Questioning the Definition and Clinical Translational Value of a Nitrate–Hydralazine “Vasoreactivity Test” in PH-HFpEF

El Shaer et al.1 present an innovative pilot linking invasive gas exchange with a nitrate–hydralazine challenge in pulmonary hypertension resulting from heart failure with preserved ejection fraction (PH-HFpEF), but 3 clarifications would strengthen clinical translation and invite a focused author response. First, the proposed “vasoreactivity” construct—concordant rises in pulmonary arterial compliance (PAC) and oxygen uptake efficiency slope—needs operational thresholds and reproducibility: please report laboratory/test–retest variability for PAC and oxygen uptake efficiency slope, effect sizes with 95% confidence intervals relative to measurement noise, and any longitudinal linkage (symptoms, admissions, or follow-up hemodynamics) to establish clinical meaning beyond physiologic fluctuation.