Correlations between physician-perceived functional status, patient-perceived health status, and cardiopulmonary exercise results in hypertrophic cardiomyopathy

Background: Dyspnea and the resulting functional impairment are a common complication in hypertrophic cardiomyopathy (HCM). The relationship between physician-perceived functional status, patient-perceived health status, and objective exercise test results has not been evaluated in this condition. Purpose: To evaluate the correlation between the Kansas City Cardiomyopathy Questionnaire (KCCQ) and (1) physician's perceived (NYHA class) and (2) objective measurement (cardiopulmonary exercise test) of functional capacity in patients with HCM. Methods: In 24 outpatients with HCM at a single, referral center, the KCCQ instrument was administered and cardiopulmonary exercise testing (CPX) was performed. Severity of symptoms as determined by physician (NYHA classification) and patient (KCCQ instrument) was obtained before exercise test results were known. Pearson correlation was used to assess the independent correlation between KCCQ score and the various exercise parameters; Spearman correlation was used to assess correlation between KCCQ score and NYHA class. Results: KCCQ results demonstrated moderate reductions in all domains, with greatest reduction in quality-of-life domain. CPX testing showed reduction in peak oxygen consumption (mean absolute VO2 20.5 ± 7.8 ml/kg/min and percent predicted VO2 76.8 ± 4.1 %). There were negative correlations between NYHA class and all KCCQ components except the self-efficacy score. The strongest correlations were between NYHA class and the overall summary score (r = -0.623, p = 0.001) as well as the physical limitation score (r = -0.604, p = 0.002). Similarly, there were statistically significant positive correlations between the KCCQ components and percent predicted peak VO2. The strongest correlation was between percent predicted peak VO2 and the physical limitation score (r = 0.474, p = 0.019), but there was also correlation between percent predicted peak VO2 and the quality-of-life score (r = 0.456, p = 0.025), the functional status score (r = 0.455, p = 0.025), and the clinical summary score (r = 0.444, p = 0.030). Conclusions: The multiple domains of the KCCQ provide data on patient-perceived health status, which correlate with physician-perceived and objective measurement of functional capacity in HCM. Additional studies are needed to evaluate the sensitivity of the KCCQ to changes in functional capacity over time or in response to therapies for this condition.