Coagulopathy in Ruptured or Dissecting Aortic Aneurysms

Acute type a aortic intramural hematoma complicated with preoperative hemopericardium: early and late surgical outcome analyses

BACKGROUND

Acute type A aortic intramural hematoma (ATAIMH) is a variant of acute type A aortic dissection (ATAAD), exhibiting an increased risk of hemopericardium and cardiac tamponade. It can be life-threatening without emergency treatment. However, comprehensive studies of the clinical features and surgical outcomes of preoperative hemopericardium in patients with ATAIMH remain scarce. This retrospective study aims to investigate the clinical features and early and late outcomes of patients who underwent aortic repair surgery for ATAIMH complicated with preoperative hemopericardium.

METHODS

We investigated 132 consecutive patients who underwent emergency ATAIMH repair at this institution between February 2007 and August 2020. These patients were dichotomized into the hemopericardium (n = 58; 43.9%) and non-hemopericardium groups (n = 74; 56.1%). We compared the clinical demographics, surgical information, postoperative complications, 5-year cumulative survival rates, and freedom from reoperation rates. Furthermore, multivariable logistic regression analysis was utilized to identify independent risk factors for patients who underwent re-exploration for bleeding.

RESULTS

In the hemopericardium group, 36.2% of patients presented with cardiac tamponade before surgery. Moreover, the hemopericardium group showed higher rates of preoperative shock and endotracheal intubation and was associated with an elevated incidence of intractable perioperative bleeding, necessitating delayed sternal closure for hemostasis. The hemopericardium group exhibited higher blood transfusion volumes and rates of re-exploration for bleeding following surgery. However, the 5-year survival (59.5% vs. 75.0%; P = 0.077) and freedom from reoperation rates (93.3% vs. 85.5%; P = 0.416) were comparable between both groups. Multivariable analysis revealed that hemopericardium, cardiopulmonary bypass time, and delayed sternal closure were the risk factors for bleeding re-exploration.

CONCLUSIONS

The presence of hemopericardium in patients with ATAIMH is associated with an elevated incidence of cardiac tamponade and unstable preoperative hemodynamics, which could lead to perioperative bleeding tendencies and high complication rates. However, patients of ATAIMH complicated with hemopericardium undergoing aggressive surgical intervention exhibited long-term surgical outcomes comparable to those without hemopericardium.

The effects of plasma to red blood cells transfusion ratio on in-hospital mortality in patients with acute type A aortic dissection

Background

Blood transfusion is a frequent and necessary practice in acute type A aortic dissection (AAAD) patients, but the effect of plasma/red blood cells (RBCs) ratio on mortality remains unclear. The aim of this study is to investigate the association between plasma/RBCs transfusion ratio and in-hospital mortality in patients with AAAD.

Methods

Patients were admitted to Xiangya Hospital of Central South University from January 1, 2016 to December 31, 2021. Clinical parameters were recorded. Multivariate Cox regression model was used to analyze the association between transfusion and in-hospital mortality. We used the smooth curve fitting and segmented regression model to assess the threshold effect between plasma/RBCs transfusion ratio and in-hospital mortality in patients with AAAD.

Results

The volumes of RBCs [14.00 (10.12-20.50) unit] and plasma [19.25 (14.72-28.15) unit] transfused in non-survivors were significantly higher than in survivors [RBCs: 8.00 (5.50-12.00) unit]; plasma: [10.35 (6.50-15.22) unit]. Multivariate Cox regression analysis showed plasma transfusion was an independent risk factor of in-hospital mortality. Adjusted HR was 1.03 (95% CI: 0.96-1.11) for RBCs transfusion and 1.08 (95% CI: 1.03-1.13) for plasma transfusion. In the spline smoothing plot, mortality risk increased with plasma/RBCs transfusion ratio leveling up to the turning point 1. Optimal plasma/RBCs transfusion ratio with least mortality risk was 1. When the plasma/RBCs ratio was <1 (adjusted HR per 0.1 ratio: 0.28, 95% CI per 0.1 ratio: 0.17-0.45), mortality risk decreased with the increase of ratio. When the plasma/RBCs ratio was 1-1.5 (adjusted HR per 0.1 ratio: 2.73, 95% CI per 0.1 ratio:1.13-6.62), mortality risk increased rapidly with the increase of ratio. When the plasma/RBCs ratio was >1.5 (adjusted HR per 0.1 ratio: 1.09, 95% CI per 0.1 ratio:0.97-1.23), mortality risk tended to reach saturation, and increased non-significantly with the increase of ratio.

Conclusion

A 1:1 plasma/RBCs ratio was associated with the lowest mortality in the patients with AAAD. And non-linear relationship existed between plasma/RBCs ratio and mortality.

Development and validation of nomogram models to discriminate between acute aortic syndromes and non-ST-elevation myocardial infarction during troponin-blind period

Background

Blood-test-based methods of distinguishing between acute aortic syndromes (AASs) and non-ST-elevation myocardial infarction (NSTEMI) during the troponin-blind period of <2-3 h of symptom onset have not been studied previously. We aimed to explore whether routine biomarkers might facilitate differential diagnosis.

Methods

Data were retrospectively collected from 178 patients with AASs and 460 patients with NSTEMI within 3 h of onset. Differential risk factors related to AASs were identified by univariate and multivariate logistic regression analyses for patients with onset <2 h and onset ≥2 h, respectively, in the cardiac troponin (cTn) cohort. Nomograms were established in the cTn cohort as a training set and validated in the high-sensitivity cTn cohort. To assess the utility of the models in clinical practice, decision curve analyses were performed.

Results

D-dimer, fibrinogen, and age were identified as differential risk factors for AASs with the onset of <2 h. D-dimer at an optimal cutoff level of 281 ng/mL for AASs had a sensitivity of 86.4% and a specificity of 91.3%. A nomogram was developed and validated with areas under the curve (AUC) of 0.934 (95% CI: 0.880-0.988) and 0.952 (95% CI: 0.874-1.000), respectively. D-dimer, neutrophil, bilirubin, and platelet were the differential risk factors for AASs with the onset of ≥2 h. D-dimer at an optimal cutoff level of 385 ng/mL has a sensitivity of 91.8% and a specificity of 91.3%. The AUC of the second nomogram in the training set and the validation set were 0.965 (95% CI: 0.942-0.988) and 0.974 (95% CI: 0.944-1.000), respectively.

Conclusion

Time-dependent quality of D-dimer should be considered for discriminating AASs from NSTEMI. Both nomogram models may have a clinical utility for evaluating the probability of AASs.

