Impact of blood coagulation and fibrinolytic system changes on early and mid term clinical outcome in patients undergoing stent endografting
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《血管的通路杂志》
Department of Cardiac Surgery, University of Naples ‘Federico II’, Via A. Falcone 258, 80127 Naples, Italy
Presented at the 55th International Congress of the European Society for Cardiovascular Surgery, St Petersburg, Russian Federation, May 11–14, 2006.
Abstract
Objective: Blood coagulation and fibrinolytic system changes after endovascular repair (EVAR) of aortic pathologies are of great interest. We have examined the risk for consumption coagulopathy and its clinical implications early, and at a mid-term follow-up, in a prospective study. Methods: From June 2002 to June 2004, 41 patients for abdominal aortic aneurysm (AAA), 16 for thoracic aortic aneurysm (TAA) and 13 for acute type-B dissection underwent EVAR. Plasminogen, fibrin degradation products (FDP) and D-dimer were monitored as markers of fibrinolysis. Platelet count, fibrinogen, antithrombin III and prothrombin were assayed as markers of coagulation. The aortic diameters were assessed by computed tomography (CT) scan. Results: FDP and D-Dimer levels significantly increased, while plasminogen values significantly decreased, on postoperative day 1 and 5, coagulation parameters significantly decreased on postoperative day 1 and 5. All parameters recovered on the 1st month of follow-up, except fibrinogen levels that showed a significant increase on month 1 and 6. We did not observe clinical complications related to coagulative disorders. There was no correlation between the preoperative diameter and the coagulative and fibrinolysis variations in the AAA and TAA group. Type-B dissection patients showed a significant correlation between the preoperative presence of a large false lumen and a high level of fibrinolysis. Conclusion: EVAR leads to changes in coagulation and fibrinolysis, with characteristic developments. These latter have no clinical relevance and have no effect on early outcome and on mid-term follow-up.
Key Words: Aortic aneurysm; Type-B dissection; Stent-endografting surgery; Blood coagulation
1. Introduction
The satisfactory short and mid term results of endovascular repair (EVAR) of thoracic and abdominal aortic aneurysms or type-B aortic dissection are actually well recognized [1–4], mostly for selected surgical high risk patients with significant co-morbidities [5,6]. The majority of studies on the clinical efficacy of EVAR consider patient clinical outcome and/or the absence of endoleaks as the primary ‘end points’ [7,8]. Very few studies have been conducted on the collateral effects after EVAR, particularly on the fibrinolytic system and blood coagulation changes, caused by the aneurysmal sac thromboexclusion and the introduction of a foreign intra-vascular material [9–11]. On the other hand, there are numerous reports on the changes that occur in coagulation parameters following conventional surgery for abdominal aortic aneurysm (AAA), thoracic aortic aneurysms (TAA) or aortic dissection [12–15]. Therefore, we have undertaken a prospective study, using a standardized protocol of hematological and instrumental recordings in order to evaluate the changes occurring in the coagulative process of patients undergoing EVAR and the influence of aneurysmal size and of basic pathology (AAA, TAA and type-B aortic dissection) on these changes. Furthermore, we assessed the potentiality of changes of coagulative process during the post-operative period and at mid-term follow-up.
2. Material and method
From March 2001 to June 2005, 157 patients underwent EVAR at our Institution. Our study included 70 patients who underwent EVAR, from June 2002 to June 2004: 41 for infrarenal AAA, 16 for descending TAA and 13 for acute (within 1 week from onset) type-B aortic dissection. Demographic and clinical characteristics are shown in Table 1. Written informed consent was obtained from all patients, after a detailed description of the procedure.
Criteria for inclusion in the study were: the technical feasibility of performing the procedure in accordance with our previously described criteria [4,6]; non-assumption of any anti-coagulant and/or anti-aggregant therapy for at least 1 week prior to the procedure; the absence of any significant disorders in preoperative coagulation.
