Do we need lower extremity physiologic studies in the age of duplex scanners?

Lower-Extremity Physiologic Studies Are No Longer Required – Wrong!

Okay Gene, consider an example from the cardiology world.

You walk up a flight of stairs and develop chest pain. Is it angina? If subsequent coronary catheterization reveals a 60% stenosis in your proximal right coronary artery, then you have an anatomic coronary lesion. But is this lesion causing angina? Maybe. If the catheter is pushed across the stenosis and a 12mm Hg resting pressure gradient is identified, the lesion also has hemodynamic significance. But is it causing angina? Possibly.

To clarify things, a functional study is necessary; specifically, you need to stress the heart (using treadmill exercise, biking, infusion of a catecholamine, etc.) and determine the subsequent cardiac response (pain, ECG changes, wall motion abnormalities, sestamibi/thallium uptake, etc.). If stress produces an abnormal cardiac response, does that mean you have angina? Probably.

Yes, it’s so simple a cardiologist can get it. Yet many vascular specialists seem to struggle with the concept that anatomic, hemodynamic, and functional tests provide different types of information about the arterial system. These tests are complimentary; when used properly they combine to yield information that no single test can provide. But the siren song of an image is hard to resist – after all, everyone loves pictures, and Duplex provides nice ones. With imaging, you can scan for aneurysms. You can see what plaque looks like. In some instances you can even perform operations or procedures solely on the basis of Duplex scanning. What more do you need? (Insert my sarcastic sneer here, Gene.)

Duplex even provides basic hemodynamic information about specific lesions (based on blood flow velocity changes across the lesion). However, it’s a mistake to think that hemodynamic changes across a particular lesion tell us much about the overall “hemodynamics” in a limb. Major arteries may be narrowed (or even completely occluded), but if the collateral vessels are good, the resulting hemodynamic compromise may be minimal. Unfortunately, Duplex scanning is relatively poor at identifying and assessing collateral flow. Tests like segmental pressures (and the ankle-brachial index, or ABI) often provide a better assessment of overall arterial status because the adequacy of collateral flow influences (and is reflected in) distal blood pressure measurements. It’s also naive to think that Duplex is the only means for noninvasively obtaining anatomic information about arterial disease; nonimaging tests using segmental pressures, multilevel pulse-volume recordings (PVRs), continuous-wave (CW) Doppler, etc. may not produce pretty pictures, but they can still localize arterial lesions to a particular anatomic level (aortoiliac vs. femoral-popliteal vs. infrapopliteal, etc.).

The combination of hemodynamic and functional testing is typically referred to as “physiologic” testing, but there’s much more to this than just CW Dopplerand pneumatic cuffs. Specific tests using Laser-Doppler to measure skin blood flow or microvascular perfusion pressure make it possible to (physiologically) assess the microcirculation. Transcutaneous Oxygen (TcPO2) measurement is available in many labs; this test provides valuable physiological information about skin viability and healing potential.

Where Duplex scanning meets its biggest challenge is in the area of functional testing. Yes, it’s possible to exercise the legs and identify subsequent flow (velocity) changes across certain lesions or vessels, but any seasoned sonographer knows that these studies are extremely difficult and time consuming. And because they typically can’t assess/account for collateral flow, they are often of questionable value for determining the adverse impact of arterial disease on the patient. In contrast, functional (exercise) studies performed with CW Doppler and air cuffs are simple, inexpensive, reliable, reproducible, and widely applicable.

Bottom line – physiologic studies are an indispensable part of noninvasive arterial testing and will certainly remain so. For any given patient, they are essential for identifying and quantifying the scope and impact of arterial disease. For populations, they are the test of choice for arterial screening. And, from a practical standpoint, they are required for IAC [intersocietal accreditation commission] laboratory accreditation in peripheral arterial testing (as you know, Duplex scanning is optional for arterial accreditation – but physiologic studies are mandatory!)

Finally, the same characteristics that make physiologic tests important for assessing arterial disease are equally – or perhaps even more – relevant for the assessment of venous disease, but the application of this approach remains in its infancy. It’s a good topic for another discussion.

