We routinely performed intravenous dipyridamole thallium imaging and resting radionuclide ventriculography on 190 patients being considered for elective vascular procedures. Patients with thallium ...redistribution underwent coronary arteriography. Patients in group 1 (n = 78) had clinical evidence of coronary artery disease, and patients in group 2 (n = 112) had no history or electrocardiographic evidence of coronary artery disease. The frequency of thallium redistribution was not significantly different in the two groups (45% in group 1 and 46% in group 2). Coronary arteriography identified severe three-vessel or left main disease in eight patients (10%) in group 1 and 16 patients (14%) in group 2. Selection of patients for dipyridamole thallium imaging prior to vascular reconstruction should be based on whether or not documentation of the extent of coronary artery disease would influence therapy rather than on clinical indicators of coronary disease.
Using the framework of E. Emre et al. (1982), an explicit relationship between transfer matrices and (right or left) polynomial fractional representations of linear continuous-time time-varying ...systems is given. The authors also show that the matrix (pI-F) for the time-varying system Sigma =(F,G,H) has a left inverse over a skew ring.< >
To evaluate the need for color duplex surveillance (CDS) for pure in situ bypasses beyond 6 months.
We reviewed our in situ surveillance data from August 1987 to April 1994. Lower-extremity ...revascularization was performed using 245 pure in situ greater saphenous vein bypasses in 219 patients. The CDS of the entire bypass and inflow and outflow arteries was done prior to discharge, at 1 month, every 3 months in the first year, every 6 months in the second year, and annually thereafter. A peak systolic velocity of less than 45 cm/s throughout the bypass or a velocity ratio of greater than 3 (peak systolic velocity at the stenosis divided by peak systolic velocity at an adjacent normal bypass segment) were defined as abnormal during the review of this patient subset. The outcomes were analyzed. Patency and limb salvage rates were calculated by life-table analysis.
The mean age of this population (120 men and 99 women) was 67 years (range, 32 to 97 years). We analyzed all bypasses that were subjected to CDS for 6 months or more and identified 171 such bypasses. These bypasses were followed up for a mean duration of 30 months (range, 6 to 82 months).
The primary and secondary patency and limb salvage rates at 5 years were 60.4%, 89%, and 92.1%, respectively (SE, < 10%). During the first 6 months of surveillance, 54 bypasses had abnormal CDS findings, and 117 had normal CDS findings. Arteriography was performed on 42 of these bypasses with abnormal CDS findings, and 37 had significant findings requiring direct surgical or endovascular intervention. Only two of 117 bypasses that had normal CDS findings for up to 6 months had to be revised later, compared with 43 of the 54 bypasses with abnormal CDS findings prior to 6 months, which were occluded or were revised (significantly different by chi 2 test P < .001).
Vigorous CDS of pure in situ bypasses for up to 6 months is useful to detect bypass-threatening lesions. Continued CDS of a normal in situ bypass after 6 months may not be justifiable, as the incidence of lesions requiring later revision is minimal.
Twenty-one patients underwent 23 bypasses for limb salvage via a lateral approach with subcutaneous graft tunneling. The reasons for utilizing a lateral approach were medial infection (10 bypasses), ...scarring from previous surgery (six), limited vein length available (three), prior local radiotherapy (two) and 'high risk' groin (two). The target artery was the anterior tibial in 16 cases, the peroneal in three, the above-knee popliteal in three and the dorsalis pedis in one. The median (range) follow-up was 22(<1-52) months. There were three early (within 30 days) and four late bypass occlusions, three of which occurred in previously revised bypasses and one in a non-compliant patient. The primary patency at 1 year was 61% and the secondary patency 86%. Only one amputation was required in the whole series. The lateral approach represents a simple solution to threatened limbs in otherwise difficult or complicated situations and may be the ideal approach for free vein grafts to the anterior tibial and distal peroneal arteries.
Intra-arterial thrombolysis with urokinase was attempted on 23 occluded infrainguinal vein bypasses. Lesions revealed by thrombolysis included 11 anastomotic stenoses, five midbypass stenoses, five ...native artery stenoses, and five unusable diffusely stenotic vein conduits. Adjunctive procedures performed immediately after successful thrombolysis included 10 local surgical revisions, five balloon angioplasties, and five new vein bypasses. Three nonanastomotic vein bypass stenoses and two common iliac artery stenoses were detected using a surveillance protocol in subsequent follow-up of patients with patent bypasses. Twelve-month patency following thrombolysis (including immediate failures) was 52.4%. The use of thrombolysis in the management of occluded vein bypasses allows the identification and correction of pathological lesions. Once revised, continued vein bypass patency may be improved with a surveillance program.
