Reducing perioperative myocardial infarction following vascular surgery. The potential role of beta-blockade

OBJECTIVE

To determine which perioperative variables may influence the occurrence of perioperative myocardial infarction (PMI) following vascular surgery.

DESIGN

Case-control study.

SETTING

Combined Veterans Affairs Medical Center-university hospital vascular service.

PATIENTS

During a 4-year period, all major vascular surgical operations (N = 2088) were evaluated with serial postoperative electrocardiography and cardiac enzyme measurements. Patients with PMI following nonemergent vascular surgery (N = 53) were matched with randomly selected control patients without PMI (N = 106) for age, gender, type of operation, hypertension, and symptoms of coronary artery disease.

MAIN OUTCOME MEASURES

The two groups were compared for operative blood loss, blood pressure, and heart rate as well as length of operation, type of anesthetic, and use of perioperative beta-blockers, nitroglycerine, calcium channel blockers, vasopressors, and angiotensin-converting enzyme inhibitors.

RESULTS

beta-Blockers were used less frequently in patients with PMI than in control patients without PMI (30% vs 50%; P = .01). Overall beta-blockade was associated with a 50% reduction in PMI (P = .03). Perioperative myocardial infarction was not associated with length of operation, type of anesthetic, blood pressure, or use of other medications.

CONCLUSIONS

beta-Blockade is associated with a decreased incidence of PMI in patients undergoing vascular surgery. Prophylactic perioperative use of beta-blockers may decrease PMI in patients requiring major vascular surgery. A prospective randomized trial of beta-blockers in these patients appears to be warranted.

Prevalence of asymptomatic carotid stenosis in patients undergoing infrainguinal bypass surgery

BACKGROUND

The prevalence of asymptomatic carotid stenosis in patients with lower-extremity ischemia is unknown. This report represents the largest carotid screening program to date of patients undergoing leg bypass.

DESIGN

Patients undergoing infrainguinal bypass from 1987 through 1993 on the vascular surgery service at Oregon Health Sciences University, Portland, underwent routine carotid duplex examinations to detect the presence of asymptomatic carotid stenosis.

PATIENTS

During the study period, 352 patients underwent infrainguinal revascularization for ischemia, of whom 225 (64%) had no prior carotid surgery, carotid arteriography, or cerebrovascular symptoms. There were 117 men and 108 women, with a mean age of 67 years. The indication for surgery was limb salvage in 67% and claudication in 33% of patients.

RESULTS

Sixty-four patients (28.4%) who required lower-extremity revascularization had hemodynamically significant asymptomatic carotid artery stenosis or occlusion; 12.4% had stenosis of 60% or greater, the qualifying level for randomization in the Asymptomatic Carotid Atherosclerosis Study. Based on these findings, eight patients with carotid stenosis of 80% or greater underwent elective carotid endarterectomy. There were no postoperative neurologic events in the 225 leg bypass patients. By multivariate logistic regression analysis, the presence of carotid bruit (P < .001) and the presence of rest pain (P = .006) were associated with carotid stenosis of 50% or greater. Limiting screening to patients with carotid bruit, limb salvage indications for surgery, and/or advanced age excluded significant numbers of patients with stenosis; thus, these were not effective screening strategies.

CONCLUSION

Screening carotid duplex scanning is indicated in patients who require lower-extremity revascularization.

Screening for asymptomatic internal carotid artery stenosis: duplex criteria for discriminating 60% to 99% stenosis

PURPOSE

The Asymptomatic Carotid Atherosclerosis Study (ACAS) showed that carotid endarterectomy reduces stroke risk in symptom-free patients with 60% or greater internal carotid artery (ICA) stenosis. This will surely lead to the performance of an increased number of screening duplex examinations. Assuming that positive study results will lead to arteriography or endarterectomy and keeping in mind the modest benefit for prophylactic endarterectomy demonstrated by ACAS (absolute risk reduction for ipsilateral stroke of 5.8% at 5 years), duplex criteria for 60% or greater ICA stenosis must have high positive predictive values (PPV). Determining criteria for 60% or greater stenosis, which emphasized high accuracy and PPV, forms the basis for this study.

METHODS

Stenoses detected by angiography in 352 ICAs were blindly compared with those detected by duplex scanning. Duplex criteria were determined for highest overall accuracy in detection of 60% or greater ICA stenosis and for 95% or greater PPV.

RESULTS

Maximal accuracy for detection of 60% or greater stenosis was 90%. This was achieved by the combination of a peak systolic velocity of 260 cm/sec or greater and an end diastolic velocity of 70 cm/sec or greater (sensitivity 84%, specificity 94%, PPV 92%). The 95% PPV for 60% or greater stenosis results from combining peak systolic velocity of 290 cm/sec or greater and end diastolic velocity of 80 cm/sec or greater.

CONCLUSIONS

With use of these criteria duplex scanning accurately detects with high PPVs the threshold level of ICA stenosis defined in ACAS as receiving stroke reduction benefit from prophylactic carotid endarterectomy. These criteria should be useful for carotid artery screening and minimizing unneeded intervention.

