Cluster analysis of symptom occurrence to identify subgroups of heart failure patients: a pilot study

Abstract

Background and research objective: The aim of this small-scale study was to explore the use of cluster analysis to identify subgroups of heart failure patients whose patterns of symptoms may help guide clinical management. The empirically derived clusters were compared on (1) demographics, (2) clinical characteristics, and (3) subscales of the Kansas City Cardiomyopathy Questionnaire.

Subjects and methods: A demographics questionnaire, the Kansas City Cardiomyopathy Questionnaire, and the investigator-developed Heart Failure Symptom Survey were mailed to a random sample of 300 patients at a Midwestern outpatient heart failure clinic.

Results and conclusions: Of 139 respondents, 33 (24%) were female and 106 (76%) were male. The mean (SD) age was 70.6 (9.7) years, and all were white, except for a single African American female. Most subjects were married (84%) with a median level of high school education, and 5% were New York Heart Association classification I, 38% class II, 52% class III, and 5% class IV. Hierarchical cluster analysis was used to derive a 3-cluster solution based on the presence or absence of 14 symptoms. Cluster 1 patients had significantly lower incidence of symptoms and were more likely to be New York Heart Association class I or class II, with lower body mass index and higher education levels compared with patients in the other clusters. Both clusters 2 and 3 were more symptomatic than cluster 1. Compared with cluster 3, patients in cluster 2 reported more shortness of breath under circumstances other than activity, and the majority reported difficulty sleeping. They also tended to report greater symptom severity and impact on physical activity and enjoyment of life. Additional differences included comorbidities and percentage of subjects on angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. Examination of the clusters suggested clinical implications related to pharmacological management and raised questions concerning potential influences of duration of the heart failure condition, presence of sleep-disordered breathing, and impact of educational level on self-management behavior and symptom patterns.