Prospective assessment of the aorto-iliac segment by visual interpretation of frequency analysed Doppler waveforms--a comparison with arteriography

Cine Phase Contrast Angiography of Normal and Diseased Peripheral Arteries

Cine phase contrast angiography (PCA) is a modified MR phase contrast sequence that acquires up to 22 coronal phase images per mean cardiac cycle. The ability of the sequence to visualise local haemodynamics was investigated in 7 normal volunteers and 9 patients with flow disturbances of the peripheral arteries using a 1.5 T imager. Functional flow information provided by coronal cine PCA was correlated with quantitative data obtained by MR flow measurements and vessel morphology confirmed by conventional angiograms. Due to the yet suboptimal image quality, an aortic dissection and 1 of 4 aneurysms could not be depicted morphologically. The temporal pattern of arterial perfusion in cine PCA corresponded with flow velocity versus time data provided by quantitative MR flow measurements. Accuracy and time resolution of cine PCA was thus sufficient to provide functional information on the severity of occlusive vascular disease.

Development of Ultrasound Techniques for Assessment of Aortoiliac Obstructive Disease

The development of ultrasound techniques for assessment of aortoiliac obstructive disease is described. This period started in 1959 with the detection of blood flow with an ultrasonic device. Continuous-wave Doppler devices were designed, and the pulse waves of readily accessible vessels like the common femoral artery were examined. It was soon recognized that the functional status of the aortoiliac arteries could be assessed by the Doppler characteristics of the common femoral artery pulse wave. Qualitative and quantitative methods were used to analyze the femoral Doppler signal. The introduction of duplex scanning made it possible to evaluate the hemodynamics of aortoiliac arteries directly. At present, duplex scanning offers the best method of evaluating the aortoiliac arteries noninvasively.

Strecker Stents in the Femoropopliteal Arteries: Value of Duplex Ultrasonography in Restenosis Assessment

Purpose:

Experience with Strecker stent implantation in the femoropopliteal arteries has been described; however, few of the reports were prospective studies, and none routinely used site-specific assessment methods for follow-up evaluation of stent patency. The purpose of this study was to evaluate 1-year Strecker stent patency using duplex ultrasound imaging to obtain a more precise delineation of stent restenosis than is possible with other noninvasive assessment modalities.

Methods:

A prospective study involved 52 patients with 57 sites treated by angioplasty and Strecker stent deployment in the femoropopliteal arteries. Assessment included clinical evaluation; ankle-brachial index (ABI) measurements at rest and after exercise; and duplex ultrasound imaging preprocedurally and at 3 and 12 months after the intervention.

Results:

All 74 stents were deployed successfully in the 35 occluded arteries and 22 stenotic lesions. Acute reocclusion occurred in 6 (10%). At 3 months, primary patency was 81% and secondary patency 84%. Mean (± SD) ABIs increased from 0.64 ± 0.15 at rest and 0.32 ± 0.17 after exercise to 0.89 ± 0.14 and 0.68 ± 0.23, respectively (p < 0.0001). At 12 months, primary patency was 79%, and secondary patency was 82%. Mean ABIs were 0.82 ± 0.15 at rest and 0.52 ± 0.22 after exercise at 12 months (p < 0.0001 compared with preprocedural ABIs). Analysis of the length of lesion treated showed better results with shorter diseased segments, but this was not statistically significant (p > 0.05). Better outcomes were also obtained when one stent was used rather than two stents at 12 months (p = 0.15), but there was no difference at 3 months (p = 0.3). Thirty-four percent of the stented segments progressed from < 20% stenosis at 3 months to > 50% stenosis at 12 months. Overall, 19 (43%) of 44 segments progressed from < 50% stenosis at 3 months to a > 50% stenosis at 12 months. Restenosis seen at 3 months generally was in the native artery just proximal or distal to the stent, but at 12 months, restenosis was mainly inside the stent.

Conclusions:

Strecker stents at 1-year demonstrated satisfactory patency in the femoropopliteal arteries when deployed for angioplasty salvage or recurrent disease. The 3- and 12-month evaluations obtained with duplex ultrasound provided site-specific hemodynamic data for stent assessment. Resting ankle pressures were a poor index of restenosis.