Upper extremity thromboembolism caused by occlusion of axillofemoral grafts

BACKGROUND

The axillofemoral bypass graft (AxFG) is increasingly accepted as treatment for lower extremity ischemia caused by aortoiliac occlusive disease in high-risk patients. The incidence of upper extremity (UE) thromboembolism caused by occlusion of an AxFG and the results of treatment form the basis for this report.

METHODS

From 1984 to the present, all patients undergoing axillofemoral bypass grafting were followed up in a vascular registry. A standardized operative technique, using an externally supported 8-mm polytetrafluoroethylene graft, was used in performing 202 AxFGs in 182 patients. UE thromboembolism caused by occlusion of an AxFG was identified by retrospective patient record review.

RESULTS

Occlusion of an AxFG occurred in 20 patients. Fifteen patients (75%) underwent immediate revision of the occluded graft. Two patients (10%) developed UE thromboembolism simultaneous with graft occlusion. One of these patients had immediate revision of the graft, and 1 had brachial embolectomy only. This patient and 4 others (25%) had the occluded AxFG left in place. Four of these 5 patients (80%) developed UE thromboembolism at 26 days, 2 years, 5 years, and 7 years, respectively, after occlusion. Overall, six UE thromboembolic complications occurred in 5 patients.

CONCLUSIONS

UE thromboembolism represents a significant and specific complication of occluded AxFGs in our series (2.7% of patients, 25% of occluded grafts). It may be prudent to prophylactically detach the axillary portion of the graft and repair the axillary artery in patients who do not require immediate revision of an occluded AxFG.

Usefulness of fasting and postprandial duplex ultrasound examinations for predicting high-grade superior mesenteric artery stenosis

PURPOSE

A fasting duplex ultrasound examination of the superior mesenteric artery (SMA) accurately detects high-grade (> 70%) stenosis. It has been postulated that postprandial mesenteric duplex scanning may further stratify stenosis and improve the ability of a fasting examination to detect a high-grade stenosis. We performed fasting and postprandial duplex scanning of 25 healthy controls and 80 patients with vascular disease undergoing aortography to determine whether postprandial mesenteric duplex scanning provides information beyond a fasting study alone.

METHODS

Patients with vascular disease were divided into three groups based on lateral aortography results: group 1, 0% to < 30% SMA stenosis (n = 61); group 2, 30% to < 70% stenosis (n = 10); and group 3, 70% to 99% stenosis (n = 9). Fasting mesenteric duplex scanning was defined as positive for 70% to 99% stenosis if the peak systolic velocity (PSV) was > or = 275 cm/s. The ability of either fasting or postprandial mesenteric duplex scanning, and their combination, to predict high-grade (70% to 99%) SMA stenosis was determined using angiographic control.

RESULTS

Mean fasting SMA PSV did not differ among controls and groups 1 and 2. Postprandial PSV increased significantly in all groups, but was not different among controls and groups 1 and 2. Mean fasting PSV was significantly higher, and the postprandial increase in PSV significantly lower, in group 3 compared with controls and with groups 1 and 2. Fasting mesenteric duplex scanning predicted 70% to 99% SMA stenosis, with 89% sensitivity, 97% specificity, 80% positive predictive value, 99% negative predictive value, and 96% accuracy. Corresponding values for postprandial scanning were 67%, 94%, 60%, 96%, 91%, and for the combination of normal fasting and postprandial scanning 67%, 100%, 100%, 96%, 96%, respectively.

CONCLUSION

Postprandial increases in SMA PSVs are blunted in patients with high-grade stenosis, but feeding velocities do not stratify between lesser degrees of stenosis. Both fasting and postprandial PSVs identify high-grade (> 70%) stenosis. Their combination marginally improves fasting duplex scan specificity and positive predictive value. Postprandial scanning is not necessary for the diagnosis of high-grade stenosis if a fasting study identifies a PSV > or = 275 cm/s. The combination of normal fasting and postprandial mesenteric duplex ultrasound scanning may effectively rule out high-grade SMA stenosis.

Antiphospholipid antibodies in vascular surgery patients. A cross-sectional study

BACKGROUND

Autoantibodies to phospholipid (aPL) have been associated with vascular thromboses in cerebral, coronary, and peripheral venous and arterial sites. To date, no large cross-sectional study has examined the incidence of occurrence of aPL in patients with peripheral arterial disease.

METHODS

A cross-sectional study was performed with patients admitted for vascular surgery procedures to treat peripheral arterial disease for 23 months between January 1, 1990 and November 1, 1991. Consecutive patients were evaluated for the presence of aPL. Medical records for each patient were reviewed in detail, and historic, operative, and postoperative parameters were tabulated for relationship to the presence of aPL.

