Computational modelling of the hybrid procedure in hypoplastic left heart syndrome: a comparison of zero-dimensional and three-dimensional approach.

Previous studies have employed generic 3D-multiscale models to predict haemodynamic effects of the hybrid procedure in hypoplastic left heart syndrome. Patient-specific models, derived from image data, may allow a more clinically relevant model. However, such models require long computation times and employ internal pulmonary artery band [dint] dimension, which limits clinical application. Simpler, zero-dimensional models utilize external PAB diameters [dext] and provide rapid analysis, which may better guide intervention. This study compared 0-D and 3-D modelling from a single patient dataset and investigated the relationship dint versus dext and hemodynamic outputs of the two models. Optimum oxygen delivery defined at dint=2mm corresponded to dext=3.1 mm and 3.4 mm when models were matched for cardiac output or systemic pressure, respectively. 0-D and 3-D models when matched for PAB dimension produced close equivalence of hemodynamics and ventricular energetics. From this study we conclude that 0-D model can provide a valid alternative to 3D-multiscale in the hybrid-HLHS circulation.

Computational modelling to optimize the hybrid configuration for hypoplastic left heart syndrome.

OBJECTIVES: Hybrid palliation for hypoplastic left heart syndrome (HLHS) is associated with mortality and late ventricular dysfunction. Increased ventricular workload and coronary perfusion limitation may be the important factors. Using mathematical modelling, this study investigated the effects of differing hybrid configurations on the demands on this single ventricle circulation. METHODS: A multicompartmental Windkessel model of hybrid HLH-aortic atresia circulation was adopted, with a time-varying elastance representing ventricular functionality. The effects of diameter increases in bilateral pulmonary artery bandings (PABs) (+0.5, 2.5-4 mm) and ductal stent (+1, 4-10 mm) on cardiovascular haemodynamics, systemic oxygenation and ventricular energetics were assessed. RESULTS: Simulations showed that an increase in PAB diameter of 2.5-4 mm resulted in an increased Q (0.61-2.66), and diastolic stent backflow (-0.2 to -0.78 l/min) with reduced systemic perfusion (0.82-0.77 l/min) and diastolic pressures (48.3-41.2 mmHg). Arterial and venous saturations increased, SaO2 (%) was 62-88 and SvO(2) 41-65. To maintain mean systemic pressures, substantial increases in cardiac output (1.3-2.8 l/min) and ventricular stroke work (576-1360 mmHg ml) were required. A decrease in the ductal stent diameter over the range 10-7 mm had a negligible haemodynamic effect: reduced systemic systolic pressure (77-72 mmHg) and increase in ventricular stroke work (781-790 mmHg ml). When the ductal diameter was restricted to <7 mm, it resulted in a significant reduced systemic flow and increased stroke work. Optimal hybrid configuration was defined at PAB 3 mm and ductal stent ≥7 mm. CONCLUSIONS: In this model, increasing the PAB diameter, or a stent diameter <7 mm, substantially increased single ventricle workload and reduced systemic perfusion and diastolic pressure. This may compromise myocardial oxygen demand-supply, particularly in the setting of retrograde-dependent coronary perfusion.

High incidence of recurrent in stent thrombosis after successful treatment of a first in stent thrombosis.

OBJECTIVES: We attempted to investigate incidence and predictors of recurrent in stent thrombosis (IST) after successful treatment of a first IST. BACKGROUND: The occurrence of recurrent IST after successful treatment of a first IST may be a decisive factor for patient clinical outcome. However, incidence and predictors of recurrent IST are currently poorly described in the literature. METHODS: Between 2003 and 2005, 2,190 patients underwent a percutaneous coronary intervention in our center. During a median follow-up of 19.4 months, 49 patients (2.24%) presented a first definite IST. Patients presenting with a first IST were followed during an additional median period of 40 months. Their baseline characteristics were listed and cardiovascular events especially recurrent IST as defined by the Academic Research Consortium definition were systematically indexed. RESULTS: Altogether 39 (80%) patients were successfully treated with an effective reperfusion after percutaneous coronary intervention. Fourteen (36%) patients presented a recurrent IST and three presented multiple recurrent IST. The median occurrence time of recurrent IST was 5 days, range between 1 and 11 days. Multivariate analysis identified history of neoplasia (HR = 11.53, 95% CI 2.32-57.37, P = 0.003), residual diameter stenosis (HR = 1.15, 95% CI 1.02-1.29, P = 0.02), and residual dissection after treatment (HR = 8.78, 95% CI 1.85-41.62, P = 0.006), as independent predictors of recurrent IST. CONCLUSION: Recurrent IST is a frequent and early event after successful treatment of a first IST. Our results suggest that mechanical factors like residual dissection and residual diameter stenosis should be carefully tracked down. In addition, patients with multiple recurrent IST and the early time course of recurrent IST also suggest a potential role of inadequate antiplatelet therapy.

Extracorporeal membrane oxygenation in severe acute respiratory failure in postpartum woman with rheumatic mitral valve disease: benefit, factors furthering the success of this procedure, and review of the literature.

Pregnancy is a common decompensation factor for women with post-rheumatic mitral disease. However, valvular heart diseases causing severe acute respiratory distress are rare. Use of extracorporeal membrane oxygenation (ECMO) early in the event of cardiorespiratory failure after cardiac surgery may be of benefit. Indeed, ECMO cardiopulmonary bypass (CPB) support could help pulmonary recovery if the mitral pathology is involved. A 31-year-old female patient at 30 weeks of amenorrhea was admitted to the obstetrics department with 40 degrees C hyperthermia and New York Heart Association (NYHA) class 4 dyspnea. The patient's medical history included a post-rheumatic mitral stenosis. Blood gases showed severe hypoxemia associated with hypocapnia. The patient needed to be rapidly intubated and was placed on ventilatory support because of acute respiratory failure. Transesophageal echocardiography showed a severe mitral stenosis, mild mitral insufficiency, and diminished left ventricular function, hypokinetic, dilated right ventricle, and a severe tricuspid regurgitation. An urgent cesarean section was performed. Because of the persistent hemodynamic instability, a mitral valvular replacement and tricuspid valve annuloplasty were performed. In view of the preoperative acute respiratory distress, we decided, at the beginning of the operation, to carry on circulatory support with oxygenation through an ECMO-type CPB at the end of the operation. This decision was totally justified by the unfeasible CPB weaning off. ECMO use led to an efficient hemodynamic state without inotropic drug support. The surgical post-operative course was uneventful. Early use of cardiorespiratory support with veno-arterial ECMO allows pulmonary and right heart recovery after cardiac surgery, thus avoiding the use of inotropic drugs and complex ventilatory support.