The study protocol for each patient required: (a) the assessment of aortic diameter by helical CT-scan, with axial and multiplanar reconstruction (MPR) and volume-rendered (VR) images prior to surgery, on the seventh postoperative day and at 3, 6 and 12 months, and yearly thereafter; (b) serial serum samples, collected before the operation and on days 1, 5 and 10 postoperatively as well as at the first and sixth month follow-up. Coagulation was monitored by measuring platelets count (normal value 130–340x103/dl), fibrinogen level (normal value 160–350 mg/dl), prothrombin activity (normal value 70–110%) and antithrombin III dosage (AT III; normal value 70%), for coagulation, while the levels of plasminogen (normal value 80–120%), fibrinogen degradation products (FDP; normal value <100 ng/ml) and D-dimer (normal value <450 ng/ml) were measured for fibrinolysis monitoring. The classification of the American Society of Anesthesiologists (ASA) was used to assess preoperative risk. The procedure was performed under epidural anesthesia for AAA patients and general anesthesia for the remaining patients.
On the basis of most-favorable angiographic morphology, we surgically exposed one femoral artery for patients suffering from TAA or dissection and both femoral arteries for patients with AAA. A bolus of 50 units/kg of heparin before sheath insertion was admonistrated intravenously, maintaining an activated coagulation time at more than 200 s. The endoprosthesis were inserted and released into the aorta on an extra stiff 300-cm-long 0.035-inch guidewire (Back-up Maier, Boston Scientific; Boston, MA), under angiographic monitoring. For patients with Type-B dissection, access was achieved through the femoral artery, using a soft guidewire (Radifocus, Terumo Corporation; Tokyo, Japan) and under angiographic monitoring. Exclusion of the aneurysm or closing of the access tear was confirmed by angiography immediately following the surgery and by a helical CT-scan on postoperative day 7. Primary success criteria were intraoperative survival, the absence of open surgical conversion, the exclusion of aneurysmal sac and of any transected or dissected tract, the absence of type I or III endoleaks, according to the White classification [16]. We used one or more Talent prostheses (Medtronic AVE, Santa Rosa, CA) in all patients: we implanted 37 prostheses (2.3±0.5 prostheses/patient) in patients with TAA and 35 prostheses in patients with dissection (2.7±0.5 prostheses/patient). In AAA patients we always implanted a bifurcated prosthesis, with 1 case (2.4%) requiring implantation of a proximal extension.
2.1. Statistics
Continuous variables are presented as mean±standard deviation and categorical variables as absolute number and percent value. Differences between groups were assessed using univariate ANOVA for continuous variables, post hoc analysis performed by Bonferroni test, or a chi-square test with the Fisher exact test and odds ratio with 95% confidence intervals for categorical variables; P<0.05 was considered significant. The computer program used was SPSS 11.0 (SPSS Inc., Chicago, IL).
3. Results
There were no in-hospital deaths. EVAR was successfully performed on all patients in accordance with the previously defined criteria. We observed 6 major complications in 4 (5.7%) patients, related to the procedure (2 cases of acute renal failure, 1 acute myocardial infarction, 1 prolonged mechanical ventilation and 2 rescue femoro-femoral bypass for acute limb ischemia) and 7 minor complications in 5 (7.1%) patients (4 cases of postimplantation syndrome, 2 cases of lymphorrhea and 1 of wound hematoma). There were no cases of paraplegia. The time required for the procedure was significantly greater for AAA group than thoracic groups. Loss of blood was contained for all groups, as shown in Table 1, with a significant difference between AAA and thoracic group (P<0.01): no patient required transfusion of erythrocyte concentrate and/or fresh frozen plasma.
Changes in coagulation and fibrinolysis parameters are illustrated in Tables 2 and 3, respectively. We noted a significant decrease in platelet level, prothrombin activity, and fibrinogen levels in the blood samples taken on the 1st, 5th and 10th post-operative day; AT-III restored normal values by the 10th day, except in dissection group. Platelets levels showed a slight, but not significant increase at 1 month from the procedure (P=0.09, 0.08 and 0.1 for AAA, TAA and dissection group, respectively). Baseline levels of all parameters completely restored at 1 month, except fibrinogen levels that were significantly increased up to 6 months. These variations were similar for all groups studied. At six months, all the parameters, except fibrinogen, had values similar to baseline. As shown in Table 3, all the parameters of fibrinolysis were compatible with activation of the fibrinolytic processes, with considerable decrease in plasminogen and concurrent increase in the FDP and D-dimer during the immediate postoperative period and on the 5th day: A persistence of a significant difference versus basal values in plasminogen and FDP levels and a trend toward normalization in D-dimer levels on the 10th postoperative day (P=0.08, 0.09 and 0.08 for AAA, TAA and dissection group, respectively) were also observed. Normal values recovered at the 1st month of follow-up for all the parameters.
