Indian Journal of Thoracic and Cardiovascular Surgery 1985-86; 4:13-18

Doppler Ultrasound - A Noninvasive Technique for the Evaluation of Chronic Lower Extremity Arterial Insufficiency RAJENDRA PATIL', MILON KARMAKAR +, AM PATWARDHAN ~', AP CHAUKAR*

ABSTRACT -" A pre l iminary report on the Dopp le r u l t r asound survey o f 96 lower ex t remi t ies

(16 normal and 80 with chronic arterial occ lus ive disease) is p resen ted to prove the

e f f i cacy o f non invas ive d iagnos i s o f an arterial occ lus ion and its h a e m o d y n a m i c signif i-

cance. T h o u g h Dopp le r u l t r asound is not a subst i tute for c l inical a r t e r iography , it has

been found to be an exce l len t addi t ional pa ramete r to c o m p l e m e n t the ana tomic in fo rma t ion

providcd by a r te r iography, a l lowing one to select the candida tes for e i ther vascular

recons t ruc t ion or conserva t ive m a n a g e m e n t and for subsequen t per iodic fo l low up studies.

KEY woRos : arterial occlusive diseases, doppler ultrasound, hemodynamics, ultrasonics.

INTRODUCTION

In the clinical management of chronic vascular occlusive disease of the lower extremity, arterio- graphy is accepted as a relatively safe, effective and widely used investigative facility. However, it is an invasive, expensive and time consuming procedure which cannot be repetitively performed as an indicator of therapeutic response. Further, it offers little help in assessing the functional signifi- cance of vaso-occlusive lesions. The Doppler ultrasonic technique of studying the velocity

�9 Lecturer, +Registrar. ~ Reader, *Professor and tIead of the Department.

From the Department of Cardiovascular and Thoracic Surgery, LTM Medical College and Hospilal, Bombay, India.

Address for correspondence : Dr. Rajendra Patil, Lecturer in Cardiovascular and Thoracic Surgery, LTM Medical College, Sion, Bombay 400 022. India.

patterns of vascular blood flow is a noninvasive aid which fulfils these lacunae. It effectively plays a complemeptary role without being a substitute for preoperative arteriography.

This paper is based on the clinical application of this technique in 16 normal and 80 diseased lower extremities. The efficacy of this procedure in the clinical set up is highlighted.

MATERIAL AND METHODS

In this study of noninvasive evaluation of chronic vascular occlusive disease of lower extremity, a Sonicaid BV 381 model of directional blood velocimeter was used with a transmitting frequency of 8 MHZ.

Sixteen lower limbs in 8 normal healthy males (age 17-32 years) without any symptoms of vascu- Iar insufficiency of lower extremity were surveyed with the Doppler ultrasound velocimeter and the

14 Patil et al

results were compared with those of 55 patients (age 22-80 years) presenting with symptoms and signs of vascular insufficiency of lower extremity. These patients, with a total of 80 diseased lower extremities, were clinically divided into 5 grades of vascular insufficiency as per the criteria laid down by CranleyL Fourteen (25%) of them were diabetics and 40 (73%) were chronic smokers against 3 smokers and no diabetic in the normal control group.

All the subjects were examined in resting supine position. By placing the ultrasound transducer over the femoral, posterior tibial and dorsalis pedis arteries with an angle of 45 ~ towards the direction of blood flow, the characteristic of Doppler shift flow signals were noted and the velocity waveforms recorded.

A standard blood pressure cuff (12.5 x 30 cms) was applied around the arm and the systolic pressure was noted as the point of return of audible signals during slow deflation of the cuff with the transducer over the brachial artery. Similarly by applying the cuff around the upper thigh, above knee, below knee and above ankle, the segmental systolic pressures were recorded over the posterior tibial and dorsalis pedis arteries.

The ratio of ankle pressure to the brachial pressure i.e., ankle pressure index (API) was calculated. Similarly pressure indices were calculated at other levels. The longitudinal p~essure gradient across each segment of the lower extremity viz., upper thigh to above knee, above knee to below knee and below knee to ankle was noted and compared with the normal.

The 80 ischaemic extremities were divided into 3 groups, according to the information obtained by clinical examination and confirmed by Doppler ultrasound survey (Table I).

Arteriography was done in a total of 11 patients from the diseased group to correlate the anatomic findings with the information obtained by this non- invasive technique and to evaluate the possibility of vascular reconstruction.

OBSERVATIONS

From the Doppler ultrasound survey of 16 normal and 80 ischaemic extremities, information was obtained in the form of audible signals, flow velocity waveforms and segmental systolic pressures.

The semiquantitative grading of the audible flow signals was done (Table II) as described by Thulesius and Gjores 2.

Waveforms obtained from normal arteries coincide with the three sounds produced by the cardiac cycle and are triphasic in form. The first major deflection represents forward flow during systole; negative deflection is caused by reverse flow during early diastole and the third deflection indicates the return to forward flow. The qualitative analysis and the significance of the waveforms, obtained during the Doppler survey of ischaemic extremities is enumerated in Table III.