Dr. Rooke is the Krehbiel Professor of Vascular Medicine at the Mayo Clinic, Rochester, Minn. He has no relevant conflicts.

Lower-Extremity Physiologic Studies Are No Longer Required – Yes ... Maybe!

My friend, Thom, makes a strong case for the value of physiologic studies in patients with lower extremity arterial disease – so strong, in fact, that one might wonder if there is any truly cogent “counterpoint” at all. To provide some perspective on this issue, let’s take a look back to see how this field started and consider why someone would even dare make the statement that is being debated here.

When clinical vascular laboratories appeared in the late 1960s, the concept of “nondestructive” or “noninvasive” testing was a novelty that was not widely accepted. The first vascular laboratory tests for the assessment of carotid, peripheral arterial, and venous disease were described as “indirect,” because they relied on detection of the physiologic alterations produced by vascular abnormalities.

These methods included the supraorbital Doppler examination and oculoplethysmography for carotid disease, ankle-brachial indices, segmental pressures, and pulse volume recordings for peripheral arterial disease, and the CW Doppler examination and impedance plethysmography for venous obstruction. In those early days, vascular testing was limited to some vascular surgery practices and physiology laboratories.

While these indirect physiologic tests were helpful for characterizing regional hemodynamics, they did not provide the detailed anatomic information on arterial lesions that vascular surgeons needed to plan treatment. It was not until direct ultrasound imaging of blood vessels became available in the late 1970s and early 1980s that interest in the non-invasive vascular laboratory increased. The “duplex concept” of combining B-mode imaging with Doppler flow detection appeared to overcome the major limitations of the indirect tests by providing two-dimensional images of an arterial lesion along with an assessment of the associated flow patterns – anatomy and hemodynamics – the best of both testing worlds.

The capabilities of duplex ultrasound were so impressive that direct duplex scanning rapidly replaced the indirect or physiologic tests for diagnosis of extracranial carotid disease and lower extremity deep venous thrombosis. But, as Thom points out, peripheral arterial disease is the only testing area in which physiologic studies are still considered as “primary” testing methods according to the IAC Standards and Guidelines for Vascular Testing Accreditation. So the challenge for the modern vascular laboratory is to determine which test to use and how to integrate physiologic testing and duplex scanning in the evaluation of patients with known or suspected peripheral arterial disease.

The clinical role of the vascular laboratory can be divided into the categories of screening, diagnosis, and follow-up. The merits of screening for peripheral arterial disease are beyond the scope of this debate, but screening tests must be safe, inexpensive, and capable of detecting the presence or absence of disease. Clearly, physiologic tests meet these requirements, and in most situations, an ankle-brachial index is all that is needed. Diagnostic testing in patients with signs and symptoms of peripheral arterial disease, including those that may be candidates for intervention, requires the specific anatomic and hemodynamic information that duplex scanning provides, but functional testing (i.e., treadmill exercise) can also be valuable in selected cases. Similarly, follow-up of peripheral arterial interventions usually requires duplex scanning to evaluate the anatomic and hemodynamic features of the treated arterial segment, while follow-up of documented but untreated peripheral arterial disease can often be accomplished primarily by physiologic tests alone.

Are lower-extremity physiologic studies no longer required in the age of modern duplex scanners? Although I am reluctant to admit it, strictly speaking, my friend, Thom, is correct when he responds with an emphatic “Wrong.” There is no reason to completely abandon the physiologic tests that have served us well since before the age of duplex scanning. A simple ankle-brachial index is easy to justify as part of almost any lower extremity arterial evaluation, and exercise treadmill testing is an excellent way to assess the functional status of a patient with peripheral arterial disease. However, vascular laboratories should consider how best to combine the use of physiologic testing and direct duplex imaging for peripheral arterial disease in order to avoid unnecessary or inappropriate testing. For most vascular laboratories, this means that initial screening should be done with physiologic tests, but the primary testing method for diagnosis and follow-up will be duplex scanning, supplemented by selective use of physiologic testing.

Dr. Zierler is professor of surgery at the University of Washington and medical director of the D.E. Strandness Jr. Vascular Laboratory at the University of Washington Medical Center and Harborview Medical Center, Seattle. He has no relevant conflicts.