A comparative review of the study groups showed no significant differences in fibrinogen and plasminogen levels, and in prothrombin activity. On postoperative day 1 the type-B dissection patients had significantly lower levels of platelets, AT III, FDP and D-dimer, compared with TAA and AAA patients; on postoperative day 5 we observed no significant differences in AT III and D-dimer levels in the type-B dissection group, compared with the TAA group, while we still observed significant differences in all parameters when compared with the AAA group. In TAA patients compared with AAA a significant difference was observed only in AT III and FDP levels on postoperative day 1 and 5. No significant differences were observed among study groups after postoperative day 10 (Table 4). The increase in value of FDP and D-dimer was significantly higher in this subgroup of type-B dissection patients, as provided in Table 5.
The preoperative values of the mean diameters of the aorta were compared with the changes in the coagulative and fibrinolysis parameters. There was no correlation between the preoperative diameter and the coagulative and fibrinolysis variations in the group of patients with AAA and TAA. The helical CT with MPR and VR images carried out prior to discharge from the hospital showed that in patients with type-B dissection there was a significant correlation between the preoperative presence of a large false lumen (70% of the aortic diameter and a false lumen up to the common iliac arteries), and a high level of fibrinolysis.
At follow-up (18–36 months, average 25.79±5.28) we observed a mean decrease of 19% in the aortic diameter for the AAA group and of 14% in the TAA group (P=n.s.), in addition to a trend toward thrombosis of the false lumen in patients with type-B dissection (complete thrombosis in 30.0% and thrombosis of >50% in 60.0% of the patients). There was no significant correlation between the changes in coagulation and fibrinolysis and the diameter decrease of the aneurysms or the extent of thrombosis of the false lumen in patients with dissection.
4. Discussion
Disease of the thoracic and abdominal aorta are frequently associated with a coagulating disorder and infrequently to a consumption coagulopathy [17–19]. The use of the cardiopulmonary bypass for the treatment of thoracic aneurysms and type-B dissections entails a higher level of risk for coagulative disorders and active consumption coagulopathy [19,20]. Bleeding is a common complication after aortic surgery, that often needs fresh frozen plasma and/or packed red blood cell transfusion.
Very few cases of coagulative disorders following treatment with EVAR have been reported in literature [21,22]. Recently, Shimazaki et al. [9] observed activation of coagulation and fibrinolysis after endovascular stent grafting of thoracic aorta in a retrospective study, without clinical evidence of triggering a postoperative consumption coagulopathy.
EVAR for AAA and TAA, excluding the aneurysm from the blood flow, causes its thrombosis and subsequent reabsorption, with reduction of the aneurysmal sac. The endovascular treatment of type-B dissection, sealing the access tear in order to decompress and to prevent expansion of the false lumen as well as any complications arising from splanchnic vessels involvement, supports the process of complete thrombosis, related to the flow remaining through distal reentry. In all cases the aim of the treatment is obviously to prevent aortic breakage. We may summarize that the use of endovascular prostheses confines the blood to the aneurysmal sac or to the dissected aortic false lumen, which normally tends toward thrombosis, setting off platelet and coagulation factors consumption.
The results of our study show an active fibrinolysis, platelet and coagulation factors consumption in patients with aortic pathologies who are treated by EVAR. We observed a significant decrease in the level of platelets, fibrinogen, plasminogen and prothrombin activity (expression of factors V, VII and X) in all patients, along with a substantial increase in FDP and D-dimer levels, as reliable and sensitive markers for hyperfibrinolisys. By analyzing the study groups, the pathophysiological difference between patients with aortic aneurysms and patients with dissection is obvious: closing of the primary tear leads to partial and variable thrombosis of the false lumen, due to a reverse flow persistence. The prolonged contact with a thrombosed area sets off a more active consumption coagulopathy, as shown by the greater increase in FDP and D-dimer in type-B dissection patients.
