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THE STAFF OF THE VASCULAR DIAGNOSITC LABORATORY:

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INTRODUCTION

The inaugural issue of the Heart and Vascular Institute (HVI) quarterly ewsletter is dedicated to the Vascular Laboratory. Future issues will highlight other imaging and treatment modalities, such as Electron Beam Tomography™ (EBT™) Ultrafast Heart Scan, MRI, Angiography and Enhanced External Counterpulsation (EECP). Regular features of this newsletter will include HVI News/Updates; the Heart and Vascular Research Institute activities and clinical trials updates; and publications and presentations by HVI staff. We welcome your comments and suggestions for topics to include for future issues.

A wide variety of non-invasive vascular studies are offered at HVI. The goal of the vascular laboratory is to provide excellent service to our patients and referring physicians along with complete and accurate test reports. We have already initiated a quality control program, CME credits for all involved in the vascular lab and have taken the early steps toward accredita-tion by the Intersocietal Commission on the Accreditation of Vascular Laboratories (ICAVL).

In this edition of the Newsletter, a brief description of several of the Vascular Lab studies currently available (with CPT codes) and a number of appropriate indications (with ICD-9 codes) are included. To facilitate patient scheduling and billing, please refer to these codes when ordering Vascular Lab examinations.

DUPLEX ULTRASOUND

Duplex ultrasound studies combine the anatomic and morphologic information obtained with gray-scale imaging (B-mode) along with hemo-dynamic data (spectral and color Doppler), such as blood flow velocity and direction. The quantitative data can then be utilized for other calculations that enhance interpretation of the study results.

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Carotid Duplex Ultrasound
[CPT 93880 Bilateral, 93882 Unilateral]

The most frequently performed study in the Vascular Lab, the carotid duplex ultrasound is a non-invasive means of evaluating not only the common, external, and internal carotid arteries, but also the vertebral and subclavian arteries. Typical study indications include: carotid bruit [ICD-9 785.9], TIA [435.9], and the periodic surveillance of known carotid disease [433.1-433.3].

B-mode imaging is performed to identify and characterize atherosclerotic plaque. Plaque can be characterized as one of three types on the ultrasound report: homogeneous, heterogeneous, or calcified.

Homogeneous plaque consists of calcium-free atheroma. The absence of any detectable calcification results in a hypoechoic (few echoes; dark) appearance on gray-scale imaging, rendering this form of plaque essentially indistinguishable from the normally anechoic (echo-free and dark) vessel lumen. On color Doppler images, however, areas with homo-geneous plaque demonstrate no flow-related color.

Heterogeneous plaque, as its name implies, has a corresponding intermediate echotexture compared to homogeneous and calcified forms. This term can also be used when areas of both homogeneous and calcified plaque can be identified in the vessel segment. This indicates the presence of some calcification, but not to the degree where the ultrasound beam can no longer penetrate the plaque producing what is known as acoustic shadowing.

Calcified plaque appears uniformly echogenic (bright) on B-mode images, often with posterior acoustic shadowing. Shadowing potentially limits the evaluation of an affected vascular segment because sound waves are unable to penetrate that area. If a velocity measurement cannot be obtained with ultrasound in an area of stenosis, this can potentially underestimate the degree of the stenosis. This is most important in distinguishing between moderate (60-79%) and severe (80-99%) degrees of stenosis, which have differing natural histories and are managed differently.

Another scenario that presents a challenge to interpretation is the velocity elevation contralateral to a carotid occlusion. This may lead to an overestimation of the degree of stenosis or the false diagnosis of stenosis, in its absence, on the ipsilateral side.

The Vascular Lab uses a modification of the Strandness classification scheme for assigning the degree of internal carotid arterial stenosis (Table 1).^{2, 3} Velocity and spectral criteria are utilized to establish a range of percent diameter stenosis for the internal carotid arteries.

No criteria have been validated for the quantitation (percent stenosis) of common carotid or external carotid disease severity. Instead, vascular disease in these locations is described as mild, moderate, or severe, based on subjective assessment of the plaque burden and peak systolic velocity. Duplex ultrasound of the carotid artery has become so accurate that most vascular surgeons are now performing a carotid endarterectomy on the basis of ultrasound alone. Since carotid angiography accounted for approximately 50% of the strokes in the Asymptomatic Carotid Atherosclerosis Study (ACAS), it should be reserved for situations where the carotid ultrasound is not clear, or technical limitations preclude an accurate examination. Most patients who have symptomatic carotid disease, however, should undergo angiography prior to percutaneous or surgical intervention.

