The long-term effect of surgical aortic valve replacement on arterial stiffness and wave reflections

Background

Assessing arterial properties in patients with aortic valve stenosis undergoing surgical aortic valve replacement (SAVR) is difficult, and the results to date have been inconclusive.

Purpose

We sought to investigate how SAVR affects vascular stiffness in the short and long term.

Methods

We included 69 patients (mean age 70.8±8.4 years, 62% men) with severe symptomatic aortic stenosis who underwent SAVR. Arterial stiffness was assessed using the carotid femoral pulse wave velocity (cfPWV) and brachial-ankle pulse wave velocity (baPWV). Measurements in patients with an ankle-brachial index (ABI) <0.9 were excluded from the analysis for baPWV measurments because a low ABI can affect the accuracy of baPWV. Augmentation index corrected for heart rate (Alx@75), central pressures and subendocardial viability ratio (SEVR) were assessed with arterial tonometry. Measurements were conducted at baseline, in the acute phase and 1 year after the operation.

Results

Immediately after SAVR there was an increase in cfPWV (8.04±1.3 m/s vs 8.54±1.6 m/s, p=0.02) that was sustained at 1 year (8.04±1.3 m/s vs 9.42±2.4 m/s, p≤0.001). Similarly, baPWV (n=55) increased in the acute phase (1633±429 cm/s vs 2014±606 cm/s, p<0.001) and persisted 1 year postoperatively (1633±429 cm/s vs 1867±408 cm/s, p<0.001). Post-SAVR we also observed a decrease in Alx@75 (31.02±10% vs 22.73±12%, p≤0.001) that was attenuated 1 year later (31.02±10% vs 26.65±8%, p≤0.001), and an increase in SEVR (136.1±30.4% vs 149.2±37.7%, p=0.01) which remained improved at 1 year (136.1±30.4% vs 147.5±30.4%, p=0.01).

Conclusions

After SAVR the arterial system shows an increase of stiffness in response to the acute relief of the obstruction, which is retained in the long term.

Funding Acknowledgement

Type of funding sources: None.

Carotid Disease and Ageing: A Literature Review on the Pathogenesis of Vascular Senescence in Older Subjects

Aging is a natural process that affects all systems of the human organism, leading to its inability to adapt to environmental changes. Advancing age has been correlated with various pathological conditions, especially cardiovascular and cerebrovascular diseases. Carotid artery (CA) is mainly affected by age-induced functional and morphological alterations causing atheromatous disease. The evolvement of biomedical sciences has allowed the elucidation of many aspects of this condition. Symptomatic carotid disease (CD) derives from critical luminar stenosis or eruption of an atheromatous plaque due to structural modifications of the vessels, such as carotid intima-media thickening. At a histologic level, the aforementioned changes are mediated by elastin fragmentation, collagen deposition, immune cell infiltration, and accumulation of cytokines and vasoconstrictors. Underlying mechanisms include chronic inflammation and oxidative stress, dysregulation of cellular homeostatic systems, and senescence. Thus, there is an imbalance in components of the vessel wall, which fails to counteract exterior stress stimuli. Consequently, arterial relaxation is impaired and atherosclerotic lesions progress. This is a review of current evidence regarding the relationship of aging with vascular senescence and CD. A deeper understanding of these mechanisms can contribute to the production of efficient prevention methods and targeted therapeutic strategies.

Reciprocal regulation of eNOS, H2S and CO-synthesizing enzymes in human atheroma: Correlation with plaque stability and effects of simvastatin

