Background: Ventilatory efficiency, commonly assessed by the minute ventilation (VE)-carbon dioxide production (VCO2) slope, is proven to be a good predictor in the heart failure (HF) population. However, it is unclear whether VE/VCO2 slope predicts prognosis in patients with acute myocardial infarction (AMI) with preserved left ventricular ejection fraction (LVEF).
Methods: We analyzed 2135 consecutive patients with AMI hospitalized in our institution. We excluded 112 patients who died in hospital, 1089 patients without data of LVEF or cardiopulmonary exercise testing at acute-phase, and 196 patients with LVEF less than 40%. Finally, we compared 126 patients (17%) with VE/VCO2 slope ≥34 (high VE/VCO2 slope group) to 612 patients (83%) with VE/CO2 slope <34 (low VE/VCO2 slope group). The primary endpoint was composite of all-cause death and rehospitalization for HF during follow-up with median 6.4 years (interquartile range 3.9-9.7 years).
Results: The high VE/VCO2 slope group was older (P<.0001), and had lower BMI (P<.01), higher BNP (P<.0001), lower hemoglobin (P<.0005), lower estimated creatinine clearance rate (P<.0001) and lower % peak VO2 (72.6 ± 15.4% vs. 78.8 ± 15.4%, P<.0001). There were no differences in sex, diabetes mellitus, peak creatine kinase, atrial fibrillation and LVEF (49.2 ± 6.1% vs. 49.5 ± 6.9%) between two groups. Kaplan-Meier analysis revealed a significantly higher incidence of the primary endpoints in the high VE/VCO2 slope group than in the low VE/VCO2 slope group (log-rank test, P<.0001) (Figure). Multivariate analysis showed VE/VCO2 slope was an independent predictor of the primary endpoint (Hazard ratio 2.55; 95% confidence interval 1.15-5.51; P<.05), while % peak VO2 was not.
Conclusions: Poor ventilator efficiency may unmask prognosis in AMI patients with preserved LVEF.