Ectopia Cordis

S. Bert Litwin, MD, pediatric thoracic surgeon

Ectopia cordis is a congenital anomaly characterized by complete or partial displacement of the heart out of the thoracic cavity. It first was reported in 1671 by Stensen and occurs in 5.5 to 7.9 per one million live births. It comprises 0.1 percent of congenital heart disease. In 1995, 220 reported cases were in the literature.

There are four types of this anomaly: cervical, thoracic, thoracicoabdominal and abdominal. The cervical form (which occurs in 3 percent of the cases) has been seen only in malformed fetuses. The thoracic type (shown below) is the most common and the most severe form. It occurs in 59 percent of ecopia cordis cases. Typically, there is a sternal defect, absence of the parietal pericardium, cephalic orientation of the cardiac apex that often beats against the infant's chin, diastasis recti and a small thoracic cavity. This is classically the "naked heart" variety with no natural covering over the cardiac mass.

The thoracicoabdominal type of ectopia cordis (which is seen 38 percent of the time) is characterized by partial absence, or cleft, of the lower sternum, deficiency of the anterior diaphragm, deficiency of the diaphragmatic pericardium, midline abdominal defect and congenital intracardiac abnormalities. These five characteristics comprise the pentalogy of cantrell. Many types of congenital heart disease have been reported with this form, including tetralogy of Fallot, VSD, ASD, tricuspid atresia, AV canal, single ventricle, pulmonary atresia, TGA and anomalous pulmonary veins. Rarely is this form of ectopia cordis without a diaphragmatic defect.

The abdominal type of ectopia cordis was first reported in 1806. All cases reported since have been thoracicoabdominal. For practical purposes, there are only two types of ectopia cordis which are of clinical significance - thoracic and thoracicoabdominal.

The etiology of ectopia cordis is unknown. The embryological development of this anomaly may be related to early fetal rupture of the ammion, teratogens or chromosomal aberrations. All forms of ectopia cordis appear to represent incomplete fusion of the converging lateral body wall in the mid line. The defect may be established as early as the third week of gestation when demarcation between intraembryonic and extraembryonic coelom is established, possibly relating to the rupture of the chorion or yolk sac.

Today, prenatal diagnosis of ectopia cordis is possible by fetal echocardiography. After birth it is important to examine the heart for intracardiac defects, which also can be accomplished with echocardiography. Previously, cardiac catheterization was suggested, however, today this should rarely be necessary.

Thoracicoabdominal ectopia cordis was first successfully treated with patient survival by Brock in 1950 and thoracic ectopia cordis by Koop in 1975. Treatment is aimed at early skin coverage of exposed organs, followed by staged repair of other anomalies. The heart, if possible, is moved to an intrathoracic position. This may not be possible due to kinking of the great vessels. If the thoracic cage is small, it may be enlarged by shifting the diaphragm attachments to the rib cage or by paralyzing the diaphragm so it will shift toward the abdomen. In the presence of an omphalocoele or diaphragm deficiency, these problems are best managed during the initial operation.

Congenital cardiac anomalies are treated by palliative or corrective surgery early or late in life. Sternal reconstruction usually is required later on. It utilizes one or more of a variety of techniques including use of native materials (rib or sternal transfer) and/or the insertion of prosthetic devices.

Of these two forms of ectopia cordis, the thoracic type has a higher mortality rate, but both forms include significant risk. In most cases, death is due to infection at the time of initial treatment. However, this anomaly is compatible with long-term survival, and attempts should be made to save these infants' lives.

Editor's note: Dr. Litwin has treated five ectopia babies, one of whom survived, which puts him among a small group of surgeons experienced in treating this rare defect.

Bloodless Open Heart Surgery for Simple Cardiac Anomalies

Chris Brabant, CCP

Hemodilution routinely is used in operations with cardiopulomonary bypass in older children and adults. One of its many benefits includes no need for blood transfusions during the operation.

However, for infants and children, repair of both simple and complex cardiac anomalies without the utilization of blood products has been more difficult, especially for children weighing 20 kilograms or less. The volume of crystalloid used to prime the cardiopulmonary bypass circuit may result in excessive hemodilution. Not only can this bring about a reduction in oxygencarrying capacity, but dilution of the patient's clotting factors may lead to serious coagulopathic consequences.