Lower-Extremity Physiologic Studies Are No Longer Required – Wrong!

Okay Gene, consider an example from the cardiology world.

You walk up a flight of stairs and develop chest pain. Is it angina? If subsequent coronary catheterization reveals a 60% stenosis in your proximal right coronary artery, then you have an anatomic coronary lesion. But is this lesion causing angina? Maybe. If the catheter is pushed across the stenosis and a 12mm Hg resting pressure gradient is identified, the lesion also has hemodynamic significance. But is it causing angina? Possibly.

To clarify things, a functional study is necessary; specifically, you need to stress the heart (using treadmill exercise, biking, infusion of a catecholamine, etc.) and determine the subsequent cardiac response (pain, ECG changes, wall motion abnormalities, sestamibi/thallium uptake, etc.). If stress produces an abnormal cardiac response, does that mean you have angina? Probably.

Yes, it’s so simple a cardiologist can get it. Yet many vascular specialists seem to struggle with the concept that anatomic, hemodynamic, and functional tests provide different types of information about the arterial system. These tests are complimentary; when used properly they combine to yield information that no single test can provide. But the siren song of an image is hard to resist – after all, everyone loves pictures, and Duplex provides nice ones. With imaging, you can scan for aneurysms. You can see what plaque looks like. In some instances you can even perform operations or procedures solely on the basis of Duplex scanning. What more do you need? (Insert my sarcastic sneer here, Gene.)

Duplex even provides basic hemodynamic information about specific lesions (based on blood flow velocity changes across the lesion). However, it’s a mistake to think that hemodynamic changes across a particular lesion tell us much about the overall “hemodynamics” in a limb. Major arteries may be narrowed (or even completely occluded), but if the collateral vessels are good, the resulting hemodynamic compromise may be minimal. Unfortunately, Duplex scanning is relatively poor at identifying and assessing collateral flow. Tests like segmental pressures (and the ankle-brachial index, or ABI) often provide a better assessment of overall arterial status because the adequacy of collateral flow influences (and is reflected in) distal blood pressure measurements. It’s also naive to think that Duplex is the only means for noninvasively obtaining anatomic information about arterial disease; nonimaging tests using segmental pressures, multilevel pulse-volume recordings (PVRs), continuous-wave (CW) Doppler, etc. may not produce pretty pictures, but they can still localize arterial lesions to a particular anatomic level (aortoiliac vs. femoral-popliteal vs. infrapopliteal, etc.).

The combination of hemodynamic and functional testing is typically referred to as “physiologic” testing, but there’s much more to this than just CW Dopplerand pneumatic cuffs. Specific tests using Laser-Doppler to measure skin blood flow or microvascular perfusion pressure make it possible to (physiologically) assess the microcirculation. Transcutaneous Oxygen (TcPO2) measurement is available in many labs; this test provides valuable physiological information about skin viability and healing potential.

Where Duplex scanning meets its biggest challenge is in the area of functional testing. Yes, it’s possible to exercise the legs and identify subsequent flow (velocity) changes across certain lesions or vessels, but any seasoned sonographer knows that these studies are extremely difficult and time consuming. And because they typically can’t assess/account for collateral flow, they are often of questionable value for determining the adverse impact of arterial disease on the patient. In contrast, functional (exercise) studies performed with CW Doppler and air cuffs are simple, inexpensive, reliable, reproducible, and widely applicable.

Bottom line – physiologic studies are an indispensable part of noninvasive arterial testing and will certainly remain so. For any given patient, they are essential for identifying and quantifying the scope and impact of arterial disease. For populations, they are the test of choice for arterial screening. And, from a practical standpoint, they are required for IAC [intersocietal accreditation commission] laboratory accreditation in peripheral arterial testing (as you know, Duplex scanning is optional for arterial accreditation – but physiologic studies are mandatory!)

Finally, the same characteristics that make physiologic tests important for assessing arterial disease are equally – or perhaps even more – relevant for the assessment of venous disease, but the application of this approach remains in its infancy. It’s a good topic for another discussion.