In our experience, this coagulative disorder did not influence the clinical outcome or did not lead to any evident hemorrhagic syndrome: in any of the groups, there was no need of fresh frozen plasma, no significant blood loss, nor hemorrhagic complications from surgical incisions. The increase in fibrinogen, peaking at 1 month and persisting up to 6 months, could be related to the inflammatory response, related to endoprosthesis implantation, since in these cases the fibrinogen acts as an aspecific inflammation marker. The clinical irrelevance of the hyperfibrinolityc state is also confirmed by the absence of any correlation with the timing and the extension of the false lumen thrombosis observed in patients with dissection at the repeated spiral CT scan (1st and 6th month follow-up). In fact, we noted a thrombosis 50% of the false lumen in more than 60% of the cases, notwithstanding the high values of the FDP and the D-dimer observed during the early postoperative period. The changes of the coagulation values and of fibrinolysis clearly indicate a presence of blood coagulation disorder, without necessarily triggering an hemorrhagic syndrome. In order to minimize this risk that, however, should be taken into account, an assiduous monitoring of the appropriate hematologic parameters and of the patients' clinical conditions is mandatory: the patient should be discharged only when a complete or a clear trend toward a complete normalization of hematochemical parameters is obtained. The contained blood loss decreases the need for transfusion and certainly limits hemorrhagic complications, and this is certainly a major advantage with respect to conventional surgery. Endovascular repair has emerged as a very important treatment modality in the management of serious and relatively frequent abdominal and thoracic aortic diseases. The reported data encourage us to a more extensive use of EVAR in treating patients with acute type-B dissection, in which conventional surgery, requiring cardiopulmonary bypass, systemic heparinization, significant blood loss and consequent transfusions, leads to a more complex and complicated maintenance of the coagulative homeostasis. Based on our study it is our belief that EVAR is preferable for patients at high risk of hemorrhagic syndromes for hepatic dysfunctions and coagulative disorders, in whom the open surgery would be a dangerous option.
In conclusion, EVAR leads to changes in coagulation and fibrinolysis in different sets of patients. However, these changes did not have any influence on the immediate and mid term clinical outcome of patients. As few long-term data exist on the durability and morbidity of stent grafts, lifelong surveillance remains necessary.
References
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Presented at the 55th International Congress of the European Society for Cardiovascular Surgery, St Petersburg, Russian Federation, May 11–14, 2006.
Abstract
Objective: Blood coagulation and fibrinolytic system changes after endovascular repair (EVAR) of aortic pathologies are of great interest. We have examined the risk for consumption coagulopathy and its clinical implications early, and at a mid-term follow-up, in a prospective study. Methods: From June 2002 to June 2004, 41 patients for abdominal aortic aneurysm (AAA), 16 for thoracic aortic aneurysm (TAA) and 13 for acute type-B dissection underwent EVAR. Plasminogen, fibrin degradation products (FDP) and D-dimer were monitored as markers of fibrinolysis. Platelet count, fibrinogen, antithrombin III and prothrombin were assayed as markers of coagulation. The aortic diameters were assessed by computed tomography (CT) scan. Results: FDP and D-Dimer levels significantly increased, while plasminogen values significantly decreased, on postoperative day 1 and 5, coagulation parameters significantly decreased on postoperative day 1 and 5. All parameters recovered on the 1st month of follow-up, except fibrinogen levels that showed a significant increase on month 1 and 6. We did not observe clinical complications related to coagulative disorders. There was no correlation between the preoperative diameter and the coagulative and fibrinolysis variations in the AAA and TAA group. Type-B dissection patients showed a significant correlation between the preoperative presence of a large false lumen and a high level of fibrinolysis. Conclusion: EVAR leads to changes in coagulation and fibrinolysis, with characteristic developments. These latter have no clinical relevance and have no effect on early outcome and on mid-term follow-up.