A case series to describe the clinical characteristics of foot ulceration in patients with rheumatoid arthritis

The aim of this study was to describe the clinical characteristics of foot ulceration in patients with rheumatoid arthritis (RA). Adults with RA and current foot ulceration but without diabetes were recruited. Clinical examination included assessment of RA disease activity, foot deformity, peripheral vascular disease, neuropathy and plantar pressures. Location, wound characteristics and time to healing were recorded for each ulcer. Participants completed the Health Assessment Questionnaire and Leeds Foot Impact Scale. Thirty-two cases with 52 current ulcers were recruited. Thirteen patients (41%) experienced more than one current ulcer: 5 (16%) had bilateral ulceration, 15 (47%) had previous ulceration at a current ulcer site. The majority (n = 33) of open ulcers were located over the dorsal aspect of the interphalangeal joints (n = 12), plantar aspect of the metatarsophalangeal joints (MTPJs) (n = 12) and medial aspect of first MTPJs (n = 9). In ulcerated limbs (n = 37), ankle brachial pressure index (ABPI) was <0.8 in 2 (5%); protective sensation was reduced in 25 (68%) and peak plantar pressures were >6 kg/cm(2) in 6 (16%). Mean ulcer size was 4.84 by 3.29 mm. Most ulcers (n = 42, 81%) were superficial; five (9.6%) were infected. Time to healing was available for 41 ulcers: mean duration was 28 weeks. Three ulcers remained open. In conclusion, foot ulceration in RA is recurrent and multiple ulcers are common. Whilst ulcers are small and shallow, time to achieve healing is slow, posing infection risk. Reduced protective sensation is common in affected patients. The prevalence of arterial disease is low but may be under estimated due to high intolerance of ABPI.

Echocardiographic evaluation of aorto-iliac occlusive disease

Several studies demonstrated feasibility of visual assessment of the common femoral artery Doppler waveform, in an indirect evaluation of aorto-iliac segment stenosis. Patients with cardiac diseases referred for echocardiography often have coexistent arterial pathology. Since many of them are potential candidates for endovascular procedures, we decided to study, whether echocardiography can be useful for detection of aorto-iliac occlusive disease. We evaluated 92 patients with abdominal aortic aneurysm or peripheral artery occlusive disease, referred from the vascular surgery department for cardiac evaluation before surgery. At the end of an echocardiographic examination, evaluation of flow in the distal external iliac arteries with an echocardiographic probe was performed. The Doppler waveform was classified into normal—with early diastolic flow reversal or abnormal—without early diastolic flow reversal. Echocardiographic results were compared in a blinded fashion with reports from computed tomography angiography. Overall there were 58 iliac segments with significant (≥70%) area stenosis or occlusion and 126 iliac segments without significant disease on computed tomography angiography. Abnormal Doppler waveform was found in 56 out of 58 abnormal iliac segments—sensitivity 97%, and normal waveform was found in 106 out of 126 normal iliac segments—specificity 84%. Positive predictive value of abnormal Doppler waveform for significant iliac disease was 74%, and negative predicting value was 98%. Detection of significant stenoses in aorto-iliac segments is feasible with echocardiography. Further studies are necessary to evaluate its potential utility in a population of patients with cardiac disease referred for echocardiographic study.

Confusion of Peripheral Arterial Doppler Waveform Terminology

Characterization of peripheral arterial waveforms is basic to the diagnosis of vascular disease. Surveys indicate inconsistent application of traditional waveform descriptors. This study reviews literature to identify areas of confusion. Publications were reviewed to determine whether triphasic, biphasic, and monophasic terms were defined; if biphasic was linked with diastolic flow reversal; whether pandiastolic flow was associated with biphasic or monophasic terminology; and whether waveform illustrations had a zero baseline. Ninety-four publications were reviewed. Triphasic and monophasic were defined in 81%, biphasic in 48%. Biphasic was classified with flow reversal in 38%. Pandiastolic flow was not addressed in 57% but associated with monophasic in 47% and biphasic in 5%. Twenty-one percent of the publications had an illustration without a zero-flow baseline. This review suggests a lack of consensus when classifying arterial blood flow with traditional waveform descriptors. Waveform characterization inconsistencies are undermining comprehension of Doppler principles and may lead to inappropriate testing. A multisocietal consensus panel should accept responsibility for resolving this issue.