RESULTS

Two hundred thirty-four patients underwent complete testing for aPL. All patients were receiving chronic aspirin therapy. This represented 86% of admissions. Antiphospholipid antibodies were detected in 60 patients (26%). No differences in age, sex, operation performed, or postoperative outcome were found between patients with and without aPL. However, patients with aPL were 1.8 times more likely to have undergone previous lower extremity (LE) vascular surgery than patients without aPL (95% confidence interval = 1.0 - 3.6, p = 0.047). Patients with aPL and previous LE vascular surgery were 5.6 times more likely to have had occlusion of that procedure than patients without aPL (95% confidence interval = 1.9 - 16.8, p = 0.03). The occluded previous LE procedures had a shorter duration of patency before occlusion in patients with aPL than in those without (mean duration of patency 17 months vs. 50 months, p < 0.003). Patients with occluded previous LE procedures and aPL were 4 times more likely to be female (95% C.I. = 1.4 - 11.3, p = 0.018).

CONCLUSIONS

The incidence of aPL in vascular surgery patients is substantial. Vascular surgery patients with aPL are more likely to have failure of previous LE bypass procedures and to be female and the bypass failure occurs significantly more rapidly than in patients without aPL. Based on these data, testing of vascular surgery patients for aPL and investigation of alternative antithrombotic treatment regimens in patients with aPL appears warranted.

Acute disruption of polytetrafluoroethylene grafts adjacent to axillary anastomoses: a complication of axillofemoral grafting

PURPOSE

Acute disruption at or adjacent to axillary anastomoses of axillofemoral grafts has been sporadically reported. We have recently reported the patency and limb salvage results of a large number of axillofemoral grafts. In this report we describe a series of axillary artery-graft disruptions that occurred in these patients.

METHODS

Beginning in 1983, axillofemoral bypass was performed by the authors using standardized operative technique and a single prosthetic graft material (8 mm externally supported polytetrafluoroethylene). Axillary anastomoses were placed on the first portion of the artery and were performed with the arm abducted and with the graft redundant. The records and operative reports of all patients with disruption were reviewed for findings and subsequent hospital course.

RESULTS

Two hundred two axillofemoral grafts were performed from 1983 to 1993. Ten patients (5%) had axillary disruption at intervals ranging from 1 to 46 days (mean 21 days) after operation. Ischemia was the indication for operation for seven of the patients and infected aortic prostheses for three. Infection did not occur in any of the axillary wounds and was not the cause of any of the disruptions. Four disruptions occurred with arm abduction/shoulder elevation movements; three awakened patients from sleep, and one occurred while the patient was sitting quietly. For the other two patients, preceding activity was unknown. Brachial plexus deficit was present in one patient. Four of the 10 disrupted grafts were also acutely occluded. Operative findings included sutures pulling out of the artery in four cases, tearing or sutures pulling out of the graft in four cases, and cause unknown in two cases. Treatment included arterial ligation in one patient, and restoration of circulation through revision of the axillofemoral grafts in the other nine patients. There were no operative deaths. One patient had a prolonged hospital course followed by nursing home placement and died 9 months later. The brachial plexus deficit did not resolve. There have been no repeat disruptions.

CONCLUSIONS

We conclude that axillofemoral grafting includes the potential for disruption of the proximal anastomosis, which has occurred in 5% of our patients. Although multiple steps have been recommended to avoid this complication, occasional cases continue to occur despite observing all precautions.

Importance of elevated plasma homocysteine levels as a risk factor for atherosclerosis

Atherosclerosis is a leading cause of death and disability in the Western world, and an important risk factor for it may be an elevated level of the plasma amino acid homocysteine. The biochemical characteristics of homocysteine, along with historical, laboratory, and clinical evidence for its pathologic role in atherosclerosis, are reviewed. Possible therapies for reducing elevated homocysteine levels and the possible impact of therapy in atherosclerosis are examined.

Late survival after perioperative myocardial infarction complicating vascular surgery

PURPOSE

Although early death from perioperative myocardial infarction (PMI) after vascular surgery is well established, long-term outcome in patients surviving PMI is unknown. This prospective study was designed to determine cardiac outcome and survival rates in patients with symptomatic and asymptomatic nonfatal PMI associated with peripheral vascular surgery.

METHODS

During a 36-month period for 1989 to 1992, all patients undergoing vascular surgery at our institution were monitored for PMI with serial creatine kinase and myocardial band isoenzymes and electrocardiography. PMIs were classified as symptomatic (associated with chest pain, arrhythmia, congestive heart failure, or hypotension) or asymptomatic (electrocardiographic changes and/or elevated creatine kinase and myocardial band isoenzymes). Patients with PMI were then prospectively monitored and compared for late survival, with control patients undergoing vascular surgery without PMI during the same interval.

RESULTS

During the study period 1561 major peripheral vascular procedures were performed. There were 47 PMIs (3.0%). Eleven (0.7%) PMIs were fatal, 31 were nonfatal, and five other patients with PMI died during operation of non-heart-related causes. Eight of 31 patients with nonfatal PMI had a "chemical PMI" with creatine kinase and myocardial band isoenzyme elevation as the sole indicator of PMI. During follow-up (mean 27.7 months), there was a higher incidence of both subsequent myocardial infarction and coronary artery revascularization among the patients with nonfatal PMI compared with control subjects (p < 0.05); however, survival for patients with nonfatal PMI at 1 and 4 years (80% and 51%) did not differ from that of control patients (90% and 60%) (p > 0.05). Patients with "chemical PMI" had similar patterns of subsequent myocardial infarction and coronary intervention as control patients.