Prevention and management of difficult hemostasis in acute type A aortic dissection repair

Postoperative bleeding after surgery for acute aortic dissection is one of the most common complications and has an important influence on mortality and morbidity. Therefore, various methods have been introduced to prevent or manage postoperative bleeding. In this article, we investigated the causes of bleeding after surgery for acute aortic dissection, and introduce appropriate transfusion or pharmacologic treatment, topical hemostatic agents, and local compressive maneuver to manage it.

The point-of-care D-dimer test provides a fast and accurate differential diagnosis of Stanford Type A aortic syndrome and ST-elevated myocardial infarction in emergencies

BACKGROUND

The research of the sensitivity and specificity point-of-care testing (POCT) of D-dimer as a diagnostic protocol for differential diagnosis of Stanford Type A aortic syndrome (hereafter as TAAS) mimicking ST-elevated myocardial infarction (STEMI) with regular STEMI in the emergency department is limited.

METHODS

Full medical information of 32 patients confirmed TAAS and 527 patients confirmed STEMI from January 1st, 2016 to October 1st, 2021 were retrospectively analyzed in Shanghai Tenth People's Hospital of Tongji University.

RESULTS

The baseline characteristics of two groups of patients were well-balanced post propensity score matching (PSM) analysis, and each group had 32 patients enrolled. Patients in the STEMI group had higher positive cardiac troponin I (cTNI) (0.174 ng/ml vs. 0.055 ng/ml, P = 0.008) results but lower D-dimer (0.365μg/ml vs. 31.50μg/ml, P < 0.001) results than the TAAS group. The D-dimer cutoff value of 2.155μg/ml had the best sensitivity of 100% and specificity of 96.9%, and the positive predictive value (PPV) as well as the negative predictive value (NPV) of the cutoff value were 96.9 and 100%, respectively, in total 64 patients, the area under the curve (AUC) values were 0.998 (95% CI:0.992-1.000, P < 0.001) for the D-dimer. No significant correlation between the D-dimer concentration and the time from symptoms onset to first medical contact in both groups (TAAS group: r = - 0.248, P = 0.170; STEMI group: r = - 0.159, P = 0.383) or significant correlation between D-dimer and creatine clearance (TAAS group: r = - 0.065, P = 0.765; STEMI group: r = 0.222, P = 0.221). The total in-hospital mortality for the patients with TAAS presenting as STEMI was 62.5% (20/32). The mortality rate for TAAS patients confirmed by computed tomography angiography (CTA) was significantly lower (40% vs. 82.4%, P = 0.014) than the mortality rate for TAAS patients confirmed by coronary angiography (CAG) and had a longer average survival time (log-rank = 0.015), less peri-surgical complications especially gastrointestinal hemorrhage (0.00% vs. 55.6%, P < 0.001). CTA diagnosis can reduce the mortality rate by 67.5% (95%CI:0.124-0.850, P = 0.16).

CONCLUSIONS

The POCT D-dimer with cut-off 2.155μg/ml would be useful to rule-out TAAS mimicking STEMI from regular STEMI prior to reperfusion therapy. CTA diagnosis is effective in reducing the probability of perioperative complications and lowering perioperative mortality than CAG diagnosis in TAAS patients.

Low-Dose Heparin Protocol in Type A Aortic Dissection Surgeries

OBJECTIVE

We aim to compare the heparin dose regimen in terms of bleeding, reoperation rate due to severe bleeding, and the amount of transfusion of the blood products in patients who underwent surgery for type A aortic dissection (TAAD).

MATERIALS AND METHODS

Between January 2018 and August 2021, 90 adult patients who underwent for TAAD were included. Primary outcome measures were postoperative bleeding amount and blood product transfusion requirements. Two different protocols performed in TAAD surgery in our clinic. In this pre- and postimplementation study, before October 2019, the standard-dose heparin protocol (SH group) was used and after November 2019, the low-dose heparin protocol (LH group) was used and two groups were compared. Mechanical ventilation duration, length of intensive care unit and hospital stay, postoperative drainage volumes, blood product transfusions, reoperations due to bleeding, and in-hospital mortality rates were recorded.

RESULTS

The dosages of heparin and activated clotting time values, as well as the additional heparin requirement, were significantly different between the two groups (p < 0.001). Standard-dose heparinization was needed only in 33.3% of patients in the LH group. In the SH group, postoperative total drainage and red blood cell (RBC) transfusion were significantly higher than the LH group (p = 0.036 and p = 0.046, respectively).

CONCLUSION

We found that the low-dose heparin regimen resulted in significantly less postoperative total drainage and RBC transfusion requirement in patients who underwent for TAAD.

Preoperative clinical application of human fibrinogen in patients with acute Stanford type A aortic dissection: A single-center retrospective study

OBJECTIVE

To evaluate the perioperative clinical efficacy of preoperative human fibrinogen treatment in patients with acute Stanford type A aortic dissection (ATAAD).

METHODS

Data of 159 patients with ATAAD who underwent emergency surgical treatment in our hospital from January 2019 to December 2020 were retrospectively analyzed. Patients were divided into two groups according to whether human fibrinogen was administered before surgery: patients in group A received fibrinogen before surgery, while those in group B did not. The preoperative clinical data, surgical data, postoperative data, complications related to the coagulation function, and mortality of the two groups were compared and analyzed.

RESULTS

The in-hospital mortality was similar in the two groups (2.9% vs. 9.3%, p = .122). However, group A had a significantly shorter operation time (279.24 ± 39.03 vs. 298.24 ± 45.90, p = .008), lower intraoperative blood loss (240.48 ± 96.75 vs. 353.70 ± 189.80, p < .001), and reduced intraoperative transfusion requirement of red blood cells (2.61 ± 1.18 vs. 6.05 ± 1.86, p < .001). The postoperative suction drainage within 24 h in group A was significantly decreased (243.24 ± 201.52 vs. 504.22 ± 341.08, p = .002). The incidence of postoperative acute kidney injury (AKI) in group A was lower than that in group B (3.8% vs. 14.8%, p = .023). Similarly, the incidence of postoperative hepatic insufficiency in group A was lower than that in group B (1.9% vs. 9.3%, p = .045). In group A, the mechanical ventilation time was shorter (47.68 ± 28.61 vs. 118.21 ± 173.16, p = .004) along with reduced intensive care unit stay time (4.06 ± 1.18 vs. 8.09 ± 9.42, p = .003), and postoperative hospitalization days (19.20 ± 14.60 vs. 23.50 ± 7.56, p = .004).

