Functional Assessment of Hypertrophic Phenotype Cardiomyopathies Using Combined Cardiopulmonary Exercise Testing and Echocardiography: A Pilot Single-Centre Study.

Background: In patients with left ventricular hypertrophy, resting structural parameters alone may not explain exertional symptoms. Hence, we investigate whether combined Cardiopulmonary Exercise Testing- Exercise Stress Echocardiography (CPET-ESE) can provide an integrated functional characterisation of hypertrophic phenotypes. Methods: As a preliminary investigation, this prospective single-centre pilot study enrols 43 patients, categorised into: obstructive hypertrophic cardiomyopathy (n = 19), transthyretin cardiac amyloidosis (n = 15), or preserved-ejection-fraction hypertrophic phenotypes (n = 9). Patients undergo symptom-limited semi-supine CPET-ESE on an electronically braked cycle ergometer with an individualised ramp protocol. Peak effort is defined by symptom limitation and respiratory exchange ratio criteria (RER≥1.05), while peak VO2 is defined as the highest 30 s averaged value. Results: Exercise responses differ across phenotypes. Patients with obstructive hypertrophic cardiomyopathy have higher peak VO2 than the other groups, despite their lower chronotropic reserve. The preserved-ejection-fraction hypertrophic group shows lower peripheral oxygen extraction, whereas transthyretin amyloidosis shows a mixed central and peripheral limitation pattern. Right ventricle-pulmonary artery uncoupling is observed in the latter two groups. Conclusions: The use of CPET-ESE may help describe distinct physiological exercise profiles in hypertrophic phenotypes, but these findings should be considered exploratory. The small, heterogeneous and single-centre cohort precludes definitive mechanistic or predictive conclusions and supports the need for larger validation studies.