New surgeon joins Herma Heart Center

James Tweddell, MD, medical director, Cardiothoracic Surgery, Herma Heart Center, Children's Hospital of Wisconsin; professor, Surgery, chief, Cardiothoracic Surgery, Medical College of Wisconsin.

Michael E. Mitchell, MD, joined our team at the Herma Heart Center at Children's Hospital of Wisconsin and the Division of Cardiothoracic Surgery at the Medical College of Wisconsin March 1, 2006. Mitchell received his medical degree from Harvard University. He completed residencies in surgery and cardiothoracic surgery at Brigham & Women's Hospital, Boston, and completed a pediatric cardiothoracic surgery fellowship at Children's Hospital of Philadelphia under the direction of Tom Spray, MD.

Mitchell's wife, Aoy Tomita-Mitchell, PhD, also is joining our team and will arrive in Milwaukee this summer. The Mitchells come to us from Louisville, where they were on the faculty of the University of Louisville and Mitchell was an attending at the Kosair Children's Hospital.

Mitchell is trained and experienced in all aspects of congenital heart surgery including transplantation and circulatory assist devices.
Tomita-Mitchell earned her doctorate from the Massachusetts Institute of Technology.

The Mitchells have a combined research interest in the genetics of congenital heart disease.

I am very excited about the ability of the Mitchells to work with DNA samples collected through the Wisconsin Pediatric Cardiac Registry. The registry was initiated by Andrew Pelech, MD, [pediatric cardiologist at Children's Hospital and an associate professor of Pediatrics (Cardiology) at the Medical College]. It is an ambitious forward thinking project that will undoubtedly reap enormous benefits as it matures in the coming years. Unlocking the genetic basis of congenital heart disease may greatly enhance treatment.

Pulmonary artery stenosis

Luke Lamers, MD, pediatric cardiologist, Herma Heart Center, Children's Hospital of Wisconsin; assistant professor, Pediatrics (Cardiology), Medical College of Wisconsin.

Stenosis of the pulmonary arteries is a condition experienced with increasing frequency due to advancements in cardiac care for infants and children with congenital heart disease. Surgical results are excellent for relieving obstruction of the pulmonary valve and main pulmonary artery; however, branch pulmonary artery stenosis often is not easily amendable to surgical repair. As a result, the standard of care has transitioned to interventional catheterization procedures. Balloon angioplasty for pulmonary artery stenosis has not been uniformly successful with several reports suggesting success rates in the range of only 50 percent, likely related to the intrinsic recoil properties of the pulmonary arteries. In 1989, the first published report documented the use of stents to treat congenital pulmonary artery stenosis. Since then stenting of pulmonary arteries has become an effective and safe intervention used to treat both congenital and acquired pulmonary artery stenosis. Intravascular stents are an ideal adjunct for treating stenotic lesions not responsive to conventional balloon dilation. Such lesions include compliant obstructions, stenosis due to kinking or external compression, and restenosis seen following successful balloon dilation. The objective of intravascular stenting is to provide a framework that supports the balloon dilated vessel wall and prevents vessel recoil and restenosis.

Current stents utilized for treatment of pulmonary artery lesions are constructed out of stainless-steel tubes with varying configurations that determine the stent size and radial strength properties. Desirable features include biocompatibility, that is, the stent must be relatively resistant to thrombsis and must promote minimal endothelial proliferation after placement. It must be immune to fatigue, corrosion and fracture. For use in pediatric patients, the stents must have a small delivery system in order to minimize vascular trauma. Most importantly in children, the stents must have features of further expandability over time as the child grows to adult size. Often times the pulmonary arteries of infants and children younger than 3 or 4 years of age are not large enough to accept placement of the adult stents. These children may require surgery or sequential balloon dilation of the areas of narrowing until they reach an age and size capable of accepting medium to large stents.       

Figure 1 - Angiography of the right pulmonary artery of a patient with transposition of the great arteries S/P arterial switch. The proximal right pulmonary artery (RPA) is narrowed to 4 mm with a good sized RPA at the hilum.

The technique utilized in our lab consists of the following: under general anesthesia a complete diagnostic catheterization assessing oxygen saturations and pressures within the right heart and the pulmonary arteries is performed, followed by selective pulmonary angiography. The dimensions of the stenotic area along with the adjacent vessel size and its relation to branching vessels are carefully evaluated (Figure 1). Further definition of the size and length of the stenotic area may be obtained using a compliant sizing balloon inflated within the area of greatest narrowing (Figure 2). A stent then is selected based on the length of the area of narrowing and desired dilated diameter of the vessel after stent implantation. The selected stent then is manually mounted onto a dilation balloon that is delivered through a long catheter sheath that has been advanced across the area of narrowing over a stiff guide wire (Figure 3).

Figure 2 - Sizing balloon inflated across the short segment of proximal RPA stenosis.

Once properly positioned, based upon sequential angiography, the stent is balloon dilated within the area of narrowing (Figure 4). The balloon then is removed and repeat pressure measurements and angiography are performed. After initial placement, further stent enlargement can be achieved with larger balloons to eliminate any residual narrowing. Within days to weeks of implantation, a thrombotic layer covering the stent struts is progressively replaced by fibromuscular tissue with eventual endothelialization and incorporation of the stent into the pulmonary artery wall. The stents can be safely redilated at later catheterizations to increase the pulmonary artery diameter as the child grows. The efficacy of the balloon/stent dilation is assessed with the following measures: increased pulsatility and mean pressure distal to the stent as well as increased vessel angiographic diameter, significant fall in right ventricular pressure and improved flow distribution by nuclear perfusion scan done after intervention. Patients typically are observed overnight in the hospital after the procedure and the risk of significant complications is generally low. 