CONCLUSION

Preoperative administration of human fibrinogen in patients undergoing ATAAD surgery can effectively reduce the intraoperative blood loss, amount of blood transfused, operation time, and postoperative complications, and improve the early prognosis of patients. In addition, this procedure is highly safe.

Therapeutic Strategies for Disseminated Intravascular Coagulation Associated with Aortic Aneurysm

Aortic aneurysms are sometimes associated with enhanced-fibrinolytic-type disseminated intravascular coagulation (DIC). In enhanced-fibrinolytic-type DIC, both coagulation and fibrinolysis are markedly activated. Typical cases show decreased platelet counts and fibrinogen levels, increased concentrations of fibrin/fibrinogen degradation products (FDP) and D-dimer, and increased FDP/D-dimer ratios. Thrombin-antithrombin complex or prothrombin fragment 1 + 2, as markers of coagulation activation, and plasmin-α₂ plasmin inhibitor complex, a marker of fibrinolytic activation, are all markedly increased. Prolongation of prothrombin time (PT) is not so obvious, and the activated partial thromboplastin time (APTT) is rather shortened in some cases. As a result, DIC can be neither diagnosed nor excluded based on PT and APTT alone. Many of the factors involved in coagulation and fibrinolysis activation are serine proteases. Treatment of enhanced-fibrinolytic-type DIC requires consideration of how to control the function of these serine proteases. The cornerstone of DIC treatment is treatment of the underlying pathology. However, in some cases surgery is either not possible or exacerbates the DIC associated with aortic aneurysm. In such cases, pharmacotherapy becomes even more important. Unfractionated heparin, other heparins, synthetic protease inhibitors, recombinant thrombomodulin, and direct oral anticoagulants (DOACs) are agents that inhibit serine proteases, and all are effective against DIC. Inhibition of activated coagulation factors by anticoagulants is key to the treatment of DIC. Among them, DOACs can be taken orally and is useful for outpatient treatment. Combination therapy of heparin and nafamostat allows fine-adjustment of anticoagulant and antifibrinolytic effects. While warfarin is an anticoagulant, this agent is ineffective in the treatment of DIC because it inhibits the production of coagulation factors as substrates without inhibiting activated coagulation factors. In addition, monotherapy using tranexamic acid in cases of enhanced-fibrinolytic-type DIC may induce fatal thrombosis. If tranexamic acid is needed for DIC, combination with anticoagulant therapy is of critical importance.

Does preoperative dual antiplatelet therapy affect bleeding and mortality after total arch repair for acute type A dissection?

OBJECTIVES

Data are scarce and mixed regarding the impact of preoperative dual antiplatelet therapy (DAPT) on the surgical outcomes of acute type A aortic dissection (ATAAD). We seek to evaluate the impact of DAPT on bleeding-related events and early- and mid-term mortality after total arch replacement and frozen elephant trunk in such patients.

METHODS

This study comprised 48 ATAAD patients on preoperative DAPT and 418 without DAPT (the whole series, i.e. unmatched cohort), from which 45 matched pairs were selected by propensity score (matched cohort). Bleeding-related events (reoperation for bleeding, bleeding of ≥1500 ml within the first 12 h postoperatively or transfusion of ≥10 units of red blood cell or use of recombinant activated factor VII), operative mortality and mid-term survival were compared in the unmatched and matched cohorts. The impact of preoperative DAPT was evaluated with multivariable analysis.

RESULTS

In the unmatched cohort, bleeding of ≥1500 ml/12 h postoperatively was more common in the DAPT group (18.8% vs 8.4%, P = 0.020); operative mortality was 9.7%, which did not differ with DAPT (12.5% vs 9.3%, P = 0.48). Nor did bleeding-related events (54.2% vs 43.5%, P = 0.16) differ significantly between 2 groups. In the matched cohort, neither were drainage of ≥1500 ml/12 h (20% vs 6.7%, P = 0.063) and bleeding-related events (53.3% vs 42.2%, P = 0.30), nor operative mortality (13.8 vs 8.9%, P = 0.50) and mid-term survival (79.3% vs 76.4%, P = 0.93) significantly different between 2 groups. DAPT was not identified as a predictor for operative mortality [odd ratio (OR) 0.97, 95% confidence interval (CI) 0.31-3.08; P = 0.96; adjusted OR 1.28, 95% CI 0.22-7.20; P = 0.78] and bleeding-related events (OR 1.50, 95% CI 0.76-2.95; P = 0.24; adjusted OR 2.03, 95% CI 0.80-3.66; P = 0.14).

CONCLUSIONS

In patients with ATAAD undergoing total arch replacement and frozen elephant trunk, although preoperative DAPT led to more postoperative bleeding, it did not increase bleeding-related events nor operative mortality nor mid-term death. The results of this study imply that for patients with ATAAD, emergency surgical repair, even if as extensive as total arch repair, should not be contraindicated or delayed simply because of ongoing DAPT.

Low postoperative blood platelet count may be a risk factor for 3-year mortality in patients with acute type A aortic dissection

Background

Mortality and complications remain high after acute type A aortic dissection (ATAAD) open surgery and are associated with coagulation dysfunction. Platelets play an important role in the process of coagulation. This study explored the relationship between postoperative platelet counts and 3-year mortality after operation in patients with ATAAD undergoing open aortic repair surgery.

Methods

Patients with ATAAD who underwent Total Arch Replacement and Frozen Elephant Trunk in Fuwai Hospital from 2011 to 2015 were selected for this study. The perioperative data were collected and sorted through the electronic clinical case system. Multivariate Logistic regression was used to analyze the risk factors for death within three years after surgery.

Results

A total of 495 patients were included in the analysis. After correction for confounding factors, decreased postoperative platelet count remained an independent factor that was associated with lower mortality (OR = 0.918, 95% CI 0.853–0.988, P = 0.023).

Conclusions

The study indicated that decreased postoperative platelet count may lead to increased 3-year mortality, in patients with ATAAD who underwent open aortic repair surgery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13019-021-01623-7.

Rotational Thromboelastometry-Guided Transfusion Protocol to Reduce Allogeneic Blood Transfusion in Proximal Aortic Surgery With Deep Hypothermic Circulatory Arrest

OBJECTIVES

To determine the impact of a rotational thromboelastometry (ROTEM)-guided transfusion protocol on the use of blood products, patient outcomes, coagulation factor concentrates, and costs.

DESIGN

A single-center retrospective cohort study.

