Metrics for Success of Balloon Pulmonary Angioplasty in Chronic Thromboembolic Pulmonary Hypertension

Balloon pulmonary angioplasty (BPA) has been developed as a compassionate procedure for symptomatic patients with chronic thromboembolic pulmonary hypertension (CTEPH) who are not candidates for pulmonary endarterectomy. With increasing physicians’ expertise, improvement of clinical results, and worldwide diffusion of the technique, definition of treatment goals has become crucial. The efficacy of BPA could be assessed from the patient’s perspective according to clinical endpoints as well as through the evaluation of surrogate endpoints that are known to hold significant prognostic value. The principal objective of BPA should be the stable relief of pulmonary hypertension (PH), with normalization of mean pulmonary artery pressure (<25 mmHg) and pulmonary vascular resistance (PVR). Importantly, clinical outcomes of BPA are the results of multiple-staged procedures, each one addressing several lesions in different lung territories. Hence, definition of metrics for success at a lesion level is a necessary step to guide the BPA procedures. To date, the best targets for BPA at the lesion level are normalization of pulmonary flow grade (PFG = 3) and abrogation of pressure gradient through the lesion (Pd/Pa < 0.8). Patients undergoing BPA represent a heterogeneous group and different target goals could be reasonably set for different patients. The effect of extensive anatomic revascularization beyond normalization of mPAP is under investigation and might be the target for selected patients. Standardization of definitions for efficacy and safety endpoints, in this context, seems necessary. This chapter describes endpoints and metrics for BPA that are commonly used in clinical practice and in the scientific literature.