Use of MRI in the Evaluation of Congenital Heart Disease

John R. Sty, MD, chief of Radiology, Children's Hospital of Wisconsin

Adult and pediatric cardiologists pioneered the techniques of cardiac catheterization, and over the last three decades augmented an invasive collection of physiologic data with angiocardiography to produce complete examinations of cardiac anatomy and physiology that are the present standard for all other types of diagnostic examination.

During the last decade, pediatric cardiologists and advanced sonographic equipment have led to sophisticated studies of the heart that noninvasively contribute enormously to the management of patients with severe complex, congenital heart anomalies. However, few pediatric or adult cardiologists have been exposed to the physics of magnetic resonance (MR) or thoroughly instructed in the technical operation of magnetic resonance imaging equipment. At the same time, although radiologists understand the technical aspects of MR, few have a background in or understand complex congenital heart disease.

The history of magnetic resonance imaging in the diagnosis of congenital heart disease has seen two distinct developmental periods - the initial period between 1985 and 1995, and since 1995. During the first era, two techniques were developed: gated spin-echo imaging (SE) and cine imaging. Both have been useful for delineating the anatomy of the heart and great vessels in patients with congenital heart disease. Although cine techniques offer only nonquantifiable information about the characteristics of blood flow, such as turbulence in the regions of valvar stenosis and regurgitation.

Initial scientific articles confirm that, using these sequences, MR produced information equivalent to existing echocardiography and angiography modalities in patients with limited abnormalities. These include particularly small, central pulmonary arteries in tetralogy of Fallot, aortic coarctation, systemic and pulmonary venoarterial connections in heterotaxy syndromes, postoperative cardiac baffles and conduits, pericardial and cardiac tumors, and anomalies of pulmonary venous connection. Because MR in this early period of development provided minimal physiologic information and was inferior to other imaging modalities for visualization of septal defects, semilunar and artrioventricular valves, cardiac MR imaging served an ancillary role.

Since 1995, cardiac MR imaging underwent an accelerated expansion of diagnostic sequences and capabilities. A technique called SPAMM (spatial modulation of magnetization) was developed as a new, sophisticated method for determining global and regional ventricular myocardial contractility.

The next development in MR imaging was the production of three-dimensional good-quality images that enabled accurate volume measurement of the total heart and its individual chambers. Scientific papers validated the volumetric data and described different methods of examining the whole heart, the separate ventricles and biventricular interaction pre- and postoperatively. These newer procedures allowed accurate quantification of blood flow in major vessels, the determination of shunt volumes, the derivation of gradients across stenotic vessels and valves, the distribution of pulmonary blood flow after various operative procedures, and other physiologic measurements previously obtainable only by invasive cardiac catheterization techniques.

Since 1998, cardiac MR has become competitive with cardiac catheterization and angiocardiography as a technique for documenting anatomic and physiologic parameters in patients with significant heart disease.

The burning question today is whether the advances in cardiac MR are significant enough to allow MR a greater role in clinical management of congenital heart disease. Echocardiography possesses strong capabilities. In many areas it is superior to MR imaging and has the enormous advantage of being relatively inexpensive and mobile. The studies also are performed by cardiologists who have the knowledge and experience with complex congenital heart disease.

Many physicians who manage congenital heart disease have argued that cardiac MR is complementary to echocardiography in the diagnosis of congenital heart disease. For demonstrating the anatomy of congenital heart disease, echocardiography is less expensive and easier to perform than cardiac MR. But, with the exceptions of evaluating semilunar and atrioventricular valve function and displaying small atrial and ventricular septal defect, MR imaging is superior to echocardiography in displaying cardiac abnormalities. The mobility of ultrasound equipment will remain the major advantage for examinations at the bedside and in the intensive care units. Similarly, transesophageal echocardiography pre- and postoperatively has become irreplaceable in the surgical repair of major congenital heart defects.

Not only is MR particularly good at demonstrating anomalies of the great arteries, it also shows the relationship of these vessels to the trachea and bronchi, which is an advantage when airway symptoms complicate pre- and postoperative congenital heart disease. MR also is superior in displaying the variable systemic and pulmonary venous anatomy in heterotaxy syndromes, the anatomy of total anomalous pulmonary venous drainage, the mediastinal pulmonary arteries to the hilar level, and surgically placed intra-and extracardiac conduits.

Cardiac MR imaging, because it displays the heart in two and three dimensions, is well suited for volumetric and functional data at all ages. Scientific articles in the last three years validate the volumetric measurement of the right ventricle and left ventricle. They also introduce unique concepts for evaluating congenital heart disease, such as total heart volume and ventricular-ventricular interaction.

