말초동맥질환 - 13. PAD(Peripheral Arterial Disease)'s Diagnosis Peripheral Arterial Disease

 PAD(Peripheral Arterial Disease)'s Diagnosis

 

Several tests may be required to diagnose PAD and determine the extent of the disease. Some of these tests may be performed in a primary care physician's office, whereas others may be performed by a vascular specialist or in a vascular lab. Most tests are non-invasive and thus should be fairly painless.

 

 ▣ Medical History and Physical Exam


Ankle-brachial index (ABI)


Treadmill Exercise Test


Reactive Hyperemia Test


Segmental Pressure Measurements


PVR Waveform Analysis


Duplex Arterial Imaging or Ultrasound Imaging


Photoplethysmography (PPG)


Arteriogram

 

1. Medical History and Physical Exam

 

A thorough physical exam is necessary to begin to look for signs of PAD, to grade its severity, and to determinethe best treatment. Your physician will ask for the following information:

 

 ♣ Review your personal history of leg or heart symptoms


The medical review of your family


Whether you smoke and how much


Other risk factors such as diabetes, high blood pressure and cholesterol levels


Any symptoms you have when you walk


Any medications or vitamins you are presently taking

 

Your doctor will also examine you by:

 

 ♣ Listening to your heart


Feeling your abdomen

Assess your pulses at various places, usually at the top of your legs, behind your knees, in the groin, 
   and at your ankles


Examining your feet

 

Blood test: Your doctor may request a blood test to look at your general health and to assess risk factors that affect the development of PAD, including your fasting blood cholesterol levels, your blood sugar, your kidney and liver function, and occasionally your homocysteine levels.

 

2. Ankle-Brachial index (ABI)

 

The ankle-brachial index (ABI) is a simple, reliable means for diagnosing PAD.  Blood pressure measurements are taken at the arms and ankles using a pencil shaped ultrasound device called a Doppler. A Doppler instrument produces sound waves (not x-rays) and is considered noninvasive because it does not require the use of needles or catheters. The ABI test is simple enough to be performed in any doctor's office or vascular laboratory. Not only is the ABI one of the most reliable tests for PAD, it is also the least expensive.

 

You will be asked to lie on your back while standard blood pressure cuffs are placed around your ankles and arms.  These cuffs will be inflated briefly above your normal systolic blood pressure.  Once the cuffs are deflated, blood pressure measurements are taken using the Doppler instrument.  The arm and ankle systolic blood pressure measurements are recorded.  Then the ankle systolic pressures are divided by the highest arm pressure to establish an ABI measurement for each leg. The ABI range that is generally considered normal is 0.95 to 1.2.

 

Although the ABI is extremely reliable, this test may not be accurate in all patients. Some patients with long-standing diabetes, kidney disease, or some elderly patients, may have rigid blood vessels. These may be difficult to compress with the blood pressure cuff and, in these patients, the ABI reading may not be accurate.

 

For patients with rigid ankle blood vessels, toe pressure measurements may be taken since toe arteries are rarely rigid. This examination is called a toe brachial index (TBI) and is a calculation based on the systolic blood pressures of the arm and the systolic blood pressures of the toes.  The examination is similar to the ABI except that it is performed with a photoplethysmograph (PPG) infrared light sensor and  a very small blood pressure cuff placed around the toe.  A TBI of .8 or greater is considered normal. Alternatively, a leg arterial ultrasound test can detect PAD if the ABI is not considered reliable.

 

The ABI Exam

 

The ABI test is used to document the presence or absence of PAD, and can be performed every year to quickly assess whether PAD is getting worse. Obviously, treatment for the disease tries to slow the rate at  which leg arteries become blocked.

 

The ABI can also predict how severe an individual's atherosclerosis is and the risk of future leg problems (such as development of future leg rest pain, poor healing of foot wounds, need for leg bypass surgery, or amputation).  It can also predict the risk of future problems from atherosclerosis in other parts of the body (such as heart attack and stroke).  Lower ABI values are associated with a higher risk. In fact, the ABI value can be an accurate predictor for patients with coronary heart disease (such as the blood cholesterol value, coronary calcium score, and C-reactive protein value).

 

An ABI value greater than 0.80 is rarely associated with short-term leg problems such as foot wounds or amputation. Nevertheless, any evidence of PAD (where the ABI measurement is less than 1.00) is associated with future risk of heart attack and/or stroke.