Dr. Rooke is the Krehbiel Professor of Vascular Medicine at the Mayo Clinic, Rochester, Minn. He has no relevant conflicts.

Lower-Extremity Physiologic Studies Are No Longer Required – Yes ... Maybe!

My friend, Thom, makes a strong case for the value of physiologic studies in patients with lower extremity arterial disease – so strong, in fact, that one might wonder if there is any truly cogent “counterpoint” at all. To provide some perspective on this issue, let’s take a look back to see how this field started and consider why someone would even dare make the statement that is being debated here.

When clinical vascular laboratories appeared in the late 1960s, the concept of “nondestructive” or “noninvasive” testing was a novelty that was not widely accepted. The first vascular laboratory tests for the assessment of carotid, peripheral arterial, and venous disease were described as “indirect,” because they relied on detection of the physiologic alterations produced by vascular abnormalities.

These methods included the supraorbital Doppler examination and oculoplethysmography for carotid disease, ankle-brachial indices, segmental pressures, and pulse volume recordings for peripheral arterial disease, and the CW Doppler examination and impedance plethysmography for venous obstruction. In those early days, vascular testing was limited to some vascular surgery practices and physiology laboratories.

While these indirect physiologic tests were helpful for characterizing regional hemodynamics, they did not provide the detailed anatomic information on arterial lesions that vascular surgeons needed to plan treatment. It was not until direct ultrasound imaging of blood vessels became available in the late 1970s and early 1980s that interest in the non-invasive vascular laboratory increased. The “duplex concept” of combining B-mode imaging with Doppler flow detection appeared to overcome the major limitations of the indirect tests by providing two-dimensional images of an arterial lesion along with an assessment of the associated flow patterns – anatomy and hemodynamics – the best of both testing worlds.

The capabilities of duplex ultrasound were so impressive that direct duplex scanning rapidly replaced the indirect or physiologic tests for diagnosis of extracranial carotid disease and lower extremity deep venous thrombosis. But, as Thom points out, peripheral arterial disease is the only testing area in which physiologic studies are still considered as “primary” testing methods according to the IAC Standards and Guidelines for Vascular Testing Accreditation. So the challenge for the modern vascular laboratory is to determine which test to use and how to integrate physiologic testing and duplex scanning in the evaluation of patients with known or suspected peripheral arterial disease.

The clinical role of the vascular laboratory can be divided into the categories of screening, diagnosis, and follow-up. The merits of screening for peripheral arterial disease are beyond the scope of this debate, but screening tests must be safe, inexpensive, and capable of detecting the presence or absence of disease. Clearly, physiologic tests meet these requirements, and in most situations, an ankle-brachial index is all that is needed. Diagnostic testing in patients with signs and symptoms of peripheral arterial disease, including those that may be candidates for intervention, requires the specific anatomic and hemodynamic information that duplex scanning provides, but functional testing (i.e., treadmill exercise) can also be valuable in selected cases. Similarly, follow-up of peripheral arterial interventions usually requires duplex scanning to evaluate the anatomic and hemodynamic features of the treated arterial segment, while follow-up of documented but untreated peripheral arterial disease can often be accomplished primarily by physiologic tests alone.

Are lower-extremity physiologic studies no longer required in the age of modern duplex scanners? Although I am reluctant to admit it, strictly speaking, my friend, Thom, is correct when he responds with an emphatic “Wrong.” There is no reason to completely abandon the physiologic tests that have served us well since before the age of duplex scanning. A simple ankle-brachial index is easy to justify as part of almost any lower extremity arterial evaluation, and exercise treadmill testing is an excellent way to assess the functional status of a patient with peripheral arterial disease. However, vascular laboratories should consider how best to combine the use of physiologic testing and direct duplex imaging for peripheral arterial disease in order to avoid unnecessary or inappropriate testing. For most vascular laboratories, this means that initial screening should be done with physiologic tests, but the primary testing method for diagnosis and follow-up will be duplex scanning, supplemented by selective use of physiologic testing.

Dr. Zierler is professor of surgery at the University of Washington and medical director of the D.E. Strandness Jr. Vascular Laboratory at the University of Washington Medical Center and Harborview Medical Center, Seattle. He has no relevant conflicts.