Fourier transformation of arterial Doppler waveforms of the lower extremity

PURPOSE

Although it is well known that the normal, triphasic pulsatile arterial Doppler waveform changes in shape as flow is impaired, interpretation of the waveform has largely been subjective. We aimed to describe the Doppler waveforms of the lower extremity objectively using Fourier transformation.

METHODS

Sixty-eight zero-crossing detector arterial recordings from 25 lower extremities were grouped as follows: group 1, no ischemic symptoms with an ankle-brachial index (ABI) > 0.9 (n = 17, 8 limbs); group 2, no ischemic symptoms with ABI < 0.9 (n = 18, 5 limbs); group 3, symptoms of claudication (n = 19, 7 limbs); group 4, rest pain or tissue loss (n = 14, 5 limbs). The waveforms were Fourier transformed and their amplitudes and phases were compared up to the third harmonic (H3).

RESULTS

Amplitudes of both the fundamental (H1) and second harmonic (H2) were predominant in group 1. In contrast, amplitudes of the H2 and H3 decreased with altered flow (p < 0.0001 for group 1 versus others). The phases of the H1 and H2 were delayed with altered flow (p < 0.05 for group 1 versus others). Phases of the H1 were different between group 2 and 4 (p < 0.05). The difference of phase between the H3 and H1 was shortened with altered flow (p < 0.05 for group 1 or 2 versus group 4). Multivariate analysis revealed that the relative amplitudes of the H2 and H3, the phases of the H1 and H2, and the relative phase of the H3 were significant discriminators among the groups.

CONCLUSION

Abnormal waveforms could be characterized by the predominant amplitude of the H1, phase delay of the H1 and H2, and shortening of the relative phase of the H3. These parameters may be useful in the evaluation of Doppler waveforms in patients with peripheral arterial disease.

Reliability of common femoral artery hemodynamics in assessing the severity of aortoiliac inflow disease

OBJECTIVES

We investigated the utility of color duplex ultrasound (CDU)-derived common femoral artery (CFA) hemodynamics for detecting significant aortoiliac occlusive disease and predicting its severity.

METHODS

From January 1997 to June 2001, 132 consecutive patients with lower extremity arterial insufficiency underwent both femoropopliteal CDU scanning and aortography with runoff studies. CDU-derived CFA waveform contour (monophasic, biphasic, or triphasic), peak systolic velocity (PSV), and acceleration time were recorded for each patient. Severity of aortoiliac occlusive disease was classified by arteriography into three distinct groups: normal or minimal disease (<50%, group 1), significant focal or diffuse stenoses (>/=50%, group 2), or total occlusion (group 3). Using probability and receiver operating characteristic curve analysis, waveform contour and PSV were compared alone and in combination with the arteriographic groups to identify waveform contours and threshold PSV, which may accurately differentiate the three categories of aortoiliac occlusive disease.

RESULTS

Of 214 limbs available for study, 112 composed group 1, 70 composed group 2, and 32 composed group 3. Concomitant femoropopliteal disease was present in 47% of limbs in group 1, 53% of limbs in group 2, and 34% of limbs in group III. An abnormal CFA waveform contour (monophasic or biphasic) differentiated group 1 from groups 2 and 3, with 95% sensitivity, 89% specificity, 89% positive predictive value (PPV), 95% negative predictive value (NPV), and 92% accuracy. Mean PSV and acceleration time for monophasic and biphasic waveforms were 39 cm/sec +/- 19, 178 msec +/- 36 vs 95 cm/sec +/- 67, 97 msec +/- 31 respectively (P <.05). In differentiating between groups 2 and 3, the specificity, PPV, and accuracy for CFA PSV of </=45 cm/sec alone and for the PSV </=45 cm/sec combined with a CFA monophasic waveform were 89%, 76%, 85% and 97%, 92%, 88%, respectively. Concomitant significant superior femoral artery and bilateral iliac disease did not influence these findings.

