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Literature Review

Gait Speed and Operative Mortality in Older Adults Following Cardiac Surgery

Afilalo J, Kim S, O’Brien S, et al. JAMA Cardiol. 2016;1(3):314-321.

Reviewers: Dan Liu, MD1; Yong G. Peng, MD PhD FASE2

  1. The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
  2. University of Florida College of Medicine, Gainesville, FL
Background

Preoperative prediction of the risk of mortality or major morbidity is a critical step in selecting reasonable therapeutic options, particularly for elderly patients undergoing cardiac surgery. Among these predictive models, some evidence has suggested that frailty marked by gait speed may be a better predictor in geriatric cardiovascular patients. However, the association of gait speed with short-term morbidity and mortality after cardiac surgery has not been systematically investigated.

Methods

This report was a prospective multicenter cohort study performed between July 2011 and March 2014. A total of 15 171 geriatric patients (age 60 or older) who underwent cardiac surgeries have been recruited for the analysis from 109 medical centers. All participating centers have joined the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database for later evaluation. A 5-m gait speed test was performed for most patients at a preoperative setting. The operative mortality within 30 days and the STS composite of mortality or major morbidity as the secondary outcome were recorded, and the correlation between 5-m gait speed and patient outcomes was analyzed.

Results

In comparison with patients in the highest gait speed group (>1m/s), patients in the slowest group (<0.83m/s) were older and had higher STS-predicted risk of mortality (STS-PROM), higher body mass index, higher proportions of women, and higher rates of combined diseases. Operative mortality was higher in the middle group (0.83–1m/s; odds ratio [OR] 1.77; 95% CI: 1.34–2.34) and the slowest group (OR 3.16; 95% CI: 2.31–4.33), and the risk of composite mortality or major morbidity also increased in modest nonlinearity among patients in the middle group (OR 1.26; 95% CI: 1.09–1.46) and the slowest group (OR 1.86; 95% CI: 1.60-2.16). After adjusting for the STS-PROM and the type of surgical procedure, gait speed remained as an independent predictor of operative mortality (OR 1.11 per 0.1-m/s decrease in gait speed; 95% CI: 1.07-1.16), and also could predict the composite of mortality or major morbidity (OR 1.03 per 0.1-m/s decrease in gait speed; 95% CI: 1–1.05). There was a change in the C-statistic of 0.005 and a change in the integrated discrimination improvement of 0.003 after adding gait speed to the STS-PROM.

Conclusion

Gait speed can be used as an independent predictor for the operative mortality and major morbidity after cardiac surgery in elderly patients. It also is a useful screening test for frailty, which can be used to improve the existing evaluation models of operative risk by helping to weigh the benefits and risks in favor of decision making in geriatric patients scheduled to undergo cardiac surgery.

Comments

Despite the operative risk, cardiac surgery is still one of the mainstay therapies for patients with cardiovascular disease. However, older patients, who have a high prevalence of frailty, should receive a more thorough preoperative evaluation. Reduced gait speed reflects impairments in lower-extremity muscle function and potentially cardiopulmonary function. This clinical marker has drawn significant attention to assessment of frailty and could be useful in preoperative prediction of the risk of mortality or major morbidity for patients scheduled to undergo cardiac surgery. This study aimed to validate the predictive value of gait speed for 30-day mortality and major morbidity after cardiac surgery in a large-scale cohort geriatric patient population. The study found that gait speed was an independent predictor of adverse outcomes after cardiac surgery, with each 0.1-m/s decrease conferring an 11% relative increase in mortality. Application of these results could improve the existing STS-PROM evaluation model of surgical risk and assist healthcare providers in selecting the best treatment options.

There were some limitations to this study. First, the 5-m gait speed test performed before cardiac surgery can be somewhat subjective. Before cardiac surgery, patients were only instructed to “walk at your comfortable pace” for the 5-m gait speed test. Therefore, several factors can affect test performance: walking habits, physical status, presence of degenerative joint diseases, etc. Additionally, more than 100 centers participated in this study, causing potential variability in the training for administering the gait speed test and inconsistency in its results. Because of these limitations, the 5-m gait speed test performed in this study may not adequately represent the true state of frailty for all geriatric patients. Supplementary strength tests may be necessary to validate patient frailty.

Another study limitation is the lack of subgroup analysis based on age, which may better support gait speed as an independent predictor of operative mortality and major morbidity in elderly patients. The study populations included patients at least 60 years of age, but incidence of frailty increases significantly with every 10 years of age.

The third limitation of this study is that, other than STS data, it lacks operative procedure-associated information such as cardiopulmonary bypass time, aortic cross-clamp time, blood transfusion rates, etc. These factors also may contribute significantly to the short-term operational morbidity and mortality rates.

The fourth limitation of this study is the potential for selection bias inherent to the study design. The 34 675 patients in the database who did not perform the 5-m gait speed test and who were thus excluded from the study may have led to somewhat different study outcomes. Patients with transcatheter aortic valve replacement procedures were not included in this study, though frailty assessment in this group may have been valuable in the analysis. Additional research is necessary to assess comprehensive frailty status and cardiac surgery outcomes in geriatric patients.