Duplex ultrasound assessment of femorodistal grafts: correlation with angiography

Criteria for identification of the "at-risk" infrainguinal bypass graft

The criteria for identifying the "at-risk" femorodistal bypass are controversial. Eighty-eight patients were entered into a surveillance programme using ankle-brachial pressure indices (ABPI), colour Duplex and intraarterial digital subtraction angiography (IADSA). Changes in ABPI of more than 0.1 identified 12/22 (51%) grafts thought to be "at-risk". In the 88 grafts, a PMV (peak mean velocity) < 45 cm per second had a sensitivity and specificity of 55 and 85% compared to 91 and 95% if a PMV < 45 cm per second and a V2/V1 ratio of greater than 2 was used to identify the 22 grafts "at-risk". In total 341 examinations were performed, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy for impedance analysis was 70, 90, 48, 97 and 91% respectively, compared to 93, 97, 77, 99 and 97% for colour Duplex in identifying the "at-risk" grafts. Between 6 weeks and 12 months the mean PMV was seen to drop by 29% and the mean impedance score by 19%. The most sensitive mode of non-invasive graft surveillance is colour Duplex providing the assessment involves both a measurement of the velocity ratio and the absolute velocity. However, impedance analysis is a better screening test than ABPI and PMV.

Duplex scan surveillance of infra-inguinal bypass grafts: the case for selectivity

A consecutive series of 270 non-reversed infra-inguinal saphenous vein bypass grafts performed by the same surgeon between January 1986 and January 1991 was reviewed. The series included 250 in situ and 20 translocated non-reversed grafts. The aims were to calculate the number of duplex scans that would have been required for surveillance, to determine the value of a non-selective prolonged scanning regimen and to identify subgroups requiring more (or less) intensive surveillance. Indications were for critical ischaemia in 194 patients, popliteal aneurysms in seven patients and incapacitating claudication in 69 patients. Patients were reviewed at 1 month and then at approximate 6 month intervals for symptoms and with resting and post-exercise ankle pressures. Primary patency of grafts placed to a popliteal distal anastomosis for critical ischaemia was 85% (s.e.m. 9.1%) at 3 years while secondary patency was 94% (s.e.m. 8.1%) at 4 years. Primary patency of grafts placed to a tibial artery or isolated popliteal segment was 68% (s.e.m. 8.4%) at 2 years while secondary patency was 76% (s.e.m. 9.9%) at 2.5 years. The difference in secondary patency between popliteal and tibial grafts was highly significant (P = 0.003). Tibial grafts required significantly more secondary early intervention than popliteal grafts. If recommended protocols for serial duplex scan (DS) surveillance had been followed, a minimum of 960 scans would have been required. If the tibial bypass group only had been monitored, 702 of these scans would have been avoided with a maximum loss of one popliteal graft and no limbs.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive assessment of lower extremity arterial disease

Although angiography is the accepted "gold standard" for demonstrating the presence of arterial occlusive disease, it is less accurate for grading the associated hemodynamic consequences and is prohibitively invasive and expensive to be used as a first-line investigation. Currently available noninvasive tests allow not only for the detection of perfusion abnormalities, but for an appreciation of their severity as well as their likely location. This information is invaluable for predicting the need for revascularization, guiding the choice of reconstructive procedure, and predicting the likelihood of healing of amputation wounds and ischemic lesions. Although some obstructive lesions are easily detected, others require more in-depth testing to reveal and quantify. Consequently, a thorough understanding of available noninvasive diagnostic modalities, including both their capabilities as well as their pitfalls, is paramount to the effective practice of vascular surgery.

Duplex ultrasound monitoring of arterial grafts: prospective evaluation in conjunction with ankle pressure indices after femorodistal bypass

Duplex scanning and ankle brachial pressure indices have been used to objectively assess 94 femoro-distal bypass grafts 4-8 weeks postoperatively. Twenty grafts were occluded. Of the 74 patent grafts, three distinct groups could be identified on the basis of the non-invasive examination. Group 1. Patent grafts with no evidence of haemodynamically significant disease. Group 2. Patent grafts with localised disease. Group 3. Patent: haemodynamically failed grafts. Ankle brachial pressure indices alone could not differentiate between occluded grafts and grafts that were patent: haemodynamically failed (group 3), or adequately separate between grafts in groups 1 and 2. Duplex scanning when combined with pressure indices identified patent grafts "at risk" due to the presence of haemodynamically significant disease. Life table analysis demonstrated appreciable differences in event free survival between group 1 grafts and "at risk" grafts (groups 2 and 3). Duplex scanning is ideal for regular postoperative surveillance and complements the use of ankle brachial pressure indices in the follow-up of femoro-distal grafts.