CONCLUSION

CFA PSV 45 cm/s or less combined with a monophasic waveform is highly predictive of ipsilateral iliac occlusion. These results were independent of contralateral iliac and distal superior femoral artery disease. CFA color duplex US scanning may be considered an alternative technique to direct duplex scanning of the aortoiliac segment in patients being evaluated for inflow endoluminal or bypass procedures.

Screening for aortoiliac lesions by visual interpretation of the common femoral Doppler waveform

OBJECTIVE

to study the accuracy of simple visual interpretation of the common femoral artery Doppler waveform for screening the aorto-iliac segment for significant occlusive disease.

DESIGN

prospective and semi-blinded study. Material ninety-four consecutive and elective patients having arteriography due to chronic lower limb ischaemia, presenting symptoms of severe claudication (23%), ischaemic rest pain (34%) or ischaemic skin lesions (43%).

METHODS

one day prior to conventional arteriography a Doppler waveform was obtained in the common femoral artery. Based on visual interpretation, the waveforms were immediately categorised as normal or abnormal. Comparison with single plane arteriography with respect to significant aorto-iliac occlusive disease was undertaken.

RESULTS

visual Doppler waveform interpretation had a sensitivity of 98% (95% CI: 90-100%), a specificity of 81% (CI: 67-90%), a positive predictive value of 86% (CI: 75-93%) and a negative predictive value of 97% (CI: 86-100%) for prediction of significant aorto-iliac occlusive disease using conventional arteriography as the gold standard. The kappa value for the agreement between Doppler waveform interpretation and arteriography was 0.81 (0.68-0.93), representing very good agreement.

CONCLUSION

a normal common femoral Doppler waveform can safely exclude significant upstream aorto-iliac lesions and is a useful timesaving screening tool in the busy vascular laboratory. The method is well tolerated, easy to perform and requires no additional equipment.

A comparison of colour duplex ultrasonography, papaverine testing and common femoral Doppler waveform analysis for assessment of the aortoiliac arteries

OBJECTIVE

to study the "accuracy" of aortoiliac colour duplex ultrasonography.

DESIGN

prospective study.

SETTING

vascular laboratory, University Hospital.

METHODS

a total of 25 aortoiliac stenoses were studied in 23 patients. For each iliac segment, colour duplex ultrasound, papaverine testing, hyperaemic common femoral Doppler waveform analysis and hyperaemic testing using a thigh pressure cuff were performed. A velocity ratio of two was used to indicate a significant 50% diameter-reducing stenosis, but the velocity differences across stenoses as well as various characteristics of the hyyperaemic common femoral waveform were also studied. Retrospective receiver-operator characteristics and Kappa values were used for analysis.

RESULTS

the Kappa agreement between ultrasonography and papaverine testing was 0.12 using peak systolic velocity ratios and 0.8 using hyperaemic peak systolic velocity differences. Hyperaemic common femoral pulsatility (PI) and resistance index (RI) both gained a Kappa level of 0.60. The reactive hyperaemia produced by a thigh cuff was more pronounced than that produced by papaverine.

CONCLUSION

although the velocity ratio did not appear to perform well against the papaverine test, its apparent over-sensitivity calls into question the sensitivity of papaverine testing itself. The hyperaemic velocity difference at the stenosis or the hyperaemic PI or RI at common femoral level appear useful, non-invasive indicators of significant aortoiliac arterial disease.

The ability of qualitative assessment of the common femoral Doppler waveform to screen for significant aortoiliac disease

OBJECTIVE

To study the ability of a qualitative assessment of the common femoral Doppler waveform to screen for significant aortoiliac disease.

DESIGN

Prospective, semi-blind study.

SETTING

Vascular laboratory, University Hospital.

METHODS

A total of 118 aortoiliac segments were studied in 73 patients. Each aortoiliac segment was graded as normal or abnormal from visual interpretation of the common femoral Doppler waveform obtained by colour duplex ultrasound. Full ultrasound assessment of the aortoiliac vessels acted as the "gold standard". Abnormal aortoiliac segments were defined by the presence of at least one > or = 50% diameter reducing lesion, whereas vessels considered "normal" included those with disease between 0-49% diameter reduction. An increase in peak systolic velocity of two-fold or greater was used to define a > or = 50% diameter reducing stenosis. Agreement between common femoral waveform analysis and the duplex scans was measured by the Kappa statistic.

