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 (PETO2) measures. We performed cardiopulmonary exercise testing (CPET) on 148 consecutively enrolled post-MI patients to determine PETO2 measured at the AT (AT PETO2) and ΔPETO2 (difference between resting PETO2 and AT PETO2). We subsequently investigated the relationship between these measures of PETO2 and the individual AT for each patient. Multivariate linear regression analysis indicated that AT PETO2 and ΔPETO2 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 PETO2 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 ΔPETO2 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 PETO2 was associated with central determinants; whereas, and ΔPETO2 was associated with peripheral determinants, The AT PETO2 and ΔPETO2 provide variable insight regarding the cause of exercise intolerance and can be used to determine appropriate therapies.