In general, recommendations for follow-up are not included in the official report because any such recommendations only apply to asymptomatic patients. In addition, there are no rules that apply to every patient and clinical decision making is necessary for each individual case. However we have prepared general guidelines that are available to all referring physicians (Table 2).

References:
1. Zwibel WJ. Doppler Evaluation of Carotid Stenosis. In Introduction to Vascular Ultrasonography. W.B. Saunders. 1992; 9:123-132.
2. Neumyer M, et al. Validation of pre-screening with duplex scanning. J. Vasc. Technology. 1987; 11:30-32.
3. Strandness DE and Taylor UW. Carotid artery duplex scanning. Clin. Ultrasound. 1987; 15:625-644.

Renal Artery Duplex Ultrasound
[CPT 93975 "RADUS"]

Since its introduction into the Vascular Lab repertoire, the volume of this study has increased enormously. This technically demanding study can identify hemodynamically significant (60-99%) renal arterial stenoses.^{1, 2} The indications for this study are: hypertension not adequately controlled despite a good antihypertensive regimen [ICD-9 401.1], unexplained azotemia [539.9], a small or atrophic kidney, or recurrent congestive heart failure or flash pulmonary edema not explained by ischemic heart disease.

Unlike the carotid ultrasound study, which relies heavily on gray-scale imaging for plaque characterization along with color Doppler and spectral information, the renal arterial study relies almost entirely on the Doppler spectral waveform and turbulence demonstrated on color Doppler. The entire length of each renal artery (include accessory arteries, when present) is evaluated via two approaches: transabdominal (with the patient in the supine position) and through the flank (with the patient in the opposite decubitus position). The presence of intestinal gas may severely limit study quality. Therefore all patients should fast (including liquids) for 12 hours prior to a renal artery duplex examination.

The abdominal aortic and renal arterial peak systolic velocities are used to calculate the renal-aortic ratio (RAR), a value used in conjunction with the absolute renal arterial peak systolic velocity to determine the severity of stenosis.

Intrarenal arterial flow velocity is also documented. The peak-systolic (PSV) and end-diastolic velocities (EDV) are used to calculate the resistive index (RI) by the formula: (PSV-EDV)/PSV. The RI value reflects the degree of resistance to flow within the kidneys. High RI values (close to 1.0) are consistent with intra-renal resistance due to parenchymal abnormalities such as nephrosclerosis and other renal pathology.

B-mode imaging is used primarily to obtain the length of each kidney. Although the ultrasound parameters are optimized for renal vascular rather than renal parenchymal evaluation, gray-scale image findings, such as cysts, masses, cortical thinning, and hydronephrosis can be detected. However, findings of uncertain significance, such as a complex renal mass, cannot be fully and properly analyzed with this technique. In such circumstances, further evaluation is advised.

The mesenteric arterial velocities are also obtained. The celiac axis and superior mesenteric artery (SMA) are routinely identified in all studies. The inferior mesenteric artery (IMA) is seen less frequently because it is often occluded in patients with abdominal aortic aneurysm and in the elderly.

References:
1. Olin JW. Role of duplex ultrasonography in screening for significant renal artery disease. Urol. Clin. of No. Amer. 1994; 21:215-226.
2. Olin JW, et al. The utility of duplex ultrasound scanning of the renal arteries for diagnosing significant renal artery stenosis. Ann. Int. Med. 1995; 122:833-838.

Mesenteric Duplex Ultrasound
[CPT 93976 RADUS-limited]

Although most mesenteric arterial stenoses are asymptomatic due to the extensive collateral network of the gastrointestinal tract, post-prandial abdominal pain and weight loss may indicate the presence of bona-fide chronic intestinal ischemia. This condition is usually associated with at least two of the three mesenteric vessels having a significant stenosis (70-99%) or occlusion. An abdominal bruit [ICD-9 789.5] may be present.