MR techniques have been developed and validated for quantifying shunt volumes, measuring blood flows, determining ejection factions, and calculating regurgitant fractions. Although Doppler echo can provide this data, it is not as extensive and possibly not as accurate as MR-derived information. Both MR and sonography cannot accurately define intraluminal pressures and in critical instances, such as determining pulmonary vascular resistance before performance of a Fontan procedure; cardiac catheterization is mandatory.

A consensus is developing that MR and ultrasound together can evaluate children for general follow-up so well that cardiac catheterization only will be necessary when a significant abnormality needs to confirmed or treated.

Information suggests cardiac catheterization as the cornerstone of diagnosis in congenital heart disease is shifting toward a combination of echocardiography and cardiac MRI. However, complex congenital heart diseases in infants still requires catheterization to sort out complicated anatomy and physiology. Also, infants and children still will need cardiac catheterization to measure pulmonary pressure and resistance accurately in those being considered for the Fontan procedure.

For a large number of children and adults requiring preoperative evaluation of relatively uncomplicated cardiac anomalies, reliance on sonography and MRI will become the modalities of choice. Similarly, for postoperative evaluation and long-term follow-up, the combined noninvasive modalities of sonography and MRI will be clinically effective and economically feasible. Only when special questions need to be resolved, or interventional techniques need to be employed, will cardiac catheterization be used.

Ross Procedure for Infants and Children with Aortic Valve Disease

Deborah Soetenga, MS, RN, clinical nurse specialist, Pediatric Intensive Care Unit, Children's Hospital of Wisconsin

The Ross, or pulmonary autograft procedure, first was described and pioneered by Donald Ross in 1967. During the procedure, the diseased aortic valve is replaced with the patient's own pulmonary valve (autograft) and a homograft valve is implanted in the pulmonary position.

Widespread application of this procedure in the U.S. did not begin until the late 1980s. The operation takes longer and is more complex than the standard aortic valve replacement surgeries and it commits the patient and the surgeon to a double valve surgery. Early morbidity and mortality during the learning curve were substantial. However, with improved surgical techniques, better myocardial protection during cardiopulmonary bypass and the availability of commercially prepared homografts, there has been a growing interest and wider use of the Ross procedure.

Historically, replacement of the aortic valve in infants and children has been associated with a number of serious problems related to prosthetic devices currently available, including mechanical grafts, heterograft and allografts. The significant drawbacks of these devices for infants and children include size mismatch, availability, durability, growth limitations and thromboembolic complications which can result in major postoperative morbidity. In addition, there is the need for early and frequent follow-up surgeries due to outgrowth of the replacement valve.

The Ross procedure now has emerged as the operation of choice in children who require aortic valve replacement because it overcomes nearly all of these complications. The pulmonary autograft is virtually always available and provides an autologous, viable tissue valve in the aortic position that maintains growth potential. It also is free of most valve-related complications, including thromboembolic events, and prevents the need for long-term anticoagulation. Although the cryopreserved allograft used to replace the pulmonary valve usually does not provide the same degree of durability as the autograft valve and may require another operation, this limitation is far less serious than repeated aortic valve replacements. The durability of the autograft valve in the aortic position has been documented in the adult population, but unfortunately long-term studies are not yet available for infants and younger children, despite increasing use in this patient population.

Technique
The current preferred technique for the Ross procedure is to insert the valve as an entire root replacement, which requires appropriate size-matching to avoid distortion and postoperative regurgitation. This has been referred to as the modified Ross procedure. In addition to the Ross procedure, when the aortic annulus is smaller than the pulmonary annulus, division of the annulus and the septum to enlarge the outflow tract has been shown to be effective. In some children who have had balloon dilatations of their aortic valves, the aortic annulus may be larger than their pulmonary valve. A number of hospitals have addressed this problem by reducing the size of the aortic annulus to slightly smaller than the pulmonary valve. This has reduced the risk of autograft dilatation and leaflet prolapse. This technique has been reported to result in excellent postoperative valve function.

The main uncertainty regarding the use of pulmonary root autografts in the aortic position is the potential for dilatation of the pulmonary artery and the development of progressive valvular regurgitation as a result of continued exposure to systemic pressure. There also is debate whether the potential for autograft root growth is consistent with somatic growth.

A number of studies regarding the modified Ross procedure in children and young adults at different centers (University of Michigan, Royal Liverpool Children's Hospital, Liverpool UK, Children's Hospital of Philadelphia, University of Oklahoma, Sahlgrenska University Hospital, Goteborg Sweden) consistently reported that aortic dilatation was rarely a problem in children. Three institutions said that when the modified Ross procedure was performed in infants and very young children, the autograft had adapted to the systemic circulation. This was demonstrated by serial echocardiograms revealing no excessive root dilatation and appropriate Z scores for age and size. The Sweden paper stated that in the first year after the modified Ross procedure there was an increase in the size of the neo-aortic root area of infants thought to be dilatation. After the first year, the rate of dilatation of the aortic root leveled off to that of somatic growth. The centers also reported that the autograft was functioning well, as demonstrated by the majority of patients having no or mild aortic regurgitation on follow-up serial echocardiograms.

