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Arm and Ankle BP Indices, PAD, and Mortality
Quick Takes
- Various BP indices were highly predictive of patients requiring PAD intervention and death.
- The ankle SBP is among the most highly predictive and discriminatory index for predicting adverse outcomes related to PAD.
Study Questions:
What is the relationship between various arm and ankle blood pressure (BP) indices with regard to clinically significant peripheral artery disease (PAD) and mortality?
Methods:
The authors used data from three large prospective clinical trials to compare baseline BP indices of the arm systolic BP (SBP), arm diastolic BP (DBP), pulse pressure (arm SBP minus DBP), ankle SBP, ankle-brachial index (ABI; ankle SBP divided by arm SBP), and ankle-pulse pressure difference (ankle SBP minus arm pulse pressure). Analyses were based on quartiles for each BP index. The three outcomes of interest were the first incidence of peripheral revascularization or amputation for PAD, all-cause death, and the composite of PAD intervention or death. Cox proportional hazards models were generated for each predictor with discrimination assessed using c-statistics and reclassification indices. These models were adjusted for several factors known to impact PAD and mortality, including diabetes, hypertension, prior cardiovascular disease, and smoking.
Results:
The study included 40,747 participants without baseline PAD who were mean age 65.6 years, 68.3% men, and 50.2% with diabetes. These participants were recruited from 53 countries. Among the cohort, 2.6% developed PAD that required an intervention and 12.2% died during 5 years of follow-up. Incident PAD requiring an intervention rose with all arm BP indices and fell with all ankle BP indices. The strongest relationship to incident PAD was noted for ankle BP indices. Compared with the highest quartile of ankle SBP, each lower quartile was associated with an increased hazard for incident PAD (adjusted hazard ratio, 1.64 [95% confidence interval, 1.31-2.04], 2.59 [2.10-3.20], and 4.23 [3.44-5.21], respectively). Incident PAD was also strongly associated with decreasing ABI and ankle-pulse pressure difference. Similar patterns were also seen for the association between various BP indices and all-cause mortality. The ankle BP indices provided the highest level of discrimination (c-statistics and reclassification indices) to predict future PAD requiring an intervention when controlling for established risk factors.
Conclusions:
The authors conclude that ankle BP indices, including ankle SBP and the ankle-pulse pressure difference, best predict PAD requiring intervention and all-cause mortality.
Perspective:
The ABI is the standard by which PAD is diagnosed and risk stratification is typically performed. However, this large analysis of four prospective clinical trials suggests that other BP indices may provide even more predictive information. Specifically, the simple measure of ankle SBP alone was found to have the highest hazard ratio for predicting PAD that required an intervention and for predicting all-cause death, with increasing risks as the ankle SBP declined. While the ABI continues to be the gold standard for the diagnosis of PAD, clinicians may find benefit from reviewing the absolute ankle SBP as a way to further assess a patient’s future risk of requiring an intervention or all-cause mortality.
Clinical Topics: Vascular Medicine, Atherosclerotic Disease (CAD/PAD)
Keywords: Ankle Brachial Index, Blood Pressure, Peripheral Arterial Disease
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