Thromboelastography of patients after fontan compared with healthy children

Utility of the Total Thrombus-Formation Analysis System as a Tool for Evaluating Thrombogenicity and Monitoring Antithrombotic Therapy in Pediatric Fontan Patients

BACKGROUND

There is no consensus regarding thromboprophylaxis after Fontan procedure, and novel tools to assess thrombogenicity are needed to establish optimal thromboprophylaxis. The Total Thrombus-formation Analysis System (T-TAS) was developed for the quantitative analysis of thrombus formation using microchips with thrombogenic surfaces. This prospective study evaluated the utility of T-TAS in the assessment of thrombogenicity in pediatric Fontan patients.

METHODS AND RESULTS

The participants included 20 consecutive Fontan patients who underwent cardiac catheterization and 30 healthy controls. Blood samples collected without and with antithrombotic therapy (aspirin or aspirin and warfarin) were used for T-TAS to compute the area under the curve (AUC) in the atheroma (AR₁₀-AUC₃₀) and platelet (PL₁₈-AUC₁₀) chips. A higher AUC indicates higher thrombogenicity. T-TAS values showed that patients in the Fontan group without antithrombotic therapy had lower thrombogenicity than those in the control group [PL₁₈-AUC₁₀, median (interquartile range) 356 (313-394) vs. 408 (392-424); AR₁₀-AUC₃₀, median (interquartile range) 1270 (1178-1351) vs. 1382 (1338-1421)]. Aspirin and warfarin therapies significantly decreased PL₁₈-AUC₁₀ and AR₁₀-AUC₃₀, respectively, compared with those of patients without antithrombotic therapy (P < 0.001 for each comparison). Subgroup analysis divided by low (< 9 mmHg) or high (≥ 9 mmHg) central venous pressure (CVP) showed that CVP affects the reduction in AR₁₀-AUC₃₀ with antithrombotic therapy.

CONCLUSIONS

T-TAS may be a useful tool for monitoring thrombogenicity and antithrombotic therapy in Fontan patients.

Position of the French Working Group on Perioperative Haemostasis (GIHP) on viscoelastic tests: What role for which indication in bleeding situations?

PURPOSE

Viscoelastic tests (VETs), thromboelastography (TEG^®) and thromboelastometry (ROTEM^®) are global tests of coagulation performed on whole blood. They evaluate the mechanical strength of a clot as it builds and develops after coagulation itself. The time required to obtain haemostasis results remains a major problem for clinicians dealing with bleeding, although some teams have developed a rapid laboratory response strategy. Indeed, the value of rapid point-of-care diagnostic devices such as VETs has increased over the years. However, VETs are not standardised and there are few recommendations from the learned societies regarding their use. In 2014, the recommendations of the International Society of Thrombosis and Haemostasis (ISTH) only concerned haemophilia. The French Working Group on Perioperative haemostasis (GIHP) therefore proposes to summarise knowledge on the clinical use of these techniques in the setting of emergency and perioperative medicine.

METHODS

A review of the literature.

PRINCIPAL FINDINGS

The role of the VETs seems established in the management of severe trauma and in cardiac surgery, both adult and paediatric. In other situations, their role remains to be defined: hepatic transplantation, postpartum haemorrhage, and non-cardiac surgery. They must be part of the global management of haemostasis based on algorithms defined in each centre and for each population of patients. Their position at the bedside or in the laboratory is a matter of discussion between clinicians and biologists.

CONCLUSION

VETs must be included in algorithms. In consultation with the biology laboratory, these devices should be situated according to the way each centre functions.

Thromboelastography in term neonates: an alternative approach to evaluating coagulopathy

OBJECTIVE

To develop normative ranges for citrate-modified and heparinase-modified thromboelastography (TEG) in term neonates.

DESIGN

Prospective observational study.

SETTING

An outborn neonatal and cardiac intensive care unit in a free-standing academic children's hospital.