SETTING

A tertiary university hospital.

PATIENTS

Adults undergoing proximal aortic surgery with deep hypothermic circulatory arrest.

INTERVENTION

ROTEM-guided transfusion protocol compared with clinically-guided transfusion.

MEASUREMENTS AND MAIN RESULTS

Two hundred seventeen patients were included; seventy-one elective and 24 emergency patients in the clinically-guided group, and 59 elective and 63 emergency patients in the ROTEM-guided transfusion protocol group. In the ROTEM-guided transfusion protocol group, a significant reduction in transfusion of red blood cells (5 [3-8] v 2 [0-4], p < 0.001), platelet concentrate (2 [2-3] v 1 [1-2], p < 0.001), and plasma (1,980 mL [1,320-3,300] v 800 mL [0-1,000], p < 0.001) was seen in elective surgery. Emergency patients received fewer red blood cells (7 [5-10] v 5 [2-10], p = 0.040), platelet concentrate (3 [2-4] v 2 [2-3], p = 0.023), and plasma (3,140 mL [1,980-3,960] v 1,000 mL [0-1,400], p < 0.001). Prothrombin complex concentrate and fibrinogen concentrate were increased significantly in elective and emergency patients. The surgical reexploration for bleeding rate was decreased in elective patients 33.8% v 5.1%.

CONCLUSION

The implementation of a ROTEM-guided transfusion protocol might have the potential to decrease blood product transfusion and may improve patient outcomes.

Impact of ABO blood group on bleeding complications after surgery for acute type A aortic dissection

Excessive bleeding is a serious complication associated with impaired survival after surgery for acute type A aortic dissection (ATAAD). Different ABO blood groups are associated with variable levels of circulating von Willebrand factor and therefore potentially altered risks of surgical haemorrhage. The current study aimed to assess the impact of blood group on bleeding complications after ATAAD surgery. This was a retrospective cohort study including 336 patients surgically treated for ATAAD between January 2004 and January 2019. Patients with blood group O were compared with non-O patients. In total, 152 blood group O patients were compared with 184 non-O patients. There were no differences in rates of massive bleeding (27.0 vs. 25.5%, P = 0.767) or re-exploration for bleeding (16.4 vs. 13.0%, P = 0.379) in blood group O and non-O patients, respectively. Median chest tube output 12 h after surgery was 520 ml (350-815 ml) in blood group O and 490 ml (278-703 ml) in non-O patients (P = 0.229). Blood group O patients received more fibrinogen concentrate (6.1 ± 4.0 vs. 4.9 ± 3.3 g, P = 0.023) but administered units of packed red blood cells [5 (2-8) vs. 4 (2-9) U, P = 0.736], platelets [4 (2-4) vs. 3 (2-5) U, P = 0.521] or plasma [4 (1-7) vs. 4 (0-7) U, P = 0.562] were similar. This study could not demonstrate any association between blood group and bleeding after surgery for ATAAD. It cannot be ruled out that potential differences were levelled out by blood group O patients receiving significantly more fibrinogen concentrate.

Management of disseminated intravascular coagulation associated with aortic aneurysm and vascular malformations

Aortic aneurysms and vascular malformations are sometimes associated with disseminated intravascular coagulation (DIC). A typical blood coagulation test shows decrease in platelet count and fibrinogen, and increases in fibrin/fibrinogen degradation products (FDP) and D-dimer. The coagulation activation marker thrombin-antithrombin complex (TAT) and the fibrinolysis activation marker plasmin-α₂ plasmin inhibitor (PIC) are significantly increased. α₂ plasmin inhibitor (α₂PI) is significantly reduced. Since no prolongation of prothrombin time (PT) is noticeable and activated partial thromboplastin time (APTT) is shortened in some cases, DIC cannot be diagnosed or ruled out by PT and APTT alone. The cornerstone of treatment for DIC is to treat the underlying disease. However, surgery is not possible in some cases. Follow-up may be appropriate in patients with abnormal results from coagulation tests and no bleeding. However, pharmacotherapy is often required in cases with bleeding. Unfractionated heparin, low molecular weight heparin, protease inhibitors, recombinant thrombomodulin, direct oral anticoagulants, and factor XIII preparations are effective. If PIC is significantly increased and α₂PI is significantly decreased, or if the bleeding is severe, tranexamic acid is used as an antifibrinolytic therapy with anticoagulant therapy. In such cases, attention should be paid not only to TAT but also changes in PIC.

Association Between D-dimer and Early Adverse Events in Patients With Acute Type A Aortic Dissection Undergoing Arch Replacement and the Frozen Elephant Trunk Implantation: A Retrospective Cohort Study

Objective

In the present study, we investigated the associations between D-dimer levels at admission and early adverse events in patients with acute type A aortic dissection undergoing arch replacement and the frozen elephant trunk (FET).

Methods

We retrospectively analyzed data of patients with acute type A aortic dissection undergoing aortic arch surgery and FET from July 2017 to December 2018 at Beijing Anzhen Hospital. D-dimer levels were evaluated within 24 h of admission. Multivariate Cox regression analysis was used to determine independent predictors of early postoperative adverse events.

Results

A total of 347 patients were included in the study. The average age of the patients was 48.07 ± 10.56 years, with male predominance (79.25%). The incidence of 90-day postoperative adverse events was 18.7%, consisting of 14.7% mortality and 4.0% permanent neurological dysfunction (PND). The median D-dimer level was 1.95 ug/ml (interquartile range, 0.77–3.16 ug/ml). Multivariable Cox regression analysis revealed that D-dimer level was independently associated with 90-day postoperative adverse events after adjustment for confounding factors (hazard ratio = 1.19 per 10 ug/ml increase in D-dimer, 95% confidence interval: 1.01–1.41; P = 0.039). Kaplan–Meier analysis revealed that the highest tertile (median 6.27 ug/ml) had more 90-day postoperative adverse events compared with the median and lowest tertiles (P = 0.0014). Sub-analysis found that the association remained unchanged.

Conclusion

Increased D-dimer levels at admission were associated with 90-day postoperative adverse events in patients with acute type A aortic dissection undergoing arch replacement and FET. These results may help clinicians optimize the risk evaluation and perioperative clinical management to reduce early adverse events.

Key Question

Explore the relationship between D-dimer and early outcomes in patients with aortic dissection with arch replacement.

Key Findings

Increased D-dimer at admission was associated with adverse events in patients with aortic dissection with arch surgery.

Take-Home Message

The high-risk patients deserve close medical monitoring.

