Evaluation of hemostatic and coagulation factor abnormalities in patients undergoing the Fontan operation

AbstractObjective: Low-velocity and nonlaminar flow patterns in the Fontan circulation, as well as abnormal liver function in some patients, may partly account for the coagulation abnormalities seen. We examined (1) coagulation factor abnormalities before and after the Fontan procedure and (2) regional coagulation factor abnormalities in the Fontan circulation. Methods: Levels of factors V, VII, VIII, X, antithrombin III, prothrombin fragment F1+2, protein C, and protein S were measured in 2 groups of patients: In 14 patients undergoing the Fontan procedure, blood was analyzed before the operation and 5 days after the operation (group 1). The median age in this group was 3.2 years. In 10 patients who had undergone the Fontan procedure, cardiac catheterization was performed and samples were taken from the femoral vein, inferior vena cava, right atrium, and pulmonary artery (group 2). The median age in this group was 6.2 years and the median follow-up from the Fontan procedure was 4.1 years. Results: In group 1 a significant increase was noted postoperatively in the concentration of factor VIII (P < .001), factor X (P < .001), and prothrombin fraction F1+2 (P < .001). A significant decrease in the levels of antithrombin III (P < .001), protein C (P < .004), and protein S (P < .02) was also found. The increase in factors VIII and X persisted at 4 years' follow-up in group 2 patients. In group 2, no significant regional differences were observed between the coagulation factors measured at different sites. Conclusions: There is an increased tendency toward coagulation after the Fontan procedure. A prothrombotic state is supported by thrombin generation associated with reduced antithrombin III concentration. This increase in coagulation may contribute to the early and late risks of thromboembolism observed after the Fontan procedure. We did not find any regional differences in coagulation abnormalities in patients late after the Fontan procedure. Therefore, the mechanisms and causes of the coagulation abnormalities remain unclear. (J Thorac Cardiovasc Surg 2000;120:778-82

The Learning Curve for a Fetal Cardiac Intervention Team

Objectives. Multiple technical difficulties are encountered when a multidisciplinary team of subspecialists begins a minimally-invasive fetal cardiac interventional program. We describe the learning curve. Study Design. Ten pregnant sheep underwent ultrasound-guided balloon valvuloplasty of the aortic valve. Team members and their roles remained constant through the trial. The time between needle insertion and entrance of the left ventricle at the aortic root was recorded. F-test was used to assess significance (P ≤ .05). Results. The time required to accurately position the needle tip at the aortic root decreased significantly over the course of the trial, from 12 minutes with the first attempt to one minute with the last (P = .003). Conclusion. A significant learning curve is encountered when a multidisciplinary team begins a minimally-invasive fetal cardiac intervention program. However, technical proficiency can be achieved with practice. Institutions interested in developing such a program should consider practice in an animal model before proceeding to the human fetus

A contemporary comparison of the effect of shunt type in hypoplastic left heart syndrome on the hemodynamics and outcome at stage 2 reconstruction

ObjectiveWe compare the hemodynamics and perioperative course of shunt type in hypoplastic left heart syndrome at the time of stage 2 reconstruction and longer-term survival.MethodsWe retrospectively reviewed the echocardiograms, catheterizations, and hospital records of all patients who had a stage 1 reconstruction between January 2002 and May 2005 and performed a cross-sectional analysis of hospital survivors.ResultsOne hundred seventy-six patients with hypoplastic left heart syndrome and variants underwent a stage 1 reconstruction with either a right ventricle–pulmonary artery conduit (n = 62) or a modified Blalock–Taussig shunt (n = 114). The median duration of follow-up is 29.1 months (range, 0-57 months). By means of Kaplan–Meier analysis, there is no difference in survival at 3 years (right ventricle–pulmonary artery conduit: 73% [95% confidence limit, 59%–83%] vs modified Blalock–Taussig shunt: 69% [95% confidence limit, 59%–77%]; P = .6). One hundred twenty-four patients have undergone stage 2 reconstruction (78 modified Blalock–Taussig shunts and 46 right ventricle–pulmonary artery conduits). At the time of the stage 2 reconstruction, patients with right ventricle–pulmonary artery conduits were younger (153 days [range, 108–340 days]; modified Blalock–Taussig shunt, 176 days [range, 80–318 days]; P = .03), had lower systemic oxygen saturation (73% [range, 58%–85%] vs 77% [range, 57%–89%], P < .01), and had higher preoperative hemoglobin levels (15.8 g/dL [range, 13–21 g/dL] vs 14.8 g/dL [range, 12–19 g/dL], P < .01) compared with those of the modified Blalock–Taussig shunt group. By means of echocardiographic evaluation, there was a higher incidence of qualitative ventricular dysfunction in patients with right ventricle–pulmonary artery conduits (14/46 [31%] vs 9/73 [12%], P = .02). However, no difference was observed in common atrial pressure or the arteriovenous oxygen difference.ConclusionInterim analyses suggest no advantage of one shunt type over another. This report raises concern of late ventricular dysfunction and outcome in patients with a right ventricle–pulmonary artery conduit