PATIENTS

Thirty term neonates were enrolled as control subjects. Seventeen infants with clinically documented bleeding requiring blood transfusion were enrolled in the comparison group.

MAIN OUTCOME MEASURES

Citrate-modified and heparinase-modified TEG parameters were calculated from blood specimens drawn via peripheral arterial stick or arterial line.

RESULTS

TEG in neonates differs from older children and adults; clotting time (R) and clot kinetics (K) values are generally lower while fibrinolysis or rate of clot breakdown (LY30) and coagulation index (CI) are often higher in neonates. TEG values in term neonates calculated as median (Q1-Q3) are as follows: R 4.150 (3.200-6.200), K 1.550 (1.200-1.800), α angle (α) 70.100 (66.000-72.900), maximum amplitude (MA) 61.850 (59.400-66.000), LY30 1.050 (0.100-1.600) and CI 1.950 (0.100 to 2.900). Cut points selected for optimal predictive value for bleeding using receiver operating curve analyses were R>6.3 (sensitivity 82.4%, specificity 80%); K>2.5 (sensitivity 82.4%, specificity 96.7%); α<59 (sensitivity 82.4%, specificity 96.7%); MA<57 (sensitivity 82.4%, specificity 86.7%); CI<-0.15 (sensitivity 88.2%, specificity 83.3%).

CONCLUSIONS

The reference ranges and cut points for citrate-modified and heparinase-modified TEG can be used to diagnose and evaluate coagulopathy in term neonates.

Impact and Challenges of a Policy Change to Early Track Extubation in the Operating Room for Fontan

While policy changes toward early extubation in the operating room (OR) have been commonly seen in palliative surgeries in single ventricle anatomy, no systematic assessment of their impact on patient outcome has been reported. All patients aged 0-17 years admitted to a PICU in a quaternary children's hospital for post-operative management following a primary Fontan procedure between 2005 and 2011 were included. Patients for revision of Fontan or patients admitted to adult Cardiovascular Intensive Care Unit were excluded. Practice policy was changed from routine extubation in the PICU to early extubation in OR in January 2008. Data were compared between the pre-policy-change era (2005-2007) and the post-policy-change era (2008-2011) to assess the impact of the change on patient outcomes. Generalized linear regression (GLM) and interrupted time series (ITS) analysis were used to access the effect of policy change on PICU length of stay and post-operative fluid balance, adjusting for potential confounders using propensity scores. Root cause analysis (RCA) was conducted to describe causes of failed extubation and challenges of this policy change. One hundred twenty-seven children met inclusion criteria. Average body weight was 14.7 kg [standard deviation (SD) 3.9], and age was 3.5 years (SD 1.9). A clear change in extubation practice occurred between the pre- versus post-policy-change eras: 97.5 % were extubated in the PICU in the pre-policy-change era, as compared to 15.0 % in the post-policy-change era. The average PICU length of stay was shortened by 4.1 days from the pre-policy-change era to the post-policy-change era [95 % CI -1.2 to -6.9, p < 0.01] in the GLM, whereas the ITS analysis did not show a statistically significant difference [95 % CI 1.8 to -2.5] (p = 0.23). No statistically significant difference was observed in the fluid balance in the 24 h post-operation in both analyses. Sixteen patients (16/127, 12.6 %) were reintubated mainly for hemodynamic instability in the pre-policy-change era (6/39, 15.4 %) and excessive bleeding or respiratory etiologies in the post-policy-change era (10/88, 11.4 %). Significant reduction of PICU length of stay was achieved without any evidence of worsening of patient outcomes. RCA suggests watchful observations with respect to bleeding and respiratory etiologies are the key to prevent failure of extubation in the current practice.

Factor VIII May Predict Catheter-Related Thrombosis in Critically Ill Children: A Preliminary Study

OBJECTIVE

If we can identify critically ill children at high risk for central venous catheter-related thrombosis, then we could target them for pharmacologic thromboprophylaxis. We determined whether factor VIII activity or G value was associated with catheter-related thrombosis in critically ill children.