The molecular and cellular mechanisms underlying plaque destabilization remain obscure. We sought to elucidate the correlation between NO, H₂S and CO-generating enzymes, nitro-oxidative stress and plaque stability in carotid arteries. Carotid atherosclerotic plaques were collected from 62 patients who had undergone endarterectomy due to internal artery stenosis. Following histological evaluation the plaques were divided into stable and unstable ones. To investigate the impact of simvastatin we divided patients with stable plaques, into those receiving and to those not receiving simvastatin. Expression and/or levels of p-eNOS/eNOS, pAkt/t-Akt, iNOS, cystathionine beta synthase (CBS), cystathionine gamma lyase (CSE), heme oxygenase-1(HO-1), soluble guanyl cyclase sGCα1, sGCβ1, NOX-4 and HIF-1α were evaluated. Oxidative stress biomarkers malondialdehyde (MDA) and nitrotyrosine (NT) were measured. NT levels were decreased in stable plaques with a concomitant increase of eNOS phosphorylation and expression and Akt activation compared to unstable lesions. An increase in HIF-1α, NOX-4, HO-1, iNOS, CBS and CSE expression was observed only in unstable plaques. 78% of patients under simvastatin were diagnosed with stable plaques whereas 23% of those not receiving simvastatin exhibited unstable plaques. Simvastatin decreased iNOS, HO-1, HIF-1α and CSE whilst it increased eNOS phosphorylation. In conclusion, enhanced eNOS and reduced iNOS and NOX-4 were observed in stable plaques; CBS and CSE positively correlated with plaque vulnerability. Simvastatin, besides its known effect on eNOS upregulation, reduced the HIF-1α and its downstream targets. The observed changes might be useful in developing biomarkers of plaque stability or could be targets for pharmacothepary against plaque vulnerability.

Role of lymphatic vessel density in colorectal cancer: prognostic significance and clinicopathologic correlations

BACKGROUNDS AND AIMS

Over the past decades the identification of several molecules that are expressed specifically in the lymphatic endothelial cells has resulted in marked advances in the field of lymphangiogenesis. We aimed to measure LVD in colorectal cancer patients and to compare it with microvascular density (MVD) - a marker of angiogenesis - and patients' clinicopathological parameters and survival, as the measurement of lymphatic vessel density (LVD) has been documented in various tumor types, including colorectal cancer.

PATIENTS AND METHODS

Fifty one patients who had undergone surgical resection for stage I-III colorectal cancer entered this study. LVD and MVD were determined immunohistochemically with the use of D2-40 and CD34 antibody respectively. The evaluation of LVD was performed by both visual and computer-aided image analysis.

RESULTS

The majority of lymphatic vessels were located in the peritumoral areas rather than within the tumor. The results obtained from the image analyzer correlated significantly with the data obtained using visual counting with light microscopy. Both visual and image analysis LVD failed to correlate with patients' age and gender and tumor location, stage, grade, MVD count and survival.

CONCLUSIONS

The biologic role of the lymphatic vasculature in tumor progression remains controversial. The present study failed to associate LVD with outcome markers and prognosis and further studies would be required to verify our results.

ICU transfer after elective abdominal aortic aneurysm repair can be succesfully reduced with a modified protocol. A fourteen year experience from a University Hospital

AIM

To compare different selective criteria for Internal Care Unit (ICU) admission in two different timeframes, after abdominal aortic aneurysm (AAA) repair. A retrospective audit of acquired data was performed.

METHODS

During a period of fourteen years (1994-2008), 1152 patients underwent an elective open operation for infrarenal abdominal aortic aneurysm, in our department. Six hundred and two patients (Group A) were treated in the period January 1994-January 2003, and 550 patients (Group B) between January 2003 and August 2008. Postoperatively, all patients were transferred to postanesthesia unit (PAU). After a 2 hours period of close observation, they were transferred either to the ICU or to the surgical ward, according to certain selective criteria (SC). In group A we used SC-A, for admission to an ICU, and in group B we used new, stricter, criteria (SC-B). Thirty-day mortality and morbidity, elective admissions to ICU, rate of subsequent ICU admission, from ward to ICU, and the mean hospital and ICU length of stay, were compared between the two groups.

RESULTS

The use of SC-B resulted in a significant reduction of elective admissions to ICU (3.1% vs 8.5%, P<0.001). Nevertheless, the portion of patients, which were transferred with a severe postoperative complication from the ward to ICU, remained similar between the two groups (1.1% vs 0,9%, in group A and B, respectively). All other endpoints were similar in both groups.

CONCLUSION

Modifying the protocol of ICU transfer, after elective abdominal aortic aneurysm repair, we can reduce the number of patients requiring ICU, without compromising patients' safety.