Acute type A aortic dissection - a review

Acute type A aortic dissection (ATAAD) is still one of the most challenging diseases that cardiac surgeons encounter. This review is based on the current literature and includes the results from the Nordic Consortium for Acute Type-A Aortic Dissection (NORCAAD) database. It covers different aspects of ATAAD and concentrates on the outcome of surgical repair. The diagnosis is occasionally delayed, and ATAAD is usually lethal if prompt repair is not performed. The dynamic nature of the disease, the variation in presentation and clinical course, and the urgency of treatment require significant attentiveness. Many surgical techniques and perfusion strategies of varying complexity have been described, ranging from simple interposition graft to total arch replacement with frozen elephant trunk and valve-sparing root reconstruction. Although more complex techniques may provide long-term benefit in selected patients, they require significant surgical expertise and experience. Short-term survival is first priority so an expedited operation that fits in with the surgeon's level of expertise is in most cases appropriate.

Predictors and impact of massive bleeding in acute type A aortic dissection

Objectives

Bleeding complications associated with acute type A aortic dissection (aTAAD) are a well-known clinical problem. Here, we evaluated predictors of massive bleeding related to aTAAD and associated surgery and assessed the impact of massive bleeding on complications and survival.

Methods

This retrospective study of 256 patients used Blood Conservation Using Antifibrinolytics in a Randomized Trial (BART) criteria to define massive bleeding, which was met by 66 individuals (Group I) who were compared to the remaining patients (Group II). Multivariable logistic regression was used to identify independent predictors of massive bleeding and in-hospital mortality, Kaplan-Meier estimates for analysis of late survival, and Cox regression analysis to evaluate independent predictors of late mortality.

Results

Independent predictors of massive bleeding included symptom duration (odds ratio [OR], 0.974 per hour increment; 95% confidence interval [CI], 0.950-0.999; P  =   0.041) and DeBakey type 1 dissection (OR, 2.652; 95% CI, 1.004-7.008; P  =   0.049). In-hospital mortality was higher in Group I (30.3% vs 8.0%, P  <0.001). Kaplan-Meier estimates of survival indicated poorer survival for Group I at 1, 3 and 5 years (68.8 ± 5.9% vs 92.8 ± 1.9%; 65.2 ± 6.2% vs 85.3 ± 2.7%; 53.9 ± 6.9% vs 82.1 ± 3.3 %, respectively; log rank P  <   0.001). Re-exploration for bleeding was an independent predictor of in-hospital (OR, 3.109; 95% CI, 1.044-9.256; P  =   0.042) and late mortalities (hazard ratio, 3.039; 95% CI, 1.605-5.757; P  =   0.001).

Conclusions

Massive bleeding in patients with aTAAD is prompted by shorter symptom duration and longer extent of dissection and has deleterious effects on outcomes of postoperative complications as well as in-hospital and late mortalities.

Coagulopathy After Ruptured Abdominal Aortic Aneurysm

Although potentially treatable, coagulopathy is often included among the predictors of a poor outcome after ruptured abdominal aortic aneurysm (rAAA). The purpose of this review was to define the incidence of coagulopathy among patients presenting with rAAA and to identify the factors contributing to its development.

The medical records of 89 consecutive patients presenting with a rAAA were retrospectively reviewed. Laboratory results (international normalized ratio [INR], partial thromboplastin time [aPTT], platelet count, fibrinogen, and fibrin degradation products [D-dimer]) measured on admission and perioperatively were recorded and related to features of the patients' prehospital and hospital course.

At least one admission coagulation study was obtained in 70 of 89 patients. All measured coagulation values were within the normal range in only 10 (14%) patients, whereas at least one value was in the coagulopathic bleeding range in 17 patients (24%). Profound abnormalities of the INR (> 2.0) were present in 24%, of the aPTT (> 60 sec) in 12%, and of the platelet count (< 50) in 7% of patients. In a multivariate model, hematocrit was the only significant predictor of an INR > 2.0, while hematocrit and degree and duration of hypotension predicted an aPTT > 60 sec. Fluid volume prior to admission did not independently predict either the INR or aPTT, although it was the only significant predictor of a platelet count <50. Admission D-dimer levels were elevated in 79% of patients and were not significantly associated with either the degree of hemorrhage or volume resuscitation. All coagulation studies showed deterioration following admission, with profound abnormalities observed in 90% and 52% of patients intraoperatively and postoperatively, respectively. Mortality was 74% among those undergoing operation and was significantly associated with advanced age and lowest systolic blood pressure, but not with admission INR or aPTT.

The majority of rAAA patients present with disordered coagulation, profound abnormalities being more related to the degree of hemorrhage than to the volume of fluid resuscitation. Evidence of intravascular fibrinolysis is even more common and may be more closely related to the aneurysm itself than to acute hemorrhage.

Chronic Aortic Dissection Complicated by Disseminated Intravascular Coagulation: Successful Treatment with Endovascular Stent-Grafting

Purpose:

To report endovascular repair of a chronic aortic dissection complicated by disseminated intravascular coagulation (DIC).

Case Report:

A 61-year-old man developed DIC associated with a chronic Stanford type B aortic dissection that occurred during cardiac catheterization 12 years earlier. At the current admission, computed tomography showed a partially thrombosed false lumen extending from the aortic arch to the left common iliac artery. On angiography, entry and re-entry tears were identified at the right subclavian and left common iliac arteries, respectively. After stent-graft implantation at the entry and re-entry sites, not only was the false lumen completely thrombosed but the DIC also resolved. The patient is doing well with no complication at 16 months after treatment.

Conclusions:

Endovascular stent-grafting is an acceptable alternative to surgical repair for aortic dissection accompanied by DIC.

