Risk Assessment in Pulmonary Arterial Hypertension Patients: The Long and Short of it

Pulmonary arterial hypertension (PAH) is a chronic and rapidly progressive disease that is characterized by extensive narrowing of the pulmonary vasculature, leading to increases in pulmonary vascular resistance, subsequent right ventricular dysfunction, and eventual death. There are currently multiple approved drugs—developed as single or combination therapies in the last few years—that have improved outcome and functionality in PAH. However, despite improvement in short-term survival with these new effective therapies, PAH remains an incurable disease with a median survival of 7 years (Figure 1).1 This chronic disease state may be characterized by morbid events such as hospitalizations that herald rapid disease progression and account for a significant disease burden (Figure 2).23 Physician ability to predict PAH disease progression is critical for determining optimal care of patients. Accurate risk assessment allows clinicians to determine the patient's prognosis, identify treatment goals, and monitor disease progression and the patient's response to treatment. Risk assessment for PAH patients should include a range of clinical, hemodynamic, and exercise parameters, performed in a serial fashion over the treatment course. Patient risk stratification can also help physicians better allocate treatment resources in settings where they are scarce. If widely adopted, risk prediction can enhance the consistency of treatment approaches across PAH practitioners and improve the timeliness of referral for lung transplantation. Hence, along with advancing PAH treatment options, comprehensive risk prediction is essential to make individualized treatment decisions in the current treatment era. Several tools are currently available for assessing risk in PAH (Figure 3). These include the 2015 European Society of Cardiology/European Respiratory Society pulmonary hypertension guidelines' risk variables,4 the French registry equation,5 the National Institutes of Health risk equation,6 or a risk score such as the one derived from the Registry to Evaluate Early And Long-term PAH Disease Management.1 These registries and evaluations of clinical trial sets have provided important insights into the importance of both modifiable (eg, 6-minute walk distance, functional class, brain natriuretic peptide, and nonmodifiable (eg, age, gender, PAH etiology) risk factors that predict survival. The following review explores commonly cited risk factors, both modifiable and nonmodifiable, and their implications for patient outcomes.