Invasive exercise hemodynamics in obstructive and nonobstructive hypertrophic cardiomyopathy

Area of Science:

• Cardiology
• Cardiovascular Physiology
• Heart Disease Research

Background:

• Hypertrophic cardiomyopathy (HCM) is a complex heart condition.
• HCM can cause shortness of breath due to left ventricular outflow tract obstruction (LVOTO), diastolic dysfunction, or left atrial issues.
• Understanding how these factors affect exercise capacity is crucial for patient management.

Purpose of the Study:

• To investigate the hemodynamic changes during exercise in patients with HCM.
• To differentiate the exercise responses between obstructive and non-obstructive HCM.
• To determine the contribution of LVOTO, diastolic dysfunction, and left atrial function to exercise limitations in HCM.

Main Methods:

• Conducted rest and exercise cardiac catheterization in 25 HCM patients.
• Classified patients into non-obstructive (no-HOCM) and obstructive (HOCM) groups.
• Overt HOCM had resting LVOTO > 30 mmHg; latent HOCM had exercise-induced LVOTO ≥ 50 mmHg.

Main Results:

• No significant difference in resting pressures (LV end-diastolic, PAWP, PAWP V waves) between groups.
• During exercise, non-obstructive HCM showed a greater increase in pulmonary artery wedge pressure (PAWP) and PAWP V waves (indicating left atrial stiffness).
• Overt obstructive HCM experienced a reduction in LVOTO during supine exercise.

Conclusions:

• Non-obstructive HCM patients may exhibit greater increases in left atrial pressure during exercise, suggesting more significant left atrial myopathy or reduced compliance.
• Obstructive HCM patients with overt obstruction may show a paradoxical decrease in LVOTO during supine exercise.
• These findings highlight distinct pathophysiological mechanisms contributing to exercise intolerance in different HCM subtypes.