Gastrointestinal stromal tumors of the rectum: report of five cases

We report on five patients (three males and two females), with a median age of 66.2 years (range, 58-73 years) who were admitted in our department from April 1998 until January 2004 with the diagnosis of rectal gastrointestinal stromal tumor (GIST). Their main symptoms were rectal bleeding, constipation and abdominal discomfort. Two patients were treated by an abdominoperineal resection of the rectum. One patient received palliative surgical treatment and adjuvant therapy with imatinib for metastatic disease. Another patient presented with complete rectal prolapse, and was treated with Delorme's procedure. The subsequent pathological examination of the resected specimen showed positive resection margins and was given adjuvant therapy with imatinib. Finally, one case was considered inoperable. However, after nine months of treatment with imatinib, the magnetic resonance imaging (MRI) scan revealed a significant reduction in the tumor size, and the patient was treated with abdominoperineal excision of the rectum. All cases have been proved to be immunohistochemically positive for the CD117 and the CD34 stain. During the follow-up period (mean duration 3.7 years), one patient died of progressive disease while the other four had no sign of recurrence.

A prospective comparison of ampullectomy with pancreaticoduodenectomy for the treatment of periampullary cancer

Local surgical treatment of periampullary neoplasms seems attractive in the context of the reduced morbidity and mortality than the more radical treatment options. The aim of our study was to compare local excision (LE) of the ampulla with standard pancreaticoduodenectomy (PD) for the treatment of periampullary cancer in terms of overall survival. Inclusion criteria were primary tumor < or = 2 cm with no evidence of lymph node involvement or distant metastasis on abdominal computed tomography (CT). Between January 2000 and January 2004, 23 patients were enrolled onto this study (9 in the LE group and 14 in the standard PD group). The two groups were homogeneous with respect to age and gender as well as the size and origin of the primary neoplasm. There was no correlation of the survival with age, gender, presence of lymph node metastasis, size of the primary tumor, type of surgery or histologic grade (x(2), p >0.05). However, the origin of the tumor had major impact on survival, with pancreatic tumors having the worst prognosis. Hospital stay was significantly reduced in the LE treated patients. Our results showed that LE for periampullary tumors is a viable option and is well suited for medically unfit patients or those who refuse more radical treatment options.

Laparoscopic fenestration of multiple giant biliary mucinous cystadenomas of the liver

Biliary cystadenomas of the liver are rare, cystic neoplasms of the biliary ductal system usually occur in middle aged women. We report a case of synchronous multiple huge biliary mucinous cystadenomas with unique features. This is, according to our knowledge, the first report in the literature about three synchronously occurring hepatobiliary cystadenomas. Cystadenomas have a strong tendency to recur, particularly following incomplete excision, and a potential of malignant transformation. A therapeutic re-evaluation may be necessary when the diagnosis of hepatobiliary cystadenoma is made after the operation and an open liver resection should be considered.

Can the diameter of endoluminal shunt influence the risk of hyperperfusion syndrome after carotid endarterectomy?

AIM

The aim of this study was to evaluate if there is a possible relation between the size of endoluminal shunt, in carotid endarterectomy (CEA), and the risk of postoperative hyperperfusion syndrome.

METHODS

We retrospectively studied prospectively collected data from 156 patients, who were subjected to CEA using shunting and vein patch angioplasty. One hundred and thirty-eight of the patients had bilateral, high grade (> or = 90%) internal carotid lesions and the remaining 18 had a high-grade stenosis (> or = 90%) and a contralateral internal carotid artery (ICA) occlusion. In 81 patients varying diameters of shunts were used (8-14 Fr) according to the diameter of ICA (group A) and in the other 75 patients (group B) only the smallest shunt was used (8 Fr). Development of hyperperfusion syndrome was evaluated both clinically and radiologically with magnetic resonance imaging.

RESULTS

Fifteen patients developed hyperperfusion syndrome (9.6%), between 0 to 6 days postoperatively. Thirteen belonged to group A (86.6%), and 2 (13.3%) belonged to group B (P<0.05). One had an intracerebral hemorrhage (0.6% of the study group) the 3rd postsurgical day.

CONCLUSIONS

During CEA in patients with high-grade bilateral lesions, we recommend the use of a shunt with small diameter: this aims at reducing the risk of hyperperfusion syndrome.

Intact germinal layer of liver hydatid cysts removed after administration of albendazole

BACKGROUND

Hydatid disease is a common health problem especially in Mediterranean and sheep-farming countries, caused by infection with the metacestode stage of the tapeworm Echinococcus. The liver is the most frequent primary site of Echinococcus granulosus infection in humans. Surgery remains the main treatment modality for cystic hepatic hydatid disease, with complete resection of the germinal layer being of major importance for recurrence. Perioperative administration of albendazole has been reported to improve surgical outcome but the results are controversial. We report here our observations on the usefulness of preoperative chemotherapy in surgical outcome in terms of morbidity and recurrence.

