Interstitial lung diseases (ILDs) include more than 200 disorders, characterized by a variable degree of inflammation and fibrosis leading to an often-irreversible loss of lung function, wide spectrum in the clinical course, treatment, and prognosis [1].

Respiratory function declines along with disease progression, and changes in lung diffusion capacity of carbon monoxide (DLCO) and forced vital capacity (FVC) are both independent predictors of worse prognosis. Pulmonary arterial hypertension (PAH) is frequently found in the early stages of ILD and the outcome is directly related to the capacity of right ventricular (RV) function to adapt to the elevated afterload. The combination of severe vascular and fibrotic abnormalities induces changes in right ventricular (RV) structure and function until heart failure onset. RV enlargement and dysfunction, as have been well described in ILD and can be used to identify patients with high risk of mortality [2-4].

RV abnormalities have been demonstrated to be evident and predict prognosis in IPF. RV abnormalities appear to be mainly due to PAH, which has a high prevalence (up to 85%) in the advanced disease stages. In ILD patients of less advanced stages (with normal TAPSE and LV EF), showed a significant reduction of RV strain, as an index of early impairment of RV systolic function [1,5].

There is paucity of studies on the Pulmonary hemodynamics and RV systolic function profile of patients diagnosed with interstitial lung diseases (ILD), in this hilly area of northern India. The present study was done to evaluate the Pulmonary hemodynamics and RV systolic function profile of Interstitial Lung Diseases (ILDs) patient.

Aims & Objectives

To study the Pulmonary hemodynamics and RV systolic function profile of 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 hemodynamics and RV systolic function profile 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).

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

Table 2: Pulmonary Hemodynamics and RV Systolic Function Profile (N=50)

Among 50 patients, 24 (48%) patientshad TR. The mean value of TRV among 24 patients was 3.7+0.7 meters/sec. There was no significant difference in mean TRV between male and female patients (4.5+0.5 vs. 3.5+0.9 meters/sec) P=0.29. Out of 50 patients the mean value of PASP was 66.29+23.61mmHg. The mean value in male and female were 72.89+18.09mmHg and 62.55+27.25mmHg respectively, statistically not significant with p-value of a 0.29. Mean pulmonary artery pressure (MPAP) was measured by tricuspid regurgitation velocity (TRV) by formula (0.61xPASP+2mmHg). Out of 24 patients who were having TR, the mean value of Mean pulmonary artery pressure (MPAP) was 42.96+14.52mmHg. No significant difference in male and female (46.45+11.04 mmHg versus 40.00+16.79mmHg, (p-value= 0.28) was reported.

Out of twenty-four patients who had TR, twenty ((83.33%) had Pulmonary artery hypertension (PAH). The PAH was more prevalent in male (100%), vs. 9 (69.2%) (p< 0.04).out of 50 patients, the mean value of mean PAP was 43.85+12.42mmHg. There was no significant difference in mean MPAP between Male and female study population, 46.4+11.0 vs. 40.0+16.8 mmHg respectively. (p= 0.28). Out of 50 patients, 44 (88%) had PAH. The PAH was equally prevalent in males and females (95.65% and 81.48%) with a p- value of 0.13.

Pulmonary vascular resistance (PVR) was measured by formula (PVR= TRV/RVOT VTI x 10+0.16 WU). The mean value of PVR was 4.11+1.41 WU. There was no significant difference in PVR among males and females’ patients (4.0+0.4 versus 3.5+0.9 WU). (p= 0.19). Majority of patients 79% had PVR of >3 WU. Predominantly male being 90.91% PVR >3wu, with a p- value of 0.21 (Table-2).

Among 50 patients the mean IVC diameter was 14.95+4.1 mm. The mean value in males and females being 15.1+4.6mm and 14.7+3.4 mm respectively, with a p-value of 0.7. The IVC diameter was significantly increase (>21 mm) in 4(8%) of patients. The systemic venous congestion was not significantly different between male and females) Patients with IVC collapsibility with inspiration >50% were 31(62%) and <50% were 19(38%) respectively. No male and female disparity of IVC collapsibility with inspiration >50% and <50% (56.52% versus (66.67%) and (43.48% versus 33.33%), with a p-value of 0.46.

Among the 50, the mean value of RA pressure was 5.36+3.63 mmHg. Male and female being 5.47+3.21mmHg and 5.25+4.01mmHg respectively, with a p- value of 0.84. Among the 50 patients, the mean value of Pulmonary flow acceleration time (PFAT) was 77.99+21.61msec. Male and female being 73.49+21.36 msec and 81.82+31.90 msec respectively, with a p-value of 0.29. Majority of (78%) patients had PFAT < 105 msec. 

Out of 50 patients, the mean value of Tricuspid annular peak systolic excursion (TAPSE) was 17.67+3.08mm. No male and female disparity (17.73+2.80mm versus 17.6+3.3mm p=0.90). Majority of patients (58%) had TAPSE of < 17mm, male outnumber than female for TAPSE <17mm (65.2% and 48.1%. with a p-value- of 0.33). (Table-2)

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. [6], 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 [7].