 

An ABI value between 0.40 ~ 0.80 is moderately decreased and such patients often experience some symptoms such as pain in the legs. Attention to foot care is extremely important to prevent accidental injury or infection. Again, any evidence of PAD is associated with future risk of heart attack and/or stroke! Serious efforts to keep one's risk factors under control is essential to keep PAD from getting worse.

 

An ABI value of less than 0.40 indicates severe PAD.  Patients should be extremely careful to avoid any foot injuries.  Proper foot care may prevent development of non-healing wounds, rest pain, or even gangrene. Usually, care from a vascular specialist is required. The specialist will evaluate the risk and benefits to improve leg blood flow through surgery or other interventions.

 

The ABI test approaches 95 percent accuracy in detecting PAD.  However, a normal ABI value does not absolutely rule out the possibility of PAD for a few individuals. Some patients with a normal or near-normal ABI results may have few symptoms suggesting PAD. A treadmill exercise or reactive hyperemia test may be recommended to test further for the disease and the cause of pain.


3. Treadmill Exercise Test

 

A treadmill exercise test provides additional information to the doctor such as how severe your symptoms may be.  By walking on a treadmill for a few minutes, this test tries to imitate the experience you may have walking at home.

 

This test can be especially helpful for individuals in whom there may be more than one cause of leg symptoms with walking, such as from lumbar back or sciatic pain, nerve pain, or joint diseases. This test can also help you and your doctor distinguish the relative importance of PAD and other heart and lung symptoms to your difficulty with walking. Treadmill exercise tests are also useful for patients that will begin a formal exercise program to improve their claudication symptoms. By monitoring the heart during the treadmill exercise, your physician can reassure you that the heart is also receiving enough blood flow.  This can offer reassurance that an exercise program will be safe as you work to increase your walking capacity.

 

The test usually follows these steps:

 

 ♣ A baseline measurement of your arm and ankle blood pressures at rest is taken. 

You will then be asked to walk slowly on a treadmill, typically for as long as you can comfortably walk
   until your symptoms become too uncomfortable to continue.
 

Lying down again, your arm and ankle blood pressure measurements will be immediately repeated.

 

In individuals without significant PAD, ankle pressures will remain the same or increase somewhat in comparison to your resting blood pressures. However, in individuals with PAD there is usually a drop in the ankle blood pressures and ABI values after exercise. When leg symptoms occur without a drop in ankle blood pressures, these symptoms are usually not caused by PAD.

 

4. Reactive Hyperemia Test

 

The reactive hyperemia test is an alternative to the baseline, ABI or treadmill test. If you are unable to walk on a treadmill due to heart problems or shortness of breath, the reactive hyperemia test can be performed to diagnose PAD.

 

You will be asked to lie on your back while standard blood pressure cuffs are placed around your thighs and ankles. The thigh cuffs will be inflated above your normal systolic blood pressure for three to five minutes. Once the thigh cuffs are deflated, the ankle cuffs are inflated briefly above your systolic blood pressure, then slowly deflated. Using the Doppler instrument, blood pressure measurements are immediately taken at both your ankles.

 

A significant (50% or greater) decrease in ankle blood pressure indicates there is a blockage in your leg arteries and thus is a diagnosis of PAD.

 

5. Segmental Pressure Measurements

 

Segmental pressure measurements are blood pressure measurements taken at multiple levels on the leg.

 

It is similar to the ABI test, with the addition of two or three additional blood pressure cuffs. These additional cuffs are placed just below the knee and one large cuff or two narrow cuffs are placed above the knee and at the upper thigh. These cuffs are then inflated above your normal systolic blood pressure, and then slowly deflated.

 

Using the Doppler instrument, blood pressure measurements are taken. The blood pressure at each cuff location on your leg is noted in your physician's report. A significant drop in pressure between two adjacent cuffs indicates a narrowing of the artery or blockage along the arteries in this portion of your leg. This allows the vascular technologist and doctor to identify more precisely the location of such blockages in the arteries of your leg.

 

6. PVR Waveform Analysis

 

The doctor or non-invasive vascular laboratory may perform blood flow waveform analysis. The Pulse Volume Recording (PVR) method measures blood volume changes that occur in your legs.

 

Using cuffs similar to those involved in segmental pressure testing, PVR cuffs are inflated, but only a little. Instead of temporarily stopping the blood flow to determine your blood pressure, the PVR cuff allows the blood to continue flowing through your leg. As blood pulses through your arteries, your blood vessels expand causing an increase or decrease in the volume of air within the cuff.

 

A recording device displays these pulse volume changes as a waveform. The shape of the waveform gives the doctor useful information about the blood flow in your legs. This test often is more informative for patients with diabetes or whose arteries have become stiff and hard to compress due to calcification.

