Gait Speed and Mortality After Cardiac Surgery
Is gait speed predictive of mortality risk after cardiac surgery?
This was a prospective cohort study conducted from July 2011 to March 2014, at 109 centers participating in the Society of Thoracic Surgeons Adult Cardiac Surgery Database. Five meter gait speed was assessed among adults ages ≥60 years undergoing cardiac surgery. Surgeries included coronary artery bypass grafting, aortic valve surgery, mitral valve surgery, or combined procedures. The primary outcome of interest was all-cause mortality during the first 30 days after surgery. Secondary outcomes included a composite outcome of mortality or major morbidity during the index hospitalization.
A total of 15,171 patients were included in the study; the median age was 71 years and 4,622 were female (30.5%). Compared with patients in the fastest gait speed tertile (>1.00 m/s), operative mortality was increased for those in the middle tertile (0.83-1.00 m/s; odds ratio [OR], 1.77; 95% confidence interval [CI], 1.34-2.34) and slowest tertile (<0.83 m/s; OR, 3.16; 95% CI, 2.31-4.33). After adjusting for the Society of Thoracic Surgeons predicted risk of mortality and the surgical procedure, gait speed remained independently predictive of operative mortality (OR, 1.11 per 0.1 m/s decrease in gait speed; 95% CI, 1.07-1.16). Gait speed was also predictive of the composite outcome of mortality or major morbidity (OR, 1.03 per 0.1 m/s decrease in gait speed; 95% CI, 1.00-1.05). Addition of gait speed to the Society of Thoracic Surgeons predicted risk resulted in a c-statistic change of 0.005 and integrated discrimination improvement of 0.003.
The investigators concluded that gait speed is an independent predictor of adverse outcomes after cardiac surgery, with each 0.1 m/s decrease conferring an 11% relative increase in mortality. Gait speed can be used to refine estimates of operative risk, to support decision making, and since incremental value is modest when used as a sole criterion for frailty, to screen older adults who could benefit from further assessment.
These data suggest that function and fragility can be assessed with a simple cost-effective measure. These data may be relevant to older adults who are weighing the risks and benefits of cardiac surgery. A more important question may be whether interventions to reduce frailty are associated with reduced mortality after cardiac surgery.
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