In young adults, especially females with an aesthenic body habitus, the celiac peak systolic velocity may vary widely during the respiratory cycle due to dynamic compression of the proximal celiac axis by the median arcuate ligament of the diaphragm (also know as celiac artery compression syndrome). Unlike the atherosclerotic form of mesenteric arterial disease, individuals with the median arcuate compression syndrome often do not have symptoms and are not at increased risk for bowel ischemia.

Although an obvious abdominal aortic aneurysm (AAA) will be documented by the technologist during both the renal arterial and the mesenteric arterial duplex studies, these tests are not intended as AAA examinations per se. The correct study to order for AAA detection is an abdominal aortic ultrasound.

Abdominal Aorta Duplex Ultrasound
[CPT 93978 Abdominal Duplex]

A palpable pulsatile mass [ICD-9 789.30] is the most common indication for this study request. In addition, approximately 20% of first degree offspring of an individual who had an abdominal aortic aneurysm will eventually have an AAA.

The technologist systematically interrogates the entire length of the abdominal aorta as well as the common iliac arteries for the presence of an enlargement. Multiple diameter measurements in the AP, transverse and sagittal views are obtained in the suprarenal, juxtarenal, and infrarenal aortic segments. Aortic and common iliac velocity measurements and waveforms are obtained using Doppler. The mesenteric and renal arteries are not evaluated during this study (see above for appropriate studies).

Other arterial duplex studies:

Not discussed in this issue of the newsletter, we also routinely perform arterial duplex of the lower extremities [CPT 93925 (unilateral) and 93926 (bilateral)] for indications such as graft surveillance and, in the post-catheterization patient, in the assessment of pseudoaneurysm and A-V fistula [ICD-9 447.0]. When appropriate, ultrasound-guided thrombin injection can be performed at the time of pseudoaneurysm diagnosis. Arterial duplex studies for the upper extremities [CPT 93930 (unilateral) and 93931 (bilateral)] and arterial mapping will also be available.

Note: In addition to the primary study indication, a second ICD-9 code [250.00 through 250.73] should be selected for any patient with diabetes. ("Diabetes" cannot be coded as a primary indication for any Vascular Lab study.)

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PVR
[CPT 93923 PVR, 93924 PVR with exercise, 93922 ABI]

The PVR (pulse-volume recording) with segmental pressures is an excellent diagnostic tool in patients suspected of having peripheral arterial disease (PAD). The information that one can get from PVRs is:

1. Confirm or rule out (PVR with exercise) the presence of peripheral arterial disease.
2. Determine the level of vascular disease.
3. Determine the severity of vascular disease.
4. Quantify functional impairment (treadmill test)
5. Predict the level of amputation in those patients without other options.
6. Provide objective evidence of improvement or worsening after a percutaneous or surgical intervention.

Blood pressure measurements are first obtained from each upper extremity (brachial). (Discrepancy between the arm pressures usually indicates sub-clavian or innominate stenosis.) Blood pressure cuffs are then applied to the thigh, calf, ankle, metatarsal region of the foot, and great toe. Pressure measurements obtained at the thigh, calf, and ankle are compared with the upper extremity (the higher of the two brachial measurements). At the level of the ankle, this ratio is known as the ABI (ankle-brachial index). Gradients (segmental pressure drops) along the extremity help to localize the general level of arterial disease and provide a clue to the vessel or vessels affected. In addition, the overall severity of PAD in an affected limb is assessed at the level of the ankle via the ABI (see Table 3).

Analysis of the waveform morphology and relative amplitude is especially important in the presence of arterial calcification, which can falsely elevate pressure readings (resulting in false negative studies). In fact, calcification can render the arteries "non-compressible", i.e. pressures registering above the scale of the equipment (over 255 mmHg).

If the study is normal at rest, an exercise study should be performed. The patient is asked to walk on the treadmill at 2.5 mph and 12% grade in an attempt to reproduce the patient's chief complaint (usually pain or discomfort in the buttocks, hip, thigh, calf, etc.).

At the end of the treadmill portion, the patient is quickly re-evaluated at the level of the ankle bilaterally with both pressure measurements and waveform analysis. A significant drop in pressure from the rest portion is consistent with PAD. However, as only the ankle measurement is obtained, the exact site of arterial narrowing in the corresponding lower extremity cannot be determined.