DESIGN

Prospective cohort study.

SETTING

Two tertiary academic centers.

PATIENTS

We enrolled children younger than 18 years who were admitted to the PICU within 24 hours after insertion of a central venous catheter. We excluded children with a recently diagnosed thrombotic event or those anticipated to receive anticoagulation. Children with thrombosis diagnosed with surveillance ultrasonography on the day of enrollment were classified as having prevalent thrombosis. Those who developed catheter-related thrombosis thereafter were classified as having incident thrombosis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We enrolled 85 children in the study. Once enrolled, we measured factor VIII activity with one-stage clotting assay and determined G value with thromboelastography. Of those enrolled, 25 had incident and 12 had prevalent thromboses. The odds ratio for incident thrombosis per SD increase in factor VIII activity was 1.98 (95% CI, 1.10-3.55). The area under the receiver operating characteristic curve was 0.66 (95% CI, 0.52-0.79). At factor VIII activity more than 100 IU/dL, which was the optimal threshold identified using Youden index, sensitivity and specificity were 92.0% and 41.3%, respectively. The association between factor VIII activity and incident thrombosis remained significant after adjusting for important clinical predictors of thrombosis (odds ratio, 1.93; 95% CI, 1.10-3.39). G value was associated with prevalent but not with incident thrombosis.

CONCLUSION

Factor VIII activity may be used to stratify critically ill children based on their risk for catheter-related thrombosis.

Assessing blood coagulation status with laser speckle rheology

We have developed and investigated a novel optical approach, Laser Speckle Rheology (LSR), to evaluate a patient's coagulation status by measuring the viscoelastic properties of blood during coagulation. In LSR, a blood sample is illuminated with laser light and temporal speckle intensity fluctuations are measured using a high-speed CMOS camera. During blood coagulation, changes in the viscoelastic properties of the clot restrict Brownian displacements of light scattering centers within the sample, altering the rate of speckle intensity fluctuations. As a result, blood coagulation status can be measured by relating the time scale of speckle intensity fluctuations with clinically relevant coagulation metrics including clotting time and fibrinogen content. Our results report a close correlation between coagulation metrics measured using LSR and conventional coagulation results of activated partial thromboplastin time, prothrombin time and functional fibrinogen levels, creating the unique opportunity to evaluate a patient's coagulation status in real-time at the point of care.

Laparoscopic antireflux surgery in infants with single ventricle physiology: a review

Laparoscopic fundoplication and gastrostomy tube placement have grown in popularity within the pediatric population for treatment of gastroesophageal reflux disease and failure to thrive, respectively. One population that has an increased need for gastric surgery in infancy is patients with congenital heart defects, especially those with "single ventricle physiology." The most common defect included in this population is hypoplastic left heart syndrome (HLHS). Because of the abnormal physiology present in this condition, there are concerns with regard to the use of laparoscopic procedures for gastric surgery in patients treated with a three-staged reconstruction. We review the staged reconstruction of infants with HLHS, address safety concerns of interstage noncardiac procedures on this patient population, and review the current literature regarding outcomes of laparoscopic gastric surgery on patients with single ventricle physiology.

Thromboembolic complications in Fontan patients: population-based prevalence and exploration of the etiology