RESULTS

The Kappa value for the agreement between common femoral waveform analysis and duplex scans was 0.74 (95% CI; 0.62-0.86). This represents substantial agreement. Doppler waveform analysis had a sensitivity of 95%, specificity of 80% and accuracy of 87% for the prediction of a significant aortoiliac stenosis seen by ultrasound.

CONCLUSION

Visual interpretation of the common femoral Doppler waveform is a sensitive and accurate technique for the prediction of significant aortoiliac stenosis. It is of particular value when full ultrasound aortoiliac assessments are not feasible due to time constraints, obesity or the presence of bowel gas.

Colour flow duplex imaging of occlusive arterial disease of the lower limb

BACKGROUND

The development of duplex ultrasonography and colour flow imaging has greatly extended the scope of non-invasive assessment of lower limb arterial disease. This review questions whether recent advances might allow colour duplex imaging to displace arteriography as the primary imaging modality for native vessel occlusive disease.

METHODS

A literature review was carried out based predominantly on a Medline database search of English language publications from 1985 to 1996.

RESULTS

Increasing evidence indicates that colour duplex ultrasonography can accurately image the lower limb native arterial tree, and that colour duplex imaging can replace diagnostic arteriography in a large proportion of patients.

CONCLUSION

Arteriography should no longer be considered the gold standard of imaging of peripheral arterial occlusive disease. Future studies should concentrate on the efficacy of colour duplex sonography in guiding clinical decision making.

Colour-coded duplex imaging can safely replace diagnostic arteriography in patients with lower-limb arterial disease

The purpose of this study was to review the outcome of adopting colour-coded duplex ultrasonography as the primary imaging modality in patients with symptomatic lower-limb arterial disease. Over a 12-month period 467 consecutive lower-limb duplex scans were performed of which 437 (94 per cent) were technically adequate. Of the 467 limbs, 184 (39 per cent) were managed conservatively, 230 (49 per cent) were referred for percutaneous transluminal angioplasty (PTA), 41 (9 per cent) underwent reconstructive surgery and 12 (3 per cent) required diagnostic arteriography. In patients referred for PTA there were only 22 (10 per cent) unexpected findings; there was agreement about superficial femoral artery occlusion length in 95 (89 per cent) of 107 limbs and about the presence or absence of a superficial femoral artery stump in 91 (85 per cent) of 107 cases. In patients referred for surgery there were no unexpected findings. Colour-coded duplex imaging can safely replace diagnostic arteriography in up to 97 per cent of lower limbs with arterial disease.

Colour duplex ultrasonography versus angiography in the diagnosis of lower-extremity arterial disease

Colour duplex scanning is reported to be an accurate non-invasive tool for the diagnosis of lower-extremity arterial disease. The authors at the South Coast Vascular Laboratory have conducted a prospective audit to determine the efficacy of colour duplex scanning in a vascular surgical practice. The aims of this prospective trial were to compare the accuracy of colour duplex scanning with intra-arterial digital subtraction angiography (DSA) in the localization and classification of aortoiliac and femoropopliteal artery disease. Ninety-one lower limbs in 50 patients were evaluated independently by colour duplex scanning and DSA. The lower-limb vasculature was divided into eight segments: infrarenal aorta, common iliac artery, external iliac artery, common femoral artery, proximal, middle and lower thirds of the combined length of the superficial femoral and above-knee popliteal artery, and lastly the below-knee popliteal artery. A total of 558 arterial segments were examined. The Kappa value of duplex scanning compared with 'gold standard' DSA was 0.57. For detecting haemodynamically significant arterial lesions of > 50% reduction in diameter, duplex scanning had a sensitivity of 75%, specificity of 90%, positive predictive value of 77% and negative predictive value of 89% compared with DSA. The level of accuracy obtained does not support the use of duplex as a sole method of investigation for lower-extremity arterial disease in the authors' case. However, the high negative predictive value of colour duplex may be useful in excluding haemodynamically significant disease. This study emphasizes the importance of prospective auditing to determine individual accuracy with duplex examination for arterial disease, and enables clinical decision making to be based on tests with a known accuracy.

