Relationship of end-tidal oxygen partial pressure to the determinants of anaerobic threshold in post-myocardial infarction patients

The anaerobic threshold (AT), obtained during cardiopulmonary exercise testing (CPET), is an important prognostic measure and can be used to develop an exercise prescription in patients after a myocardial infarction (post-MI). The purpose of this study was to examine the central and peripheral determinants of AT in post-MI patients end-tidal oxygen partial pressure (PETO 2 ) measures. We performed cardiopulmonary exercise testing (CPET) on 148 consecutively enrolled post-MI patients to determine PETO 2 measured at the AT (AT PETO 2 ) and ΔPETO 2 (difference between resting PETO 2 and AT PETO 2 ). We subsequently investigated the relationship between these measures of PETO 2 and the individual AT for each patient. Multivariate linear regression analysis indicated that AT PETO 2 and ΔPETO 2 were independently and significantly associated with the AT ( β = −0.344, p < 0.001 and β = 0.228, p < 0.001, respectively). Furthermore, the independent factors of AT PETO 2 were left ventricular ejection fraction ( p = 0.005), resting ventilatory equivalent for carbon dioxide ( p = 0.002), and resting dead-space gas volume to tidal volume ratio ( p < 0.001). However, the independent factors for ΔPETO 2 were history of diabetes ( p = 0.047), estimated glomerular filtration rate ( p = 0.001), and resting systolic blood pressure ( p = 0.017). These findings suggested that AT PETO 2 was associated with central determinants; whereas, and ΔPETO 2 was associated with peripheral determinants, The AT PETO 2 and ΔPETO 2 provide variable insight regarding the cause of exercise intolerance and can be used to determine appropriate therapies.