Reflections on five decades of the Fontan Kreutzer procedure.

The first successful total right heart bypass via atriopulmonary anastomosis, (APA) were reported in 1971 for patients with tricuspid atresia. At the Children&#180;s Hospital of Buenos Aires, the cohort of such procedures started in July, when the first fenestrated right heart by pass was performed, with the interposition of a homograft between the right atrial appendage and the main pulmonary artery. In the second patient, instead of placing a homograft, the APA was achieved with the patient&#180;s own pulmonary root harvested from the outflow tract of the right ventricle. These techniques were soon replaced in 1978 with the development of the direct valveless posterior atriopulmonary anastomosis. Since the very beginning the principle was that the right atrium only functions as a pathway rather than a pump (reason why no inferior vena cava valves were ever used), and the diastolic properties of the systemic ventricle regulate the only real pump of this system. The late hemodynamic problems inherent of the APA diminished with modern surgical techniques like the lateral tunnel (LT) or the extracardiac conduit (EC). In spite of the improvement in prognosis and quality of life that the modern techniques have brought for univentricular hearts, with the passing of time, deterioration of this system is frequently seen, due to chronic low cardiac output and elevated central venous pressure. Progressive increase in pulmonary vascular resistances and ventricular dysfunction result in a decline in quality of life and survival. However, the timing of this occurrence is variable, and many survivors enjoy today a satisfactory clinical status. The challenge is to develop a better solution for univentricular hearts, but in the mean time the Fontan Kreutzer palliation represents the best and only surgical option. It is undoubtedly one of the triumphs of cardiac surgery in congenital heart disease

Time domain attack and release modeling - applied to spectral domain sound synthesis

We introduce a time-domain model for the synthesis of attack and release parts of musical sounds. This approach is an extension of a spectral synthesis model we developed: the Parametric Synthesis Model (PSM). The attack and release model is independent from a preceeding spectral analysis as it is based on the time domain sustain part of the sound. We apply a shaping function to this sustain part to obtain the sound attack and the release. The model has been tested with linear and polynomial shaping functions and produces good results for three different instruments. The time-domain approach also overcomes the problem of synthesis artifacts that often occur when using spectral analysis/synthesis methods for sounds with transient events. Moreover, the model can be combined with any synthesis model of the sustain part and offers the possibility to determine the duration of the attack and release parts of the sound

A parametric model for spectral sound synthesis of musical sounds

We introduce a reduced parameter synthesis model for the spectral synthesis of musical sounds, which preserves the timbre and the naturalness of the musical sound. It also provides large flexibility for the user and reduces the number of synthesis parameters compared to traditional analysis/re-synthesis methods. The proposed model is almost completely independent from a previous spectral analysis. We present a frequency estimation method using a random walk to keep the naturalness of the sound without using a separate noise model. Three different approaches have been tested to estimate the amplitude values for the synthesis, namely, local optimization, the use of a lowpass filter and polynomial fitting. All of these approaches give good results, especially for the sustain part of the signal