Lower-Extremity Physiologic Studies Are No Longer Required – Wrong!

Okay Gene, consider an example from the cardiology world.

You walk up a flight of stairs and develop chest pain. Is it angina? If subsequent coronary catheterization reveals a 60% stenosis in your proximal right coronary artery, then you have an anatomic coronary lesion. But is this lesion causing angina? Maybe. If the catheter is pushed across the stenosis and a 12mm Hg resting pressure gradient is identified, the lesion also has hemodynamic significance. But is it causing angina? Possibly.

To clarify things, a functional study is necessary; specifically, you need to stress the heart (using treadmill exercise, biking, infusion of a catecholamine, etc.) and determine the subsequent cardiac response (pain, ECG changes, wall motion abnormalities, sestamibi/thallium uptake, etc.). If stress produces an abnormal cardiac response, does that mean you have angina? Probably.

Yes, it’s so simple a cardiologist can get it. Yet many vascular specialists seem to struggle with the concept that anatomic, hemodynamic, and functional tests provide different types of information about the arterial system. These tests are complimentary; when used properly they combine to yield information that no single test can provide. But the siren song of an image is hard to resist – after all, everyone loves pictures, and Duplex provides nice ones. With imaging, you can scan for aneurysms. You can see what plaque looks like. In some instances you can even perform operations or procedures solely on the basis of Duplex scanning. What more do you need? (Insert my sarcastic sneer here, Gene.)

Duplex even provides basic hemodynamic information about specific lesions (based on blood flow velocity changes across the lesion). However, it’s a mistake to think that hemodynamic changes across a particular lesion tell us much about the overall “hemodynamics” in a limb. Major arteries may be narrowed (or even completely occluded), but if the collateral vessels are good, the resulting hemodynamic compromise may be minimal. Unfortunately, Duplex scanning is relatively poor at identifying and assessing collateral flow. Tests like segmental pressures (and the ankle-brachial index, or ABI) often provide a better assessment of overall arterial status because the adequacy of collateral flow influences (and is reflected in) distal blood pressure measurements. It’s also naive to think that Duplex is the only means for noninvasively obtaining anatomic information about arterial disease; nonimaging tests using segmental pressures, multilevel pulse-volume recordings (PVRs), continuous-wave (CW) Doppler, etc. may not produce pretty pictures, but they can still localize arterial lesions to a particular anatomic level (aortoiliac vs. femoral-popliteal vs. infrapopliteal, etc.).

The combination of hemodynamic and functional testing is typically referred to as “physiologic” testing, but there’s much more to this than just CW Dopplerand pneumatic cuffs. Specific tests using Laser-Doppler to measure skin blood flow or microvascular perfusion pressure make it possible to (physiologically) assess the microcirculation. Transcutaneous Oxygen (TcPO2) measurement is available in many labs; this test provides valuable physiological information about skin viability and healing potential.

Where Duplex scanning meets its biggest challenge is in the area of functional testing. Yes, it’s possible to exercise the legs and identify subsequent flow (velocity) changes across certain lesions or vessels, but any seasoned sonographer knows that these studies are extremely difficult and time consuming. And because they typically can’t assess/account for collateral flow, they are often of questionable value for determining the adverse impact of arterial disease on the patient. In contrast, functional (exercise) studies performed with CW Doppler and air cuffs are simple, inexpensive, reliable, reproducible, and widely applicable.

Bottom line – physiologic studies are an indispensable part of noninvasive arterial testing and will certainly remain so. For any given patient, they are essential for identifying and quantifying the scope and impact of arterial disease. For populations, they are the test of choice for arterial screening. And, from a practical standpoint, they are required for IAC [intersocietal accreditation commission] laboratory accreditation in peripheral arterial testing (as you know, Duplex scanning is optional for arterial accreditation – but physiologic studies are mandatory!)

Finally, the same characteristics that make physiologic tests important for assessing arterial disease are equally – or perhaps even more – relevant for the assessment of venous disease, but the application of this approach remains in its infancy. It’s a good topic for another discussion.

Dr. Rooke is the Krehbiel Professor of Vascular Medicine at the Mayo Clinic, Rochester, Minn. He has no relevant conflicts.

