Practical Insights On Current And Emerging Options For PAD Assessment

Peripheral arterial disease can present in a multitude of ways in podiatric practice. How are physicians best able to assess and formulate treatment plans for these patients? Here the panelists share their experience with diagnostic protocols, including existing and newer modalities that may provide insight into the status of lower extremity blood flow, oxygenation and perfusion.

Q:When you suspect peripheral arterial disease (PAD) in patient with or at-risk for wounds, what is your typical diagnostic protocol?

A:

All of the panelists agree that a comprehensive medical history is crucial to timely and accurate PAD diagnosis. They cite that eliciting information, especially in older individuals, regarding a history of hypertension, diabetes, dyslipidemia, obesity, multiple stages of renal disease, tobacco use and family history are all important.

John Evans, DPM, FACFAS feels that podiatrists are the most appropriate specialty to identify patients at-risk for PAD. He says he additionally questions his patients, who otherwise may not think to volunteer such information, about details such as blood pressure control, history of cardiac events or interventions and past PAD testing. Gathering clues from a patient’s medication list, he says he looks for treatments for hypertension, cholesterol, angina or arteriosclerotic heart disease.

“They may be totally unaware that the medicines they take are for cardiovascular problems,” he adds. “For this patient group, PAD is a potential concern until otherwise ruled out.”

Adriana Strimbu, DPM also asks similar questions, also probing into any presence of specific symptoms like pain or heaviness in the legs with ambulation. She also performs a comprehensive lower extremity vascular examination including evaluating pedal pulses, capillary filling time, edema, skin condition, digital hair growth and Buerger’s test. She relates using macrovascular testing such as ordering an ankle-brachial index (ABI), toe-brachial index (TBI) and arterial dopplers, being careful to consider results consistent with calcified vessels. She shares that she also assesses microvascular status in the feet.

Raymond Abdo, DPM, CWS also points out that when learning about a patient’s symptoms, it is important to differentiate nocturnal muscle cramps from true rest pain, along with ruling out pseudoclaudication.

“In our office, we have a laser-doppler based machine to measure pulse volume recordings (PVRs) and a skin perfusion pressure (SPP) machine, which gives me a good picture of lower extremity perfusion and allows me to diagnosis PAD and critical limb ischemia (CLI), says Kazu Suzuki, DPM, CWS.

He relates for existing inpatients that he typically orders arterial dopplers, including ABIs as well as a qualitative ultrasound of lower extremity perfusion from the waist to the toes. TBIs may not be possible, he adds, if there is a history of digital amputation. Lastly, he says that transcutaneous oximetry (TCOM or TcPO2) is also available, but he doesn’t typically rely on it as a sole study.

Q:Have you incorporated any newer PAD diagnostic technology into your practice? If not, are there any modalities you find interesting, and why?

A:

Dr. Suzuki says he has tried newer methods of scanning skin surface oxygenation and saturation, but he feels that in his experience the medical evidence is not enough to support his medical decision making at this point. He feels their role is more supplemental to traditional methods and he expresses concern with associated costs.

Dr. Abdo incorporates Snapshot NIR (Kent Imaging) in his office to determine tissue oxygenation, and relates accurate, clinically beneficial images as a result. After identifying a deficit, he sends the image to his planned referral, such as an interventional cardiologist or vascular surgeon.

“What we like about the device is its portability and usefulness in the OR as well,” he explains. “This assists during amputation as to what level or tissue requires resection.”

Both Dr. Evans and Dr. Strimbu share that they have used the Clarifi® imaging system (Modulim) in their offices for over one year.

“It provides a real-time microvascular assessment of the patient’s foot and leg, employing spatial frequency domain imaging (SFDI), a non-contact optical imaging technology … to quantify and map subsurface (two to three mm in depth) five separate biomarkers associated with delivery and extraction of oxygen within dermal tissue,” explains Dr. Evans.

Dr. Strimbu adds that she has found great clinical value in using Clarifi for microvascular assessment.

“It does not expose the patient to any harmful radiation,” she points out. “I like to use it because it gives me a clear map of my patient’s circulation. Looking at a patient’s foot, everything might seem normal, but many times when I perform the Clarifi testing on a patient, it will show me the real picture about the patient’s microcirculation, which may allow me to develop a treatment plan to avoid future ulceration and limb loss.”