METHODS

Five patients with complex liver hydatid cysts received 28 days of albendazole prior to partial cystectomy. Radiological examinations with computed tomography and ultrasound and surgical outcome were used to assess the efficacy of the regimen.

RESULTS

Three patients underwent a complete removal of the germinal layer of the cyst and there were no cases of biliary fistula in these patients. There were no relapses in any of the patients at 12 months' follow-up.

CONCLUSIONS

Preoperative use of medical therapy consisting of albendazole facilitates complete resection of the germinal layer by detaching it from the laminar layer, thus reducing not only the recurrence rates but also the postoperative complications, especially bilious fistulas.

Inguinal dermoid cyst of the round ligament. A case report and review of the literature

INTRODUCTION

Dermoid cysts are rarely located in extraovarian sites, representing an extremely uncommon lesion of the round ligament. The differential diagnosis of an inguinal lesion that proved to be a dermoid cyst deriving from the round ligament is presented with a review of the literature.

CASE REPORT

A case of a 27-year-old female with a dermoid cyst arising from the round ligament and lying inside the inguinal canal, which was tender and palpable, is reported.

DISCUSSION

Underlining their origin, clinical manifestation, gross appearance and pathology, we differentiate dermoid cysts mainly from epidermoid cysts and mature cystic teratomas, analyzing the importance of such a distinction to the possibility of malignant degeneration and recurrence of a dermoid cyst in the round ligament.

Expanding ulnar artery aneurysm presenting with signs of threatened rupture

The case of a 25-year-old man admitted with an ulnar artery aneurysm of the wrist is presented. The size of the aneurysm (1.5 x 2.7 cm) and progressive pain gave the impression of a threatened rupture. Radiologic examinations confirmed the existence of a non-thrombosed ulnar artery aneurysm with occlusion of the 4th and 5th digital arteries. During an urgent surgical exploration a pseudo-aneurysm was found and resected and the artery was repaired. Thrombolysis of the digital arteries was performed with a good result. The combination of a large-sized pseudo-aneurysm, lack of a history of penetrating trauma and presentation of threatened rupture are unique and not reported previously in the literature.

Lower Extremity Bypass Procedures in Diabetic Patients with End-Stage Renal Disease: Is It Worthwhile?

BACKGROUND/AIMS

Limb-threatening ischemia in patients with end-stage renal disease (ESRD) represents a challenging therapeutic problem. Furthermore, diabetes mellitus is frequently associated with ischemic gangrene, persistent infection and impaired wound healing. The present study was undertaken to examine graft patency, limb salvage and survival in patients with ESRD and diabetes following bypass grafting to treat lower limb critical ischemia.

METHODS

A retrospective analysis of 56 arterial reconstructions performed in 39 patients with diabetes mellitus and ESRD during a period of 8 years. The indications for bypass grafting were: ischemic rest pain (n = 13), non-healing ulcer (n = 18) or foot gangrene (n = 25). Risk factors in association with surgical morbidity and mortality, limb loss and graft patency were evaluated.

RESULTS

Thirty-four patients were on hemodialysis and 5 on peritoneal dialysis. Forty-nine infrainguinal reconstructions were performed; the site of distal anastomosis was the below knee popliteal artery (n = 22), the anterior tibial artery (n = 12), the posterior tibial artery (n = 8), and the peroneal artery (n = 7). Seven axillofemoral reconstructions were also performed; the site of distal anastomosis was the common femoral artery (n = 5) and the above knee popliteal artery (n = 2). The 30-day operative mortality rate was 18% (7 patients). The mean follow-up was 11.5 (range 1-93) months. Patient survival rate at 1 and 2 years was 63 and 45%, respectively. Primary patency rate was 64% at 1 year and 58% at 2 years. The limb salvage rate was 65% in the first year.

CONCLUSION

Limb salvage rate in patients with ESRD and diabetes justifies an aggressive policy of revascularization, despite decreased survival of this population.

Does octreotide impair anastomotic healing after small bowel resection?