CONCLUSIONS

Patients surviving nonfatal PMI after peripheral vascular surgery have a higher incidence of subsequent adverse cardiac events and coronary artery revascularization than patients undergoing vascular surgery without PMI, but they have similar survival rates at 1 and 4 years. Patients in the enzyme-only PMI group have a similar outcome compared with control subjects suggesting that a perioperative "chemical MI" may not be a significant clinical event.

Surgical treatment of threatened reversed infrainguinal vein grafts

PURPOSE

Current information concerning the results of surgical revision of threatened infrainguinal vein grafts is largely limited to in situ conduits. Infrainguinal grafts may be threatened by intrinsic graft lesions or significant stenosis in the adjacent inflow or outflow arteries. To assess the results of operative revision of infrainguinal reversed vein grafts, we reviewed our experience with surgical revision of threatened infrainguinal reversed vein grafts identified through a program of postoperative clinical and vascular laboratory graft surveillance.

METHODS

All patients who underwent surgical revision of a threatened but patent infrainguinal reversed vein graft from January 1987 through April 1993 were identified through review of our vascular registry. Data were analyzed for type of vein used, date of original reversed vein graft, clinical and vascular laboratory findings leading to reversed vein graft revision, results of preoperative angiography, patient risk factors, operative techniques and complications, and long-term assisted primary graft patency and limb salvage.

RESULTS

Ninety-six patients with 100 infrainguinal reversed vein grafts (69) femoral-popliteal, 31 femoral-tibial) underwent 117 surgical vein graft revisions or inflow procedures during the study period. Eighty-one percent of the original reversed vein grafts consisted of a single segment of greater saphenous vein. All revised grafts had at least a 50% stenosis in the graft itself or the proximal or distal artery. A single revision was performed in 85 grafts, two revisions in 13 grafts, and three revisions in two grafts. There were nine (8%) isolated inflow procedures, eight (7%) vein patch angioplasties, 62 (53%) interposition vein grafts, and 29 (25%) vein graft extensions to a new distal anastomotic site. The remaining nine (8%) procedures consisted of combinations of the above. Median time to primary graft revision after initial graft implantation was 15 months (range 2 days to 316 months). Mean time to secondary revision after primary revision was 21 months. Operative mortality was 0.9%. Cumulative assisted primary patency of the original grafts revised for stenotic lesions was 99%, 96%, and 92% at 1, 3, and 5 years, respectively. Limb salvage was 99%, 97%, and 97% at 1, 3, and 5 years, respectively.

CONCLUSIONS

Although surgical revision of reversed vein graft requires much use of alternative vein sources, these procedures can be performed with minimum mortality and provide excellent assisted primary graft patency and limb salvage.

Isolated bypass to the superior mesenteric artery for intestinal ischemia

OBJECTIVE

A number of reports indicate revascularization for intestinal ischemia should include the superior mesenteric artery (SMA) and the celiac artery. However, no controlled or randomized studies have proven this approach superior to SMA bypass alone. We report our results using bypass to only the SMA for intestinal ischemia.

DESIGN

Retrospective review with mean follow-up of 40 months (range, 2 to 110 months).

SETTING

University medical center and Veterans Affairs hospital.

PATIENTS/METHODS

The records of patients who underwent intestinal revascularization of the SMA alone from 1982 through 1993 were reviewed. Patients were assessed for indication for operation, operative technique, perioperative mortality, and long-term outcome. The SMA grafts were examined for patency within the last 6 months using duplex scanning or arteriography. Patient survival and graft patency rates were calculated using life-table methods.

RESULTS

Twenty-nine bypasses to only the SMA were performed in 26 patients (16 female and 10 male; mean age, 59 years; age range, 13 to 81 years). Indication for operation was symptomatic chronic mesenteric ischemia in 23 cases and acute intestinal ischemia in five cases. One bypass was performed for asymptomatic SMA occlusion. There were three perioperative deaths (10% mortality rate), all in patients with acute intestinal ischemia and previous mesenteric arterial surgery. Life-table 4-year primary graft patency and patient survival rates were 89% and 82%, respectively. Symptomatic improvement was maintained in all patients available for follow-up.

CONCLUSION

Revascularization of only the SMA for intestinal ischemia provides excellent graft patency with acceptable perioperative mortality and long-term patient survival. The SMA bypass alone for intestinal ischemia appears as successful as bypasses to multiple visceral vessels.