Lower-Extremity Physiologic Studies Are No Longer Required – Yes ... Maybe!

My friend, Thom, makes a strong case for the value of physiologic studies in patients with lower extremity arterial disease – so strong, in fact, that one might wonder if there is any truly cogent “counterpoint” at all. To provide some perspective on this issue, let’s take a look back to see how this field started and consider why someone would even dare make the statement that is being debated here.

When clinical vascular laboratories appeared in the late 1960s, the concept of “nondestructive” or “noninvasive” testing was a novelty that was not widely accepted. The first vascular laboratory tests for the assessment of carotid, peripheral arterial, and venous disease were described as “indirect,” because they relied on detection of the physiologic alterations produced by vascular abnormalities.

These methods included the supraorbital Doppler examination and oculoplethysmography for carotid disease, ankle-brachial indices, segmental pressures, and pulse volume recordings for peripheral arterial disease, and the CW Doppler examination and impedance plethysmography for venous obstruction. In those early days, vascular testing was limited to some vascular surgery practices and physiology laboratories.

While these indirect physiologic tests were helpful for characterizing regional hemodynamics, they did not provide the detailed anatomic information on arterial lesions that vascular surgeons needed to plan treatment. It was not until direct ultrasound imaging of blood vessels became available in the late 1970s and early 1980s that interest in the non-invasive vascular laboratory increased. The “duplex concept” of combining B-mode imaging with Doppler flow detection appeared to overcome the major limitations of the indirect tests by providing two-dimensional images of an arterial lesion along with an assessment of the associated flow patterns – anatomy and hemodynamics – the best of both testing worlds.

The capabilities of duplex ultrasound were so impressive that direct duplex scanning rapidly replaced the indirect or physiologic tests for diagnosis of extracranial carotid disease and lower extremity deep venous thrombosis. But, as Thom points out, peripheral arterial disease is the only testing area in which physiologic studies are still considered as “primary” testing methods according to the IAC Standards and Guidelines for Vascular Testing Accreditation. So the challenge for the modern vascular laboratory is to determine which test to use and how to integrate physiologic testing and duplex scanning in the evaluation of patients with known or suspected peripheral arterial disease.

The clinical role of the vascular laboratory can be divided into the categories of screening, diagnosis, and follow-up. The merits of screening for peripheral arterial disease are beyond the scope of this debate, but screening tests must be safe, inexpensive, and capable of detecting the presence or absence of disease. Clearly, physiologic tests meet these requirements, and in most situations, an ankle-brachial index is all that is needed. Diagnostic testing in patients with signs and symptoms of peripheral arterial disease, including those that may be candidates for intervention, requires the specific anatomic and hemodynamic information that duplex scanning provides, but functional testing (i.e., treadmill exercise) can also be valuable in selected cases. Similarly, follow-up of peripheral arterial interventions usually requires duplex scanning to evaluate the anatomic and hemodynamic features of the treated arterial segment, while follow-up of documented but untreated peripheral arterial disease can often be accomplished primarily by physiologic tests alone.

Are lower-extremity physiologic studies no longer required in the age of modern duplex scanners? Although I am reluctant to admit it, strictly speaking, my friend, Thom, is correct when he responds with an emphatic “Wrong.” There is no reason to completely abandon the physiologic tests that have served us well since before the age of duplex scanning. A simple ankle-brachial index is easy to justify as part of almost any lower extremity arterial evaluation, and exercise treadmill testing is an excellent way to assess the functional status of a patient with peripheral arterial disease. However, vascular laboratories should consider how best to combine the use of physiologic testing and direct duplex imaging for peripheral arterial disease in order to avoid unnecessary or inappropriate testing. For most vascular laboratories, this means that initial screening should be done with physiologic tests, but the primary testing method for diagnosis and follow-up will be duplex scanning, supplemented by selective use of physiologic testing.

Dr. Zierler is professor of surgery at the University of Washington and medical director of the D.E. Strandness Jr. Vascular Laboratory at the University of Washington Medical Center and Harborview Medical Center, Seattle. He has no relevant conflicts.