Right ventricular–pulmonary artery coupling in chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension occurs in a proportion of patients with prior acute pulmonary embolism and is characterised by breathlessness, persistently raised pulmonary pressures and right heart failure. Surgical pulmonary endarterectomy (PEA) offers significant prognostic and symptomatic benefits for patients with proximal disease distribution. For those with inoperable disease, management options include balloon pulmonary angioplasty (BPA) and medical therapy. Current clinical practice relies on the evaluation of pulmonary haemodynamics to assess disease severity, timing of and response to treatment. However, pulmonary haemodynamics correlate poorly with patient symptoms, which are influenced by right ventricular tolerance of the increased afterload. How best to manage symptomatic patients with chronic thromboembolic pulmonary disease (CTEPD) in the absence of pulmonary hypertension is not resolved. Right ventricular–pulmonary artery coupling (RV-PAC) describes the energy transfer within the whole cardiopulmonary unit. Thus, it can identify the earliest signs of decompensation even before pulmonary hypertension is overt. Invasive measurement of coupling using pressure volume loop technology is well established in research settings. The development of efficient and less invasive measurement methods has revived interest in coupling as a viable clinical tool. Significant improvement in RV-PAC has been demonstrated after both PEA and BPA. Further studies are required to understand its clinical utility and prognostic value, in particular, its potential to guide management in patients with CTEPD. Finally, given the reported differences in coupling between sexes in pulmonary arterial hypertension, further work is required to understand the applicability of proposed thresholds for decoupling in therapeutic decision making.