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Background The ventilatory efficiency represented cardiovascular, pulmonary, and musculoskeletal performance into an integrate index has been used as long-term and short-term prognostic variables in congestive heart failure. The heart failure patients post heart transplantation, whether the ventilatory efficiency was also normalized is still unknown. Methods This was a cross-sectional study. We measured ventilation to carbon dioxide production slope and oxygen consumption in peak exercise (peak VO2) by cardiopulmonary exercise test, which represented ventilatory efficiency and functional capacity respectively. Strength of hand grip, the 30-second chair stand test, and 6-minute walking test were also evaluated. Patients with ventilation to carbon dioxide production slope Results There were 51 clinically stable post-heart transplantation patients (age 53 ± 12.4 years; 86.3% were male) at 65.14 ± 41.17 months after transplantation. The ventilation to carbon dioxide production slope was 29.2 ± 5.6, which significantly improved compared to that recorded 1 month after heart transplantation (32.6 ± 6.4). There were 20 patients in the abnormal group, characterized by lower 6-minute walking test distance (normal vs abnormal, 422.5 ± 97.8 vs 532.6 ± 87.6 m) and peak VO2 (normal vs abnormal, 14.9 ± 5.3 vs 18.8 ± 5.1 mL/kg/min). The abnormal ventilation to carbon dioxide production slope was significantly correlated with 6-minute walking test distances in multivariate analyses. Conclusion Our findings indicate that the ventilation to carbon dioxide production slope is partially abnormal among patients post-heart transplantation. A ventilation to carbon dioxide production slope above the normal range is characterized by a lower peak VO2 during cardiopulmonary exercise test and lower 6-minute walking test distance. The ventilation to carbon dioxide production slope is also significantly negatively correlated with peak VO2, peak work rate, and 6-minute walking test distance. The prognostic utility of the ventilation to carbon dioxide production slope for patients post-heart transplantation requires further investigation.

A high slope of the ventilation vs. carbon dioxide relationship (VE/VCO₂ slope) during incremental exercise has been reported in several congenital heart disease (CHD) types, but it is not clear whether the main cause of high VE/VCO₂ slope is excessive ventilation or reduced perfusion.We studied 169 adolescent and adult patients with repaired, noncyanotic CHD, divided into 2 groups according to VE/VCO₂ slope %predicted values (≤120 and120), and 15 age- and sex-matched normals. VCO₂/VE max and VO₂/VE max were considered proxies of the perfusion/ventilation relationship, with VCO₂ and VO₂ as indirect descriptors of cardiac output.VCO₂/VE max was significantly and inversely related to VE/VCO₂ slope (r=-0.73, p0.0001), and higher in normals and ≤120 than in120 (39.6 ± 7.7, 36.1 ± 5.3 and 28.5 ± 4.1, respectively, p0.0001). Similarly, VCO₂ at VCO₂/VE max was higher in normals and ≤120 than in120 (1701 ± 474, 1480 ± 492 and 1169 ± 388 ml/min, respectively, p0.0001), whereas ventilation at VCO₂/VE max showed no changes (43 ± 8, 41 ± 12, 41 ± 11 and 41 ± 9l/min, respectively, p=0.82) between groups. Thus, differences in VCO₂/VE max and VE/VCO₂ slope between groups were due mostly to changes in VCO₂, i.e. in cardiac output, rather than ventilation. The same behavior was observed for VO₂/VE max.A high VE/VCO₂ slope observed in patients with repaired, noncyanotic CHD seems not to depend on excessive ventilation but on hypoperfusion due to impaired cardiac output response to incremental exercise. This finding should focus researchers' attention mainly on the heart when addressing exercise pathophysiology of this patient population.

Ventilatory efficiency, as indicated by the increment in minute ventilation (VE) relative to CO2 production (VCO2), reflects right ventricular-pulmonary vascular (RV-PV) function during exercise. In patients with heart failure (HF), a VE/VCO2 slope greater than 34 purports a poor prognosis. Less is