Seventy two rats underwent small bowel resection followed by end-to-end anastomosis. The octreotide group consisted of 36 rats treated with octreotide (subcutaneously, 7 microg/kg/day, in two equal doses), and the control group consisted of 36 rats treated with the same volume saline. Twelve animals from each group were re-explored on the 4th, 8th and 15th postoperative day. Leakages, adhesions, obstructions were the clinical postoperative findings identified and recorded. Anastomotic bursting pressures were measured. Histochemical studies included haematoxylin-eosin and Van Gieson staining techniques and focused on the microscopic characterization of the healing process. Adhesions, leakages and obstructions were not different between octreotide and control groups. Anastomoses of the octreotide group had increased bursting pressures on the 8th and the 15th day (p < .05 , p < .05, respectively). Regarding the histogical results, on the 8th day the octreotide group compared to the control group, showed healing in more layers (p < .05), increased bright red collagen fibers and quantity of fibroblasts (p < .05), and on the 15th day, the octreotide group showed fewer gaps (p < .05), increased bright red collagen fibers and quantity of fibroblasts (p < .05). In this experimental model, it appeared that octreotide does not impair healing of small bowel anastomoses, but in contrast, there is some evidence that it enhances healing on the 8th and the 15th postoperative day.

Selective use of the intensive care unit after elective infrarenal abdominal aortic aneurysm repair

AIM

Abdominal aortic aneurysm (AAA) repair has traditionally involved admission to the intensive care unit (ICU). This paper reports on an experience of using preoperative medical criteria and a list of intraoperative factors for selective use of the ICU. These criteria were evaluated in relation to their impact on the safety and short term results after open AAA repair.

METHODS

All elective open infrarenal AAA repairs during a 9 year period (1994-2003), following a specific algorithm towards selective use of the ICU, were retrospectively evaluated. Patients were clinically evaluated, before the operative procedures, and divided into categories according to their medical risk (cardiac and pulmonary status). Patients with an ejection fraction <30% and a FVC or FEV1 <50% of the predicted value were transferred immediately from the operating room to the ICU. A list of intraoperative factors: 1) prolonged operative time; 2) prolonged aortic clamping time; 3) suprarenal clamping; 4) quantity of blood transfusion; 5) intraoperative acute renal failure; 6) intraoperative hemodynamic instability; 7) intraoperative cardiac dysfunction were also considered criteria for transfer from the operating room to the ICU. Patients who did not meet any of the above criteria were extubated and transferred to the surgical floor.

RESULTS

Elective AAA repair was performed on 602 patients, among whom, 551 (91.5%) were extubated in the operating room and thereafter treated in the surgical floor and 51 (8.5%) were transferred from the operating room to the ICU. However, later transfer from the floor to the ICU was required in 7 more patients (1.1%), increasing the total percentage of patients treated in the ICU to 9.6%. (51 patients initially and 7 later on). The total postoperative 30 days mortality rate was 0.7% (4 patients) and the morbidity rate was 18.8% in this series. The mean length of in-hospital stay was 9.9 days and the mean ICU length of stay was 4.2 days.

CONCLUSION

Elective AAA repair with selective use of the ICU can be a considerable safe policy in a single high volume hospital. It can reduce resource use without a negative impact on the quality of care.

Current practice--routine use of shunting in carotid endarterectomy. Cost reduction and surgical training

BACKGROUND

Sophisticated methods of determining cerebral blood flow have reduced the use of shunting in carotid endarterectomy in 6-25% of cases. However teaching university hospitals still have to provide their young vascular surgeons with experience in the shunting procedure. Since complications of shunting have been related to the surgeon's experience in the technique, our study aimed to evaluate a policy of the routine use of shunting in carotid endarterectomy by vascular surgeons in training. In addition to concluding how this policy would affect the optimum outcome of our patients. The probable reduction of hospital charges was also evaluated.

METHODS

A prospective audit of the results of 423 consecutive carotid endarterectomies performed by a senior vascular surgeon (the first 97 cases) and a vascular surgeon in training under the supervision of a senior vascular surgeon (326 cases), with routine use of an indwelling intraluminal shunt, in a university hospital in Athens.

