“杂交”手术治疗20例小婴儿主动脉缩窄合并室间隔缺损

目的 评价“杂交”手术治疗6月龄内小婴儿主动脉缩窄合并室间隔缺损的早期治疗结果.方法 2010年1月至2011年7月,20例小婴儿主动脉缩窄合并室间隔缺损患儿,手术年龄(56±45)天,体重(4.5±1.6)kg.主动脉缩窄压差30 ～56 mm Hg(1 mm Hg =0.133 kPa),其中5例伴主动脉弓发育不良;室间隔缺损8 ～ 16 mm.均行“杂交”手术治疗.结果 全组无手术及围术期死亡.围术期并发症4例(20％).术中造影发现主动脉弓缩窄最严重处直径为1.5 ～ 3.4 mm,选择最大球囊直径4～12 mm,扩张后即刻主动脉缩窄处压差为0～ 27 mm Hg.全组体外循环40～ 87 min,主动脉阻断20 ～ 41min,无延迟关胸.术后患儿机械通气(2.2±1.4)天,住监护室(5±3)天.患儿均随访(10.0±3.6)个月,主动脉弓缩窄扩张处末见有动脉瘤发生,无气道受压.末次随访2例患儿主动脉弓残余梗阻,压差12 ～ 35 mm Hg,再次手术干预.结论 主动脉弓缩窄球囊扩张联合体外循环下室间隔缺损修补手术治疗小婴儿主动脉缩窄合并室间隔缺损可以避免深低温停循环,具有较高的安全性,早期疗效满意.     

Mimicking of cerebral autoregulation by flow-dependent cerebrovascular resistance: a feasibility study

Understanding circulatory autoregulation is essential for improving physiological control of rotary blood pumps and support conditions during cardiopulmonary bypass (CPB). Cerebral autoregulation (CAR), arguably the most critical, is the body's intrinsic ability to maintain sufficient cerebral blood flow (CBF) despite changes in aortic perfusion pressure. It is therefore imperative to include this mechanism into computational fluid dynamics (CFD), particle image velocimetry (PIV), or mock circulation loop (MCL) studies. Without such inclusions, potential losses of CBF are overestimated. In this study, a mathematical model to mimic CAR is implemented in a MCL‐ and PIV‐validated CFD model. A three‐dimensional model of the human vascular system was created from magnetic resonance imaging records. Numerical flow simulations were performed for physiological conditions and CPB. The inlet flow was varied between 4.5 and 6 L/min. Arterial outlets were modeled using vessel‐specific, flow‐dependent cerebrovascular resistances (CVRs), resulting in a variation of the pressure drop between 0 and 80 mm Hg. CBF is highly dependent on the level of CAR during CPB. By varying the CVR parameters up to the beginning of plateau phase, it can be regulated between 0 and 80% of physiological CBF. So while implementing autoregulation, CBF remains unchanged during a simulated native cardiac output of 5 L/min or CPB support of 6 L/min. Neglecting CAR, constant backflow from the brain occurs for some cannula positions. Using flow‐dependent CVR, CBF returns to its baseline at a rate of recovery of 0.25 s. Results demonstrate that modeling of CAR by flow‐dependent CVR delivers feasible results. The presented method can be used to optimize physiological control of assist devices dependent upon different levels of CAR representing different patients.     

Ventricular assist device support in children and adolescents with heart failure: the Children's Medical Center of Dallas experience

Children with heart failure unresponsive to medical therapy are left with few options for survival. Ventricular assist devices (VADs) are life-saving options for such patients, allowing for bridge to transplantation or cardiac recovery. Retrospective review of cases from May 2006 to October 2010 was undertaken. Fourteen patients underwent implantation of VADs for refractory heart failure. Mean age was 9 years (range 1-17 years), and weight was 41 kg (range 9.7-71 kg). Indications for support: end-stage cardiomyopathy (n = 8), myocarditis (n = 3), univentricular failure (n = 2), and congenital heart disease/postcardiotomy (n = 1). Level of limitation at time of implant included critical cardiogenic shock in six (43%) and progressive decline in eight (57%). Extracorporeal membrane oxygenation was used as a bridge to VAD in five (36%) patients. Preimplant variables: 86% of patients requiring mechanical ventilation (mean 10.3 days), hyperbilirubinemia in 75%, and acute renal insufficiency in 79%. Device selection was systemic VAD in 11 (79%) and biventricular assist device in three (21%). Berlin Heart EXCOR was used in eight patients, while six patients received a Thoratec implantable VAD or paracorporeal VAD. Mean duration of support was 68 days (range 8-363 days). Overall survival was 79%. Ten patients (71%) were successfully bridged to transplantation, three (21%) died while on a device, one remains on support, and no patients were weaned from VAD. Children supported for single ventricle heart failure had a 50% survival with none currently bridged to transplantation. Complications included bleeding requiring reoperation in 21% (n = 3), stroke in 29% (n = 4), and driveline infections in 7% (n = 1). In two patients, a total of six pump exchanges were performed for thrombus formation. Survival for pediatric patients of all ages is excellent using current device technology with a majority of patients being successfully bridged to transplantation. Morbidity is acceptably low considering the severity of illness. Significant challenges exist with long-term extracorporeal support due to lack of donor availability and the high incidence of preformed alloantibodies especially in the failing single ventricle.     