After the Fontan procedure, patients face an increased risk for thromboembolic events (TE). The etiology for this increased thrombogenecity is incompletely understood. This study aimed to determine the prevalence of TE in Danish Fontan patients and to bring new insights into the etiology of TE. Using a population-based design, we retrospectively identified all TEs in 210 Fontan patients. Whole blood assays (thromboelastography, thromboelastography functional fibrinogen and Multiplate) reflecting global hemostasis, clot strength and platelet aggregation were analyzed prospectively in 112 patients and plasma was analyzed in 76 patients for biomarkers reflecting endothelial-, glycocalyx-, platelet-, and fibrinolysis function (histone-complexed DNA fragments, Protein C, soluble CD40 ligand, soluble thrombomodulin, syndecan-1, tissue-type plasminogen activator). The results were compared in groups stratified according to age, antithrombotic therapy, TE, and glycocalyx degradation (syndecan-1 < or ≥ median). Correlation between biomarkers and demographic-, anatomical-, clinical- and biochemical parameters was investigated. The prevalence of TE was 8.1 % after a mean follow-up of 8.4 years. None of the stratified groups demonstrated evidence of hypercoagulability in the whole blood assays and no unexpected significant differences were found between the groups. All biomarkers, except protein C, correlated with one another and after stratification of glycocalyx degradation only syndecan-1 levels ≥ median correlated with other biomarkers. The prevalence of TEs was 8.1 % after mean follow-up of 8.4 years. Overall, the hemostatic profile appeared normal, however, in a subset of patients, evidence of some endothelial activation/damage including glycocalyx degradation and fibrinolysis was found, identifying a potentially more thrombogenic group.

Major stroke in a 19-year-old patient with a univentricular heart

Patients with univentricular heart malformations are at increased risk of suffering from thromboembolic events. We present a case of a 19-year-old woman born with a univentricular heart who suffered a major stroke while being treated with only salicylic acid. At least 20% of patients with univentricular hearts have been reported to experience thromboembolic events, of which 25% are fatal. Despite the high incidence of thromboembolic events, no consensus has been reached regarding the role of long-term anti-thrombotic treatment in this group of patients. This lack of consensus warrants future studies that compare the different therapeutic strategies.

Non-invasive assessment of liver fibrosis in patients after the Fontan operation

BACKGROUND

This study analyzed the change in liver fibrosis markers after the Fontan operation and investigated their clinical usefulness as an index of congestive liver fibrosis.

METHODS

The study enrolled 24 patients who underwent the Fontan operation between January 1994 and December 2008. We subdivided the postoperative period into four intervals and then compared the hepatological markers during each. Eighteen patients underwent postoperative cardiac catheterization and the correlation between hepatological markers and the inferior vena cava (IVC) pressure was analyzed.

RESULTS

The mean age of the patients was 138.6 months and the mean interval between the Fontan operation and the examination was 97.8 months. Type IV collagen was extremely high in every interval (I, 286 ± 93; II, 265 ± 93; III, 305 ± 143; IV, 206 ± 70), while none of the laboratory variables changed significantly in each interval. A significant positive correlation was observed between type IV collagen and the IVC pressure, but no significant correlation with any other hepatological marker was detected.

CONCLUSIONS

No specific parameter that reflects the progress in liver fibrosis was identified in this study. The possibility exists that type IV collagen reflects the degree of hepatic congestion.

Rare problems associated with the Fontan circulation

The Fontan operation, originally described for the surgical management of tricuspid atresia, is now the final surgery in the strategy of staged palliation for a number of different forms of congenital cardiac disease with a functionally univentricular heart. Despite the improved technical outcomes of the Fontan operation, staged palliation does not recreate a normal physiology. Without a pumping chamber delivering blood to the lungs, the cardiovascular system is less efficient; cardiac output is generally diminished, and the systemic venous pressure is increased. As a result, patients with "Fontan physiology" may face a number of rare but potentially life-threatening complications including hepatic dysfunction, abnormalities of coagulation, protein-losing enteropathy, and plastic bronchitis. Despite the staged palliation resulting in remarkable survival, the possible complications for this group of patients are complex, involve multiple organ systems, and can be life threatening. Identifying the mechanisms associated with each of the rare complications, and developing strategies to treat them, requires the work of many people at many institutions. Continued collaboration between sub-specialists and between institutions will be required to optimise the care for this group of survivors with functionally univentricular hearts.