Maximal exercise oxygen pulse as a predictor of mortality among male veterans referred for exercise testing
Received 10 September 2008; accepted 31 December 2008.
Background
Maximal oxygen pulse (O2 pulse) mirrors the stroke volume response to exercise, and should therefore be a strong predictor of mortality. Limited and conflicting data are, however, available on this issue.
Methods
Nine hundred forty-eight participants, classified as those with cardiopulmonary disease (CPD) and those without (non-CPD), underwent cardiopulmonary exercise testing (CPX) for clinical reasons between 1993 and 2003. The ability of maximal O2 pulse and maximal oxygen uptake (peak VO2) to predict mortality was investigated using proportional hazards and Akaike information criterion analyses. All-cause mortality was the endpoint.
Results
Over a mean follow-up of 6.3±3.2 years, there were 126 deaths. Maximal O2 pulse, expressed in either absolute or relative to age-predicted terms, and peak VO2 were significant and independent predictors of mortality in those with and without CPD (P<0.04). Akaike information criterion analysis revealed that the model including both maximal O2 pulse and peak VO2 had the highest accuracy for predicting mortality. The optimal cut-points for O2 pulse and peak VO2 (<12; ≥12ml/beat and <16; ≥16ml/(kg·min) respectively) were established by the area under the receiver-operating-characteristic curve. The relative risks of mortality were 3.4 and 2.2 (CPD and non-CPD, respectively) among participants with both maximal O2 pulse and peak VO2 responses below these cut-points compared with participants with both responses above these cut-points.
Conclusion
These results indicate that maximal O2 pulse is a significant predictor of mortality in patients with and without CPD. The addition of absolute and relative O2 pulse data provides complementary information for risk-stratifying heterogeneous participants referred for CPX and should be routinely included in the CPX report.
bCLINIMEX – Clínica de Medicina do Exercício, Rio de Janeiro, Brazil
cDivision of Cardiovascular Medicine, Stanford University and Veterans Affairs Palo Alto Health Care System, Palo Alto, California, USA
Correspondence to Dr Ricardo B. Oliveira, PhD, VA Palo Alto Health Care System, Cardiology 111C, 3801 Miranda Avenue, Palo Alto, CA 94043, USA Tel: +1 650 493 5000 x64661; fax: +1 650 852 3473;
ABSTRACT