From the Journals

Microvascular disease: An independent and exacerbating risk factor for amputation



Individuals with microvascular disease (MVD) showed a significantly increased risk of lower limb amputation in the absence of peripheral artery disease (PAD), according to the results of a large database analysis published online in Circulation.

Diabetic retinopathy from the eye of a diabetic is shown. memorisz/iStock/Getty Images

Furthermore, those who had both MVD and PAD had a greater than 20-fold increased risk of amputation than if they had either PAD or MVD alone, according to Joshua A. Beckman, MD, of Vanderbilt University, Nashville, Tenn., and colleagues.

“The novelty of these findings becomes clear when put into the current framework of critical limb ischemia,” they wrote.

“In a recent state of the art review of [critical limb ischemia], MVD as a whole or its components did not receive a single mention. Our work shows that MVD helps identify a population not previously considered at particularly high risk for amputation and, when added to PAD, identify a group of patients at very high risk for amputation,” they continued.

Dr. Beckman and colleagues assessed individuals in the Veterans Aging Cohort Study (VACS), a prospective longitudinal cohort of veterans. They included all VACS participants who were alive as of April 1, 2003 with the baseline as a participant’s first clinic visit on or after this date. Participants were followed from baseline to the minimum of: date of lower extremity amputation, death, or Dec. 31, 2014.

They assessed four levels of vascular involvement: neither MVD nor PAD, MVD alone, PAD alone, and MVD plus PAD, with the primary outcome being lower limb amputation, all based on a variety of measures including appropriate ICD-9 or CPT codes.

The rate of incident amputation over a median of 9.3 years of follow-up was 1.16 per 1000 person-years. At the time of amputation, retinopathy was present in 69%, nephropathy in 67%, and neuropathy in 78% of participants.

After multivariable adjustment for 216 demographic characteristics, cardiovascular disease risk factors, and other potential confounders, they found that, compared with participants without either vascular disease, the presence of MVD alone was associated with a 3.7-fold increased risk of amputation, PAD alone conferred a 13.9-fold elevated risk of amputation, and the combination of PAD and MVD was associated with a 22.7-fold increased risk of amputation.

They also found that the location of amputation also varied depending on the type of vascular disease at the time of amputation.

Participants with MVD alone accounted for 18% of all amputations, 21% of below ankle amputations, 15% of below knee amputations, and 6% of all above knee amputations. Participants with PAD alone accounted for 22% of all amputations, 17% of below ankle, 25% of below knee, and 39% of above knee amputations. The combination of MVD and PAD accounted for 45% of all amputation and caused the most amputation at all limb levels. In addition, they found a statistically significant variation in vascular involvement and level of amputation, with MVD more likely to cause a below-ankle amputation and PAD more likely to cause below- and above-knee amputations (P less than .001)

“MVD likely participates importantly in the development of adverse limb events in PAD and suggests additional patient populations who may benefit from greater foot surveillance to minimize amputation,” the researchers concluded.

The study was supported by grants from the American Heart Association. Dr. Beckman reported consulting for multiple pharmaceutical companies and serving on the DSMC for Bayer and Novartis.

SOURCE: Beckman JA et al. Circulation. 2019. doi: 10.1161/CIRCULATIONAHA.119.040672.

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