time. 

In this study, the mean age of patients among the PH group was 60.07+13.15 years with a p-value 0.003. Patients of older age had PH in this study. Hassan et al. [6] in their study reported the mean age of 72±13.5 years, patients were S as older compare to our study. In our study the sample size was small and different types of ILD were included, on the contrary, they included IPF patients in their study.

In our study, no gender disparity among PH groups (equally distributed) was seen. Agarwal et al. [4], in their study had a number of the female as compared to male (not clear is it female predominance) Our sample was larger and we included a different type of ILD and we considered pulmonary flow acceleration time <105 msec and as compared <100msec in Agarwal et al. [4] study.

The majority of patients in our study belong to a rural background in the PH group 38%. The reason might be the majority (around 90%) of the population in Himachal lives in a rural area.In our study, the majority of patients in the PH group belong to class III (upper lower class) of SES 26%. No male-female disparity. In our study, various types of ILD and the majority of patients were from rural backgrounds.

In our study the majority of the patients were never smoked among the PH group, females were more in number 27(54%). Hassan et al. [6], in their study observed majority were smoker, in their study majority had the male population and the sample size was large. In our study female were predominant and the sample size was small.

In our study, the mean duration of ILD was 3.034±2.62 in the PH group, with no male and female disparity. Agarwal. et al. [4] in their study observed the mean duration of ILD was 3.01±3.1 which is comparable with our study.

In our study, the majority of the patients had IPF, followed by sarcoidosis and SSc respectively among the PH group. In the various study, it was concluded that IPF patients had more chances of PH. In patients who had H/o ATT intake and those patients who were in the long term, o₂ therapy had fewer numbers among the PH group. No relevant study was found.

There was very high prevalence of PAH among ILD Patients. PAH was high in males, those having rural  back-
ground, those belong to lower class, smokers, having history of ATT & Oxygen therapy and having IPF but there was no statistically difference among various socio-demographic variables.

Limitations of the Study

The small number of the population were included in this study represents a methodological limitation and study over a larger population is recommended.

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4. Agarwal, R., et al. "Noninvasive estimation of clinically asymptomatic pulmonary hypertension in idiopathic pulmonary fibrosis." The Indian Journal of Chest Diseases & Allied Sciences, vol. 47, no. 4, 2005, pp. 267–271.

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