The mean segmental systolic pressures, interseg- mental gradients as well as thigh and ankle pressure

TABLE I Classification of ischaemic extremities according to the information obtained by Doppler ultrasound survey

Doppler ultrasound 15

TABLE II Semiquantitative grading of blood flow velocity signals

TABLE III Qualitative analysis of blood flow velocity waveforms

indices measured in normal control group and the diseased group are summarised in Table IV. The brachial-thigh gradient in aortoiliac group was reversed significantly (mean +36) which indicated occlusive lesion proximal to the femoral artery. Similar pattern was noted in femoropopliteal and infrapopliteal occlusion. In Group C there was marked drop in all the segmental pressures especially ankle pressure.

The resting API correlated well with the level of vascular occlusion (Fig. 1) and the degree of vascular insufficiency (Fig. 2).

Clinical arteriography done in 11 patients, 6 from aortoiliac and 5 from femoropopliteal group confirmed the noninvasive diagnosis in all but one patient who had multilevel occlusive disease in both lower extremities.

DISCUSSION

The application of Doppler ultrasound technique has emerged ~ one of the most useful and promising

TABLE IV Haemodynamic data obtained in normal and diseased groups

AK-above knee, BK-below knee

16 Pmil et al

I . I RESTING ' ' I No,mo~ ~ C~oue,co,,o,. I R,s, poin I GonQre.e I J

ANKLE PRESSURE INDEX (Ankle systolic B.P./Arm systolic B.P.) ~I'~F ~'''

Meon ~ 0 3 0 " 7 0':55 0 2 / ~ _ _ L _ _ L 1 / I

I ~ I I L . . . . . . . . . , . . . . . . . . . Fig.2 Correlation between the resting ankle pressure

Normol Popliteot Aor'~od~oe MuHdevel index and the degree of vascular insufficzency 8, Below Knee

. . . . . LOCATION OF DISEASE

continuous mixed high and low frequency sounds, lacking pulsatility. Thumping signals with marked Fig.1 Corret.ation between the resting ankle pressure

index and the leve[ of vascular occlusion

noninvasive studies of the lower extremity vascular insufficiency due to chronic occlusive disease. This noninvasive technique in a vascular laboratory pro- vides information in the form of (a) audible signals varying in pitch with velocity, (b) meter readings with direction of blood flow and (c) blood velocity waveforms for analysis and documentary record.

In the present study the severity of arterial insufficiency was estimated by clinical findings and by Doppler ultrasound technique. Out of 11 patients subjected to preoperative arteriography (6 translum- bar aortograms and 5 femoral arteriograms), 10 showed absolute correlation with the noninvasive diagnosis. The sole exception was a diabetic who had diffuse multilevel disease. Delius and Erikson -~ showed 95 per cent correlation between angiogra- phic and haemodynamic findings in vascular occlusions. The fallacies included patients with severe diabetes and multilevel occlusions. The limitations of using pulse as an indication of blood flow are two, viz., (a) there may be excellent blood flow in the absence of a palpable pulse due to collateral circulation and (b) in a pulsating artery, blood flow may be absent if occlusion is only 1 mm distal to the point of pulsations.

The collateral flow in the distal arteries with proximal occlusion is indicated by a low pitched signal and a monophasic attenuated velocity waveform. A turbulent flow is indicated by

attenuation of reverse flow in a velocity waveform are obtained from a strong pulse proximal to an obstruction.

The measurement of ankle systolic pressure and API are very useful parameters for the evaluation of peripheral arterial disease. The resting mean ankle pressure value in normal subjects was found to be 128 mm Hg (range 110-150) with a mean API of 1.03 (range 0.92-1.18). The API value obtained by Fronek et al 4 and Cutajar et al ~ using a standard cuff size of 12.5 • 30 cms was 1.08+0.09 and 1.08 + 0.10 respectively.

In this study the APl.values were highest in the femoropopliteal and infrapopliteal group (B) with a mean of 0.66 (0.26-1.07) and lowest in the multilevel disease group (C) with a mean of 0.24 (0.0-0.46). Carter z found that the API was highest (more than 0.5) when the lesion was confined to the femoropopliteal or below knee arteries and with a single block, in 85 per cent of patients. In 95 per cent it was found less than 0.5 with two or more blocks. In our study the API was less than 0.5 in 21 per cent of cases in Group A and 20 per cent in Group B.

The API also correlates well with the degree of functional severity of the disease process. In patients with intermittent claudication the values were highest with a mean of 0.7 (0.47-1.07). Lowest values of API were found in patients with gangrene in the range of 0 to 0,4, with a mean ankle pressure

Doppler ultrasound 17

of 36 mm Hg (range 20--48). In a documented 7 study of 326 limbs with a correlation between API and functional impairment, the intermittent claudication group showed an API of 0.59+0.15 and the gangrene group 0.05_+0.08 (0.0-1.3).