A Fever in Acute Aortic Dissection is Caused by Endogenous Mediators that Influence the Extrinsic Coagulation Pathway and Do Not Elevate Procalcitonin

Objective A fever is observed in approximately one-third of cases of acute aortic dissection (AAD); however, the causes remain unclear. We investigated the mechanism of a fever in AAD by measuring the serum concentrations of inflammatory markers, mediators of coagulation and fibrinolysis, and procalcitonin, a marker of bacterial infection. Methods We retrospectively studied 43 patients with medically treated AAD without apparent infection. Patients were divided into those with (Group A; n=19) and without (Group B; n=24) a maximum body temperature >38°C. We established which patients fulfilled the criteria for systemic inflammatory response syndrome (SIRS), and its relationship with a fever was examined. Mediators of inflammation, coagulation and fibrinolysis were compared by a univariate analysis. Factors independently associated with a fever were established by a multivariate analysis. Results The criteria for SIRS were fulfilled in a greater proportion of patients in Group A (79%) than in Group B (42%, p=0.001). There was no difference in the procalcitonin concentration between Groups A and B (0.15±0.17 ng/mL vs. 0.11±0.12 ng/mL, respectively; p=0.572). Serum procalcitonin concentrations lay within the normal range in all patients in whom it was measured, which showed that the fever was caused by endogenous mediators. On the multivariate analysis, there was a borderline significant relationship between a fever and the prothrombin time-International Normalized Ratio (p=0.065), likely reflecting the extrinsic pathway activity initiated by tissue factor. Conclusion Our findings suggest that a fever in AAD could be caused by SIRS, provoked by endogenous mediators that influence the extrinsic coagulation pathway without elevating the serum procalcitonin concentration.

Admission Values of D-dimer and C-reactive Protein (CRP) Predict the Long-term Outcomes in Acute Aortic Dissection

Objective Admission D-dimer and C-reactive protein (CRP) values have been reported to predict the short-term outcomes in acute aortic dissection (AAD). However, the association between D-dimer values and the long-term outcomes has not been investigated. Methods The primary endpoints included events determined to be all-cause death, recurrence of aortic dissection, aortic rupture, and surgical intervention for the aortic aneurysm following the first hospital discharge. We performed a receiver operating characteristic analysis and determined the optimal cut-off levels of admission D-dimer, admission CRP and peak CRP values in terms of the sensitivity and specificity for predicting the presence of events. Using the optimal cut-off values, we performed a multiple Cox analysis and investigated the hazard ratio of admission D-dimer, admission CRP and peak CRP. Patients We retrospectively identified 173 AAD patients hospitalized between January 2005 and December 2013. Results A multiple Cox regression analysis revealed that the hazard ratios were 3.4 for admission D-dimer [95% Confidence Interval (CI) 1.5 to 7.3, p=0.004] and 2.7 for admission CRP (95% CI 1.2 to 5.5, p=0.014). Conclusion Admission D-dimer and CRP values may predict the long-term outcomes in AAD. Moreover, admission D-dimer values may be a valuable marker to predict not only the short-term outcomes, but also the long-term outcomes in AAD.

Predictors of massive transfusion with thoracic aortic procedures involving deep hypothermic circulatory arrest

OBJECTIVE

Massive perioperative blood product transfusion may be required with thoracic aortic operations and is associated with poor outcomes. We analyzed independent predictors of massive transfusion in thoracic aortic surgical patients undergoing deep hypothermic circulatory arrest.

METHODS

The study consisted of 168 consecutive patients undergoing open thoracic aortic procedures involving deep hypothermic circulatory arrest between July 2005 and August 2008. We identified 26 preoperative and procedural variables as potentially related to blood product use, tested for association with total blood products transfused by multivariate linear regression model, and constructed logistic regression model for massive transfusion (requiring ≥ 5 units of transfused packed red blood cells between incision and 48 postoperative hours).

RESULTS

Multivariate linear regression determined that 6 significant variables accounted for 42% of variation in total blood products transfused: age (P = .008), preoperative hemoglobin (P = .04), weight (P = .02), cardiopulmonary bypass time (P < .0001), emergency status (P < .0001), and resternotomy (P < .0001). Final predictive logistic regression model included 1-g/dL increase in preoperative hemoglobin (odds ratio, 0.54; 95% confidence interval, 0.43-0.69; P < .0001), 10-minute increase in cardiopulmonary bypass time (odds ratio, 1.15; 95% confidence interval, 1.05-1.26; P = .0026), and emergency status (odds ratio, 4.02; 95% confidence interval, 1.53-10.55; P = .0047.

CONCLUSIONS

Cardiopulmonary bypass time, emergency status, and preoperative hemoglobin were independent predictors of massive transfusion. These variables, along with weight, age, and resternotomy, were associated with total blood product use in thoracic aortic operations involving deep hypothermic circulatory arrest.

Aortic Aneurysm–Induced Disseminated Intravascular Coagulopathy: Successful Surgical Repair

Aortic aneurysm is a rare cause of disseminated intravascular coagulopathy (DIC). We present the developmental course of DIC in a 70-year-old male patient who had a thoracoabdominal aortic aneurysm characterized by a progressive descending aortic aneurysm presenting as subcutaneous hemorrhage of acute onset. He was diagnosed as having aortic aneurysm–induced DIC. After adequate infusion of blood components, surgical repair of the descending aortic aneurysm was carried out successfully. The patient's bleeding tendency stopped dramatically in the early postoperative period as identified by clinical and laboratory findings. We concluded that the occurrence of DIC was due mainly to the progressive descending aortic aneurysm in the present patient and that surgical repair could be the definitive treatment of DIC in this setting.

Recombinant activated factor VII for refractory bleeding after acute aortic dissection surgery: A propensity score analysis*

OBJECTIVE

The aim of this study was to assess safety and effectiveness of recombinant activated factor VII (rFVIIa) in patients with refractory bleeding undergoing acute aortic dissection surgery with deep hypothermic circulatory arrest.

DESIGN

Propensity score-matched analysis.

SETTING

University hospital.

PATIENTS

Twenty-three cardiac surgery patients receiving rFVIIa compared with 23 matched controls.

INTERVENTIONS

An intravenous bolus of rFVIIa (70 microg/kg) was administered at the end of a complete transfusion protocol. Five patients received rFVIIa in the operating room, and 18 patients received rFVIIa in the intensive care unit. Four of the intensive care unit patients required a second dose.

MEASUREMENTS AND MAIN RESULTS

Blood loss and transfusion requirements were significantly reduced in the period after rFVIIa administration. A highly significant reduction in hourly blood loss was found at -1 hr vs. 0 hrs and 0 hrs vs. 1 hr (-194 and -77.5 mL, respectively; both adjusted p < .001). In addition, significant improvements of international normalized ratio (p < .001), partial thromboplastin time (p < .001), platelet count (p < .001), fibrinogen (p < .001), and antithrombin (p < .001) were detected after rFVIIa administration. The two groups did not differ regarding adverse events.

CONCLUSIONS

rFVIIa was successfully used as an additional therapy both during and after acute aortic dissection surgery with deep hypothermic circulatory arrest, when bleeding was refractory to conventional methods. Randomized studies are necessary to confirm the safety and efficacy of rFVIIa in this setting.

