Functional Assessment of Hypertrophic Phenotype Cardiomyopathies Using Combined Cardiopulmonary Exercise Testing and...

Area of Science:

• Cardiology
• Exercise Physiology
• Medical Imaging

Background:

• Resting structural parameters in left ventricular hypertrophy may not fully explain exertional symptoms.
• Integrated functional assessment is needed to characterize hypertrophic phenotypes during exercise.

Purpose of the Study:

• To investigate the utility of combined Cardiopulmonary Exercise Testing-Exercise Stress Echocardiography (CPET-ESE) for functional characterization of hypertrophic phenotypes.
• To differentiate physiological exercise profiles across obstructive hypertrophic cardiomyopathy, transthyretin cardiac amyloidosis, and preserved-ejection-fraction hypertrophic phenotypes.

Main Methods:

• Prospective pilot study involving 43 patients with distinct hypertrophic phenotypes.
• Symptom-limited semi-supine CPET-ESE performed using an individualized ramp protocol.
• Peak effort defined by symptom limitation and respiratory exchange ratio (RER≥1.05); peak VO2 assessed.

Main Results:

• Obstructive hypertrophic cardiomyopathy patients exhibited higher peak VO2 compared to other groups, despite lower chronotropic reserve.
• Preserved-ejection-fraction group showed reduced peripheral oxygen extraction; transthyretin amyloidosis displayed mixed central/peripheral limitation.
• Right ventricle-pulmonary artery uncoupling was noted in transthyretin amyloidosis and preserved-ejection-fraction groups.

Conclusions:

• CPET-ESE may differentiate physiological exercise profiles in hypertrophic phenotypes.
• Findings are exploratory due to small, heterogeneous, single-center cohort.
• Larger validation studies are necessary to confirm mechanistic and predictive conclusions.