Key Words: Aortic aneurysm; Type-B dissection; Stent-endografting surgery; Blood coagulation
1. Introduction
The satisfactory short and mid term results of endovascular repair (EVAR) of thoracic and abdominal aortic aneurysms or type-B aortic dissection are actually well recognized [1–4], mostly for selected surgical high risk patients with significant co-morbidities [5,6]. The majority of studies on the clinical efficacy of EVAR consider patient clinical outcome and/or the absence of endoleaks as the primary ‘end points’ [7,8]. Very few studies have been conducted on the collateral effects after EVAR, particularly on the fibrinolytic system and blood coagulation changes, caused by the aneurysmal sac thromboexclusion and the introduction of a foreign intra-vascular material [9–11]. On the other hand, there are numerous reports on the changes that occur in coagulation parameters following conventional surgery for abdominal aortic aneurysm (AAA), thoracic aortic aneurysms (TAA) or aortic dissection [12–15]. Therefore, we have undertaken a prospective study, using a standardized protocol of hematological and instrumental recordings in order to evaluate the changes occurring in the coagulative process of patients undergoing EVAR and the influence of aneurysmal size and of basic pathology (AAA, TAA and type-B aortic dissection) on these changes. Furthermore, we assessed the potentiality of changes of coagulative process during the post-operative period and at mid-term follow-up.
2. Material and method
From March 2001 to June 2005, 157 patients underwent EVAR at our Institution. Our study included 70 patients who underwent EVAR, from June 2002 to June 2004: 41 for infrarenal AAA, 16 for descending TAA and 13 for acute (within 1 week from onset) type-B aortic dissection. Demographic and clinical characteristics are shown in Table 1. Written informed consent was obtained from all patients, after a detailed description of the procedure.
Criteria for inclusion in the study were: the technical feasibility of performing the procedure in accordance with our previously described criteria [4,6]; non-assumption of any anti-coagulant and/or anti-aggregant therapy for at least 1 week prior to the procedure; the absence of any significant disorders in preoperative coagulation.
The study protocol for each patient required: (a) the assessment of aortic diameter by helical CT-scan, with axial and multiplanar reconstruction (MPR) and volume-rendered (VR) images prior to surgery, on the seventh postoperative day and at 3, 6 and 12 months, and yearly thereafter; (b) serial serum samples, collected before the operation and on days 1, 5 and 10 postoperatively as well as at the first and sixth month follow-up. Coagulation was monitored by measuring platelets count (normal value 130–340x103/dl), fibrinogen level (normal value 160–350 mg/dl), prothrombin activity (normal value 70–110%) and antithrombin III dosage (AT III; normal value 70%), for coagulation, while the levels of plasminogen (normal value 80–120%), fibrinogen degradation products (FDP; normal value <100 ng/ml) and D-dimer (normal value <450 ng/ml) were measured for fibrinolysis monitoring. The classification of the American Society of Anesthesiologists (ASA) was used to assess preoperative risk. The procedure was performed under epidural anesthesia for AAA patients and general anesthesia for the remaining patients.
On the basis of most-favorable angiographic morphology, we surgically exposed one femoral artery for patients suffering from TAA or dissection and both femoral arteries for patients with AAA. A bolus of 50 units/kg of heparin before sheath insertion was admonistrated intravenously, maintaining an activated coagulation time at more than 200 s. The endoprosthesis were inserted and released into the aorta on an extra stiff 300-cm-long 0.035-inch guidewire (Back-up Maier, Boston Scientific; Boston, MA), under angiographic monitoring. For patients with Type-B dissection, access was achieved through the femoral artery, using a soft guidewire (Radifocus, Terumo Corporation; Tokyo, Japan) and under angiographic monitoring. Exclusion of the aneurysm or closing of the access tear was confirmed by angiography immediately following the surgery and by a helical CT-scan on postoperative day 7. Primary success criteria were intraoperative survival, the absence of open surgical conversion, the exclusion of aneurysmal sac and of any transected or dissected tract, the absence of type I or III endoleaks, according to the White classification [16]. We used one or more Talent prostheses (Medtronic AVE, Santa Rosa, CA) in all patients: we implanted 37 prostheses (2.3±0.5 prostheses/patient) in patients with TAA and 35 prostheses in patients with dissection (2.7±0.5 prostheses/patient). In AAA patients we always implanted a bifurcated prosthesis, with 1 case (2.4%) requiring implantation of a proximal extension.
