Role of catheter and surgical ablation in congenital heart disease

The role of surgery and radiofrequency current ablation for the treatment of tachycardias in patients with congenital heart disease The use of radiofrequency current application as a treatment strategy has stimulated a revolution in our understanding of tachycardia mechanisms. The extension of its use to patients with congenital heart defects and tachyarrhythmias has opened the door to new treatments with known success rates and known risks for mortality and morbidity. Antiarrhythmic surgery aims to dissect or excavate a responsible substrate and is especially worth considering if cardiac surgery is being undertaken for other reasons. With suitable surgical skill and interest, and with strong electrophysiologic support, high success rates have been documented. Antiarrhythmic surgical incisions have the advantage of being visually controllable regarding the extent and location of damage to myocardial tissue. In other situations, radiofrequency current ablation is preferred because of its less-invasive character, its use of local anesthesia, and the avoidance of surgical trauma. Both surgery and catheter ablation require precise clarification of the tachycardia mechanism and precise localization of the underlying substrate. The importation of such techniques into the realm of open chest surgery would be difficult in light of the need for multiple intracardiac catheters and repeated fluoroscopically guided catheter positioning. Electrophysiologic studies performed during the antiarrhythmic surgical procedure cannot provide complete information, and their use is thus restricted to the arrhythmogenic myocardial target only [32,45]. In contrast, catheter-mediated electrophysiologic studies offer the option of exact diagnosis, precise substrate localization, and interventional treatment in a single session. Moreover, validation of the linear lesion's completeness has become a reliable predictor for mid- and long-term success in avoiding recurrences. As a result, the application of catheter-mediated ablation has exploded within the past 15 years. Antiarrhythmic surgery has survived as a discipline in a decreasing number of experienced hands [43,44]. As a result of recent experiences and modern technology, success rates above 90% [74-76, 81,88] for the interventional treatment of congenital tachycardias have become comparable to those reported in patients with "normal" hearts. For acquired tachycardias, acute success rates today range about 80% at the atrial level. The rate of recurrence is still relatively high at about 10-25% [73,76,77,79,91,96,102]. Further improvements are being pursued. Data on the treatment of acquired tachycardias at the ventricular level is largely anecdotal. Good early success rates are combined with a tendency to recurrence in longer-term follow-up [50,76,103-108]. Some of the late VT ablation recurrences may be explained by the fact that fibrotic, scarred, and hypertrophic myocardial tissue at the targeted site often prevents effective radiofrequency current application and lesion generation. In order to improve RF lesion depth and continuity, newly designed technologies for radiofrequency current ("cooled tip electrode", Cordis Webster, Baldwin Park, CA), and alternative energy sources (cryo-ablation, micro-wave, or ultrasound) are being readied for introduction in the very near future. For patients suffering from recurrent tachycardias and having other reasons for open-heart surgery, a hybrid concept can be created, utilizing modern 3-D electro-anatomical reconstruction as a basis for an electrophysiologically informed surgical procedure. Following such a concept, a hemodynamic catheterization can be combined with an electrophysiologic study to define critical myocardial zones for induced macro-re-entry tachycardias, or of those zones expected to play an arrhythmogenic role in the future. With such information, surgical incisions for cardiac access and repair can be planned and performed. The role of surgery in antiarrhythmic treatment can become preventive. Myocardial tissue is incised for cannulation and repair in a way that can reduce the chance of later scar-associated tachycardias [109]. The extension of surgical cuts to physiologic barriers of electrical conduction is a major strategy for the primary prevention of postsurgical or incisional arrhythmias. In addition, the simultaneous treatment at heart surgery of already existing tachycardias can be offered within the same session as a secondary preventive concept. Despite the immense growth of knowledge and experience in recent years, there is still a need for more knowledge about the factors causing arrhythmogenesis and their interactions. Prospective and randomized studies are needed to show the most effective strategies to prevent arrhythmia-mediated death. The future of antiarrhythmic treatment will less be directed by the limitations of current interventional tools, which will be improved, and more by an evolutionary process in philosophy regarding the understanding of arrhythmogenesis in these patients as the basis for new concepts of arrhythmia prevention and treatment.     

