Long-term outcome of nonobstructive versus obstructive hypertrophic cardiomyopathy: A systematic review and meta-analysis

Background: Prognosis of hypertrophic cardiomyopathy (HCM) is particularly heterogeneous. Patients with nonobstructive HCM (NOCM) are thought to be at relatively low-risk as compared with obstructive HCM (HOCM) with no need of major treatment options. However, available evidence of NOCM comes mainly from tertiary centers where a referral bias is likely to occur. Aim of this study was to perform a systematic review and meta-analysis of the published literature on hypertrophic cardiomyopathy (HCM) in order to outline differences in presenting features and long-term outcome between NOCM and HOCM.

Methods: MEDLINE/Pubmed, EMBASE and Cochrane databases up to December 31, 2016, and reviewed cited references to identify relevant studies were used. The primary endpoints were HCM-related overall mortality rate and yearly rate of cardiac death. Other endpoints were incidences of sudden and congestive heart failure deaths.

Results: A total of 20 studies entered the meta-analysis on the long-term outcome of NOCM vs HOCM. They included a total of 7731 patients, 5058 patients with NOCM (65%) and 2673 patients with HOCM (35%). During the follow-up, annual mortality related to HCM averaged 1.55% in NOCM and 1.77% in HOCM (Relative Risk: 0.89, 95% confidence intervals: 0.68 to 1.17, p=0.40). Overall, 5 studies reported significantly higher mortality for HOCM, 3 higher mortality for NOCM, and 12 no significant differences.

Conclusion: This large study-level meta-analysis shows that long-term mortality of patients with NOCM is not negligible and not significantly different from HOCM.