Vasoreactive testing prevalence and characteristics in patients with idiopathic pulmonary arterial hypertension

The choice of treatment strategy in patients with idiopathic pulmonary arterial hypertension (IPAH)/HPAH/DPAH (Hereditary pulmonary arterial hypertension/ Drug-induced pulmonary arterial hypertension) II-III functional class (FC) (WHO) based on an acute vasoreactive testing result (VRT). Positive VRT (VRT+) is an indication for calcium channel blockers therapy. Long-term vasoresponders demonstrate sustained low-risk status and the highest survival among all PH subtypes.

To characterize VRT performance in IPAH patients and differences in presentation between patients with positive, negative VRT, and patients with not done VRT due to physicians' decision.

One hundred and sixty-six adult IPAH patients (44.2 ± 15.3 years, 34 males) comprised into prospective single-center study between 2008 and 2023 years. Inhaled iloprost was used for VRT. Positive VRT was defined with established Sitbon criteria. Standard baseline pulmonary arterial hypertension (PAH) evaluation including cardiopulmonary exercise test (CPET) was performed. Risk status was evaluated using ESC/ERS (European Society of Cardiology/European Respiratory Society) risk scale 2015. Survival was assessed with the Kaplan-Mayer method.

Eighty-five (51.2%) patients underwent VRT. VRT not done (ND VRT) due to the physicians' decision in 26.7% patients, due to the technical inability in 15.4% and IV FC (WHO) in 16.2% patients. Positive VRT registered in 26 (15.6%) patients. Patients with negative VRT demonstrated worse hemodynamics and exercise tolerance, higher N-terminal pro-brain-type natriuretic peptide (NT-proBNP) level, and right heart dilatation compared with VRT+. Patients with ND VRT due to the physicians decision were often older than 60 years, had higher body mass index, symptoms of right heart failure, hemoptysis, arrhythmias, high NT-proBNP, and hemodynamic criteria of high risk in comparison with patients with done VRT. Some CPET parameters were similar between VRT + group and patients ND VRT group. Loss of vasoreactivity and PAH worsening were detected in 50% of VRT + patients in a 1.76 year of follow-up. Patients with vasoreactivity loss exhibited the criteria of intermediate risk at a baseline. Five-year survival was 97% in VRT + group in comparison with 61% in VRT - and 53% in ND VRT group.

Physicians' decision was the most common reason for not doing VRT in IPAH patients. Intermediate high-risk criteria presence at a baseline were associated with not done VRT due to physicians decision, negative VRT, and the vasoreactivity loss during the follow-up. CPET should be used more widely to detect the early signs of PAH progression in low risk or VRT + patients.