BACKGROUND: Right heart abnormalities and pulmonary hypertension (PH) may be secondary to chronic lung disease. Chronic lung disease is common in children with HIV. In the BREATHE trial ( Trial registration: NCT02426112), azithromycin (AZM) reduced the risk of acute respiratory exacerbations in children aged 6-19 years with HIV-associated chronic lung disease (HCLD) taking antiretroviral therapy. We assessed the possible effect of AZM on right heart dysfunction and/or PH in the trial. METHODS: A standardised transthoracic echocardiogram using M-mode, two-dimensional and Doppler was performed, at baseline and at completion of weight-based AZM given weekly for 48 weeks. Linear regression was used to compare trial arms. RESULTS: A total of 169 participants (82 AZM arm; 87 placebo arm) were included. Participants in the placebo arm were older, median age 16.2 (13.0-18.2) vs 15.3 (12.9-17.4) years, p = 0.184 in the AZM arm. At baseline, right heart abnormalities (right ventricular systolic dysfunction (RVSD), dilatation, or PH) were observed in 7(4%). Following treatment, there was no difference in prevalence of RVSD between arms (p = 0.761). There was one incident case of suspected PH, and overall, no difference in pulmonary pressures. CONCLUSION: In children with HCLD, there was evidence of secondary cardiac effects, but AZM had no effect on right heart function. Long-term follow-up in children with HIV should be part of future research to understand the clinical implications of right heart abnormalities.