Limitations of these studies include their small numbers and the length of follow-up. Future research is needed to document the long-term function and size of the autograft as well as to monitor fuctionality and freedom from morbidity in these patients. However, early evidence points to the modified Ross procedure as the operation of choice for children with aortic stenosis and/or complex left ventriclar outflow obstruction.

Benefits include improved postoperative hemodynamics compared to the traditional valve replacement patients, and lower long-term cost for Ross patients - especially when long-term anticoagulation regulation (mechanical valve recipients) and decreased rate of re-operation is considered.

Parenting Young Children with Congenital Heart Disease

Lynn Carey, MS, RN, PhD, director, Educational Services, Children's Hospital of Wisconsin

Child-rearing practices are influenced by many determinants. A child's health status is an example of a factor that may influence the parenting experience and practices.

With the advances in health care and medical technology, many children with a chronic illness have an increased life expectancy. In fact, more than 90 percent of children with chronic illness will survive to young adulthood. Because of improvements in surgical, technical and perioperative care, most children with congenital heart disease have the potential to live to adulthood. These children and their families need ongoing support, not only medically and therapeutically, but also developmentally, socially and psychologically.

Parents of children with congenital heart disease may be confronted with the reality of having a child who is different from their expectations or experiences. This can alter a parent's expectation of him or herself as a parent, adjust their expectations of their child's behavior and transform social interactions within and outside of the family.

Parenting can be challenging and difficult, even in the best of situations, for many parents. Coupled with childhood chronic illness, one must speculate as to the additional challenges facing parents. The processes that parents use to establish behavioral expectations, nurture, and discipline their child with chronic illness is an area that deserves more attention. This is an important focus for increased research because of the limited understanding of how parents support their children with a chronic condition through important developmental tasks and how parental decision-making is influenced by their child's illness.

I studied the effect of congenital heart disease on maternal parenting and child-rearing practices. The method I used included a comparative study of parenting practices, stress, perceptions of child behavior, and mother/child interactions of mothers of young children with congenital heart disease and mothers of healthy young children.

Parental perceptions of discipline, nurturing and developmental expectations, stress, and perceptions of their child's behavior were assessed using standardized self-report tools as well as videotaped observations of mother/child interactions. A family information form captured demographic information and maternal perceptions of parenting. The tools used in this study included the Parent Behavior Checklist, Parenting Stress Index-Short Form, Behavior Screening Questionnaire, and the Eyberg Child Behavior Inventory. The videotaped maternal-child interactions were coded using the Dyadic Parent-Child Interaction Coding System to assess specific behaviors and qualities of the interactions.

Subjects / data
A sample of 60 mothers was divided into two groups. The first group included 30 mothers of children with congenital heart disease. The second included 30 mothers of healthy children. The groups were matched for child age and gender and maternal marital status. All of the children with congenital heart disease had moderate to severe congenital heart disease such as aortic stenosis, tetralogy of Fallot and hypoplastic left heart syndrome. All of the children were diagnosed within the first nine months of their lives with the majority diagnosed within the first month of life.

Data was collected between April and August 1999. A home visit was arranged at the mother's convenience. The procedure used during the home visit included completion of a demographic questionnaire, maternal response to the question "How is parenting (child's name) different from what you expected," a 15- minute videotaped play session, and completion of the four parenting assessment tools.

A series of data analyses indicated no significant difference between the two groups on discipline, nurturing, developmental expectations, stress, perceptions of child behavior or maternal-child interactions. This study suggests that having a child with moderate to severe congenital heart disease does not alter parenting outcomes. However, there were qualitative differences in the maternal responses to the interview question "How is parenting (child's name) different from what you expected?" Mothers of children with congenital heart disease reported increased vigilance, uncertainty and fear. They discussed the unexpected, such as receiving the diagnosis, surgeries, and hospitalizations.

Implications
Several implications can be identified for practice, including the promotion of positive child rearing practices as parents provide care and monitor their child for symptoms. This study supports that families, overall, can do well in parenting a child with a chronic illness. This information alone can be helpful and encouraging to families. It becomes more beneficial to include specific strategies that the families can use to facilitate the parenting process.

The factor of social support appears to be an important element. The need for a comprehensive psychosocial assessment, including social supports, strengths and resources is indicated. Clinicians can help parents develop formal and informal social support networks and should look beyond the obvious, such as family and friends and support groups, to the use of technology such as online support and information.

Parents commonly are advised to construct their lives, interact and treat their child as normally as possible. It is important to consider that little is known about the actual plausibility or consequences of normalization. Normalization is a complex process, and clinicians need a sound understanding of the attributes and manifestations of normalization to effectively manage family life while parenting a child with a chronic illness.