MR pulsatility measurements in peripheral arteries: preliminary results

Phase contrast flow velocity measurements were performed in six healthy volunteers and 30 patients with arteriosclerotic disease. The iliac arteries were investigated in 8 cases and the femoral arteries in 28 cases. In the first 24 patients, 16 evenly distributed data sets were acquired during one cardiac cycle. In the last 12 patients, a trigger pulse followed by the acquisition of 30 evenly distributed data sets was applied every second heart beat. This procedure allowed data to be acquired over a full heart cycle without any acquisition gap. The measured flow velocities were displayed as function of time. Systolic acceleration, postsystolic deceleration and pulsatility of flow velocity were calculated and compared with stenosis grades determined from DSA angiograms. Flattening of the flow velocity patterns was found to correlate with the local severity of arteriosclerotic disease.

Postocclusive hyperaemic duplex scan: a new method of aortoiliac assessment

Aortoiliac duplex scanning, while accurate, is time-consuming and technically demanding. This study aimed to develop a fast, non-invasive screening test for aortoiliac disease. Colour duplex scanning was used to record common femoral Doppler ultrasonographic waveforms following 3 min of arterial occlusion using a thigh cuff in 25 patients with normal aortoiliac segments and 25 patients with significant aortoiliac disease. The latter patients had a prolonged period of postocclusive hyperaemic flow compared with the former. End diastolic velocity, 70 s after cuff release, was a significant discriminant between the two groups (sensitivity of 88 per cent, accuracy of 92 per cent). The postocclusive hyperaemic duplex (PHD) test performed well when used prospectively in a further 50 limbs (sensitivity of 86 per cent, accuracy of 84 per cent). The test was more sensitive than femoral pulse palpation and compared favourably with arteriography. The PHD test provides a simple, noninvasive assessment for aortoiliac disease that can be performed on the initial outpatient clinic visit.

Strecker stents in the femoropopliteal arteries: value of duplex ultrasonography in restenosis assessment

PURPOSE

Experience with Strecker stent implantation in the femoropopliteal arteries has been described; however, few of the reports were prospective studies, and none routinely used site-specific assessment methods for follow-up evaluation of stent patency. The purpose of this study was to evaluate 1-year Strecker stent patency using duplex ultrasound imaging to obtain a more precise delineation of stent restenosis than is possible with other noninvasive assessment modalities.

METHODS

A prospective study involved 52 patients with 57 sites treated by angioplasty and Strecker stent deployment in the femoropopliteal arteries. Assessment included clinical evaluation; ankle-brachial index (ABI) measurements at rest and after exercise; and duplex ultrasound imaging preprocedurally and at 3 and 12 months after the intervention.

RESULTS

All 74 stents were deployed successfully in the 35 occluded arteries and 22 stenotic lesions. Acute reocclusion occurred in 6 (10%). At 3 months, primary patency was 81% and secondary patency 84%. Mean ( +/- SD) ABIs increased from 0.64 +/- 0.15 at rest and 0.32 +/- 0.17 after exercise to 0.89 +/- 0.14 and 0.68 +/- 0.23, respectively (p < 0.0001). At 12 months, primary patency was 79%, and secondary patency was 82%. Mean ABIs were 0.82 +/- 0.15 at rest and 0.52 +/- 0.22 after exercise at 12 months (p < 0.0002 compared with preprocedural ABIs). Analysis of the length of lesion treated showed betted results with shorter diseased segments, but this was not statistically significant (p > 0.05). Better outcomes were also obtained when one stent was used rather than two stents at 12 months (p = 0.15), but there was no difference at 3 months (p = 0.3). Thirty-four percent of the stented segments progressed from < 20% stenosis at 3 months to > 50% stenosis at 12 months. Overall, 19 (43%) of 44 segments progressed from < 50% stenosis at 3 months to a > 50% stenosis at 12 months. Restenosis seen at 3 months generally was in the native artery just proximal or distal to the stent, but at 12 months, restenosis was mainly inside the stent.

