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Functional Decline in Peripheral Arterial Disease Associations With the Ankle Brachial Index and Leg Symptoms

Background: Patients with Peripheral Arterial Disease in their lower extremities have varying degrees of functional impairment when comparing their Ankle Brachial Index and Leg symptoms. The relationship between these characteristics and functional decline is undefined.

Objective: The objective of this study is to define whether Peripheral Arterial Disease, Ankle Brachial index, and Specific leg symptoms can be used to predict functional decline at 2-year follow-up.

Methods: The study was a prospective cohort study that identified patients by consecutively choosing individuals over the age of 55 years with and without Peripheral Arterial Disease. The patients had follow-up visits at 1 and 2 years after the beginning of the study. There were 676 patients initially enrolled in the study. All participants underwent ABI testing at their baseline study visit. PAD was defined as ABI less than 0.90. Patients with dementia, recent major surgery, or foot or leg amputation were excluded as were nursing home residents, wheelchair-bound patients, non-English speaking patients, and individuals with ABI’s greater than 1.50. Individuals with PAD diagnosed in the noninvasive vascular laboratory were excluded if their ABI at the baseline visit indicated absence of PAD. Patients with an ABI of 0.90 or greater and with prior lower-extremity revascularization (n=16) were excluded since they could not clearly be classified as with or without PAD. Participants with PAD who underwent lower-extremity revascularization after baseline were excluded (n=17) since revascularization may affect the natural history of lower-extremity functioning. There were 417 patients assigned to the PAD participants group and 259 patients assigned to the non-PAD participants group. Main Outcomes were measured by Six-minute walk performance, Summary performance Score, and Four meter walking velocity. The other measures that were obtained are height, weight, BMI, cigarette smoking (by patient report) Repeated chair rises, and Standing Balance. The power of this study was 80% power to detect a minimum detectable difference in annual change for the functional measures between these 2 ABI groups of 0.15 SDs based on a 2-tailed test at alpha=0.5.

Results: There were 623 participants who completed the study. The annual mean (95% CI) decline in 6 minute walk performance -73.0 (-142 to –4.2) ft for ABI <0.50; -58.8 -83.5 to -34.0 ft for ABI 0.50 to <0.90; and -12.6 -40.3 to 15.1 ft for ABI 0.90 to 1.5, P=.02. Compared with patients without PAD, PAD participants with leg pain on exertion and rest at baseline had greater mean annual decline in 6-minute walk performance -111 (-173 to -50.0) ft and -8.67 (-36.9 to 19.5) ft respectively, P=.004, usual pace 4 meter walking velocity -0.06 (-0.09 to -0.02) m/sec and -0.01 (-0.03 to 0.003) m/sec respectively, P=.02, and a decline in fastest pace 4 meter walking velocity -0.07 (-0.11 to -0.03) m/sec and -0.02 (-0.04 to -0.006) m/sec respectively, P=.046. Compared with participants without PAD, asymptomatic PAD was associated with greater mean annual decline in 6 minute walk performance -76.8 [-135 to -18.6] ft and -8.67 (-36.9 to 19.5) ft respectively, P=.04 and an increased odds ratio (95% CI) for becoming unable to walk for 6 minutes continuously or 3.63 (1.58 to 8.36); P=.002.

Strengths: The study took into consideration patients who might have apprehension regarding treadmills or other types of equipment by using a corridor for the 6-minute walk. The study used appropriate measures to assess functionality of lower legs and the results are easy to extrapolate.

Weaknesses: Specific explanations were not available for all participants who returned for follow-up testing but did not perform the functional measures. The a priori classification scheme assigned many patients who did not complete follow-up tests as being too disabled to do so, but there is no information available regarding those patients functionality. Some participants did not complete all follow-up visits. The statistical methods adjusted for missing data, which is expected to reduce the influence of missing data on our findings. The data may not be able to be generalized to individuals who declined participation because it may not correlate to the actual scores that would have been obtained if follow-up had been performed. The group of participants with PAD having atypical exertional leg pain/carry-on was relatively small. The study lacked statistical power to demonstrate significant differences in some outcomes between these participants with PAD vs. those without PAD. The data does not address the degree to which comorbid diseases contributed to the nature of leg symptoms or functional decline in participants with PAD to be determined.

Conclusion: This study has shown a correlation between functional decline and peripheral arterial disease as assessed by ABI and leg symptoms. The results of this study will bring attention to a matter that has not been addressed until now. Based on ABI scores, the study shows that there is an increased risk of functional decline in patients with PAD compared to patients without PAD. Hopefully this study will lead to clinicians identifying the problem of PAD earlier and spark future research into developing a more efficacious treatment.

Scott Kincaid, PharmD. Candidate