Analysis of flow within a left ventricle model fully assisted with continuous flow through the aortic valve

Blood compatibility of a ventricular assist device (VAD) depends on the dynamics of blood flow. The focus in most previous studies was on blood flow in the VAD. However, the tip shape and position of the VAD inflow cannula influence the dynamics of intraventricular blood flow and thus thrombus formation in the ventricle. In this study, blood flow in the left ventricle (LV) under support with a catheter-type continuous flow blood pump was investigated. The flow field was analyzed both numerically and experimentally to investigate the effects of catheter tip shape and its insertion depth on intraventricular flow patterns. A computational model of the LV cavity with a simplified shape was constructed using computer-aided design software. Models of catheters with three different tip shapes were constructed and each was integrated to the LV model. In addition, three variations of insertion depth were prepared for all models. The fully supported intraventricular flow field was calculated by computational fluid dynamics (CFD). A transparent LV model made of silicone was also fabricated to analyze the intraventricular flow field by the particle image velocimetry technique. A mock circulation loop was constructed and water containing tracer particles was circulated in the loop. The motion of particles in the LV model was recorded with a digital high-speed video camera and analyzed to reveal the flow field. The results of numerical and experimental analyses indicated the formation of two large vortices in the bisector plane of the mitral and aortic valve planes. The shape and positioning of the catheter tip affected the flow distribution in the LV, and some of these combinations elongated the upper vortex toward the ventricular apex. Assessment based on average wall shear stress on the LV wall indicated that the flow distribution improved the washout effect. The flow patterns obtained from flow visualization coincided with those calculated by CFD analysis. Through these comparisons, the numerical analysis was validated. In conclusion, results of these numerical and experimental analyses of flow field in the LV cavity provide useful information when designing catheter-type VADs.     

Reevaluation of the harboe assay as a standardized method of assessment for the hemolytic performance of ventricular assist devices

The Harboe spectrophotometric assay is regarded as one of the safest and most reproducible methods for measuring plasma free hemoglobin (pfHb). However, there is still some ambiguity in the application of the assay when assessing the hemolytic performance of ventricular assist devices (VADs). The purpose of this study was to reexamine and compare values of pfHb obtained using different concentrations of plasma diluent (Na(2) CO(3) ) as cited by various studies such that a standard practice may be recommended for the application of the Harboe assay in the hemolytic evaluation of VADs, allowing reliable comparisons to be made between laboratories. As a means to examine the Harboe assay, a BioMedicus BPX-80 was tested using both whole blood and a washed suspension of red blood cells (RBCs). Results show that for whole blood, the pfHb may be underestimated by 13-23%, dependent upon the concentration of Na(2) CO(3) diluent solution. This trend was not observed for the washed suspension of RBCs. Furthermore, it is shown that the concentration of diluent influences the stability of a sample. The results of this study show that the problems associated with the incongruity of pfHb readings are a direct result of the precipitation of proteins from the plasma under alkaline conditions; as the molarity of the diluent controls pH, it becomes essential to use the appropriate concentration of Na(2) CO(3) diluent in order to avoid turbidity of the solution and the consequent misrepresentation of pfHb values. Such standardization is pertinent when measuring the very low levels of pfHb observed during the in vivo testing of modern ventricular assist devices.     

Aortic valve replacement in severe aortic stenosis with left ventricular dysfunction: determinants of cardiac mortality and ventricular function recovery

Objective: The influence of left ventricular (LV) dysfunction on survival of patients with severe aortic stenosis is poorly characterized. Few data are available about preoperative predictors of cardiac mortality and LV function recovery after aortic valve replacement of such patients. The aim of our study was to examine the outcome and the preoperative predictors of postoperative cardiac death and of LV function recovery in these patients. Methods: We evaluated 85 consecutive patients with severe aortic stenosis (aortic valve area <1 cm²) and severe depression of LV ejection fraction (EF) <35% at cardiac catheterization. Among them, 52 underwent aortic valve replacement and they were compared to patients who were not operated on. All patients had a mean clinical follow-up of 53 months and 94% of them had a mean echocardiographic follow-up of 14 months after aortic valve replacement. Results: The mean baseline characteristics included: LVEF 28±6%, peak-to-peak transvalvular gradient 51±29 mmHg, aortic valve area 0.63±0.25 cm². Thirty-three patients did not undergo aortic valve replacement: 32 of them died within 3 years. Fifty-two patients underwent aortic valve replacement and 16 had a concomitant coronary bypass surgery. In-hospital mortality was 8%. Postoperative NYHA functional class changed from 2.84±0.67 to 1.43±0.44 (P<0.001) and LVEF from 29±6% to 43±10% (P<0.001). At follow-up 10 patients died of heart disease. By multivariate analysis, preoperative LV end-systolic volume index (ESVI) was the only covariate of cardiac death (LVESVI/10 ml/m², OR 1.3, CI 1.1–1.8, P<0.028). By using a receiver operating characteristic curve, LVESVI≤90 ml/m² was the best cut-off value (sensitivity and specificity 78%) to fit with a better survival (93% vs. 63%, P<0.01) and with LVEF recovery after aortic valve replacement (EF improved by 15±10% vs. 8±5%, P<0.001). Conclusions: Despite LV dysfunction, aortic valve replacement appears to change drastically the natural history of severe aortic stenosis. Preoperative LV levels predict different postoperative survival rate and LVEF recovery.     

