Peak oxygen consumption and prognosis in heart failure: 14 mL/kg/min is not a "gender-neutral" reference

Peak oxygen consumption (VO2) predictive authority in heart failure (HF) has been established from male cohorts. We evaluated the gender impact on the prognostic meaning of low peak VO2.

We followed 529 HF patients (116 female), with peak VO2 ≤ 14 mL/kg/min, until cardiovascular death (CVD) and urgent heart transplantation.

During follow up, 156 (29%) patients had cardiac events. Female gender, age, left ventricular ejection fraction, peak VO2, peak systolic blood pressure, and beta-blocker treatment all contributed to increase the risk ability of the hierarchical multivariate model. Two-year survival was higher in women: 85 vs 66%; χ(2)=15.7, p<0.0001. Peculiarly, outcome results were similar when only CVD was considered. Females showed a multivariate adjusted hazard ratio (HR) of 0.46. Since a 1-mL/kg/min increment in peak VO2 was equated with a 12% improvement in prognosis, the same gender adjusted HR was achieved when mean peak VO2 was reduced by 5 units in women: thus, a HF woman with peak VO2 of 9 mL/kg/min has the same 2-year outcome as a HF man with peak VO2 of 14 mL/kg/min.

Although HF women have a comparatively lower peak VO2 than men, they live longer. We discovered that the traditional cut point value for peak VO2, i.e. ≤ 14 mL/kg/min is not a "gender-neutral" reference since lumping HF men and women together with the same VO2 value is unlikely to describe the true risk. These preliminary findings do underline the need to assimilate gender-specific issues into clinical practice in HF, when appropriate.