Why PAD monitoring needs a real-time view of blood flow between visits

HN Summary

• PAD can cause serious complications, and recurrent artery narrowing after treatment makes ongoing monitoring important to protect patients’ limbs.

•Current surveillance provides snapshots during scheduled visits, leaving gaps when blood flow may decline unnoticed.

•Emerging portable technologies could enable more frequent tissue blood-flow monitoring, but research is needed to establish their effectiveness and impact on PAD outcomes.

An estimated 800,000 Canadians are living with peripheral artery disease (PAD), though some experts say the true number is likely higher. PAD causes reduced blood flow to the legs, resulting from atherosclerosis narrowing the arteries and limiting the oxygen that reaches muscles and tissue. As the disease progresses, poor circulation can lead to pain at rest, wounds that won’t heal and, in the most severe cases, amputation. Each year in Canada, roughly 7,720 lower-limb amputations are performed in adults with diabetes, of whom 86% also have a documented PAD diagnosis. Because the plaque behind PAD is usually present elsewhere in the body as well, people with the condition also face a higher risk of heart attack and stroke.

Treatment for PAD begins with managing the disease and its risk factors, typically through smoking cessation, structured exercise, and medications that lower cholesterol, control blood pressure and blood sugar, and reduce the risk of blood clots. When those fail to control symptoms, or when a limb is at risk, revascularization becomes the next step, and endovascular approaches are now first-line for many patients. 

Because the underlying atherosclerosis remains after the procedure, restenosis is the main threat to long-term durability, with one-year rates as high as 30% to 60% reported in patients with chronic limb-threatening ischemia. Post-procedure monitoring after revascularization gives clinicians the chance to catch recurrent narrowing and reintervene before the vessel occludes. However, the tools used to monitor blood flow after treatment have not kept pace with treatment options. Emerging technologies that measure tissue perfusion directly could give clinicians more information between scheduled visits, and research now underway will help determine how that information should guide care.

Current tools for post-procedure monitoring

Surveillance after revascularization typically relies on some combination of clinical assessment, the ankle-brachial index (ABI), and arterial duplex ultrasound. The ABI is inexpensive and easy to perform in an office, while duplex offers detailed imaging of the treated segment and is the most accurate noninvasive option. Practice varies widely, in part because clinical guidelines consider the effectiveness of routine surveillance in asymptomatic patients uncertain. Canadian data on PAD care are limited, but U.S. figures point to a significant shortfall. In an analysis using historical data of more than 1.4 million Medicare patients who underwent lower extremity bypass or peripheral vascular intervention, just over half received any follow-up imaging within a year of their procedure. 

Even when patients do return for follow-up, the tools differ considerably in what they catch. A 2024 systematic review of surveillance after femoropopliteal endovascular treatment found that the ABI detected restenosis with a sensitivity of 55% to 67% and clinical follow-up with a sensitivity of 52% to 64%, meaning either approach on its own can miss a third to nearly half of recurrent lesions. Duplex, which shows blood flow through the treated segment in real time, performed far better, reaching 91% sensitivity and 100% specificity in the one study the review identified, but it requires a vascular lab, a trained sonographer, and a scheduled visit. Those requirements limit how often it can be repeated and tie surveillance to patients keeping their appointments, leaving long stretches between visits when restenosis can develop unobserved.

How advanced monitoring benefits pad patients

Nearly every tool used after revascularization captures perfusion at a single point in time during a scheduled visit. Continuous or more frequent monitoring could track perfusion between appointments and flag a decline that might otherwise go unnoticed until symptoms return, much as remote monitoring of heart rhythm and blood glucose lets clinicians act on trends in other chronic conditions. Because perfusion measurements assess circulation in the tissue, they could help support a combined diagnostic alongside imaging of the treated artery. While research in PAD is still early, investigators are testing the feasibility of optical techniques such as laser speckle contrast imaging to measure perfusion around revascularization.

Portable blood flow technology is also being studied in stroke, a condition closely linked to PAD because the same atherosclerosis often affects other arteries. In a 2024 study of 135 patients evaluated for suspected stroke, an algorithm based on scans from a portable optical blood flow monitor detected large vessel occlusion with 79% sensitivity after a 70-second scan, compared with 60% and 50% for two stroke scales commonly used by emergency medical services. The study shows how a compact device could potentially measure blood flow directly without a vascular lab or imaging suite, making more frequent monitoring accessible to more patients.

Building the evidence for better pad monitoring

While blood flow restoration techniques have advanced to support more patients with PAD, the monitoring they receive after a procedure has remained relatively unchanged. Restenosis remains common, surveillance practices vary widely, and the tools in routine use capture only occasional snapshots of a process that unfolds gradually between visits. 

Other areas of chronic disease care suggest a better path. In conditions such as heart failure and diabetes, direct monitoring gives clinicians a steadier stream of data and has allowed them to recognize problems earlier and adjust treatment before patients deteriorate. There is good reason to believe PAD patients could benefit in a similar way, particularly those with diabetes, kidney disease, or limb-threatening disease, for whom a missed restenosis carries the greatest consequences. Research on post-procedure monitoring in PAD, including studies that compare monitoring approaches and measure their effect on limb outcomes, would give vascular specialists a clearer picture of how to protect the results of revascularization long after patients leave the procedure room.

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