“It fills a diagnostic void for my patients by revealing if oxygen is getting to the tissue where it is required,” says Dr. Evans. “And for patients with diabetes, this can be a critical piece of information not easily quantified by conventional methods. Recognizing areas of low oxygen supply in combination with understanding the pathomechanics of the foot, allows the physician to form a more complete treatment plan aimed at reducing the risk of, or in some cases to heal, the dreaded foot ulcer.”

Q:What challenges do you feel exist with respect to the proper diagnosis of PAD for patients with or at-risk for wounds?

A:

Dr. Abdo begins by saying that ABIs are adequate but not always accurate, noting that alternatives such as arterial duplex, laser doppler, TCPo2 are available.

“What is challenging is that all these tests may require a referral and take time to obtain results,” he says. “What does the patient or physician do until then?”

His relates his experience with Snapshot NIR has been useful for immediate in-office results, communicable to the treatment team.

Dr. Evans echoes the challenge of referring out for testing, stating that the restrictions of the current medical system prevent some podiatrists from providing such in-office vascular testing. He feels this places more responsibility on patients for follow-through and often results in greater cost to the health-care system.

Although referring out for testing has drawbacks, Dr. Suzuki stresses that forming good reciprocal working relationships with vascular specialists in the area is important after one makes a diagnosis of PAD. He opines that there could be very positive educational and clinical ramifications if it were possible to screen at-risk patients for PAD in a similar fashion as recommended for colonoscopy at age 50.

“Most people associate chest pain as a dangerous sign of myocardiac ischemia, but don’t recognize leg cramps from walking (claudication) as worsening PAD,” he explains.

“One of the most important challenges we face regarding PAD is simply ‘awareness,’” agrees Dr. Evans. “Most people with PAD are not aware of their disease, and in many cases, neither are their physicians. More than 50 percent of people with arterial insufficiency are unaware of their condition, and the same can be said for up to 30 percent of their physicians.”¹

He points out that many patients may not present with classic symptoms, or may be completely asymptomatic.

“The podiatrist needs to be aware of the signs and symptoms of asymptomatic or atypical PAD to best care for this at-risk population,” he explains, “and then share this information with the patient and their primary care team.”

Dr. Strimbu agrees that asymptomatic or minimally-symptomatic PAD can result in delays in diagnosis and advanced disease states at time of diagnosis.

“We need to consider macrovascular and microvascular status,” she says. “It is important to note that traditional noninvasive circulatory tests … provide information about the macrovascular status of the large blood vessels. Also, the results may be technician dependent.”

She continues to say that in her experience with the Clarifi Imaging system, she is able to obtain information about the microvascular status of the small blood vessels, in a clear and reproducible fashion, possibly before any visible concerning signs appear. 

Dr. Abdo is a Certified Wound Specialist and is Chief of Podiatry at Mercy South Hospital in St. Louis, Mo. He also practices in St. Louis, Mo. Dr. Abdo discloses that he is a medical advisor for Reprise Biomedical.

Dr. Evans is a Diplomate of the American Board of Foot and Ankle Surgery and the American Board of Podiatric Medicine. He is Chief of Podiatry at Beaumont Hospital in Dearborn, Mich., a Fellow of the American College of Foot and Ankle Surgeons and is in practice in Allen Park, Mich.

Dr. Strimbu is the current President of the Miami Dade County Podiatric Medical Association and is Chair of the Public Affairs Committee for the Florida Podiatric Medical Association. She is in practice in Hallandale Beach, Fla.

Dr. Suzuki is the Medical Director of the Apex Wound Care Clinic in Los Angeles. He is also a member of the attending staff of Cedars-Sinai Medical Center in Los Angeles. He can be reached at Kazu.Suzuki@ cshs.org.

Editor’s Note: Dr. Spector (Managing Editor, Podiatry Today) discloses that she is a member of the Medical Advisory Board for Modulim.

1. Novo S. Classification, epidemiology, risk factors, and natural history of peripheral arterial disease. Diabetes Obes Metab. 2002;4(Suppl 2):S1.