Is there a difference between patients with peak oxygen consumption during exercise below 10 ml/kg/min and between 10 and 14 ml/kg/min? Does the „grey zone” really exist?

Background: Maximal oxygen uptake is an important component of evaluation when orthotopic heart transplantation (OHT) in a chronic heart failure patient is considered. Authors call into question the accuracy of peak oxygen consumption during exercise (V02max) interpretation used at present.
Material/Methods: 302 patients with chronic heart failure were analysed in 3 groups according to V02max (ml/kg/min) - group 1: <10 (37 patients), group 2: 10-14 (121 patients), group 3: >14 (144 patients). Mean observation time was 3.41 years. Mortality, number of OHT, time to OHT if transplantation was performed, time to death and pulmonary function tests (PFT) were compared between the groups. ANOVA rang Kruskan-Wallis test was used for analysis in Statistica 7.1.
Results: There were no important differences in mortality (48.6 vs. 33.1%), number of OHT (24.3 vs. 32.2%), time to OHT (4.6 vs. 6.9 months), time to death (15.4 vs. 16.6 months) or pulmonary function tests (forced expiratory volume in the first second - FEV1: 2.29 vs. 2.58l and 69 vs. 77%, forced vital capacity - FVC: 2.97 vs. 3.32l and 73 vs. 81%, FEV1 to FVC ratio - FEV1%FVC: 76 vs. 77%, peak expiratory fl ow - PEF: 6.06 vs. 6.19l and 73 vs. 75%, all given as direct values and as percents of normal values) between group 1 and 2 (p>0.05) but group's 3 mortality (21.5%), number of OHT (14.6%), time to death (34.4 months) and pulmonary function tests (FEV1: 3.10l and 88%, FVC: 3.94l and 91%, PEF: 7.40l and 87%) differed significantly when compared to groups 1 and 2 (p<0.05). Percent of vital capacity normal value (VC%) differed significantly between all the groups (72 vs. 81 vs. 91% accordingly).
Conclusions: No convincing reasons to feel less worried about patients with V02max between 10-14 then below 10 ml/kg/min were found in this research. Analysis of PFT could show additional specifi c risk factors in the chronic heart failure.

Keywords: Heart Transplantation, clinical outcome