To Compare the Efficacy of Combination Therapy vs Monotherapy for Pulmonary Arterial Hypertension in Systemic Sclerosis

All patients fulfilling the SSc classification criteria of American College of Rheumatology during the study period will be screened for presence of PAH. Diagnosed cases of PAH based on CD echo with PAP \>35mmHg based on echocardiography will be enrolled in study.Baseline NYHA functional class and 6 min walk distance in meters will be assessed. Heamogram and LFT will be measured Patients will be assessed at two weeks for side effects/safety issues. 6MWT and NYHA functional class will be reassessed at 3 months and 6 months.2D echo will be done at 6 months to measure mPAP RandomizationAll eligible patients will be randomized in a 1:1 ratio in blocks of ten between the two arms. Randomization will be stratified based on severity of PAH. The drugs will be labelled as A and B randomly by another staff member, who will not be involved in deciding the treatment of the study subjects. The randomization sequence will be generated using computer random number generator. Blinding will be ensured by matching placebo for ERA in one group and will labelled one treatment arm as 'A' and other treatment arm as 'B'. Allocation concealment will be ensured by means of enclosing the randomization sequence in sealed opaque envelopes. Sealed opaque envelopes will contain Code 'A' or Code 'B'. Intervention-The study consists of two treatment arms. The study drugs mainly Bosentan and Placebo will be packed into matching tablets at the dosage 62.5 mg. One treatment arm will contain Sildenafil and Placebo while other treatment arm will contain Sildenafil and Bosentan. Treatment will be initiated as 20 mg twice a day for Sildena-fil in combination with placebo once a day in one treatment arm and with Bosentan 62.5 mg once a day in other treatment arm .Dose of Sildenafil will be increased to 20 mg thrice a day at four weeks and that of Bosentan to 62.5 mg twice a day. Placebo will be also be provided twice a day.This will be continued till end of study period.. Dose adjustments in case of adverse events will be made depending on the severity of adverse events. Statistical analysis- Intention to treat analysis will be carried for the primary and secondary outcomes. For continuous outcomes, unpaired t-test and for dichotomous outcomes chi-squares test with Yate's correction will be used. P\<0.05 will be considered significant