Effect of pre-discharge cardiopulmonary fitness on outcomes in patients with ST-elevation myocardial infarction after percutaneous coronary intervention

Abstract

Background: The purpose of this study was to analyze cardiopulmonary fitness in Phase I cardiac rehabilitation on the prognosis of patients with ST-Elevation Myocardial Infarction (STEMI) after percutaneous coronary intervention (PCI).

Methods: The study enrolled a total of 499 STEMI patients treated with PCI between January 2015 and December 2015. Patients were assigned to individualized exercise prescriptions (IEP) group and non-individualized exercise prescriptions (NIEP) group according to whether they accept or refuse individualized exercise prescriptions. We compared the incidence of major cardiovascular events between the two groups. IEP group were further divided into two subgroups based on prognosis status, namely good prognosis (GP) group and poor prognosis (PP) group. Key cardio-pulmonary exercise testing (CPX) variables that may affect the prognosis of patients were identified through comparison of the cardio-respiratory fitness (CRF).

Results: There is no significant difference in the incidence of cardio-genetic death, re-hospitalization, heart failure, stroke, or atrial fibrillation between the IEP and the NIEP group. But the incidence of total major adverse cardiac events (MACE) was significantly lower in the IEP group than in the NIEP group (P = 0.039). The oxygen consumption (VO₂) at ventilation threshold (VT), minute CO₂ ventilation (E-VCO₂), margin of minute ventilation carbon dioxide production (△CO₂)_, rest partial pressure of end-tidal carbon dioxide(R-P_ETCO₂), exercise partial pressure of end-tidal carbon dioxide(E-P_ETCO₂) and margin of partial pressure of end-tidal carbon dioxide(△P_ETCO₂) were significantly higher in the GP subgroup than in the PP subgroup; and the slope for minute ventilation/carbon dioxide production (V_E/VCO₂) was significantly lower in GP subgroup than in PP subgroup (P = 0.010). The VO₂ at VT, V_E/VCO₂ slope, E-VCO₂, △CO₂, R-P_ETCO₂, E-P_ETCO₂ and margin of partial pressure of end-tidal carbon dioxide CO₂ (△P_ETCO₂) were predictive of adverse events. The VO₂ at VT was an independent risk factor for cardiovascular disease prognosis.

Conclusions: Individualized exercise prescription of Phase I cardiac rehabilitation reduced the incidence of cardiovascular events in patients with STEMI after PCI. VO₂ at VT is an independent risk factor for cardiovascular disease prognosis, and could be used as an important evaluating indicator for Phase I cardiac rehabilitation.

Keywords: Cardiac rehabilitation; Cardio-pulmonary exercise; Percutaneous coronary intervention; ST-segment elevation myocardial infarction.

Fig. 1

The Kaplan-Mayer curves of MACE-free survival. IEP group: individualized exercise prescriptions group; NIEP group: non-individualized exercise prescriptions group; MACE: major cardiac events

Fig. 2

The ROC curve of Ve/VCO₂ slope. Ve/VCO₂ slope: Slope for minute ventilation/carbon dioxide production

Fig. 3

The ROC curve of VO₂ at VT, E-VCO₂, △CO₂, R-PETCO₂, E-PETCO₂, and △PETCO₂. VO₂ at VT: Oxygen consumption per kilogram of weight per minute at anaerobic threshold; E-VCO₂: Exercise carbon dioxide production; △CO₂: Margin of Minute ventilation carbon dioxide production; R-P_ETCO₂: Rest partial pressure of end-tidal carbon dioxide; E-P_ETCO₂: Exercise partial pressure of end-tidal carbon dioxide; △P_ETCO₂: Margin of partial pressure of end-tidal carbon dioxide

Fig. 4

The Kaplan-Mayer curves of MACE-free survival. VO₂ at VT: Oxygen consumption per kilogram of weight per minute at anaerobic threshold, MACE: major cardiac events