A cardiac patient's family often has many questions and concerns about their child's procedure. One of the most frequently asked questions relates to the potential use of blood. Issues of blood safety concerning hepatitis or retrovirus (HIV) transmission have dominated mainstream media attention. Although the consequence of infection caused by blood or blood components cannot be underestimated, the media may have helped create a disproportionate fear of blood product administration. The movement to restrict or eliminate the utilization of homologous blood has gained a tremendous amount of momentum.

Recently, the question was raised about the minimum weight for a child to undergo a simple cardiac anomaly repair without the administration of blood. "Simple cardiac anomaly" is defined as a condition requiring less than one hour of cardiopulmonary bypass time. To help answer this question, Children's Hospital staff did a retrospective review of all children weighing 10 kilograms or more who had a secundum atrial septal defect repair in the last two years. Seventy-six percent of the patients received at least one blood transfusion. The smallest child to leave the hospital without receiving blood was 18 kilograms.

Most of the responsibility for the frequent use of blood can be traced to the cardiopulmonary bypass circuit. The bypass circuit can be simply defined as an artificial extension of the patient's circulatory system. In order to make this circuit part of the patient's circulatory system, the bypass components must be primed with a crystalloid solution such as plasmalyte or normosol. The joining of the patient's circulatory system and the bypass machine results in a profound hemodilution of the patient's total circulating blood volume. For example, if a patient has a circulating blood volume of 1,000 milliliters with a hemotocrit of 35 percent, and the bypass circuit prime is 1,000 milliliters, the patient's hematocrit is reduced to 17.5 percent.

A relative amount of hemodilution is desirable during cardiopulmonary bypass because the resulting decreased blood viscosity may allow for better blood flow to the patient's microcirculation. However, if the degree of hemodilution is too great, the decreased oxygen capacity of the diluted blood can be problematic, both on cardiopulmonary bypass and after surgery. To avoid these potential problems, the use of blood products, usually in the form of whole blood, is required.

The most direct way to reduce the incidence of blood transfusions caused by the cardiopulmonary bypass circuit is to make the bypass circuit smaller. Making it smaller means less crystalloid prime solution is used. Consequently, the patient is less hemodiluted. Reducing the size of the bypass circuit allows us to operate on smaller patients without using blood or blood components.

Many steps are implemented intraoperatively in order to limit or prevent blood transfusions. A meticulous surgical technique emphasizes hemostasis. Suction devices return lost blood from the operative field back to the patient, minimizing blood loss from the surgical site. Immediately following cardioulmonary bypass, modified ultrafiltration removes plasma water from the patient, resulting in red blood cell concentration. Finally, after modified ultrafiltration, the remaining contents of the bypass circuit are taken, a large percentage of the crystalloid solution is removed, and the high hematocrit blood is returned to the patient.

All of our simple cardiac anomaly patients have done well after their heart operations, without evidence of immediate transfusion-related consequences. Despite the widespread interest in reducing or eliminating blood use in cardiac procedures, the requirement for homologous blood remains.

Children's Hospital staff are working to implement a coordinated, multidisciplinary approach to safely restrict the administration of blood and blood components.

Thoratec VAD system

Heather Nelson, RN, CV nurse clinician

Bridging patients to a heart transplant has been a challenging concept, especially with pediatric patients. Recently, Children's Hospital purchased a device that enables the cardiovasular and cardiology teams to provide short-term and potentially long-term support to patients awaiting a heart transplant.

The Thoratec Ventricular Assist Device System includes a ventricular assist device designed to support the circulation of blood in the pulmonary and/or systemic circulation when the natural heart, with the help of standard drug therapy, is unable to maintain normal blood flows and pressures in those vascular beds.

The Thoratec offers many important clinical advantages. Currently, it is the only circulatory assist device approved by the FDA to support a patient both before transplant and as a postcardiotomy/bridge to recovery. This is a significant advance in the options of care for the few patients who experience postcardiotomy failure. Its availability allows these patients to avoid the added complications related to premature device removal and gives them time to recover not only ventricular function, but also other vital end-organ function. One of its greatest assets is its ability to be used in small patients. Patients supported by the device have been as young as 7 years old, weighing 17 kg. The Thoratec system is paracorporeal. Thus, the pump resides outside the body, eliminating the need for abdominal surgery and, as stated above, allows implantation in a much smaller BSA patient population. Also, the paracorporeal system is more easily removed at the time of transplant or postcardiotomy recovery.

Adverse events and complications with Thoratec VAD support are similar to or significantly fewer than with other support devices. Adverse events include cardiovascular, hepatic or renal dysfunction, bleeding due to surgical reasons, coagulapathy, infection and thromboembolism. Patients on the Thoratec VAD are maintained on an anticoagulation protocol.