Feasibility of diaphragm pacing in patients after bilateral lung transplantation

Recent animal studies and intraoperative studies in humans suggested that phrenic nerve stimulation could attenuate ventilator‐induced diaphragm dysfunction. The purpose of the present study is to examine the safety and feasibility of diaphragm pacing during the weaning process after bilateral lung transplantation. Four patients, suffering from chronic pulmonary disease, were included, and diaphragm pacing was evaluated after lung transplantation. Implantation of electrodes at the end of the lung transplant procedure was possible in three of the four patients. In all implanted patients, stimulation of the diaphragm could trigger the ventilator. Implanted electrodes were completely removed by percutaneous retraction after up to 7 days of pacing. Adverse events related to pacing included occurrence of pain. Diaphragm pacing with temporary electrodes, inserted during surgery, is feasible and is able to trigger the ventilator in patients after bilateral lung transplantation. The use of intradiaphragmatic electrodes creates the additional opportunity to monitor the evolution of diaphragm electromyography during the postoperative weaning process.     

多层螺旋CT评估左心室功能的应用进展

左心室功能评估对心脏疾病的诊断、风险分层、治疗及预后分析具有重要意义。心脏CT血管成像(CCTA)作为一种无创性成像技术,目前在心脏疾病的诊断中发挥着越来越重要的作用,它既可评估冠状动脉狭窄,也能获取左心室容积和功能方面的信息。64层及以上的多层螺旋CT(MSCT)可一站式评价冠状动脉和左心室功能,无需对比剂和辐射的重复暴露,心功能分析结果可重复性高,具有较高的临床应用价值。     

Laparoscopic cholecystectomy in a patient with a biventricular cardiac assist device.

Evaluation and management of abdominal pathology in patients with ventricular assist devices is likely to become increasingly important as the utilization of these devices expands. Ventricular assist devices represent a class of intracorporeal or paracorporeal mechanical devices that augment cardiac output in patients with congestive heart failure. Patients with ventricular assist devices supporting both right and left ventricles (biventricular assist devices) are uniquely challenging to the general surgeon because these devices restrict direct access to the abdominal cavity and because of the perioperative implications of biventricular heart failure. We describe herein the first reported successful laparoscopic cholecystectomy in a patient with a paracorporeal biventricular assist device. Cholecystectomy was performed in this patient for acute cholecystitis that occurred while the patient was awaiting heart transplantation. Our results add weight to the small body of evidence that laparoscopy is well tolerated in ventricular assist devices patients. The unique aspects of the biventricular assist device patient make laparoscopic abdominal intervention particularly suitable in this patient population.     

心肌梗死并发室间隔穿孔的外科治疗

目的:探讨提高心肌梗死并发室间隔穿孔(VSR)外科治疗疗效的方法.方法:回顾性分析1994年10月至2007年10月37例接受手术治疗的VSR患者的临床资料.男性24例,女性13例,平均年龄(63.4±7.6)岁.其中VSR修补合并同期冠状动脉再血管化26例(再血管化组),单纯VSR修补11例(单纯修补组).结果:围手术期再血管化组病死率15.4%(4/26),低于单纯修补组的63.6%(7/11),P=0.006.出院患者26例均获得随访,平均随访(34.0±29.8)个月,总随访时间57人年.再血管化组晚期死亡2例,单纯修补组3例.再血管化组6～8年生存率为(64.3 ±21.0)%,单纯修补组4年生存率为(25.0±21.7)%,组间差异有统计学意义.21例患者获得中长期生存,心功能Ⅰ～Ⅱ级17例,Ⅲ～Ⅳ级4例.再发VSR 4例.多因素分析发现未冉血管化、心源性休克、急诊手术为早期死亡危险因子,未再血管化、术后低心排是晚期死亡的危险因子.结论:VSR修补术同期施行再血管化手术可提高围手术期生存率和中长期生存率,合理选择手术时机、手术方法,对提高VSR围手术期生存率、减少VSR再发非常重要.