The absolute level of ankle pressure is also important. Rest pain, ischaemic ulcers and gangrene seldom occur when the ankle pressure exceeds 50 mm Hg, unless there is an additional pedal or digital arterial disease 8. Symptoms are common when this pressure falls below 40 mm Hg. Sumner and Strandness 9 found that 71 per cent of pa- tients with rest pain had ankle pressure less than 40 mm Hg and only 13 per cent had ankle pressure exceeding 50 mm Hg. In our study, 22 (71%) out of 31 with rest pain and gangrene had ankle pressure less than 40 mm Hg and in 21 per cent it was more than 40 mm Hg. Thus patients with ankle pressure above 50 mm Hg can usually be assured that gangrene is not imminent.

Ankle pressure is also valuable in predicting the healing of the lesions. Raines and Darling t~ found that lesions of the foot and toes are unlikely to heal if the ankle pressure is less than 65 mm Hg in nondiabetic patients or less than 80 mm Hg in diabetic patients. The prospects of wound healing are better when the ankle pressure is more than 65 mm Hg in nondiabetic and more than 90 mm Hg in diabetic patients.

Since API is quite stable from one examination to the next in the same individual, provided there has been no change in the obstructive process, it provides a very effective means of following the patients' course. A consistent decrease in AP1 always indicates worsening of the obstructive process while a spontaneous increase suggests development of collateral circulation.

The measurement of segmental systolic pressures and their longitudinal and horizontal comparison gives information about the site of occlusion and its functional significance.

Cutajar e t a l 5 report that a thigh pressure equal to or lower than the brachial pressure indicates significant aortoiliac obstruction, the normal thigh

pressure being 30-40 mm Hg above the brachial pressure due to the cuff size. When the thigh pressure index (TPI) is between 0.80 and 1.20, aortoiliac occlusive disease is usually present, though not complete (Fig.3). TPI below 0.80 suggests complete aortoiliac occlusion. Between any two levels in the leg the pressure gradient of 30 mm Hg or more strongly suggest a significant degree of arterial obstruction 4"~ ~. A horizontal difference of more than 20 mm Hg at the same segmental level implies greater disease at or above this level in the leg with lower pressure.

O ~ 4.40 130 ?.,J 130

_ i

L E F T AORTO-ILIAC BLOCK

t40 I 1 98 80

63

60

BRACHIAL S', 'STOLIC=120mrn/Hg

Fig. 3 Segmenm! systolic pressures ~,~/ Hw lower eatremifies ~h'picting Is aorloiliac occ/u,~iYm

In a study of 16 normal extremities the mean brachial-thigh pressure gradient was -25 mm Hg which is comparable to the values obtained by others ~2. The longitudinal gradients were below +I0 mm Hg which is also comparable with reported values j-'.

C O N C L U S I O N S

�9 l)oppler ultrasound is an excellent noninvasive diagnostic tool for the evaluation of lower extremity with chronic arterial occlusive disease.

�9 Using audible signals, llow velocity wavefomls and systolic pressure measurement, the presence of any significant arterial occlusion can be confirmed or denied instantly.

18 Patil et al

�9 It gives important objective data regarding the level and haemodynamic severity of the occlusive lesion, enabling one to select patients for arterial reconstructive surgery, avoiding a misadventure on the operation table.

�9 The procedure is simple, can be used repetitively and gives a bard copy objective baseline for the subsequent follow up studies, either postoperatively or after conservative management.

�9 It is not a substitute for preoperative arteriography, but an additional parameter to complement the anatomic information provided by arteriography.

References

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2. THULESIUS O, GJORES JE. Use of Doppler detector for determining peripheral arterial blood pressure. Angiology 1712; 22: 594-603.

3. DELIUS W, ERIKSON V. Correlation between angio- graphic and hemodynamic findings in occlusion of arteries of the extremities. Vasc Surg 1969; 3: 201-9.

4. FRONEK A, GOEL M, BERNSTEIN EF, Quantitative ultrasonographic studies of lower extremity flow

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CUTAJAR EL, MARSTAN A, NEWCOMB JE. Value of cuff occlusion pressures in assessment of peripheral vascular disease. Br Med J 1973; 2: 392-5.

CARTER SA. Indirect systolic pressure and pulse wave in arterial occlusive disease of lower extremity. Circulation 1968; 37: 624-37.

YAO JST. Haemodynamic studies in peripheral arterial disease. Br J Surg 1970; 57: 761-6.

LENNmAN R JR, MACKERETH MA. Ankle pressure in arterial occlusive disease involving the legs. Surg Clin North Am 1973; 63: 657-66.

SUMNER DS, SaXA.~DNESS DE. The relationship between calf blood flow and ankle blood pressure in patients with intermittent claudication. Surgery 1969; 65: 763-71.

RA1NES JK, DARLlNG RG. Vascular laborato~, criteria for the management of peripheral vascular disease of the lower extremity. Surgery 1976; 79: 21-9.

STRAr~DNESS DE JR, McCUTCHF.Or~ EP, RUSHMAR RF. Application of a transcutaneous Doppler formula in evaluation of occlusive arterial disease. Surg Gynecol Obstet 1966; 122: 1039-45.

SUMNER DS. Measurement of segmental arterial pressure. In: Rutherford RB ed. Vascular Surgery. Philadelphia: WB Saunders, 1984: 109-35.