Predictive Value of V̇O _2peak in Adult Congenital Heart Disease in Comparison with Heart Failure with Reduced Ejection Fraction

BACKGROUND

Peak oxygen consumption (V̇O _2peak ) is used to predict outcomes and the timing of transplantation in patients with heart failure with reduced ejection fraction (HFrEF); V̇O _2peak also has predictive utility in patients with adult congenital heart disease (ACHD). However, the predictive value of a given V̇O _2peak in patients with ACHD compared to those with HFrEF, especially after adjustment for age and sex, is not clear.

METHODS

To address this, we performed a longitudinal cohort study comparing patients with ACHD to patients with HFrEF. The ACHD and HFrEF cohorts were matched for sex and age (+/- 10 y). V̇O _2peak tests were conducted between 1993 and 2012. Events were defined as death, cardiac transplantation, or left ventricular assist device placement. Outcome data were obtained via electronic medical record, Social Security Death Index, and phone interview. Cox proportional-hazard regressions were used to evaluate relationships of event-free survival with predictor variables.

RESULTS

Patients with ACHD (N=137) and HFrEF (N=137) with a median follow-up time of 14.5 (13.4-15.6) y in the ACHD cohort and 19 (14.8-21.1) y in the HFrEF cohort. Higher V̇O _2peak was associated with lower risk for a cardiac outcome, independent of age and sex, in both ACHD (HR 0.89, 95% CI 0.83-0.96, P =0.002) and HFrEF (HR 0.85, 95% CI 0.81-0.89, P <0.001Male sex was associated with greater risk of a cardiac outcome ( P =0.001) in ACHD (HR 3.34) and HFrEF (HR 1.83). After multivariable adjustment (that included age, sex, and V̇O _2peak ) having ACHD conferred a 66% lower risk of a cardiovascular event compared to a HFrEF diagnosis (HR 0.34, 95% CI 0.22-0.53, P <0.001).

CONCLUSIONS

V̇O _2peak independently predicts event-free survival among adults with ACHD or HFrEF and has clinical utility in the outpatient setting. Patients with ACHD, however, have a better prognosis for any given V̇O _2peak compared to those with HFrEF.

WHAT IS NEW?

• In an age- and sex-matched longitudinal cohort study with over 7 y of follow-up, adults with congenital heart disease (ACHD) were found to have a better event-free (no transplant or LVAD) survival than adults with heart failure with reduced ejection fraction (HFrEF) even after multivariable adjustment that included age, sex, and V̇O _2peak . Thus, for any given V̇O _2peak a better event-free survival would be expected in ACHD compared with HFrEF. For both groups, a higher V̇O _2peak did still confer an improved event-free survival and male sex conferred a worse event-free survival.

WHAT ARE THE CLINICAL IMPLICATIONS?

Patients with HFrEF commonly undergo V̇O _2peak testing to evaluate clinical status, exercise capabilities, and timing for transplantation. Less commonly, patients with ACHD undergo V̇O _2peak testing. This study confirmed that a higher V̇O _2peak is still an excellent predictor of freedom from cardiac events and survival in both groups; however, for a given V̇O _2peak , a patient with ACHD would be expected to have a markedly improved event-free survival vs. a patient with HFrEF even after adjusting for age and sex. Moreover, our analysis adds to the understanding of how much of an advantage a higher V̇O _2peak confers for each mL·min ^-1 ·kg ^-1 confers in each group, with a slightly greater incremental benefit for the ACHD group. This finding has implications for timing of referral to cardiac transplantation for patients with ACHD. Future studies are needed to determine the optimal V̇O _2peak cut-off for transplantation for those with ACHD. Furthermore, more studies are needed to investigate the potential mechanism(s) for the ACHD survival advantage.