The ability and option to use the Thoratec VAD here at Children's Hospital offers an exciting new prospect in the treatment of heart failure and bridge to transplant for our pediatric population.

Interventional Electrophysiology

Alexis Sullivan, RN, PICU

Radio frequency (RF) catheter ablation for cardiac arrhythmias in children was presented at the 5th annual Update on Pediatric Cardiology by Ed Walsh, MD, director of Electrophysiology Services at Boston Children's Hospital.

RF as treatment for accessory pathways (APs) - is the most common cause of paroxysmal SVT in young children. The potential for spontaneous resolution of AP-mediated tachycardias after the first few years of age often encourages medical therapy during the first year of life. Symptoms usually are nonspecific. Patients may have cyanosis or SOB.

Incessant tachycardias with secondary cardiomyopathy
EAT - ectopic atrial tachycardia - is caused by a single focus of automaticity outside the sinus node. Its focus can be in LA or RA, not usually near pulmonary veins or appendages. EAT is very difficult to treat with drug therapy, and surgical excision is not consistently effective.

A small number of patients may have spontaneous cure, but RF ablation is preferred when there is ventricular dysfunction. Mapping is done by identifying the site of the earliest atrial electrical activity (usually precedes the onset of the surface p-wave by 20 to 70 milliseconds). Success usually is rapid (within three seconds of RF application) and permanent, with acute success rates greater than 90 percent and low recurrence, with ventricular function recovering within six months.

PJRT - permanent junctional reciprocating tachycardia - is caused by a slowly conducting accessory pathway which usually is located in the posterior septal atrioventricular groove. PJRT responds poorly to medical management but has a high success rate for treatment with RF ablation and return of ventricular function. The mapping process is similar to that of EAT.

Preop and postop arrhythmias in CHD
There is a strong association between right-sided accessory pathways and Ebstien's malformation or corrected TGA. If possible, attempts are made to eliminate the accessory pathway preop or at the time of surgery. A change in the position of normal conduction systems is associated with many forms of CHD. Normal AV node and HIS bundle need to be properly identified to avoid causing complete heart block. There is a growing number of older patients S/P CHD repairs who now have late postop arrhythmias. For example, A-flutter after Mustard or Senning for TGA, or post Fontan for single ventricle physiology can involve highly variable circuits with reentry around atriotomy scars, anastamosis suture lines and ASD patches. There is limited experience, but there has been some success with fast postop V-tach S/P repairs with ventriculotomy or VSD patch (i.e. TOF repair).

Technical issues
1) Sedation - Many centers use general anesthesia and mechanical ventilation in patients younger than 12 years of isoflurane age. Isoflurahe and propofol have shown minimal electrophysiologic effects. Conscious sedation is preferable at times, with an autonomic atrial or ventricular focus, as these are difficult to induce under deep anesthesia.

2) Vascular access/catheter choice - The number and size depends on patient size and the arrhythmia targeted. Multipolar catheters can combine recording and pacing abilities. Esophageal electrodes are used for atrial stimulation and recording. Many studies can be done with one to three catheters. Left heart mapping/ablation in younger patients usually is done transseptally through a PFO instead of a retrograd arterial approach. A 7 French catheter is used for adults and older children, and a 5 French cather is used for infants.

Cylexin Trial Terminated

Kathy Mussatto, RN, clinical research nurse

The clinical trial to evaluate the safety and efficacy of Cylexin (PET-205) was terminated March 30. The study was undertaken at 11 major cardiac centers across the United States and Canada. At completion, 230 infants had been enrolled in the trials. Here at Children's Hospital of Wisconsin, 19 infants received primary treatment, and three were re-treated with subsequent operations.

Cylexin was developed with the goal of preventing or reducing reperfusion injury following cardiopulmonary bypass by blocking neutrophil adhesion to the vascular endothelium. Analysis of the predetermined efficacy endpoints failed to demonstrate a significant benefit from Cylexin as compared to placebo. No areas of safety concern were identified by the Data Safety Monitoring Board, either. Given these findings the study sponsor elected not to pursue further development of the drug.

As a follow-up, all parents of participating children will be informed whether their child was treated with the study drug or placebo. Families also may choose to have their child receive a developmental assessment at 1 year of age, as had been originally planned in the study proposal.

We would like to thank each of you for your participation in and support of this interesting, multicenter research.