Rapid HPLC determination of total homocysteine and other thiols in serum and plasma: sex differences and correlation with cobalamin and folate concentrations in healthy subjects

High-performance liquid chromatography with fluorescence detection has been utilized for the rapid determination of total homocysteine, cysteine, and cysteinylglycine in human serum and plasma. Our earlier procedure (Anal Biochem 1989;178:208), which used monobromobimane to specifically derivatize thiols, has been extensively modified to allow for rapid processing of samples. As a result, > 80 samples a day can be assayed for total homocysteine, cysteine, and cysteinylglycine. The method is sensitive (lower limit of detection < or = 4 pmol in the assay) and precise (intra- and interassay CV for homocysteine, 3.31% and 4.85%, respectively). Mean total homocysteine concentrations in plasma and serum were significantly different, both from healthy male donors (9.26 and 12.30 mumol/L, respectively; P < 0.001) and healthy female donors (7.85 and 10.34 mumol/L, respectively; P < 0.001). The differences in total homocysteine between sexes were also significant (P = 0.002 for both plasma and serum). Similar differences were found for cysteine and cysteinylglycine. We found a significant inverse correlation between serum cobalamin and total homocysteine in men (P = 0.0102) and women (P = 0.0174). Serum folate also inversely correlated with total homocysteine in both sexes.

Rapid HPLC determination of total homocysteine and other thiols in serum and plasma: sex differences and correlation with cobalamin and folate concentrations in healthy subjects

High-performance liquid chromatography with fluorescence detection has been utilized for the rapid determination of total homocysteine, cysteine, and cysteinylglycine in human serum and plasma. Our earlier procedure (Anal Biochem 1989;178:208), which used monobromobimane to specifically derivatize thiols, has been extensively modified to allow for rapid processing of samples. As a result, &gt; 80 samples a day can be assayed for total homocysteine, cysteine, and cysteinylglycine. The method is sensitive (lower limit of detection &lt; or = 4 pmol in the assay) and precise (intra- and interassay CV for homocysteine, 3.31% and 4.85%, respectively). Mean total homocysteine concentrations in plasma and serum were significantly different, both from healthy male donors (9.26 and 12.30 mumol/L, respectively; P &lt; 0.001) and healthy female donors (7.85 and 10.34 mumol/L, respectively; P &lt; 0.001). The differences in total homocysteine between sexes were also significant (P = 0.002 for both plasma and serum). Similar differences were found for cysteine and cysteinylglycine. We found a significant inverse correlation between serum cobalamin and total homocysteine in men (P = 0.0102) and women (P = 0.0174). Serum folate also inversely correlated with total homocysteine in both sexes.

Axillofemoral grafting with externally supported polytetrafluoroethylene

OBJECTIVE

To evaluate the results of axillofemoral bypass grafting using externally supported polytetrafluoroethylene.

DESIGN

Consecutive patients who were operated on by us from 1983 to the present were prospectively followed up in a vascular registry. The results of surgery with respect to morbidity and mortality, patency, limb salvage, and patient survival were determined by life-table methods.

PATIENTS

A standardized operative technique was used to perform 184 axillofemoral bypass procedures in 164 consecutive patients (age range, 14 to 90 years; mean age, 67 years; female, 33%). Follow-up ranged from 0 to 95 months (mean, 23 months).

RESULTS

Ischemia was the indication for 83% of the procedures, and aortic sepsis was the indication for 16%. There were nine operative deaths (5%) and 17 major complications. Life-table primary patency, limb salvage, and survival rates at 5 years were 71%, 92%, and 52%, respectively. Indication for surgery, patency of the superficial femoral artery, and the performance of multilevel procedures did not significantly influence patency.

CONCLUSIONS

The results of axillofemoral grafting using polytetrafluoroethylene are equivalent to those achieved with other accepted methods of treatment for lower extremity ischemia, including balloon angioplasty, aortofemoral bypass, and infrainguinal bypass. Axillofemoral bypass is an appropriate technique that is deserving of more widespread use.

Cooling augments human saphenous vein reactivity to electrical stimulation

Human saphenous veins were obtained at operation and assayed immediately (n = 10). The veins were cut into rings, suspended in organ chambers, and connected to force transducers for recording of isometric tension. One ring served as control; others were treated with either the alpha 1-adrenoceptor antagonist prazosin (Pz, 3 x 10(-7) M) or the alpha 2-adrenoceptor antagonist rauwolscine (Rw1, 10(-7) M). Cooling from 37 degrees to 24 degrees C had no significant effect on the resting tone of quiescent rings. Electrical stimulation (0.2-16 Hz) caused frequency-dependent contractions in control vessels. The contractions were inhibited by Pz (p < 0.001) and by Rw (p < 0.001). In control rings, cooling potentiated contractions evoked at all frequencies. Similar augmentations were induced by cooling in rings treated with the alpha 1-antagonist Pz. In contrast, rings treated with Rw before being electrically stimulated showed no significant change in contractile force when cooled. The data indicate that in the human saphenous vein, both alpha 1- and alpha 2-adrenoceptors are innervated, contributing to contractile response evoked by neuronal excitation. Cold augments saphenous vein reactivity to endogenously released norepinephrine (NE) by an apparent increase in the responsiveness of alpha 2-adrenoceptors to agonists. This relationship between temperature and adrenoceptor responsiveness is consistent with the hypothesized role of alpha 2-adrenoceptors in cold-induced vasospasm.

