The Noninvasive Vascular Laboratory of The Cardiovascular Care Group is a specially designed laboratory that has both equipment and personnel to diagnose problems of the vascular system in a manner that is safe, pain-free, and accurate. The improvement in ultrasound technology has brought the Noninvasive Vascular Laboratory to the forefront in the diagnosis of vascular disease. The use of Duplex ultrasound and other technologies, such as plethysmography, has become indispensable to the cardiovascular physician.

In our laboratories, tests are performed by certified technologists whose only responsibility is to perform these studies. These technologists have achieved the highly regarded status of RVT (Registered Vascular Technologist) by completing extra courses and passing a very difficult examination. They are certified by a national accrediting organization, ARDMS, whose standards are exceptionally high. These personnel specialize in vascular disease limiting their focus to non-invasive examinations of the vascular system. Since these technologists focus solely on diseases of the arteries and veins, their fund of knowledge regarding vascular disease is, both by training and experience, very comprehensive. Additionally, the laboratories of The Group are certified by the Intersocietal Commission on the Accreditation of Vascular Laboratories (ICAVL link to website)—a national accrediting body charged with assuring quality of care in the delivery of vascular laboratory care.

Many diseases of the cardiovascular system can be diagnosed in the Non-Invasive Vascular Laboratory using Duplex ultrasound and Plethysmography. State of the art equipment is used to find plaques in the carotid arteries to prevent stroke; narrowing in the kidney arteries that may cause high blood pressure; atherosclerosis in the legs that cause pain while walking; and aneurysms of the aorta that can rupture. In addition, blood clots in the arms and legs can be accurately diagnosed to prevent dislodgement of the clot to the lungs. Finally, patients with hemodialysis access shunts can be evaluated to ensure proper functioning.

The Noninvasive Vascular Laboratory exists to answer the question: Is there disease and, if so, how severe is it? Quite often, a noninvasive study simply confirms the findings at physical examination. A pulse examination, palpation of the abdominal aorta or auscultation of the carotid, renal or femoral arteries frequently provides enough information to make a preliminary diagnosis.

Physiologic Tests (such as Pulse Volume Recordings or PVRs) provide information on the amount of circulation to the extremities. There are two components to PVRs: Ankle Brachial Index (ABI) and plethysmographic waveform analysis. ABIs—comparison of ankle systolic to brachial systolic blood pressures—are simple to perform and can yield valuable information. While used to identify peripheral vascular disease, they are also a marker for unsuspected coronary artery disease. The ABI is of limited value in patients with calcified arteries (for example, diabetics or those with advanced renal disease.) The addition of PVRs—production of waveforms using plethysmographic techniques—greatly enhances the utility and accuracy of ABIs when assessing the extremities for arterial insufficiency. Analysis of the waveform at various levels allows one to localize the occlusive disease to specific segments of the arterial tree.

Duplex Ultrasound examination involves two distinct portions to the study: B-mode analysis (black-and-white imaging) and Color Doppler Flow analysis. B-mode gives information about the structural integrity of the vascular system identifying narrowed areas and blocked vessels. Color Flow Doppler analysis provides information on turbulence of flow providing a method to quantify degree of narrowing in a vessel.

Venous Duplex Scans are the gold standard for determining the presence of venous thrombosis. Veins are assessed for compressibility and for augmentation. A normal vein will be able to have its contents (liquid blood) fully displaced by compressing the probe thereby coating the anterior and posterior walls of the vein. However, in the presence of a solid structure (such as a thrombus within the vein) compression with the ultrasound probe will not allow complete apposition of the vein walls. Augmentation of flow occurs when, for example, the calf muscle is compressed and blood is propelled up the venous tree towards the heart. If one places the probe in the mid-thigh, if there is not obstruction between the point of compression and the point of insonation, one can assume there is no blood clot.

Arterial Duplex Scans (peripheral arterial, carotid, renal or mesenteric) also utilize two phases—B-mode and Color waveform analysis. B-mode allows for identification of plaque with an approximation of the degree of narrowing caused by the plaque. Waveform analysis allows for the measurement of flow rates at various points in the arterial tree utilizing the Doppler equation. Much like the “garden hose phenomenon” (reducing the diameter of the hose by placing one’s finger across the opening results in much faster flow rates) an arterial stenosis will result in faster flow rates at a specific point in the artery. Correlations are made in each individual Vascular Laboratory relating the rate of flow with the degree of narrowing within the artery.

Aortic Scans also utilize duplex ultrasound with a greater dependence on the B-mode than other arterial interrogations. Identification of the edges of the aortic wall with color analysis of the lumen, allows one to measure the diameter of the aorta. Information as to location relative to the renal arteries and degree of thrombus within the aortic aneurysm sac is valuable to developing treatment strategies.

Utilizing the Noninvasive Vascular Laboratory to answer specific questions is valuable in the management of patients. The more refined the question, the more useful the answer will be.