Minimum-workload exercise testing for the detection of exercise pulmonary hypertension

Background Exercise right heart catheterisation is essential for evaluating unexplained exertional dyspnoea and for the detection of exercise pulmonary hypertension (exPH). The 2022 ESC guidelines define exPH as an mPAP/CO slope >3 mmHg/L/min. However, the minimal workload required to reliably elicit abnormal haemodynamic responses remains unclear. Purpose We aimed to determine whether haemodynamic parameters obtained during the earliest phase of exercise (0 W) accurately identify exPH. Methods We retrospectively analysed 220 consecutive exercise right heart catheterisation studies (153 patients) performed between June 2021 and December 2025. Cardiac output was measured using the direct Fick method with simultaneous respiratory gas analysis. A multistage, symptom-limited protocol with increased workload by 10 or 20 W every 3 minutes was performed. To evaluate the diagnostic utility of minimal exercise stress, we defined three parameters calculated from rest to 0 W: the early exercise mPAP/CO slope (Ee slope), change in mPAP and cardiac index (CI) at early exercise stage (Ee ΔmPAP and Ee ΔCI, respectively). After excluding 17 studies due to inadequate measurements, 203 studies were included in the final analysis. Results In all 153 patients, the median age was 65 years (IQR 53-76), and 31.5 % of patients were male. Most studies were performed in patients with CTEPH or CTED without resting PH (n=175), followed by idiopathic pulmonary arterial hypertension (n=23). At rest, median mPAP was 22 mmHg (IQR 17–28), CI 2.77 L/min/m² (IQR 2.33–3.15), and PVR 3.03 WU (IQR 2.05–4.81). During exercise, the median overall mPAP/CO slope was 6.19 mmHg/L/min (IQR 4.13-9.39), with a median peak workload of 40 W (IQR 20-60). At the 0 W load, Ee slope was 7.74 mmHg/L/min (IQR 4.04–14.12), Ee ΔmPAP was 10 mmHg (IQR 6-15), and Ee ΔCI was 0.75 L/min/m² (IQR 0.38–1.17). Both Ee slope (ρ=0.61, p<0.001) and Ee ΔmPAP (ρ=0.64, p<0.001) were strongly correlated with the overall mPAP/CO slope. For detecting exPH (mPAP/CO slope >3 mmHg/L/min), Ee ΔmPAP achieved an AUC of 0.894 (95% CI 0.828-0.939), and Ee slope achieved an AUC of 0.881 (95% CI 0.823-0.939). In contrast, Ee ΔCI showed poor discrimination (AUC 0.34). Conclusion Early exercise mPAP/CO slope and early exercise ΔmPAP strongly correlate with the conventional mPAP/CO slope and demonstrate high diagnostic accuracy. Identifying exPH before substantial exercise stress reduces patient burden and enhances feasibility, particularly in elderly or frail individuals.