Aortic Arch Surgery: Thoracoabdominal Perfusion During Antegrade Cerebral Perfusion May Reduce Postoperative Morbidity

BACKGROUND

This study aimed to assess the results of the introduction of thoracoabdominal perfusion (TAP) in the surgical strategy for aortic arch replacement with cerebral protection.

METHODS

Two hundred two arch procedures performed with moderate hypothermia (22 degrees to 26 degrees C) and antegrade cerebral perfusion (ACP) were the objects of retrospective investigation. Acute type A dissection was the indication in 164 patients, aortic aneurysm in 38. In 80 patients, during ACP, the thoracoabdominal aorta was perfused either in an antegrade fashion through proximal descending aorta endoluminal cannulation (in 62 dissections), or retrograde through femoral artery cannulation with proximal descending aorta endoluminal occlusion (in 18 aneurysms). Hospital mortality and morbidity rates were compared between the two treatments (group A: ACP only, 122 patients; group B: ACP plus TAP, 80 patients) and the underlying aortic disease (dissection/aneurysm) was stratified.

RESULTS

Cerebral perfusion (p = 0.008) and cardiopulmonary bypass times (p = 0.035) were significantly longer in group B. No complication related to the TAP technique was observed in group B. Overall hospital mortality was 12.9%, without significant difference between groups. No differences were found in terms of permanent neurological dysfunction between groups A (9.3%) and B (9.1%; p = 0.58). Group B patients showed lower rates of respiratory failure (18.2% versus 30.5% in group A; p = 0.038), shorter mechanical ventilation times (18.1 +/- 26 hours versus 57.9 +/- 70.1; p < 0.001) and lower incidence of acute renal failure (6.5% versus 18.6%; p = 0.012). Shorter intensive care and hospital stays were observed in group B (p = 0.02).

CONCLUSIONS

The adjunction of TAP to ACP was associated with lower rates of end-organ complications, even in more extensive and time-consuming procedures.

Effect of combined therapy of danaparoid sodium and tranexamic acid on chronic disseminated intravascular coagulation associated with abdominal aortic aneurysm

Chronic disseminated intravascular coagulation (DIC) is a well-known complication of aortic aneurysm. A 63-year-old man with bleeding tendency and a large palpable abdominal aortic aneurysm (AAA) was diagnosed as having fibrinolysis dominant DIC by the excessive activation of both coagulation and fibrinolysis (plasmin -alpha2 plasmin inhibitor complex concentration is usually >4 microg/ml). Although several treatments were tried, DIC could not be controlled until the patient was given combined therapy of danaparoid (1,250 U/12 h, bolus IV) and tranexamic acid (0.5 g x 3/day, oral administration). This therapy may be beneficial when control for bleeding is required without restricting the ambulatory movement of patients by continuous drip.

Disseminated intravascular coagulopathy in aortic aneurysms

Aneurysm-induced disseminated intravascular coagulopathy (DIC) constitutes a rare presentation form of aortic aneurysms. The majority of DIC cases are asymptomatic and this condition is usually diagnosed during the perioperative workup; yet, in a minority of cases, DIC leads to the diagnosis of the vascular abnormality. The management of aneurysm-induced DIC is based both on the treatment of the underlying disorder and on an active scrutiny of the hemodynamic and blood support requirements. Blood replacement therapy should be individualized, guided by the clinical situation of the patient (especially considering the bleeding risk or the presence of hemorrhages), and accompanied by a close monitoring of the coagulation status. Fresh frozen plasma is usually the preferred initial option to replace coagulation factors, but fibrinogen, cryoprecipitates, and platelet concentrates are adequate options in certain contexts. Heparins, both non-fractionated and low-weight molecular types, are the most widely accepted agents for achieving adequate control of the coagulation activation and consumption. Other antithrombotic drugs are under study, including antithrombin III and activated protein C, although only the latter has demonstrated a benefit in terms of survival in a comparative, randomized context. Antifibrinolytic agents such as gabexate mesilate, tranexamic acid, and epsilon-aminocaproic acid (EACA) have been used with conflicting results. These agents may have a role for patients with catastrophic bleeding resistant to other therapeutical options, but their relevance as a first line of treatment is, at present, undefined. An assessment of the multitude of therapeutic approaches available would seem to indicate that there is a lack of standardization in the management of these patients. Multi-center, randomized clinical trials are needed to elucidate the most adequate therapy in this context.

Anesthesia and Neurocerebral Monitoring for Aortic Dissection

Patients presenting to the operating room for repair of aortic dissection are challenging in all aspects of their care. Without exception, they require a multidisciplinary team approach. This article will review some of the specific challenges faced by anesthesiologists and neurologists when confronted with such a diagnosis. Specifically, we will discuss the myriad anesthetic issues that present in the preoperative stage and continue into the postoperative period. Neurologic complications during dissection repair result in increased morbidity and mortality. A variety of neurophysiologic monitoring techniques exist that may reduce this risk and will be discussed in detail. Finally, we will present some "controversies in care," emphasizing that our respective fields continue to grow, learn, and improve what information we have on the morbidity and mortality of aortic dissection.

Nonneurologic morbidity and profound hypothermia in aortic surgery

BACKGROUND

Use of profoundly hypothermic cardiopulmonary bypass may increase the risk of postoperative bleeding and lung and renal dysfunction. The aim of this study was to analyze postoperative blood loss and indices of pulmonary and renal dysfunction in patients undergoing proximal aortic surgery with and without the use of profound hypothermia to determine risk factors for nonneurologic morbidity.

METHODS

Risk factors for blood loss, transfusion requirement, and pulmonary and renal dysfunction were studied in 116 patients undergoing thoracic aortic surgery with profoundly or moderately hypothermic cardiopulmonary bypass.

RESULTS

Overall mortality was 8.6%. Mean (+/- standard deviation) cardiopulmonary bypass times were 191 +/- 53 minutes (profoundly hypothermic group) and 131 +/- 48 minutes (moderately hypothermic group; p < 0.0001). The incidence of blood loss more than 1 L or resternotomy for bleeding was 25% (29 patients). Fifteen patients (12.9%) experienced postoperative pulmonary dysfunction, and 25 patients (21.6%) had postoperative renal dysfunction. Forty-one patients (35.3%) had a prolonged intensive therapy unit length of stay. Multivariate analysis demonstrated that prolonged cardiopulmonary bypass time was the only predictor of postoperative hemorrhage and resternotomy for bleeding (p = 0.03). Increased intensive therapy unit length of stay was predicted by total arch replacement (p = 0.01) and low 6-hour ratio of partial pressure of arterial oxygen to inspired fraction of oxygen (p = 0.05). Increased preoperative creatinine (p = 0.002) and emergency status (p = 0.015) predicted postoperative renal dysfunction. Low 6-hour ratio of partial pressure of arterial oxygen to inspired fraction of oxygen was predicted by increased preoperative creatinine (p = 0.03) and prolonged cardiopulmonary bypass time (p = 0.03).