Hemodynamic assessment of combined aortoiliac/femoropopliteal occlusive disease and selection of single or multilevel revascularization

Approximately 25% of patients with multilevel arterial occlusive disease will require both inflow and outflow revascularization in order to successfully resolve their symptoms of lower limb ischemia. The preoperative selection of patients for multilevel concurrent arterial reconstruction is guided by symptoms, information from the noninvasive vascular laboratory, the predicted postoperative ABI, and detailed multiview angiography including pull-back intra-arterial pressure measurements. Properly selected patients will benefit from a carefully planned and expeditiously performed simultaneous revascularization. Current results indicate no significant increase in operative morbidity or mortality rates and excellent graft patency rates with these combined procedures.

Repeat leg bypass after multiple prior bypass failures

PURPOSE

The optimal treatment of patients with severe lower extremity ischemia after multiple failed prior bypasses is unclear. It is presently unknown whether failure of attempted revascularization in these patients is so likely that such operation should not be elected. We have maintained an aggressive surgical policy of repeated revascularization regardless of prior failures. A review of our clinical experience with this difficult patient group was performed to determine the results of this policy.

METHODS

From 1980 to 1992, 85 revascularization procedures were performed in 81 patients with lower extremity ischemia after failure of two or more prior infrainguinal bypasses in the same leg. All patients were prospectively entered and monitored in our vascular registry. Seventy-two operations were the third procedure, six operations were the fourth procedure, and seven operations were the fifth procedure on the same extremity. Twenty-six of the 85 procedures (30%) were revisions of failing grafts discovered by routine surveillance methods, whereas 59 were replacements of thrombosed grafts. Autogenous reconstruction was used in 67 procedures (79%), and prosthetic reconstruction was used in 18 procedures (21%). The distal anastomosis was to the popliteal artery in 19 patients and infrapopliteal artery in 66.

RESULTS

Mean time to failure of the first leg bypass was 24 months and 4.9 months for the second bypass. Detailed hematologic screening revealed identifiable hypercoagulable disorders in nine (15%) of 59 patients screened after 1987. All nine had anticardiolipin antibodies. The operative mortality rate was 4%. Mean follow-up after the most recent operation was 17 months. The primary patency rate at 4 years was 79.8%. The limb salvage rate was 69.6% at 4 years.

CONCLUSIONS

These results indicate that limb revascularization after two or more failed leg bypasses results in low operative mortality rates and surprisingly good primary patency and limb salvage rates at 4 years. The patient survival rate through 4 years is unexpectedly high. In our opinion these results justify an aggressive policy of limb vascularization after multiple failed prior bypasses.

Osteoclast differentiation in cocultures of a clonal chondrogenic cell line and mouse bone marrow cells

Previous reports have demonstrated that hemopoietic progenitor cells derived from mouse bone marrow can form osteoclast-like cells when cultured in the presence of stromal cells and 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. We show here that in cocultures of mouse bone marrow cells and a clonal chondrogenic cell line (C5.18), a stimulation of the number of tartrate-resistant acid phosphatase-positive (TRAP+) colonies is seen with or without the addition of 1,25-(OH)2D3 to the cultures. A large proportion of the TRAP+ cells had calcitonin receptors. In addition resorption lacunae were observed on bone slices on which cocultures were maintained, thus these cells had the characteristics of osteoclasts. The number of osteoclast-containing colonies that formed in cocultures varied with the plating density of the C5.18 cells and the length of time the C5.18 cells were cultured before adding mouse bone marrow. These results suggested that osteoclast differentiation decreased with increasing cartilage differentiation. C5.18 cells treated with 1,25-(OH)2D3 before coculture stimulated TRAP+ osteoclast colony formation to a greater extent than untreated C5.18 cells, whereas C5.18 cells cultured in the presence of dexamethasone before coculture inhibited TRAP+ osteoclast colony formation relative to untreated C5.18 cells. Since 1,25-(OH)2D3 inhibits and dexamethasone stimulates cartilage differentiation in C5.18 cells, these results agree with the view that chondroprogenitor cells stimulate osteoclast colony formation, whereas cultures containing predominantly mature chondrocytes do not. Osteoclast-containing colonies were frequently associated with colonies of alkaline phosphatase-positive (AP+) cells. This raised the possibility that C5.18 cells stimulated osteoclast differentiation indirectly by increasing the numbers of AP+ stromal cells from the marrow population, which in turn could stimulate osteoclast differentiation from marrow hemopoietic progenitors. In cocultures in which the C5.18 cells were physically separated from the marrow cells, we also observed increased numbers of TRAP+ colonies growing in association with large colonies of AP+ cells, suggesting that C5.18 cells release a soluble factor that mediates these effects.

Perimalleolar subcutaneous tissue pressure effects of elastic compression stockings

PURPOSE

We hypothesized that the clinical benefit of elastic compression stockings (ECS) is at least in part due to an increase in subcutaneous pressure that may promote resorption of extracellular fluids, providing more efficient diffusion of oxygen and nutrients from the microcirculation to the skin and subcutaneous tissues.