A novel role for cardiac neural crest in heart development

It is well known that cardiac neural crest participates in development of the cardiac outflow septation and patterning of the great arteries. Less well known is that ablation of the cardiac neural crest leads to a primary myocardial dysfunction. Recent data suggests that the myocardial dysfunction occurs because of the absence of an interaction of neural crest and pharyngeal endoderm to alter signaling from the endoderm. Continuation of an FGF-like signal from the endoderm past a precise time in development appears to be detrimental to myocardial maturation.     

产前重复超声检查在发现胎儿复杂型先天性心脏病中的作用

目的探讨产前重复超声检查在发现胎儿复杂型先天性心脏病(先心病)中的作用。方法回顾性分析5例孕中期初次超声检查胎儿心脏正常而孕晚期超声复查发现复杂型先心病的病例资料,分析初次检查漏诊原因和重复超声复查的作用。结果初查发现胎儿复杂型先心病17例,初查胎儿心脏正常而超声复查发现复杂型先心病5例,两次超声检查共发现胎儿复杂型先心病22例,占我院产检病例的0.6%。结论产前诊断胎儿先心病受多因素影响,有一定的漏诊率,要提高产前诊断的准确率,需同时重视孕中期的初次超声检查及孕晚期的重复超声检查,多次的超声检查可使先心病在产前的检出率达到最大。     

The right heart in congenital heart disease

The clinical presentation of right ventricular (RV) dysfunction due to congenital heart disease (CHD) is similar to that of cor pulmonale. RV volume and pressure loads, and primary RV myocardial dysfunction are mechanisms by which CHD affects right heart function. RV volume load may arise from pre-tricuspid left to right shunts (e.g., atrial septal defect) or regurgitant lesions in the right heart (e.g., Ebstein's anomaly of the tricuspid valve and pulmonary insufficiency after repair of tetralogy of Fallot). RV pressure load may be caused by anatomic obstruction to RV outflow and by pulmonary arteriolar hypertension. The latter can result from Eisenmenger syndrome secondary to congenital and postoperative left to right shunts or from defects that cause pulmonary venous hypertension (e.g., pulmonary vein stenosis, cor triatriatum, or mitral stenosis). The RV myocardium may be affected by a primary cardiomyopathy or by congenital abnormalities of the coronary vessels. Finally, CHD may be associated with airway obstruction, scoliosis, or pulmonary emboli, which, in turn, may lead to the development of cor pulmonale. Congenital heart disease, therefore, must be included in the differential diagnosis of patients who present with right ventricular dysfunction.     

Arrhythmias in congenital heart disease

Opinion statement  

Role of echocardiography versus MRI for the diagnosis of congenital heart disease

During the last few decades, significant strides have been made in the field of noninvasive imaging for the patient with congenital heart disease. Echocardiography and MRI continue to provide improved means of anatomic and functional assessment in children and adults with congenital heart lesions. This review reports some of the recent advances in tissue Doppler, strain rate, and integrated backscatter, and highlights exciting current and future potential developments in their application. We also discuss advances in MR in evaluation of cardiac anatomy and function in congenital heart disease.     

Genetics of congenital heart disease

Cardiovascular malformations are the most common type of birth defect and result in significant mortality worldwide. The etiology for the majority of these anomalies remains unknown but genetic factors are being recognized as playing an increasingly important role. Advances in our molecular understanding of normal heart development have led to the identification of numerous genes necessary for cardiac morphogenesis. This work has aided the discovery of an increasing number of monogenic causes of human cardiovascular malformations. More recently, studies have identified single nucleotide polymorphisms and submicroscopic copy number abnormalities as having a role in the pathogenesis of congenital heart disease. This review discusses these discoveries and summarizes our increasing understanding of the genetic basis of congenital heart disease.     