PVR's can also be obtained in the upper extremities in patients with arm claudication or ulcerations on the fingers. In patients with symptoms suggestive of thoracic outlet syndrome, a specific thoracic outlet study should be obtained.

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Lower Extremity Venous Duplex Ultrasound
[CPT 93970 Bilateral, 93971 Unilateral]

These studies are almost always ordered to confirm or exclude the presence of a clinically suspected deep venous thrombosis (DVT) in patients with lower extremity pain [ICD-9 729.5] and/or swelling [729.81]. The lower extremity venous tree is evaluated using Doppler maneuvers, B-mode imaging to visualize thrombus and by using compression. Features of an acute DVT ultrasonographically are:

1. A dilated vein segment.
2. Inability to compress the vein (cannot get the walls to coapt).
3. May or may not visualize thrombus in the acute stage since it is less echogenic than subacute or chronic thrombus.

If the vein is not dilated, or highly echogenic thrombus is visualized, the report may read either "DVT, age indeterminate" or "remote DVT". In this situation, clinical judgement will be necessary to determine how the patient should be treated. Once a patient is started on anti-thrombotic therapy, there is no need to repeat the duplex venous study unless new symptoms occur.

A lower extremity duplex study for acute DVT will be performed the same day it is ordered. If you have difficulty obtaining this study, call one of us immediately. We will also be performing venous insufficiency studies and upper extremity duplex studies.

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Accreditation

The Intersocietal Commission for the Accreditation of Vascular Laboratories (ICAVL) is formed by representatives from multiple organizations which include, among others, the American College of Cardiology (ACC), the American Institute of Ultrasound in Medicine (AIUM), the Society of Cardiovascular and Interventional Radiology (SCVIR), the Society for Vascular Medicine and Biology (SVMB), the Society for Vascular Surgery (SVS), and the Society of Vascular Technology (SVT). Personnel, instrumentation, components of study performance, reporting, correlation with other imaging studies, quality assurance, and procedure volume are some of the Vascular Lab features which are examined.

For greater detail, a copy of the ICAVL's "Standards 2000" is available at each Vascular Lab location.

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The Society of Vascular Medicine and Biology

Founded in 1989, SVMB fosters the integration of vascular biological advances into clinical practice and promotes an interactive collegial approach for delivering the highest quality care to patients with vascular disorders. The mission of the Society also includes the formation of formal research and educational opportunities for doctors-in-training as well as continuing medical education for practicing physicians.

If you are interested in becoming a member or learning more about the Society, please contact Dr. Jeffrey Olin, the Society's current president, or visit the Society's website at www.svmb.org.

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Appropriate ICD-9 codes

• Carotid duplex [CPT 93880, 92882]
  
  
• Arterial duplex [lower extremity 93925 (bilateral) and 93926 (unilateral), upper extremity bilateral (93930) and unilateral (93931)] and PVR [at rest only 93923, with exercise 93924, ABI 93922]
  
  
• Venous duplex [CPT 93970 (bilateral) and 93971 (unilateral)]

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HVI Staff & Hours

The Heart & Vascular Institute
111 Madison Avenue, Morristown, NJ 07960
Phone: 973-656-0555
Fax: 973-656-0174

Hours: Monday - Friday: 7:30 AM- 5:30 PM

Staff:

Jeffrey W. Olin, DO, FACC, FACP
Director, The Heart & Vascular Institute Co-Director, Vascular Diagnostic Laboratory

Michael R. Jaff, DO, FACP, FACC
Director, Vascular Medicine Program Co-Director, Vascular Diagnostic Laboratory

Peter L. Smith, MD, MACR
Director, Endovascular Services

Julianna M. Czum, MD
Director, Vascular MR

James F. London, MD
Director, Cardiac MR

Patricia E. Houser, RN
Administrator

Ann McKnight
Office Supervisor

Linda Carricarte
Administrative Assistant

Maureen Lowe, RT (AS, R, CT)
CT Technologist

John Jacobacci, RT (R, MR)
MR Technologist

Christopher Konkus, RT (R, MR)
MR Technologist

Ken Brown, RT (R)
Angiography Technologist

Stan Ort, RVT
Technical Director, Vascular Laboratory

Eileen M. MacCallum, RN, APN, C
Nurse Practitioner

Marla Lynne Bell, RN, APN, C
Nurse Practitioner

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