METHODS

To test this hypothesis we designed and standardized a device for measuring subcutaneous pressure in patients. We then measured the supine perimalleolar subcutaneous pressure from a single limb in four groups: group 1 consisted of control subjects (n = 8); group 2 consisted of patients with varicose veins and superficial venous insufficiency without lipodermatosclerosis or edema (n = 5); group 3 consisted of patients with deep venous insufficiency and lipodermatosclerosis but without edema (n = 8); and group 4 consisted of patients with deep venous insufficiency, lipodermatosclerosis, and clinically evident edema (n = 8). Measurements were made at baseline and after application of 20 to 30 mm Hg and 30 to 40 mm Hg ECS.

RESULTS

There was no significant difference in the baseline subcutaneous pressure between the three groups without clinical edema (p > 0.05). Baseline perimalleolar pressure was elevated, however, in group 4 patients compared with groups 1, 2, and 3 (p < 0.05). All three groups with chronic venous insufficiency (CVI) (groups 2, 3, 4) demonstrated increases in subcutaneous pressure with application of ECS, which was statistically significant in groups 3 and 4. There was no difference between the increase in perimalleolar subcutaneous pressure induced by 20 to 30 mm Hg or 30 to 40 mm Hg ECS in groups 3 and 4.

CONCLUSIONS

Patients with CVI and edema have significant elevations in supine resting perimalleolar subcutaneous pressure compared with control subjects and patients with CVI without edema. Twenty to 30 mm Hg and 30 to 40 mm Hg ECS increased measured perimalleolar subcutaneous pressure in patients with CVI with and without clinical edema but not in control patients. These results suggest the mechanism of benefit of ECS in patients with CVI is due at least in part to an increase in subcutaneous pressure that may act to promote more efficient absorption of perimalleolar extracellular fluid.

Outcome of infrainguinal arterial reconstruction in women

PURPOSE

The outcome of leg bypass in women is unknown. To date, most series of lower extremity bypass have included few women, and the results in women compared with those in men have not been reported. The experience with infrainguinal arterial reconstruction in women treated at the Oregon Health Sciences University has been greater than previously reported. We have reviewed our recent experience with lower extremity bypass to determine whether results in women differ significantly from those in men.

METHODS

In the past 11 years we have performed 823 infrainguinal arterial reconstructions for lower extremity ischemia in 585 patients, of which 357 procedures were performed in women and 466 procedures were performed in men. The mean ages were 65 years for men and 68 years for women. Diabetes was present in 59% of the men and 48% of the women. Among men, 84% had a history of tobacco use compared with 66% of the women. Bypasses in men were performed for limb salvage in 73%, claudication in 22%, and a failing bypass graft in 5% of cases. Bypasses in women were performed for limb salvage in 79%, claudication in 15%, and a failing graft in 6% of cases. Previous revascularizations had been performed in 63% of the men and 71% of the women. Autogenous vein was used in 97% of the bypasses in men and 96% of bypasses in women. Graft distribution among infrainguinal arterial target sites was similar between the groups. Bypasses in men were femoral to above-knee popliteal in 11%, femoral to below-knee popliteal in 40%, femoral to tibial in 38%, popliteal to tibial in 10%, and tibial to tibial in 1% of cases. Bypasses in women were femoral to above-knee popliteal in 14%, femoral to below-knee popliteal in 43%, femoral to tibial in 33%, popliteal to tibial in 9%, and tibial to tibial in 1% of cases.

RESULTS

Perioperative 30-day mortality rates were 3.7% overall, 4.3% in men, and 2.9% in women. Long-term survival at 1, 3, and 5 years in men was 80%, 59%, and 44%, respectively. Long-term survival at 1, 3, and 5 years in women was 83%, 69%, and 44%, respectively. Life-table primary patency rates at 1, 3, and 5 years were 86%, 77%, and 71% for men and 87%, 74%, and 67% for women. Limb-salvage results at 1 and 5 years were 93% and 91% for men and 96% and 96% for women.

CONCLUSIONS

These results indicate that long-term graft patency and limb salvage results in women are identical to those obtained in men in this experience with autogenous vein. Infrainguinal arterial reconstruction can be performed in women with mortality rates similar to those of men. In this series long-term survival was similar for both men and women.

Anticoagulation followed by elective carotid surgery in patients with repetitive transient ischemic attacks and high-grade carotid stenosis

OBJECTIVE

To evaluate the results of preoperative heparin therapy followed by carotid surgery for patients with repetitive transient ischemic attacks (TIAs) and high-grade carotid stenoses.

DESIGN

A 4-year prospective study.

SETTING

Oregon Health Science University Hospital and Portland (Ore) Veterans Affairs Hospital.

PATIENTS

Twenty-nine consecutive patients with repetitive TIAs referable to 30 high-grade (> or = 70%) ipsilateral carotid stenoses were treated with short-term heparin anticoagulation, followed by cerebral angiography, routine preoperative evaluation, and subsequent carotid reconstruction.

INTERVENTIONS

Heparin sodium anticoagulation was maintained for a mean of 5 days. Surgical management consisted of 24 standard endarterectomies, five bypasses to the internal carotid artery, and one external carotid endarterectomy.