 

7. Duplex Arterial Imaging or Ultrasound Imaging

 

Another waveform method used by the physician or vascular laboratory is Doppler waveform analysis produced from a pencil shaped ultrasound probe or within ultrasound-imaging equipment. The Doppler probe will show blood movement in your arteries as a waveform that looks similar to a heart EKG. The shape of the waveform gives the doctor useful information about the blood flow at the location being examined.

 

This test uses high-frequency ultrasound to visualize the anatomy and blood flow in legs. This is the same type of instrument used to examine unborn babies, the size or structure of abdominal organs, such as the gall bladder, or to evaluate the blood flow in the neck and the carotid arteries. The name "duplex" comes from combining the two meanings:

 

the conversion of ultrasound signals into sounds that you can hear and

  ♣ pictures that you can see.

 

The Doppler part of the test works by sending a high-frequency sound (ultrasound) wave through a transmitting gel into the body. This sound wave bounces off the layers of the body, such as muscle, bone, blood vessels, and various organs. Each type of body tissue absorbs ultrasound signals differently. For example, if you took a tennis ball and bounced it on different surfaces, it would bounce differently. It bounces high on a hard surface like cement, yet barely at all on a soft surface such as grass. In a similar manner that bats and submarines use sound to see were they are going, your vascular specialist uses ultrasound to see images of your body.

 

You will be asked to lie on your back. Water-based gel will be placed along segments on your legs. The pencil shaped ultrasound probe will be placed in the gel to display a segment of your artery. The doctor or technologist will move the probe slowly up and down the arteries to see and hear the blood flow. Your legs may be repositioned to allow a better view of the artery.

 

These images help to determine if you have cholesterol plaque, narrowed arteries or blockages in the blood vessels of your legs. In addition, most duplex imaging systems also show the direction of your blood flow in color. This information allows the vascular specialist to determine if the blood is flowing away (arterial) or toward (venous) your heart.

 

8. Photoplethysmography (PPG) Exam

 

This system uses infrared light to assess blood flow near the surface of the skin.  It may be used to take a blood pressure in a toe, or used for waveform analysis. Instead of a sound signal, the PPG uses infrared light to produce a waveform. This may be used for people in whom the ankle arteries have become stiff and hard to compress due to calcification, as noted in the ABI section above (individuals with longstanding diabetes, kidney disease, or some elderly individuals).

 

The examination is similar to the ankle- brachial index except that it is performed using a PPG sensor and a very small blood pressure cuff around the toe. While lying on your back, a tiny probe is placed over one or more of your toes on each foot and waveforms recordings will be displayed and blood pressure measurements taken. The measurements are called a TBI and when it is at 0.80 (80% of an ABI of 1.00) it is considered normal.

 

9. Arteriogram

 

Arteriography is a minimally invasive test in which an arteriogram or "road map" of the arteries is made. An arteriogram looks a lot like an x-ray and is used to plan or guide treatments such as surgery, angioplasty, or stent placement.

 

You will be asked not to eat for several hours prior to the exam so mild sedation can be given safely. You may need to have some simple laboratory blood tests prior to the arteriogram. Your physician will explain the procedure and answer any questions you might have. Then you will go to a room with sophisticated imaging equipment. You will be given medicines through an intravenous line to make you sleepy and comfortable, and a sterile drape will cover you from your chest down. A tiny tube or catheter is then placed into the artery in the upper portion of the thigh after the skin is made numb. The catheter is then steered to its intended destination inside your vascular system using x-rays for guidance. A clear liquid called contrast dye is then injected through the catheter and a series of pictures are taken. You will usually feel a mild warm "flush" when the dye is injected. Pressure will be applied to the groin after the sheath is removed in order to prevent bleeding from the artery.

After the procedure and a short observation period, you may go home. Sometimes if a treatment with a balloon or stent is performed you may stay in the hospital overnight.

 

These pictures or images can be used to diagnose the cause of arterial blockage or to precisely guide an angioplasty balloon or stent into place to treat a blockage. The arteriogram may also be used to plan a surgical treatment such as a bypass graft.

 

An angioplasty balloon is a tiny balloon mounted on a catheter or small tube. The balloon is positioned into the blocked area of the artery and is used to stretch open the artery. A stent is a tubular scaffolding of metal wire that is also mounted on a small catheter. The stent is placed across a blockage and holds the artery open like the hoops on a barrel. An important difference is that the stent stays in the artery while the balloon is removed from the artery after it is used.







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