Abstract 3160: The Initial Slope of the VO2/VCO2 Curve (s1) in Cardiopulmonary Exercise Testing is the Strongest Predictor of Outcome in Patients with Chronic Post-Infarction Heart Failure
Prognosis of chronic heart failure (HF) remains poor despite novel therapeutic strategies, making identification of parameters to detect patients (pts) at risk a major goal. We assessed 103 HF-pts with previous myocardial infarction (MI) by sequential cardiopulmonary exercise testing (CPET), repetitive measurements of BNP and LV ejection fraction (EF), determined by volumetric analysis of LV angiograms. Anaerobic threshold (AT) was calculated by the v-slope method. All pts received optimized medical therapy (beta blocker, ACE inhibitor and diuretics).
Results: EF (41 %) and CPET-parameters (VO2max: 16 ml/kg/min, maximal O2 pulse O2Pmax: 12ml) were reduced, BNP-levels were elevated (1250 pmol/ml). After a mean follow up of 351 days, the combined endpoint of cardiac death, stroke, MI, HF-rehospitalization and progression of CAD (determined as de novo lesions in previously affected or unaffected coronary arteries) occured in 23 pts. Surprisingly, neither EF, NYHA class or VO2max was associated with an elevated risk for adverse outcome. Instead, BNP (p = 0.03) and the submaximal CPET parameter s1 (p= 0.02), which represents the slope of the VO2/VCO2 curve until reaching the AT, were associated with an adverse event. Both, VO2max and O2Pmax only correlated with cardiac death. Multivariate analysis disclosed s1 as the predominant independent predictor of death (p = 0.001). In contrast to VO2max and O2Pmax, s1 did not correlate with BNP levels. Repetitive CPET after 3 and 12 months did not provide additional information about adverse outcome, whereas repetitive measurement of BNP after 1 year indicated pts at risk: Δ-BNP correlated significantly with death, stroke, MI and HF-rehospitalization.
Conclusion: In pts with moderate to severe HF, EF and NYHA-class did not provide sufficient predictive information for future events. In contrast, s1 proved to be the strongest independent predictor of outcome. As some pts are not capable or willing to attain maximal exertion, prognostic impact of maximal CPET-parameters might be overestimated. s1, in contrast, is easily obtained at submaximal exercise levels and might provide a more reliable prognostic parameter for HF-pts under optimized treatment.