2.1. Statistics
Continuous variables are presented as mean±standard deviation and categorical variables as absolute number and percent value. Differences between groups were assessed using univariate ANOVA for continuous variables, post hoc analysis performed by Bonferroni test, or a chi-square test with the Fisher exact test and odds ratio with 95% confidence intervals for categorical variables; P<0.05 was considered significant. The computer program used was SPSS 11.0 (SPSS Inc., Chicago, IL).
3. Results
There were no in-hospital deaths. EVAR was successfully performed on all patients in accordance with the previously defined criteria. We observed 6 major complications in 4 (5.7%) patients, related to the procedure (2 cases of acute renal failure, 1 acute myocardial infarction, 1 prolonged mechanical ventilation and 2 rescue femoro-femoral bypass for acute limb ischemia) and 7 minor complications in 5 (7.1%) patients (4 cases of postimplantation syndrome, 2 cases of lymphorrhea and 1 of wound hematoma). There were no cases of paraplegia. The time required for the procedure was significantly greater for AAA group than thoracic groups. Loss of blood was contained for all groups, as shown in Table 1, with a significant difference between AAA and thoracic group (P<0.01): no patient required transfusion of erythrocyte concentrate and/or fresh frozen plasma.
Changes in coagulation and fibrinolysis parameters are illustrated in Tables 2 and 3, respectively. We noted a significant decrease in platelet level, prothrombin activity, and fibrinogen levels in the blood samples taken on the 1st, 5th and 10th post-operative day; AT-III restored normal values by the 10th day, except in dissection group. Platelets levels showed a slight, but not significant increase at 1 month from the procedure (P=0.09, 0.08 and 0.1 for AAA, TAA and dissection group, respectively). Baseline levels of all parameters completely restored at 1 month, except fibrinogen levels that were significantly increased up to 6 months. These variations were similar for all groups studied. At six months, all the parameters, except fibrinogen, had values similar to baseline. As shown in Table 3, all the parameters of fibrinolysis were compatible with activation of the fibrinolytic processes, with considerable decrease in plasminogen and concurrent increase in the FDP and D-dimer during the immediate postoperative period and on the 5th day: A persistence of a significant difference versus basal values in plasminogen and FDP levels and a trend toward normalization in D-dimer levels on the 10th postoperative day (P=0.08, 0.09 and 0.08 for AAA, TAA and dissection group, respectively) were also observed. Normal values recovered at the 1st month of follow-up for all the parameters.
A comparative review of the study groups showed no significant differences in fibrinogen and plasminogen levels, and in prothrombin activity. On postoperative day 1 the type-B dissection patients had significantly lower levels of platelets, AT III, FDP and D-dimer, compared with TAA and AAA patients; on postoperative day 5 we observed no significant differences in AT III and D-dimer levels in the type-B dissection group, compared with the TAA group, while we still observed significant differences in all parameters when compared with the AAA group. In TAA patients compared with AAA a significant difference was observed only in AT III and FDP levels on postoperative day 1 and 5. No significant differences were observed among study groups after postoperative day 10 (Table 4). The increase in value of FDP and D-dimer was significantly higher in this subgroup of type-B dissection patients, as provided in Table 5.
The preoperative values of the mean diameters of the aorta were compared with the changes in the coagulative and fibrinolysis parameters. There was no correlation between the preoperative diameter and the coagulative and fibrinolysis variations in the group of patients with AAA and TAA. The helical CT with MPR and VR images carried out prior to discharge from the hospital showed that in patients with type-B dissection there was a significant correlation between the preoperative presence of a large false lumen (70% of the aortic diameter and a false lumen up to the common iliac arteries), and a high level of fibrinolysis.
At follow-up (18–36 months, average 25.79±5.28) we observed a mean decrease of 19% in the aortic diameter for the AAA group and of 14% in the TAA group (P=n.s.), in addition to a trend toward thrombosis of the false lumen in patients with type-B dissection (complete thrombosis in 30.0% and thrombosis of >50% in 60.0% of the patients). There was no significant correlation between the changes in coagulation and fibrinolysis and the diameter decrease of the aneurysms or the extent of thrombosis of the false lumen in patients with dissection.
