Moderate mitral regurgitation associated with higher risk of primary outcome in HFrEF patientsTrial shows moderate mitral regurgitation impacts heart failure outcomes

This randomized controlled trial enrolled a large cohort of 8232 patients with heart failure and reduced ejection fraction (HFrEF) to evaluate the impact of mitral regurgitation (MR) on clinical outcomes and the effects of omecamtiv mecarbil. The study specifically examined how different severities of MR influenced the risk of the primary outcome, defined as the first heart failure (HF) event or cardiovascular death.

Patients were categorized by MR severity at baseline. The prevalence of MR in the study population was 72.3% no MR, 12.1% mild MR, 15.3% moderate MR, and 0.3% severe MR. These percentages correspond to 7998 patients with baseline data, specifically 5782 patients with no MR, 970 with mild MR, 1221 with moderate MR, and 25 with severe MR.

Regarding the primary outcome, patients with moderate MR demonstrated a higher risk compared to those without MR, with a reported hazard ratio (HR) of 1.11 (95% CI 1.01-1.23). In contrast, the risk of the primary outcome in patients with mild MR was not higher compared to those without MR. Furthermore, the study found that MR was not associated with mortality. A critical finding for the treatment of HFrEF was that the effect of omecamtiv mecarbil on clinical outcomes was not modified by the presence or severity of MR.

Safety and tolerability data, including specific adverse event rates or discontinuation rates, were not reported. The study noted that the association between moderate MR and the primary outcome was most prominent in patients with less severe heart failure, characterized by milder NYHA class, higher LVEF, and lower NT-proBNP. These results remained consistent even when patients with severe MR were included in the analysis.

Methodological limitations included a small number of patients with severe MR (n=25), which may limit the ability to draw firm conclusions regarding that specific subgroup. However, the primary findings regarding moderate MR were robust across the analyzed populations.

These results suggest that moderate MR may serve as a clinical indicator for increased risk in HFrEF patients, particularly those with less severe clinical markers. While the presence of moderate MR identifies a higher risk group, the pharmacological impact of omecamtiv mecarbil remains consistent regardless of MR status. This distinction is important for clinicians when risk-stratifying patients with HFrEF and mitral regurgitation.

Questions remain regarding the long-term management of patients identified with moderate MR and the specific mechanisms driving the increased risk in those with less severe heart failure. Further investigation into the specific factors that make the moderate MR group more susceptible to the primary outcome in the absence of severe heart failure symptoms is warranted.