Ventilatory efficiency and resting hemodynamics in hypertrophic cardiomyopathy

Purpose: In patients with systolic heart failure, the ability of cardiopulmonary exercise testing (CPX) variables to reflect pathophysiology is well established. The relationship between CPX and pathophysiology has, however, not been thoroughly investigated in patients with nonobstructive hypertrophic cardionryopathy (NHCM). The objective of this study was to assess the ability of CPX variables to reflect resting hemodynamics in patients with nonobstructive hypertrophic cardionryopathy NHCM. Methods: We performed CPX and right heart catheterization on 83 subjects with NHCM (51 male/32 female, mean age = 38 +/- 10 yr, NYHA I-III mean = 1.7). Peak oxygen consumption (VO2) and minute ventilation/carbon dioxide ratio (V-E/VCO2) at peak exercise were compared to resting hemodynamics including pulmonary artery systolic, diastolic and mean pressures (PASP, PADP and MPAP), and pulmonary capillary wedge pressure (PCWP). Results: Elevations in PCWP (>= 15 mm Hg), PASP (>= 30 and >= 40 mm Hg), PADP (> 15 mm Hg) and MPAP (>= 20 mm Hg) were detected in 22, 33, 10, and 23% of subjects, respectively. Peak V-E/VCO2 (positive correlation) and peak VO2 (negative correlation) correlated modestly with all pressure measurements (r = 0.33-0.51, P < 0.01 for all measurements). By receiver operating curve analysis, a V-E/VCO2 >35.5 exhibited the best diagnostic accuracy with a curve areas of 0.81 for PAP 30 mm Hg (sensitivity/specificity = 86%/67%), 0.87 for PAP >= 40 mm Hg (77%/100%), 0.86 for MPAP > 20 into Hg (83%/79%), and 0.84 for PCWP : 15 mm Hg (80%/06%). Conclusions: CPX can accurately identify abnormal resting hemodynamics in patients with NHCM. Further testing of this modality in other forms of diastolic dysfunction may be warranted.