Peripheral Vascular Disease

VIRCHOW TRIAD

Virchow triad describes the three factors that are commonly associated with the formation of thrombi:

1. Stasis (arrhythmias, MI, CHF, heart failure, immobilization, obesity, varicose veins, dehydration)

2. Blood vessel injury (trauma, fractures, IV)

3. Hypercoagulability (neoplasm, oral contraceptives, pregnancy, surgery, polycythemia)

STAGES OF ARTERIAL OCCLUSION

Intermittent Claudication

Bilateral pain, usually in the calf, occurs after the patient walks a distance. The pain is relieved by rest and reoccurs if the patient resumes activity. The pain is due to the arteries’ inability to meet the metabolic demands of the exercising muscle.

Rest Pain

As occlusion worsens, the blood supply is not sufficient to supply the demands of even the resting muscle and pain develops even when not active. Pain is constant but usually worse at night when other distracting stimuli are at a minimum. Night pain may lessen if the legs are allowed to dangle off the bed, which allows more blood to enter the extremity. Night pain relieved by walking indicates a venous problem.

Gangrene

Death of tissue, associated with loss of vascular supply. Dry gangrene occurs gradually as a result
of occlusion of blood supply and is not usually associated with bacterial infection. Wet gangrene is the result of sudden stoppage of blood (burns, freezing, embolism) with subsequent bacterial infection.

NONINVASIVE VASCULAR STUDIES

Serial Pressures

What toe pressure in diabetics is associated with healing wounds?

>55 mm Hg: Healing

45-55 mm Hg: Range of uncertainty

<45 mm Hg: No wound healing

At least 30 mm Hg required for healing of a wound on the digits

Ankle/Arm Index (a.k.a. Ankle/Brachial Index, Ischemic Index)

Used to predict the severity of peripheral arterial disease by taking the ratio of the lower leg blood pressure over the arm blood pressure. These values should be the same, making the ratio equal to 1. Values of 0.5 to 0.8 are associated with intermittent claudication, and less than 0.5 are associated with rest pain and ulcers. Values greater than one indicate calcified vessels.

Technique

Determine brachial systolic pressure.

Determine ankle systolic pressure.

Place BP cuff just above ankle and elevate until no arterial pulsation can be heard through Doppler over posterior tibial artery. The point at which arterial sound returns is the systolic pressure of the artery. Repeat on the dorsalis pedis and peroneal artery. The highest of the three values is used as the ankle systolic pressure.

Divide ankle systolic by arm systolic.

Doppler

The Doppler uses ultrasound with an audible output, which the physician uses for interpretation of the velocity and flow pattern.

Normal arteries: Sharp, high-pitched sound, bi- or triphasic. The second sound represents backward flow. Small digital arteries may be monophasic because they are too small and blood flow at this level is too smooth for backward flow.

Abnormal arteries: Monophasic, lower-pitched, longer “swishing” sound. This indicates an occluded vessel or collateral flow.

Elevation-Dependency Test

In an ischemic foot, elevation of the foot produces pallor, while having the foot in the dependent position produces erythema. Be careful not to note color change due to venous blood, which will produce a false-positive. Patients with severe ischemia may not have erythema on dependency due to occlusion.

Exercise Test

Record pedal blood pressure, with foot at heart level, and then elevate leg to 30°. Against slight resistance, dorsiflex and plantarflex foot for
1 minute (at a rate of around 1 cycle per second). Return leg to heart level and record pedal BPs again every 30 seconds for 2 minutes.

Explanation

The reason for the drop in pressure is that the blood going into the foot is diverted to the exercising calf muscles where there is less resistance to flow.

5-Minute Reactive Hyperemic Test

Pt lies supine with legs raised 30°, and foot is dorsiflexed and plantarflexed several times to empty venous blood. Apply ankle cuff; inflate to 100 mm Hg above ankle systolic pressure. Place foot at heart level. After 5 minutes, quickly deflate cuff. Time the interval between cuff let down and color return to foot.

Results

Normal: Color returns almost instantaneously, with maximum erythema occurring at approximately 1 minute. Foot should be uniformly erythematous.

Vasospastic disease: Return of color is uniform, but slightly delayed especially in toes (5 to 8 seconds). Maximum erythema takes approximately 2 minutes and may be markedly erythematous.

Organic occlusive disease: Return of color is not uniform and requires at least 15 seconds to reach toes. Maximum erythema exceeds 2 minutes, and the amount of erythema is less than normal.

Perthes Test

The Perthes test is used to detect deep vein valvular incompetence.

A tourniquet is placed around the elevated leg and inflated to 30 to 60 mm Hg to occlude superficial venous flow. The tourniquet is placed at midthigh or proximal calf level to obstruct superficial veins.

The patient is asked to walk. The purpose of walking is to assess muscle pumping function on the deep veins, which may help to evacuate blood or, with incompetent valves, may accentuate the abnormal flow through perforators into the varicosities.

Trendelenburg Maneuver

This test is used to differentiate between deep and superficial venous incompetence.

Technique

Elevate the leg to empty venous blood. Place the tourniquet around the upper thigh at a pressure of 30 to 60 mm Hg to occlude superficial venous flow. Have the patient stand.

RAYNAUD’S DISEASE/PHENOMENON

Paroxysmal vasospasm of the digits in response to cold or emotional stress resulting in digital ischemia. Raynaud’s phenomenon is a condition that develops secondary to another disease such as occlusive arterial disease, connective tissue disorders especially scleroderma, neurogenic disorders, drugs, or exposure to chemicals. Raynaud’s disease is a primary disorder of unknown origin. Raynaud’s phenomenon is more common in females. Raynaud’s disease is more gradual onset and tends to be more bilateral and symmetrical than Raynaud’s phenomenon.

ARTERIAL INSUFFICIENCY

Arteriosclerosis Obliterans (ASO, Arteriosclerotic Occlusive Disease)

Description

Arteriosclerosis in which proliferation of the intima of small vessels has caused complete obliteration of the lumen, causing an insidious development of tissue ischemia.