Cardiopulmonary exercise testing in long-term calcium channel blockers responders, does it normalize in the same way as pulmonary vascular resistance?

Abstract Background and aims Long-term calcium channel blockers (CCB) responders represent <10% of pulmonary arterial hypertension (PAH) patients and are known to have an excellent prognosis on high dose CCB. The few reports of lung histology of these patients suggest a predominant muscular thickening of the precapillary arterioles. Nevertheless, the classic intimal proliferation characteristic of PAH has also been reported, although to a lesser extent. Hence, we hypothesized that long-term CCB responders are likely to exhibit some degree of ventilatory inefficiency as a result of their impaired alveolo-capillary membrane. In this study, we aimed to evaluate the exercise performance of a contemporary cohort of long-term responders to CCB in terms of both exercise capacity and ventilatory efficiency, and whether there are differences depending on the haemodynamic severity. Methods We evaluated all long-term CCB responders with regular follow-up at our institution between 1996 to 2024 with at least one cardiopulmonary exercise test (CPET) and a right heart catheterization (RHC) within a three-year period, provided they had remained clinically stable without changes in pulmonary vasodilator treatment. Patients with additional PAH specific treatment were excluded. For data analysis purposes, the population was divided into 2 groups according to pulmonary vascular resistance (PVR). The cut-off point for PVR was set at ≥3. Results Twenty-four patients (91,6% female) with complete data were retrospectively enrolled. Baseline characteristics were as follows: median age 45.5 years (59-33) median mean pulmonary artery pressure of 26 mmHg (29-24) and median PVR of 3 WU (3-2.6). Regarding the whole cohort, peak oxygen consumption (pVO2) revealed mild impairment of functional capacity (mean pVO2: 1281 ± 245 ml/kg – 75 ± 15% of predicted). Ventilatory efficiency parameters were also mildy affected with low end-tidal carbon dioxide pressure at the anaerobic threshold (PETCO2@AT) (33.7±3.6mmHg), and increased minute ventilation (VE)/carbon dioxide output (VCO2) slope (33.5±4.5). The subgroup analysis depending on PVR showed no significant differences between groups in terms of pVO2 (1291.9 ±240 Vs. 1150 ±350 ml/kg, p:0.29 / 79%±16 vs 67%±12, p:0.8), VE/VCO2 slope (33 Vs. 34, p:0.21), or PETC02@AT (35 Vs. 33 mmHg, p:0.25). All CPET parameters by subgroups are displayed in Table 1. Conclusions Long-term CCB responders exhibit mildly reduced functional capacity. Moreover, they often fail to normalize the ventilatory efficiency parameters in most of the cases, even when PVR reaches close to normal values, suggesting persistent endothelial impairment.Results according to PVR