The added prognostic value of ventilatory efficiency to the Weber classification system in patients with heart failure

Background: The Weber classification system is a well established method for categorizing patients according to peak oxygen consumption (VO2), but it is unknown whether ventilatory efficiency adds prognostic value. The purpose of the current study was to assess the added prognostic value of the minute ventilation/carbon dioxide production (VE/VCO2) slope to the Weber classification system in patients diagnosed with heart failure (HF). Methods: Five hundred and forty-eight subjects with HF participated in this analysis. Mean left ventricular ejection fraction was 32.9 ±13.3%. Subjects were tracked for cardiac-related mortality following the exercise test. Results: The numbers of subjects in Weber Classes A-D were 144, 119, 212 and 71, respectively. One hundred and eight major cardiac events (91 deaths, 10 emergent heart transplants and 7 LVAD implantations) occurred during a mean tracking period of 33.8 ± 28.6 months. Receiver operating characteristic (ROC) curve analysis revealed the VE/VCO2 slope prognostic classification schemes were significant in each of the four Weber classes (A: area = 0.84, optimal threshold = 31.3, 79% sensitivity/90% specificity, p < 0.01; B: area = 0.66, optimal threshold = 33.9, 73% sensitivity/67% specificity, p < 0.05; C: area = 0.71, optimal threshold = 36.0, 65% sensitivity/68% specificity, p < 0.01; D: area = 0.66, optimal threshold = 41.8, 68% sensitivity/58% specificity, p < 0.05). Conclusions: These results indicate that the VE/VCO2 slope improves the identification of individuals at higher risk for mortality within each Weber class. These findings further support the routine clinical application of ventilatory efficiency in the HF population.