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ANNUAL MEETING ABSTRACTS From the Midwestern Vascular Surgical Society The Fifteenth Annual Meeting of the Midwestern Vascular Surgical Society will be held in Chicago, Ill., on Sept. 20-21, 1991. Selected abstracts from that meeting are published here in order of presentation at the meeting. Mechanics of vein patch following carotid end- arterectomy: implications for rupture of ankle vein patches Philip B. Dobrin, MD, LoyoLa University Medical Center, Maywood, Ill Saphenous vein patches frequently are used to close the carotid artery after endarterectomy. Recent publications report that in a few cases patches constructed from saphenous vein obtained from the ankle region rupture soon after surgery. To investigate the mechanisms of vein patch rupture we examined the geometric characteristics and mechanical properties of vein patches. After measuring the dimensions of patched carotid arteries at surgery, engineering analysis was used to determine the forces required of the vein to maintain equilibrium in a curved patch at 100 mm Hg, and in a patch at elevated arterial pressures. Thirty-nine segments of normal human saphe- nous vein then were obtained from the ankle, calf, knee, and groin at surgery. These 39 vessels were mounted as cylinders in a tissue bath and were studied at 37” C with use of displacement transducers and radiographic methods to measure the diameter, length, and wall thickness of the veins. Values were obtained at 25 mm Hg, pressure intervals between 0 and 200 mm Hg. By use of these data, as well as bursting pressures for normal saphenous vein segments, it was possible to determine (1) the wall stress required of the vein over the full range of arterial pressures when it is used as a patch for the carotid artery and (2) the wall stress required of the vein patch at bursting pressure. Analysis showed that at 100 mm Hg the wall stress is 2.44 -+ .03 x lo5 N/m’, and at 200 mm Hg it is 4.88 t .05 x lo5 N/m’. At bursting pressure the wall stress is 6.0 ? .72 x lo7 N/m’. Thus at arterial pressures the vein wall is subject to less than 1% of bursting stress (p < 0.01). These data show that normal ankle vein is not overloaded and has a great safety margin. Therefore rupture of ankle vein must be the result of a structural defect in the vessel wall, possibly caused by chronic exposure to elevated hydrostatic venous pressures, trauma, thrombosis, or inflammation. Carotid endarterectomy with vein patch angioplasty for radiation induced symptomatic carotid atherosclerosis Joseph J. Hurley, MD, Aksel G. Nordestgaard, MD, John J. Woods, Jr., MD, Arthur I. Auer, MD, and Mary K. Milyard, RN, St. John’sMercy Medical Center, St. Louis, MO. Symptomatic carotid artery disease after high-dose radiotherapy for head and neck cancer occurs with twice the incidence as in nonradiated patients and may become more common as improved treatment results in longer. survival. The surgical experience is limited, and fewer than 50 reported cases exist. Earlier reports have shown a high frequency of perioperative neurologic deficit and throm- bosis rate. Controversy regarding the appropriate surgical approach exists. We report our experience with a uniform initial surgical approach in six patients, eight carotid arteries, and 10 operations. One patient who had occlusion of the common carotid artery after mastectomy and radiation therapy was excluded. Five men and one woman with a mean age of 56 years (range, 27 to 7X years) were admitted with symptomatic carotid artery disease (amau- rosis fugax 2, TIAs 3, and CVA 1) between 4 and 23 years (mean, 13 years) after receiving radiotherapy for head and neck cancer (squamous cell cancer of mouth 1, oropharynx 2, and unknown 1, larynx cancer 1, and craniopharyngeal lymphoma 1). Two patients had undergone radical neck dissection and one total laryngectomy. Nine carotid endarterectomies with saphenous vein patch angioplasty were performed, including two bilateral endarterectomies, a third patient had the contralateral internal carotid artery occluded, and two patients required reoperation on the ipsilateral carotid artery. Immediate surgical outcome was uniformly good with no perioperative neurologic compli- cations. Follow-up duplex imaging on all eight arteries from 1 to 98 months (mean, 37 months) demonstrated six arteries continued patent without significant restenosis, whereas two arteries developed significant restenosis re- quiring reoperation. One underwent repeat endarterec- tomy and vein patch, and the other had saphenous vein interposition grafting. One patient died after 42 months from metastatic disease, however, neurologically intact. We conclude that radiation associated carotid artery stenosis appears to occur at a young age, with a higher incidence of bilateral than conventional atherosclerosis stenosis. Eight arteries treated with a uniform surgical procedure revealed no perioperative neurologic events. Recurrence in two patients is discussed. Acetazolamide enhanced SPECT evaluation of cerebral perfusion before and after carotid endarterectomy Dolores F. Cikrit, MD, Robert W. Burt, MD, Stephen G. Lalka, MD, Michael C. Dalsing, MD, and Alan P. Sawchuk, MD, Indiana University Medical Ceater, India- napolis, Ind. Twenty-five patients were tested before and after carotid endarterectomy (CEA) with acetazolamide (ACZ) enhanced SPECT (ACZS) using HMPAO or IMP, which are both widely available radiopharmaceuticals. They are used for imaging the distribution of cerebral blood flow 419

Mechanics of vein patch following carotid endarterectomy: implications for rupture of ankle vein patches

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Page 1: Mechanics of vein patch following carotid endarterectomy: implications for rupture of ankle vein patches

ANNUAL MEETING ABSTRACTS From the Midwestern Vascular Surgical Society

The Fifteenth Annual Meeting of the Midwestern Vascular Surgical Society will be held in Chicago, Ill., on Sept. 20-21, 1991. Selected abstracts from that meeting are published here in order of presentation at the meeting.