In our study, the echocardiographic variables were recorded. The mean TRV was 3.77+0.77 (n=24) among twenty-four patients in which tricuspid regurgitation was present. No male and female differences (4.00+0.54 versus 3.58+0.94 p=0.19) statistically not significant. In our study, the majority of the patients had TRV > 3.4 msec. No male and female disparity, finding was. As per ESC guidelines for PH 2015.

In our study, the mean IVC diameter was 14.95+4.13 among fifty patients, with no male-female disparity (15.13+4.66 and, 14.78+3.47 with a p-value 0.7). IVC diameter < 21mm and respiratory variation < 50% had no male and female difference (95.65% versus 89% respectively) and (43% versus 33% respective). 

In our study, the mean RA pressure was 5.36+3.63 in fifty patients, no male, and female disparity statically not significant. In our study, the mean PASP was 66.29+23.61 in twenty-four patients in those TR was present. The majority of patients had PASP between 51 to 80mmHg, female had predominantly PASP in 50to 80mmHg with a p-value of 05. Hasan et al.,9 in their study reported with a total of twenty-seven patients had PASP >50mmHg with male predominant of 81.2%, with a p-value of 0.014 and mean PASP 72mmHg. In our study female were predominantly involved (61%), in their study sample size was large and secondly, a study was conducted on IPF patients. IPF mostly involve male more than female. In our study the sample size is small and the study involves six different types of ILD. 

In our study, the mean value of MPAP calculated by Chemla’s formula was 42.96+14.52 mmHg in twenty-four patients who had TR. No male and female disparity. Kasai et al.,10 reported in their study the MPAP 35.9+11.3 which is lower as compared to our study. In their study, MPAP was observed in chronic pulmonary thromboembolic PH. In our study sample is small and MPAP was observed in ILD patients. Baughman et al.,11 another study done on patients for sarcoidosis reported 80% had MPAP >25mmHg. In their study the sample size was large. In our study pulmonary hypertension (PH) calculated by chela’s (TR derived) formula (0.61xPASP+2mmHg) among patients who had tricuspid regurgitation (n=24) was 20(83.33%), predominantly male patients. Agarwal. et al.,6 in their study reported 36% of patients had PH. 

In our study, the mean value of Pulmonary artery acceleration time was 77.99+21.61, in both male and female had almost equal mean value. A total of 39(78%) patients had PFAT <105 predominantly male were more in number. Pulmonary artery acceleration time cut off was taken as per the ESC 2015 guideline of pulmonary hypertension.

In our study, the mean value of MPAP calculated by mahn formula (79-.45xPFAT) was 43.85+12.42. No male and female differences were noted. Pulmonary artery hypertension based on this formula was reported in 44(88%) patients. Equally distributed among males and females. Various studies have shown the prevalence of PH 14% to 80%. Agarwal et al. [6] their study observed 36%, their sample size was small. In our study different types of ILD were included with a large sample.

In our study pulmonary vascular resistance (PVR) the mean value was 4.11+1.41WU among patients who had TR, 79% had PVR >3WU. No male and female disparity. PVR > 3WU was taken as per SC 2015 guideline of pulmonary hypertension.

Majority of ILD patients, had Tricuspid Regurgitation (TR), Pulmonary artery hypertension (PAH), Pulmonary Vascular Resistance (PVR) of >3 WU, IVC collapsibility with inspiration >50%, Pulmonary flow acceleration time (PFAT) < 105 msec and Tricuspid annular peak systolic excursion (TAPSE) of < 17mm.

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.

1. Buonauro, A. et al. "Impaired right and left ventricular longitudinal function in patients with fibrotic interstitial lung diseases." Journal of Clinical Medicine, vol. 9, no. 2, 2020, p. 587.

2. Kimura, M. et al. "pulmonary hypertension as a prognostic indicator at the initial evaluation in idiopathic pulmonary fibrosis." Respiration, vol. 85, no. 6, 2013, pp. 456–463.

3. Fein, D.G. et al "Pulmonary hypertension due to common respiratory conditions: classification, evaluation, and management strategies." Journal of Clinical Medicine, vol. 5, no. 9, 2016, p. 75.

4. Rivera-Lebron, B.N. et al. "Echocardiographic and hemodynamic predictors of mortality in idiopathic pulmonary fibrosis." Chest, vol. 144, no. 2, 2013, pp. 564–570.

5. D’Andrea, A. et al. "Right ventricular strain: an independent predictor of survival in idiopathic pulmonary fibrosis." International Journal of Cardiology, vol. 222, 2016, pp. 908–910.

6. 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.

7. Indian ILD Registry. Lung India, vol. 31, no. 4, 2014, pp. 320–322.