Indications for heart transplantation in congenital heart disease

In this review we have looked at indications for cardiac transplantation in congenital heart disease. An outline of the general principles of the use of transplant as a management strategy both as a first line treatment and following other surgical interventions is discussed. We explore the importance of the timing of patient referral and the evaluations undertaken, and how the results of these may vary between patients with congenital heart disease and patients with other causes of end-stage heart failure. The potential complications associated with patients with congenital heart disease need to be both anticipated and managed appropriately by an experienced team. Timing of transplantation in congenital heart disease is difficult to standardize as the group of patients is heterogeneous. We discuss the role and limitations of investigations such as BNP, 6 minute walk, metabolic exercise testing and self estimated physical functioning. We also discuss the suitability for listing. It is clear that congenital heart patients should not be considered to be at uniform high risk of death at transplant. Morbidity varies greatly in the congenital patient population with the failing Fontan circulation having a far higher risk than a failing Mustard circulation. However the underlying issue of imbalance between donor organ supply and demand needs to be addressed as transplant teams are finding themselves in the increasingly difficult situation of supporting growing numbers of patients with a diverse range of pathologies with declining numbers of donor organs.     

Prevalence of congenital heart disease

Background

Today most patients with congenital heart disease survive childhood to be cared for by adult cardiologists. The number of physicians that should be trained to manage these lesions is unknown because we do not know the number of patients.

Methods

To answer this question, the expected numbers of infants with each major type of congenital heart defect born in each 5-year period since 1940 were estimated from birth rates and incidence. The numbers expected to survive with or without treatment were estimated from data on natural history and the results of treatment. Finally, lesions were categorized as simple, moderate, or complex, based on the amount of expertise in management needed for optimal patient care.

Results

From 1940 to 2002, about 1 million patients with simple lesions, and half that number each with moderate and complex lesions, were born in the United States. If all were treated, there would be 750,000 survivors with simple lesions, 400,000 with moderate lesions, and 180,000 with complex lesions; in addition, there would be 3,000,000 subjects alive with bicuspid aortic valves. Without treatment, the survival in each group would be 400,000, 220,000, and 30,000, respectively. The actual numbers surviving will be between these 2 sets of estimates.

Conclusions

Survival of patients with congenital heart disease, treated or untreated, is expected to produce large numbers of adults with congenital disease, and it is likely that many more adult cardiologists will need to be trained to manage moderate and complex congenital lesions.     

Akt信号通路在紫绀型先天性心脏病患儿心肌慢性缺氧适应中的作用

目的:探讨Akt信号通路在紫绀型先天性心脏病患儿心肌慢性缺氧适应中的意义。方法:收集紫绀型和非紫绀型先天性心脏病患儿共50例,其中紫绀型26例(紫绀组),动脉血氧饱和度(SaO2)60%～89%;非紫绀型24例(非紫绀组),SaO2>95%,均不伴肺动脉高压[肺动脉收缩压<30mmHg(1mmHg=0.133kPa)]。心脏外科手术体外循环前留取右心耳组织,应用Western blot方法检测心肌组织蛋白激酶B(总Akt)和磷酸化蛋白激酶B(Ser473P-Akt)表达水平,免疫组织化学技术检测心肌组织总Akt和Ser473 P-Akt蛋白表达部位与水平。结果:与非紫绀组相比,紫绀组患儿心肌组织Ser473P-Akt蛋白表达水平明显增高(P<0.01),而2组患儿总Akt蛋白表达水平差异无统计学意义(P>0.05)。紫绀组患儿心肌组织Ser473P-Akt蛋白大部分表达在心肌细胞的胞质,胞核亦有微弱表达,而非紫绀组心肌细胞则无明显Ser473P-Akt蛋白表达。2组患儿总Akt蛋白绝大部分也表达在心肌细胞的胞质,胞核亦有微弱表达,但表达部位和水平差异无统计学意义。紫绀组患儿心肌组织Ser473 P-Akt蛋白表达水平与患儿术前SaO2呈负相关(r=-0.771,P<0.01)。结论:Akt信号通路激活可能是紫绀型先天性心脏病患儿心肌慢性缺氧适应的重要信号调控机制之一。