Mechanics of vein patch following carotid end- arterectomy: implications for rupture of ankle vein patches Philip B. Dobrin, MD, LoyoLa University Medical Center, Maywood, Ill

Saphenous vein patches frequently are used to close the carotid artery after endarterectomy. Recent publications report that in a few cases patches constructed from saphenous vein obtained from the ankle region rupture soon after surgery. To investigate the mechanisms of vein patch rupture we examined the geometric characteristics and mechanical properties of vein patches. After measuring the dimensions of patched carotid arteries at surgery, engineering analysis was used to determine the forces required of the vein to maintain equilibrium in a curved patch at 100 mm Hg, and in a patch at elevated arterial pressures. Thirty-nine segments of normal human saphe- nous vein then were obtained from the ankle, calf, knee, and groin at surgery. These 39 vessels were mounted as cylinders in a tissue bath and were studied at 37” C with use of displacement transducers and radiographic methods to measure the diameter, length, and wall thickness of the veins. Values were obtained at 25 mm Hg, pressure intervals between 0 and 200 mm Hg. By use of these data, as well as bursting pressures for normal saphenous vein segments, it was possible to determine (1) the wall stress required of the vein over the full range of arterial pressures when it is used as a patch for the carotid artery and (2) the wall stress required of the vein patch at bursting pressure. Analysis showed that at 100 mm Hg the wall stress is 2.44 -+ .03 x lo5 N/m’, and at 200 mm Hg it is 4.88 t .05 x lo5 N/m’. At bursting pressure the wall stress is 6.0 ? .72 x lo7 N/m’. Thus at arterial pressures the vein wall is subject to less than 1% of bursting stress (p < 0.01). These data show that normal ankle vein is not overloaded and has a great safety margin. Therefore rupture of ankle vein must be the result of a structural defect in the vessel wall, possibly caused by chronic exposure to elevated hydrostatic venous pressures, trauma, thrombosis, or inflammation.

Carotid endarterectomy with vein patch angioplasty for radiation induced symptomatic carotid atherosclerosis Joseph J. Hurley, MD, Aksel G. Nordestgaard, MD, John J. Woods, Jr., MD, Arthur I. Auer, MD, and Mary K. Milyard, RN, St. John’sMercy Medical Center, St. Louis, MO.

Symptomatic carotid artery disease after high-dose radiotherapy for head and neck cancer occurs with twice the incidence as in nonradiated patients and may become more

common as improved treatment results in longer. survival. The surgical experience is limited, and fewer than 50 reported cases exist. Earlier reports have shown a high frequency of perioperative neurologic deficit and throm- bosis rate. Controversy regarding the appropriate surgical approach exists. We report our experience with a uniform initial surgical approach in six patients, eight carotid arteries, and 10 operations. One patient who had occlusion of the common carotid artery after mastectomy and radiation therapy was excluded. Five men and one woman with a mean age of 56 years (range, 27 to 7X years) were admitted with symptomatic carotid artery disease (amau- rosis fugax 2, TIAs 3, and CVA 1) between 4 and 23 years (mean, 13 years) after receiving radiotherapy for head and neck cancer (squamous cell cancer of mouth 1, oropharynx 2, and unknown 1, larynx cancer 1, and craniopharyngeal lymphoma 1). Two patients had undergone radical neck dissection and one total laryngectomy. Nine carotid endarterectomies with saphenous vein patch angioplasty were performed, including two bilateral endarterectomies, a third patient had the contralateral internal carotid artery occluded, and two patients required reoperation on the ipsilateral carotid artery. Immediate surgical outcome was uniformly good with no perioperative neurologic compli- cations. Follow-up duplex imaging on all eight arteries from 1 to 98 months (mean, 37 months) demonstrated six arteries continued patent without significant restenosis, whereas two arteries developed significant restenosis re- quiring reoperation. One underwent repeat endarterec- tomy and vein patch, and the other had saphenous vein interposition grafting. One patient died after 42 months from metastatic disease, however, neurologically intact.

We conclude that radiation associated carotid artery stenosis appears to occur at a young age, with a higher incidence of bilateral than conventional atherosclerosis stenosis. Eight arteries treated with a uniform surgical procedure revealed no perioperative neurologic events. Recurrence in two patients is discussed.

Acetazolamide enhanced SPECT evaluation of cerebral perfusion before and after carotid endarterectomy Dolores F. Cikrit, MD, Robert W. Burt, MD, Stephen G. Lalka, MD, Michael C. Dalsing, MD, and Alan P. Sawchuk, MD, Indiana University Medical Ceater, India- napolis, Ind.

Twenty-five patients were tested before and after carotid endarterectomy (CEA) with acetazolamide (ACZ) enhanced SPECT (ACZS) using HMPAO or IMP, which are both widely available radiopharmaceuticals. They are used for imaging the distribution of cerebral blood flow

419