Improved Peak Oxygen Uptake Reduces Cardiac Events After 3 Weeks of Inpatient Cardiac Rehabilitation for Chronic Heart Failure Patients

Figure 1.. Peak oxygen uptake (V̇O2) before and after 3 weeks of an inpatient cardiac rehabilitation program (CRP). Data are the mean±SD.

Figure 2.. Receiver operating characteristic (ROC) curve analysis of peak oxygen uptake (V̇O2) and improvements in V̇O2 for predicting cardiovascular (CV) events. After 3 weeks of an inpatient cardiac rehabilitation program (3w In-CRP), the area under the curve (AUC) of peak V̇O2 (Post peak V̇O2) was 0.777 (95% confidence interval [CI] 0.671–0.884; P<0.01), with a cut-off of 11.6 mL/min/kg having a sensitivity of 0.621 and a specificity of 0.805 for predicting future CV events. The AUC for the improvement in V̇O2 (Imp V̇O2) was 0.724 (95% CI 0.599–0.849; P<0.01), with a cut-off of 6.1% having a sensitivity of 0.655 and a specificity of 0.805 for predicting future CV events.

Figure 3.. Kaplan-Meier curves for cardiovascular (CV) event-free survival in patients with (A) higher (>11.6 mL/min/kg) and lower (≤11.6 mL/min/kg) peak oxygen uptake (V̇O2) and (B) higher (>6.1%) and lower (≤6.1%) improvements (Imp) in peak V̇O2 after 3 weeks of an inpatient cardiac rehabilitation program (3w In-CRP). (A) There were fewer CV events in the group with higher (>11.6 mL/min/kg) than lower (≤11.6 mL/min/kg) peak V̇O2 after 3w In-CRP (log-rank [Mantel-Cox] χ2=31.502, P<0.01). (B) Similarly, there fewer CV events in the group with a higher (>6.1%) than lower (≤6.1%) improvement in peak V̇O2 (log-rank [Mantel-Cox] χ2=27.892; P<0.01).

Figure 4.. Kaplan-Meier curves for cardiovascular (CV) event-free survival according to levels of peak oxygen uptake (V̇O2; high [>11.6 mL/min/kg] or low [≤11.6 mL/min/kg]), and improvements in peak V̇O2 (high [>6.1%] or low [≤6.1%]) after 3 weeks of an inpatient cardiac rehabilitation program (3w In-CRP). There were significantly fewer CV events in the group with high peak V̇O2 and high improvements in peak V̇O2 after 3w In-CRP than in the other groups. In addition, there were fewer CV events among patients with a high improvement in peak V̇O2 than among those with a low improvement peak V̇O2 and either a high peak V̇O2 (log-rank [Mantel-Cox] χ2=9.741, P<0.01; “A”) or a low peak V̇O2 (log-rank [Mantel-Cox] χ2=5.118, P=0.02; “B”). (All, log-rank (Mantel-Cox) χ2=56.649, P<0.01.) ppV̇O2, post-3w In-CRP peak V̇O2; imp V̇O2, improvement in peak V̇O2. *P value <0.05.