4. Discussion
Disease of the thoracic and abdominal aorta are frequently associated with a coagulating disorder and infrequently to a consumption coagulopathy [17–19]. The use of the cardiopulmonary bypass for the treatment of thoracic aneurysms and type-B dissections entails a higher level of risk for coagulative disorders and active consumption coagulopathy [19,20]. Bleeding is a common complication after aortic surgery, that often needs fresh frozen plasma and/or packed red blood cell transfusion.
Very few cases of coagulative disorders following treatment with EVAR have been reported in literature [21,22]. Recently, Shimazaki et al. [9] observed activation of coagulation and fibrinolysis after endovascular stent grafting of thoracic aorta in a retrospective study, without clinical evidence of triggering a postoperative consumption coagulopathy.
EVAR for AAA and TAA, excluding the aneurysm from the blood flow, causes its thrombosis and subsequent reabsorption, with reduction of the aneurysmal sac. The endovascular treatment of type-B dissection, sealing the access tear in order to decompress and to prevent expansion of the false lumen as well as any complications arising from splanchnic vessels involvement, supports the process of complete thrombosis, related to the flow remaining through distal reentry. In all cases the aim of the treatment is obviously to prevent aortic breakage. We may summarize that the use of endovascular prostheses confines the blood to the aneurysmal sac or to the dissected aortic false lumen, which normally tends toward thrombosis, setting off platelet and coagulation factors consumption.
The results of our study show an active fibrinolysis, platelet and coagulation factors consumption in patients with aortic pathologies who are treated by EVAR. We observed a significant decrease in the level of platelets, fibrinogen, plasminogen and prothrombin activity (expression of factors V, VII and X) in all patients, along with a substantial increase in FDP and D-dimer levels, as reliable and sensitive markers for hyperfibrinolisys. By analyzing the study groups, the pathophysiological difference between patients with aortic aneurysms and patients with dissection is obvious: closing of the primary tear leads to partial and variable thrombosis of the false lumen, due to a reverse flow persistence. The prolonged contact with a thrombosed area sets off a more active consumption coagulopathy, as shown by the greater increase in FDP and D-dimer in type-B dissection patients.
In our experience, this coagulative disorder did not influence the clinical outcome or did not lead to any evident hemorrhagic syndrome: in any of the groups, there was no need of fresh frozen plasma, no significant blood loss, nor hemorrhagic complications from surgical incisions. The increase in fibrinogen, peaking at 1 month and persisting up to 6 months, could be related to the inflammatory response, related to endoprosthesis implantation, since in these cases the fibrinogen acts as an aspecific inflammation marker. The clinical irrelevance of the hyperfibrinolityc state is also confirmed by the absence of any correlation with the timing and the extension of the false lumen thrombosis observed in patients with dissection at the repeated spiral CT scan (1st and 6th month follow-up). In fact, we noted a thrombosis 50% of the false lumen in more than 60% of the cases, notwithstanding the high values of the FDP and the D-dimer observed during the early postoperative period. The changes of the coagulation values and of fibrinolysis clearly indicate a presence of blood coagulation disorder, without necessarily triggering an hemorrhagic syndrome. In order to minimize this risk that, however, should be taken into account, an assiduous monitoring of the appropriate hematologic parameters and of the patients' clinical conditions is mandatory: the patient should be discharged only when a complete or a clear trend toward a complete normalization of hematochemical parameters is obtained. The contained blood loss decreases the need for transfusion and certainly limits hemorrhagic complications, and this is certainly a major advantage with respect to conventional surgery. Endovascular repair has emerged as a very important treatment modality in the management of serious and relatively frequent abdominal and thoracic aortic diseases. The reported data encourage us to a more extensive use of EVAR in treating patients with acute type-B dissection, in which conventional surgery, requiring cardiopulmonary bypass, systemic heparinization, significant blood loss and consequent transfusions, leads to a more complex and complicated maintenance of the coagulative homeostasis. Based on our study it is our belief that EVAR is preferable for patients at high risk of hemorrhagic syndromes for hepatic dysfunctions and coagulative disorders, in whom the open surgery would be a dangerous option.
In conclusion, EVAR leads to changes in coagulation and fibrinolysis in different sets of patients. However, these changes did not have any influence on the immediate and mid term clinical outcome of patients. As few long-term data exist on the durability and morbidity of stent grafts, lifelong surveillance remains necessary.
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