CONCLUSIONS

Strecker stents at 1-year demonstrated satisfactory patency in the femoropopliteal arteries when deployed for angioplasty salvage or recurrent disease. The 3- and 12-month evaluations obtained with duplex ultrasound provided site-specific hemodynamic data for stent assessment. Resting ankle pressures were a poor index of restenosis.

Phase-contrast pulsatility measurements: preliminary results in normal and arteriosclerotic iliofemoral arteries. Work in progress

Magnetic resonance (MR) flow measurements were obtained in six healthy volunteers and 30 patients with arteriosclerotic disease with a 1.5-T imager and a pulse sequence for flow quantification based on flow-induced phase shifts. The iliac arteries were investigated in eight and the femoral arteries in 28 subjects. A trigger pulse, followed by the acquisition of 30 evenly distributed data sets, was applied every second heartbeat, thus eliminating any acquisition gap in a full heart cycle. For quantitative analysis, flow velocity was plotted as a function of time. Systolic acceleration, postsystolic deceleration, and pulsatility of flow were calculated and compared with stenosis grades determined from recent intraarterial digital subtraction angiograms. The flattening of the temporal flow patterns correlated with local severity of vascular occlusive disease.

Presentation of colour flow maps of the peripheral circulation

The use of continuous wave Doppler ultrasound for lower limb arterial assessment is a well established technique in most district hospitals. Patients found to have disturbances in blood flow attributable to arterial plaques are often referred for arteriographic visualization of the disease with its inherent risks and complications. The availability of colour flow mapping on modern ultrasound scanners provides a non-invasive way of detecting the size and extent of these plaques and, in some institutions, is replacing arteriography. One possible disadvantage of the use of colour flow mapping is that it does not provide a permanent record showing the relationship of the plaques to the patient's gross anatomy in the same way as arteriography. This may limit the acceptability of this technique. At Lincoln work was undertaken to develop a system for presenting images of a whole segment of a limb simultaneously along with the associated blood velocity spectrum. This was performed first by hand and then a suite of computer software was developed to automate the process. Comparisons were made between the ultrasound based images and arteriography, showing the techniques to be of similar diagnostic value. The technique provides composite images showing anatomical detail, blood flow and velocity spectra for ease of interpretation. Further studies will be undertaken in order to define patient groups where diagnostic arteriography can be avoided.

Limitations of ultrasonic duplex scanning for diagnosing lower limb arterial stenoses in the presence of adjacent segment disease

PURPOSE

The purpose of this study was to provide a quantitative evaluation of the effect of adjacent segment lesions on disease classification in lower limb arteries by ultrasonic duplex scanning.

METHODS

Lower limb arterial duplex scanning from the distal aorta to the popliteal artery was performed in 55 patients. Arterial lesions evaluated by visual interpretation of Doppler spectra were compared blindly with those measured by angiography.

RESULTS

To recognize severe stenoses (50% to 100% diameter reduction) in any arterial segment, duplex scanning had sensitivity and specificity rates of 74% and 96%, respectively. However, sensitivity and specificity rates increased to 80% and 98%, respectively, when there was no 50% to 100% diameter-reducing lesion in adjacent segments, whereas they decreased to 66% and 94%, respectively, when there was at least one 50% to 100% diameter-reducing lesion in adjacent segments. Moreover, among the 48 duplex misclassifications underestimating or overestimating the degree of arterial stenoses, 30 (62.5%) involved a segment with at least one 50% to 100% lesion in adjacent segments. The segments mostly affected by proximal and distal arterial lesions were the popliteal arteries and the common and deep femoral arteries, where it was found that 86% (24/28) of the misclassifications involved the presence of either proximal or distal severe stenoses.

CONCLUSION

The results demonstrated that the presence of multiple stenoses was an important limitation of duplex scanning for the detection and quantification of lower limb arterial disease.