CONCLUSIONS

Profound hypothermia may cause a coagulopathy, but procedure extent is the primary determinant of postoperative bleeding. Profoundly hypothermic cardiopulmonary bypass does not appear to be a risk factor for renal or early pulmonary dysfunction or intensive therapy unit length of stay.

Coagulation Disorders and Blood Product Use in Patients Undergoing Thoracoabdominal Aortic Aneurysm Repair

Repair of thoracoabdominal aortic aneurysms (TAAA) is associated with major blood loss, often exceeding the patient's intravascular volume, and complex intraoperative and postoperative coagulopathies necessitating large-volume transfusion of blood products. Abnormalities sufficient to cause thrombocytopenia or clinically important prolongation of clotting parameters are rarely present before surgery in elective aneurysms but are more common with ruptured aneurysms. The finding of intraoperative and postoperative deficiencies of clotting factors, along with thrombin generation and activation of the thrombolytic system, is reflective of massive blood losses, visceral ischemia, and massive transfusions. An aggressive strategy of transfusion of blood products is critical to the prevention of clinically significant coagulopathy during surgery. Adjuncts to reduce blood losses and blood product use include low-dose aprotinin or epsilon -aminocaproic acid, intraoperative blood salvaging, and acute normovolemic hemodilution. In TAAA repair, an average blood loss of 5000 to 6000 mL and average transfusion of allogeneic blood products of 50 to 60 U are to be anticipated.

A Rapid Bedside D-Dimer Assay (Cardiac D-Dimer) for Screening of Clinically Suspected Acute Aortic Dissection

BACKGROUND

A rapid laboratory test for diagnosis of acute aortic dissection (AAD) has not been available. We performed this prospective study to determine the utility of a rapid bedside D-dimer (DD) assay for detection of AAD.

METHODS AND RESULTS

Patients with suspected AAD were recruited and their DD levels were measured by rapid bedside assay. They were divided into 2 groups according to enhanced computed tomography findings: an AAD group (n = 30) and a non-AAD group (n = 48). The median DD level was higher in the AAD group (1.80 microg/ml) than in the non-AAD group (0.42 microg/ml) (p = 0.000). The rapid bedside DD assay showed 100% sensitivity, 54% specificity, 58% positive predictive value and 100% negative predictive value for detection of AAD with a normal DD level of up to 0.5 microg/ml. The combination of DD level >0.5 microg/ml and systolic blood pressure > or = 180 mmHg showed 86% positive predictive value for detection of AAD. Conclusions We conclude that the rapid bedside DD assay is a highly sensitive method for early exclusion of AAD in patients with chest and/or back pain suggestive of AAD. Acute aortic dissection is highly probable if a rapid DD assay shows the elevated DD level with systolic blood pressure > or = 180 mmHg on admission.

Coagulopathy and Hyperfibrinolysis in Ruptured Abdominal Aortic Aneurysm Repair

Perioperative hemorrhage is one of the principal causes of death in patients with ruptured abdominal aortic aneurysm (AAA). This study examines perioperative coagulation and fibrinolysis in patients undergoing ruptured AAA repair complicated by coagulopathy. Eight patients (8 men of median age 74, range 69-87, years) who developed clinical and laboratory evidence of coagulopathy during attempted repair of ruptured infrarenal AAA were prospectively studied. Platelet count, fibrinogen, clotting times, prothrombin fragment (PF) 1+2, and tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI) activities were measured preoperatively, immediately before, and 5 min and 24 hr after aortic declamping. Six patients died, three intraoperatively, one within 24 hr, and two in the late postoperative period. All patients had thrombocytopenia and prolonged clotting times intraoperatively with evidence of increased thrombin generation (as demonstrated by elevated PF 1+2). Five patients had increased systemic fibrinolysis (as demonstrated by elevated t-PA activity) preoperatively and/or before aortic declamping and all of these patients died. Three patients had perioperative inhibition of systemic fibrinolysis (as demonstrated by elevated PAI activity) and two survived. These data demonstrate that coagulopathy in ruptured AAA repair may be associated with a hyperfibrinolytic state. Further research is required to determine if (a) a causal relationship exists between hyperfibrinolysis and coagulopathy and (b) whether antifibrinolytic agents can improve outcome if targeted at this group of patients.

Platelet dysfunction in acute type A aortic dissection evaluated by the laser light-scattering method

OBJECTIVES

Platelet dysfunction contributes to bleeding tendency in acute type A aortic dissection. Particle counting by new laser light-scattering methods more accurately quantifies changes in the number of different-sized platelet aggregates than do conventional optical density methods. We studied platelet aggregation kinetics and patterns of aggregation deficiency in acute-phase aortic dissection with laser light scattering.

METHODS

Blood from 20 acute type A aortic dissection patients undergoing surgery was sampled during acute (9.1 +/- 6.8 hours from onset) and chronic (postoperative day 20, control) phases of aortic dissection. Platelet count and aggregability were assessed by optical density and laser light-scattering methods after aggregation was induced (addition of 2.0 microg/mL collagen to samples).

RESULTS

Optical density showed significant reduction in acute-phase platelet aggregation (acute vs chronic: 65 +/- 27% vs 77 +/- 17%, P <.03). Laser light scattering showed significant reduction in medium (25-50 microm) and large (50-70 microm) but not small aggregate (9-25 microm) generation (acute vs chronic: small, 1.2 +/- 0.6 x 10(7) vs 1.5 +/- 1.0 x 10(7), NS; medium, 0.6 +/- 0.3 x 10(7) vs 1.1 +/- 0.5 x 10(7), P <.001; large, 1.4 +/- 1.2 x 10(7) vs 2.6 +/- 1.7 x 10(7), P <.001). Acute- versus chronic-phase platelet counts were significantly decreased (1.7 +/- 0.1 x 10(5)/microL vs 3.6 +/- 0.3 x 10(5)/microL, P <.001).

CONCLUSIONS

Platelet aggregation is suppressed in acute-phase aortic dissection. This suppression does not occur in the initial phase of small aggregate formation; rather, it occurs during the conglomeration of small aggregates into larger aggregates.