Discordant Values in Lower Extremity Physiologic Studies Predict Increased Cardiovascular Risk

Area of Science:

• Vascular Medicine
• Cardiovascular Diagnostics
• Epidemiology

Background:

• Ankle-brachial index (ABI) is a key noninvasive tool for diagnosing peripheral arterial disease (PAD) and assessing cardiovascular risk.
• Standard ABI calculation uses the highest systolic blood pressure from four ankle arteries (dorsalis pedis and posterior tibial, bilaterally).
• Discordant ABI results, where some readings are normal and others abnormal, may underestimate cardiovascular risk.

Purpose of the Study:

• To investigate the association between discordant ABI results and cardiovascular outcomes.
• To determine if discordant ABIs predict a higher risk of myocardial infarction, ischemic stroke, and all-cause mortality compared to concordant normal ABIs.

Main Methods:

• Retrospective study of patients undergoing ABI measurement between January 1996 and June 2018.
• Included patients with initially normal ABI range (1.00-1.39).
• Compared outcomes between patients with all four normal ABIs (n=15,577) and those with at least one abnormal ABI (≤0.99) (n=2095).

Main Results:

• Patients with discordant ABIs were more likely to be older, female, smokers, and have comorbidities like CKD, CAD, diabetes, COPD, hypertension, or prior stroke.
• Discordant ABIs were significantly associated with increased risk of myocardial infarction (HR 1.31), ischemic stroke (HR 1.53), and all-cause mortality (HR 1.27), even after adjusting for comorbidities.

Conclusions:

• Discordant ABI results are linked to elevated risks of major adverse cardiovascular events and mortality.
• Clinicians should analyze ABI calculations from all four ankle arteries to accurately identify patients at higher cardiovascular risk.