Invasive exercise hemodynamics in obstructive and nonobstructive hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a heterogeneous disease that may lead to exertional dyspnea through dynamic left ventricular outflow tract obstruction (LVOTO), left ventricular (LV) diastolic dysfunction, and/or left atrial myopathy. Deciphering the relative contribution of these alterations to exercise pathophysiology may be clinically relevant. We sought to characterize the hemodynamic adaptation to exercise of patients with HCM, using supine left and right heart catheterization. Twenty-five patients with HCM underwent rest and exercise cardiac catheterization. Patients were subdivided into nonobstructive HCM (no-HOCM) and obstructive HCM (HOCM); the latter were defined by LVOTO > 30 mmHg at rest (overt HOCM, irrespective of exercise LVOTO) or ≥50 mmHg during or after exercise despite LVOTO < 30 mmHg at rest (latent HOCM). Ten patients (40%) were classified as no-HOCM, whereas 15 (60%) were classified as HOCM (8 with overt HOCM and 7 with latent or postexercise HOCM). LV end-diastolic pressure, mean pulmonary artery wedge pressure (PAWP), and PAWP V waves (the latter a marker of left atrial stiffness) did not differ between HOCM and no-HOCM at rest. However, during exercise, both PAWP and PAWP V waves increased to a larger extent in no-HOCM (+24 ± 3 vs. +13 ± 3 mmHg and +28 ± 4 vs. +14 ± 3 mmHg, respectively, P < 0.05). In overt HOCM, LVOTO was reduced by 22 ± 8 mmHg (P < 0.01) during exercise. Our findings suggest that during exercise, no-HOCM patients may display a steeper increase in left atrial pressure than HOCM, suggesting more advanced left atrial myopathy/low left atrial compliance. LVOTO may paradoxically reduce during supine exercise in overt HOCM.NEW & NOTEWORTHY Patients with hypertrophic cardiomyopathy (HCM) quite invariably display high left heart filling pressure during exercise. Mean pulmonary artery wedge pressure increase, together with tall V waves, may be steeper in patients with nonobstructive HCM than in patients with obstructive HCM, witnessing more severe left atrial myopathy. Patients with overt obstructive HCM (i.e., with significant left ventricular outflow tract pressure gradient at rest) may present with a paradoxical reduction of left ventricular outflow tract obstruction during supine exercise.