OBJECTIVES: To undertake a systematic literature review (SLR) of observational studies reporting associations between prognostic factors (at study baseline) and follow-up outcomes and/or between potential surrogate endpoints (occurring after baseline) and follow-up outcomes in obstructive hypertrophic cardiomyopathy (HCM).

METHODS: An SLR was conducted using a prespecified protocol. Searches of MEDLINE, Embase, and Cochrane were conducted on 16 December 2022. Titles and abstracts followed by full-text articles were screened for relevance according to predefined criteria. The subset of studies and results providing evidence for a potential relationship between prognostic factors and follow-up outcomes in a subpopulation largely without (<20% at baseline) septal reduction therapy experience were summarized. This population is similar to those eligible for clinical trials of new pharmacological interventions for obstructive HCM.

RESULTS: Of 2,408 records identified, 8 studies were eligible for inclusion. Although the follow-up outcome definitions varied across studies, all studies included all-cause or cardiovascular death alone or composite with non-fatal cardiac outcomes. The relationships reported were between baseline New York Heart Association (NYHA) class and the follow-up outcome and between resting left ventricular outflow tract (LVOT) gradient and the follow-up outcome. An increased baseline value was associated with an increased risk of the outcome in 4 out of 5 studies assessing NYHA class, and in 2 out of 4 studies assessing resting LVOT gradient. No studies reported a surrogate endpoint relationship. There was considerable heterogeneity between individual study aims and the methods for assessing the relationships.

CONCLUSIONS: A relationship between increased NYHA class and increased risk of death was identified. The relationship between LVOT gradient and mortality was less certain. Evidence is lacking for relationships with other prognostic factors and surrogate outcomes that are of importance in obstructive HCM. Further research is needed to determine if the available data can be quantitatively synthesized.