RESULTS

During the study period, 337 patients admitted to our department were managed surgically independently of any demanding surgery due to the anatomy and the extension of internal carotid artery disease. The perioperative stroke/death rate at 30 days was 0.47%, but the stroke rate alone was 0%. Minor complications amounted to 5.4%, with an increased but not significant difference in patients presenting contralateral internal carotid occlusion. There was no difference in complication rates when a young surgeon performed the shunting procedure compared with the experienced senior surgeon's results, but this was achieved after training in the method in the first 97 cases. The reduction of the total cost was related to avoidance of cost of the devices necessary for determination of the cerebral circulation during carotid clamping and the cost of specially trained personnel. Our policy resulted in only eight patients having to be treated in the intensive care unit for a total of 13 days.

CONCLUSIONS

Experience in a large number of shunting procedures are required for a young vascular surgeon's training, in order to achieve optimum results. This can be done in teaching hospitals by using the method more frequently than required. Moreover in the contest of continuing changes in the practice of carotid endarterectomy and the economic restrictions on health expenditure, the routine use of shunting resulted in cost saving without jeopardizing the patients' outcome.

Study comparing sutures and nonpenetrating titanium clips for arteriotomy closure after embolectomy

BACKGROUND

The vascular closure staple (VCS) clip applier system is an alternative to suture for closing arteriotomies and performing vascular anastomoses. This study was designed to evaluate the possible advantages of its use in closing arteriotomies after embolectomy.

METHODS

In this study, 26 patients with upper or lower extremity embolism underwent embolectomy, and the arteriotomy was closed using either VCS clips (group A) or sutures (group B).

RESULTS

The time required for arteriotomy closure with clips (11.2 +/- 2.7s) was considerably shorter than the time required with sutures (241.2 +/- 48.7s; p < 0.0001), resulting also in shorter clamp times (380.8 +/- 127.3s vs 612.7 +/- 112.6 s; p < 0.0001). No hemodynamically significant stenoses or pseudoaneurysms were detected at the arteriotomy sites in any of the patients up to 1 year after embolectomy.

CONCLUSIONS

The VCS clip applier system, a quick and easy method for closing arteriotomies, is as safe as sutures in terms of narrowing of the artery and formation of pseudoaneurysm.

Pathological changes of hepatic artery and portal vein, after allyl-alcohol and carbon tetrachloride administration. An experimental study

BACKGROUND

Allyl-alcohol (AA) and carbon tetrachloride (CC14) are known to cause peritoneal and pericentral liver necrosis, respectively. This study investigates pathological changes of hepatic artery and portal vein after simultaneous administration of AA and CC14 in rats.

METHODS

The study comprised 130 male Wistar rats divided randomly into 2 groups: I (n=10) sham and II (n=120) AA injection (intraperitoneally: 0.62 mmol/kg) and rhinogastric administration of CC14 (0.66 ml/kg, 1:1 volume dilution in corn oil). After injection was completed, animals of group II were assigned in 12 categories and sacrificed 2, 4, 6, 12, 18, 24, 33, 48, 57, 81, and 153 hrs after. Tissue was obtained from the left anterior lobe and the hilum of the liver, and histological examination included H&E, silver methenamine and van Giesson stains.

RESULTS

Liver sections from group II (AA+CC14) demonstrated periportal together with pericentral necrosis; the peak was 57 hrs after injection. In all 120 cases, H&E stain showed evidence of regeneration originated from zone 2, extending to zone 1 and occasionally to zone 3, and accomplished mainly by non-necrotic cell proliferation. Sections from the liver hilum showed thrombosis of the portal vein, whereas the hepatic artery and its branches developed a variety of changes. Initially (2, 4 hrs), endothelial hypertrophy was observed which was followed by focal fibrinoid necrosis of the arterial wall (6 hrs). Later on (9-153 hrs) the following findings were present: hyperplasia and non-isometric cytoplasmic vacuolisation of media, disruption of the elastic lamina, aggregation of foam cells and macrophages in intima, media, and focally in adventitia of hepatic artery; and lymphocytic inflammation of intimal and periadventitial area. In 2 cases (153 hrs) hepatic artery thrombosis was present.

CONCLUSIONS

Additionally to liver parenchymal changes, simultaneous administration of allyl-alcohol and carbon tetrachloride in rats results to vascular changes mainly in the hepatic artery and its branches. During liver parenchymal regeneration, the hepatic artery and its branches develop microscopic features that morphologically resemble those of atherosclerosis. These changes may result in hepatic artery thrombosis and or obstruction.