Validation of the Kansas City Cardiomyopathy Questionnaire in Symptomatic Obstructive Hypertrophic Cardiomyopathy

Background: The primary goal for treating patients with obstructive hypertrophic cardiomyopathy (oHCM) is to improve their symptoms, function, and quality of life. Although the Kansas City Cardiomyopathy Questionnaire (KCCQ) is a valid, reliable, and sensitive measure for other etiologies of heart failure, its appropriateness for patients with oHCM is unknown.

Objectives: The purpose of this study was to establish the interpretability, validity, reliability, and responsiveness of the KCCQ in patients with oHCM.

Methods: Cognitive debriefing of the KCCQ was performed in 26 patients with oHCM. The validity, reliability, responsiveness, and interpretability of the KCCQ were tested in 196 participants from the EXPLORER-HCM trial by comparing each scale with relevant comparators, describing the internal reliability and the mean change in stable patients, and comparing the mean change in patients who reported different degrees of clinical change using a patient-reported global impression of change (PGIC).

Results: All KCCQ domains demonstrated strong correlations with external standards of symptoms, function, social limitation, and quality of life, including a recently designed instrument measuring symptoms not captured by the KCCQ (P < 0.0001 for all). Mean changes in stable patients were nonsignificant, ranging from 0.21 to 2.3 points (P > 0.30 for all), with high intraclass correlation coefficients. The mean changes in patients with small, moderate, and large clinical changes were consistent with the 5-, 10-, and 20-point mean differences observed in other etiologies of heart failure.

Conclusions: The KCCQ is well understood by patients with oHCM and has strong evidence of good psychometric performance. It can not only serve as a relevant endpoint in clinical trials of oHCM therapy, but may also prove useful in the clinical care of patients with oHCM. (Clinical Study to Evaluate Mavacamten [MYK-461] in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy [EXPLORER-HCM]; NCT03470545).