MAIN OUTCOME MEASURES

Primary outcome variables included perioperative hemorrhage, thrombocytopenia, stroke, and death. Secondary outcome variables included carotid occlusion and recurrent TIAs with heparin therapy.

RESULTS

One symptomatic common carotid occlusion and one asymptomatic internal carotid occlusion occurred during preoperative heparin therapy. Thirteen patients had additional sporadic TIAs while receiving heparin. There were no preoperative cerebral infarcts, thrombocytopenia, or clinical bleeding associated with heparin therapy. There was one postoperative stroke and one death due to myocardial infarction.

CONCLUSION

When necessary, heparin anticoagulation and delayed carotid reconstruction would appear to be an acceptable alternative to emergency carotid surgery in patients with high-grade carotid stenosis and acute repetitive TIAs.

Surgery for chronic lower extremity ischemia in patients eighty or more years of age: operative results and assessment of postoperative independence

PURPOSE

Revascularization for chronic lower extremity ischemia (CLEI) in patients 80 or more years of age is controversial. High operative mortality, short remaining life span, and nonambulatory nursing home existence are cited as frequent outcomes in this patient group. Despite these considerations we have maintained an aggressive policy of lower extremity revascularization in functional and potentially functional patients 80 or more years of age with limb-threatening ischemia or claudication sufficient to threaten their independence.

METHODS

The records of all patients 80 or more years of age who underwent lower extremity revascularization for CLEI from 1981 through 1991 were reviewed. Patients were evaluated for surgical indication, perioperative mortality, late survival, graft patency, and limb salvage. In addition, the patient's preoperative and postoperative independence determined by living situation (home versus nursing home) and ambulatory status were examined.

RESULTS

During the period reviewed 88 patients 80 or more years of age underwent 95 arterial reconstructions for CLEI; 95% for limb salvage and 5% for short-distance claudication. There were 81 (85%) infrainguinal bypasses and 14 (15%) extra-anatomic bypasses, 5 of which also included a simultaneously placed infrainguinal bypass. The perioperative mortality rate was 6%. Mean hospitalization was 18 days (range 6 to 62). The 1- and 3-year primary graft patency rates were 88% and 66%, limb salvage rates 94% and 91%, and patient survival rates 73% and 51%, respectively. One year after operation 88% of patients were ambulatory, 85% were living at home, and 80% were both living at home and ambulatory. At 3 years these results were 86%, 76%, and 71%, respectively. Of the patients living at home and ambulatory before operation, 100% and 84% of survivors were still living at home and ambulatory 1 and 3 years after operation. Of patients living at home who had late graft occlusions, 67% required amputation and subsequent nursing home placement.

CONCLUSION

Although survival in this group is predictably lower than that of age-matched control subjects, octogenarians have satisfactory 1- and 3-year graft patency, limb salvage, and functional results. Revascularization for CLEI in patients 80 or more years of age is appropriate and results in maintenance of independent living in a large majority.

Human saphenous vein grafts explanted from the arterial circulation demonstrate altered smooth-muscle and endothelial responses

PURPOSE

Animal models have been used to assess the function of vascular smooth muscle and endothelium of veins grafted into arterial circulation. The primary model consists of grafting the external jugular vein into the carotid artery of the rabbit. These studies suggest a selective increase in the responsiveness of the grafted veins to serotonin. However, in both human cardiac and peripheral vascular operations, the saphenous, not the jugular, is the vein most frequently used. Thus the propriety of the rabbit model is unknown.

METHODS

Human saphenous veins and vein grafts were obtained from patients undergoing leg vein bypass graft revisions (n = 8). The reversed vein grafts were placed into arterial circulation for periods ranging from 4 to 26 months before removal (mean 16 months). All vessels were immediately cut into rings and suspended in organ chambers for recording isometric contractions to norepinephrine and serotonin.

RESULTS

The maximal contractions elicited by both norepinephrine and serotonin were reduced in human vein grafts in comparison to the results in human saphenous vein (maximal response to norepinephrine 1.42 +/- 0.34 gm [vein graft] vs 4.59 +/- 1.13 gm [saphenous vein], p = 0.031; maximal response to serotonin 2.68 +/- 0.58 gm [vein graft] vs 4.72 +/- 1.11 gm [saphenous vein], p = 0.042). Human vein grafts were less responsive to norepinephrine than was saphenous vein (negative log of concentration that caused 50% of the maximal response -5.91 +/- 0.10 and -6.84 +/- 0.22, respectively; p < 0.009). After precontraction with norepinephrine (to 30% of the maximal response), saphenous vein, but not vein grafts, demonstrated endothelium-dependent relaxation to acetylcholine (maximum relaxation 27.4% +/- 6.8%; p = 0.001).

CONCLUSIONS

Human saphenous veins grafted into arterial circulation exhibit loss of endothelium-dependent relaxation to acetylcholine and diminished contractions to agonists (norepinephrine and serotonin). In contrast to rabbit data, serotonin elicits dose-dependent contractions in both human saphenous vein and human vein grafts. Since the vascular wall contractility varies widely across species, the relevance of rabbit vein graft data to human bypass grafts is uncertain.