The collection of qualitative data was valuable and provided rich information regarding the parenting experience. Providing time for families to tell their stories is critical to understanding the lived experience of parenting a child with congenital heart disease.

Summary
The purpose of this study was to better understand how parenting and child-rearing practices are influenced by a child's chronic illness. The complexities of parenting a young child with a chronic illness should not be minimized or dismissed. While the quantitative measures of this study suggest that parenting a young child with congenital heart disease is not significantly different from parenting a healthy child, the qualitative data describes a very different experience. Increased maternal and family stress, the necessity for vigilance in caring for their child and the focus on normalization were reported by mothers of children with congenital heart disease. The subjective experience of parenting calls for adaptation and adjustments by the mother. The importance of a strong social support network was identified in this study. One must consider that there may be a significant cost to mothers and families as they work to normalize their lives. Further research of both parenting outcomes and the subjective experience will provide for a deeper understanding of this compelling life experience.

Saving Hearts in Trinidad

James Tweddell, MD, pediatric cardiovascular surgeon, Children's Hospital of Wisconsin; associate professor, Surgery and Pediatrics, Medical College of Wisconsin

Through support by Caribbean Heart Care Ltd., the Community Chest of Trinidad and Tobago and the Northwest Regional Health Authority, major heart centers in the US travel to Trinidad to do heart surgery on children who otherwise do not have access to this specialized service.

As one of the largest pediatric heart centers in the US, Children's Hospital of Wisconsin has been represented twice. Staff from the hospital made up the majority of the participants in the most recent trip in May. They included me, an anesthesiologist, a pediatric critical care specialist, a perfusionist, a surgical technician, an operating room nurse clinician, a pediatric intensive care unit (PICU) clinical nurse specialist and three PICU nurses. In addition, a congenital heart surgeon and nurse from St. Louis Children's Hospital, and a nurse from Boston Children's Hospital, made the trip.

We had several goals for the trip. First and foremost was to achieve a good outcome for our patients. Another was to provide education and training for the personnel at Mount Hope Hospital in Trinidad.

Patient's cardiac diagnoses included atrial septal defects (3), ventricular septal defects (4), severe aortic insufficiency with VSD (1), tetralogy of Fallot (1) and severe pulmonary stenosis (1). They ranged in age from 8 months to 13 years and in weight from 5 kg to 24 kg.

We arrived on a Sunday evening and began operating Monday morning. The surgeon from St. Louis and I alternated performing surgery, assisted by a local cardiac surgeon seeking training in pediatrics.

During the four days, we performed 10 open heart cases. Despite a severe shortage of blood we were able to proceed safely with the cases. During the week, we only used two units of blood. In order to simplify postoperative care, we kept the use intracardiac lines and pacemaker wires to a minimum. All patients were extubated in the operating room, although the patient with tetrology of Fallot required reintubation one day postop.

Although the patients would have undergone operations at an earlier age in the US, they all did well and were discharged from the hospital within one week of our departure. The good outcomes were due to the dedication of the entire team who worked well together. It is important to mention and thank Children's Hospital of Wisconsin administration who rearranged schedules to make it possible for us to take this trip and the many staff members who stayed behind and covered shifts in our absence.

The week went by too quickly and sadly, we did not get to see much of the country, but we all were rewarded by the happy faces of the families we helped. Through our efforts they will live healthier, longer lives.

The Role of the Internet in Family Education

Mary Grosel, RN, Pediatric Intensive Care Unit, Children's Hospital of Wisconsin

In an effort to provide the best care and make information available to patients and families, the Internet can play an important role.

Topics relating to the Internet were presented at the Cardiology Y2K conference in Orlando in February. Following are some of the Web sites they suggest:

www.tchin.org
www.bcm.tmc.edu/pedi/cardio/chd_terms.html
www.naspe.org

It should be noted that information on the Internet should never substitute for professional advice. Although medical personnel are encouraged to offer the Web sites listed here as sources of information and support, the best source for medical information always should be a qualified professional with knowledge of the specific child and problem.

Comments made during a chat session held on the Congenital Heart Disease Information and Resources Web site seem to suggest families are looking for personal stories, photographs, interactive opportunities (such as chat rooms), as well as medical information. Families said they would like to see more physician participation online. They also would like to see statistics, long-term outcomes data for children with particular defects, and current research.

The issues of reliability and bias also were addressed. Most parents recognize these issues, but said they sought out their child's cardiologist or another professional to make sure they really understood the information.

Parents said participating in online support groups has made them less anxious about their child's diagnosis and treatment. Many were reassured by reading about other children who survived the same defect their child has. It made them feel they are not alone.

Overall, these families said they have a positive view of the Internet. They hope for even more information and a blending of patients, parents and professionals that will lead to best care for their children.