Monitoring of recovery following exercise in the Doppler ultrasound evaluation of lower limb arterial disease

Measurement of the ratio of ankle to brachial systolic blood pressure (pressure index) is an integral part of the Doppler ultrasound investigation of lower limb arterial disease. The recovery of this index following exercise gives further information regarding the clinical significance of the disease. However, serial sphygmomanometry may prolong recovery time by intermittent reduction of blood flow and for certain categories of patients the technique may prove impossible or will lead to unreliable results. The aim of this study was to investigate the use of Pourcelot's Resistance Index, measured from the Doppler blood velocity spectrum, as an alternative means of monitoring recovery. The results show that peripheral resistance is likely to fall following pressure measurement, indicating a potential effect on recovery time. There is reasonable correlation between post-exercise pressure and resistance indices (r = 0.69, P less than 0.001), and good correlation between their recovery times (r = 0.84, P less than 0.001) with no systematic deviation. Resistance index is therefore a viable alternative to pressure index for the monitoring of post-exercise recovery, and overcomes the problems associated with sphygmomanometry.

Hemodynamic assessment of aortoiliac segment

Routine noninvasive tests often fail to identify advanced aortoiliac stenosis, especially in cases with multilevel disease. At present, direct measurements of femoral artery pressure provide the best assessment of the hemodynamic effect of a proximal lesion, especially when flow is increased in order to simulate exercise. In the future, duplex scanning may replace invasive pressure studies.

A computer controlled flow phantom for generation of physiological Doppler waveforms

A flow phantom for the generation of physiological Doppler waveforms is described. The suspension of scattering particles is driven by a gear pump powered by a stepping motor. The speed of the stepping motor is controlled by a BBC microcomputer. The waveform shape is selected from a library of waveforms from disc. Use of the microcomputer allows the waveform shape and mean flow to be easily changed. Sephadex particles suspended in a solution of glycerol were used as artificial blood. Thin walled heat shrink tubing which had been moulded around metal rods was used. Distortions in the waveforms caused by reflections from the end of the tubing were largely removed by reducing the pipe diameter to half of its value for 30 cm from the end of the pipe. There was good agreement between the control waveforms and the Doppler waveforms over a wide range of waveform pulsatility.

Quantitative Doppler ultrasound evaluation of occlusive arterial disease in the lower limb

Forty consecutive patients with lower limb arterial disease were evaluated using a multi-gated pulsed Doppler system. Doppler signals were sampled at 4 sites in each limb, and following spectral analysis, the pulse rise time (PRT) was measured. The value obtained at the location giving the longest duration of PRT was used for comparison with ankle/brachial pressure index (A/B index) and angiography. A highly significant correlation was found between PRT and A/B index (r = -0.75, P less than 0.001). Based on receiver operating characteristic curves an overall diagnostic accuracy of 90% in diagnosing a pressure reduction greater than 20% was obtained. The diagnostic accuracy in detecting an angiographic stenosis greater than 50% was almost identical. Based on combined quantitative and qualitative analysis of Doppler signals sampled at the common femoral and popliteal artery, the aorto-iliac segments and the femoro-popliteal segments were evaluated separately. Comparison with arteriography revealed overall accuracies of 96% in the aorto-iliac segments and 87% in the femoro-popliteal segments. It is concluded that simple quantitatively measurable parameters in the Doppler spectrum may accurately predict and localize hemodynamically significant arterial lesions of the lower extremities.

Duplex ultrasound assessment of femorodistal grafts: correlation with angiography

Fifty-eight grafts have been assessed using duplex scanning and ankle brachial pressure indices. This assessment is compared with the findings by angiography. Eighteen grafts were occluded and 40 patent. Duplex scanning defined graft status with a greater accuracy than pressure indices. Pressure indices alone would not differentiate "satisfactory" grafts from those with localised, haemodynamically significant disease. Only 55% of those grafts with localised stenoses demonstrated a fall of greater than 0.2 in ankle brachial pressure index after exercise. When the information obtained using pressure indices and duplex scanning was combined non-invasive assessment had a sensitivity of 86% and specificity of 94% for detection of localised, haemodynamically significant disease in patent grafts. Haemodynamically significant disease, as defined by angiography, can be detected and localised with duplex scanning complementing the use of pressure indices in graft assessment.