Figure 3 - Stent and balloon positioned across RPA stenosis prior to deployment.

In 2005, the cardiac catheterization lab at Children's Hospital of Wisconsin performed six primary stent placements and four stent redilation procedures in patients with two-ventricle physiology. From 2000 to 2005, 16 patients with cavo-pulmonary connections underwent branch pulmonary artery stenting. Under both circumstances we observed significant improvements in pulmonary artery anatomy with limited complications. Research is ongoing to further advance stent technology for pediatric patients with congenital heart disease. Anticipated areas of advancement include stents premounted upon delivery balloons allowing for easier and more precise placement, covered stents that can be used to exclude aneurismal areas, and valved stents placed within the right ventricular outflow tract to treat both pulmonary stenosis and insufficiency.

Figure 4 - Stent in RPA post deployment. Area of stenosis persists, however RPA diameter improved to 12 mm.

Aortopulmonary window

L. Eliot May, PA-C, physician assistant, Herma Heart Center, Children's Hospital of Wisconsin.

Aortopulmonary window  (also referred to as AP window, aortopulmonary septal defect or APSD) is an uncommon congenital heart defect. AP windows occur at a frequency of about 0.1-0.3 percent of all congenital heart defects in children (contrast this to hypoplastic left heart syndrome which occurs in about 7 percent or ventricular septal defects which occurs in about 25 percent of children with congenital heart disease). The defect is characterized by a deficiency in the wall that separates the ascending aorta from the pulmonary artery. AP window occurs as an isolated lesion in about half of cases, and in conjunction with other defects in half.
Developmentally, AP windows occur when there is incomplete separation of the common tube of the truncus arteriosus into the ascending aorta and the pulmonary artery. Commonly associated lesions include: patent ductus arteriosus, interrupted aortic arch or severe coarctation of the aorta, tetralogy of Fallot and anomalous origin of a coronary artery.

Prenatally, the fetus is largely unaffected by the presence of the AP window. Following birth, as the pulmonary artery vascular resistance drops, significant left-to-right shunting occurs resulting in the typical signs of congestive heart failure. Symptoms typically occur between the second and eighth weeks of life. Physical exam findings are those of a patient with a large patent ductus arteriosus. Tachypnea, tachycardia and increased work of breathing prevail. Pulse pressure is wide due to the continuous run-off into the pulmonary circulation through the AP window during diastole. The precordium is hyperdynamic from the increased volume load on the left ventricle. Auscultation reveals a loud single second heart sound with a continuous murmur at the left upper sternal border into the back. Often a gallop rhythm and an apical diastolic rumble are audible. Hepatomegaly and failure to thrive are common findings. In some patients, however, pulmonary artery vascular resistance fails to fall. This results in few signs and symptoms of congestive heart failure. Instead, pulmonary vascular obstructive disease (PVOD) and cyanosis can develop at an early age.

Repair of AP window is carried out soon after the diagnosis is made. Repair involves median sternotomy and usually requires cardiopulmonary bypass. Rarely, the defect can be separated without the use of bypass, but most commonly, bypass is utilized to more precisely divide the aorticopulmonary connection. In this case, a patch made of Dacron or bovine pericardium is used to separate the AP window.

Usual post-bypass invasive and non-invasive monitors are utilized, including arterial line, left atrial line, central venous line and often a pulmonary artery catheter. Pulse oximetry and near-infrared regional oximeter (NIRs) probes are used. Delayed sternal closure is employed in some cases.

Postoperative recovery often is uneventful, but can be more complex in patients who present with elevated pulmonary vascular resistance, have concomitant defects, or in patients who present with severe congestive heart failure. In the more favorable instances, hospital stay averages one to three weeks. Long-term prognosis for patients with an isolated AP window is excellent if surgical correction is performed early in life and late complications are unlikely if the AP window is adequately repaired.

Feeding challenges for infants with congenital heart disease

Katherine Frontier, MS, CCC-SLP, speech-language pathologist, Masters Family Speech and Hearing Center, Children's Hospital of Wisconsin.

Infants with congenital heart disease (CHD) often have several hurtles to overcome following cardiac surgery.  Even with improved cardiac function, one of the most natural, but challenging tasks for infants is reaching safe and efficient oral feeding. Failure to thrive in this population is well documented in the literature; therefore, maximizing nutrition is a primary objective of the medical team.  Due to surgical needs, initiating oral feeding is delayed in some populations of infants with CHD. Infants then miss this instinctive period in establishing feeding patterns. Attaining the strength and coordination of sucking, swallowing and breathing as well as the endurance for safe feeding often is a barrier that may delay hospital discharge.  Families describe this period of time as frustrating and in some ways more challenging than the surgery itself. 

There often are several factors that impede feeding success for an infant with CHD. These include decreased endurance, early satiety and decreased hunger drive and other associated factors. As a general rule, an awake, alert infant should be able to take a full feeding in less than 30 minutes. Infants with CHD often tire quickly, preventing them from completing full volume feedings by bottle.   When feeding takes longer than 20-30 minutes, the infant likely is using an inefficient feeding pattern, further expending unnecessary energy. The infant may show hunger readiness cues (crying, rooting, organized non-nutritive suckling) but fall asleep within a few minutes of beginning feeding, preventing adequate volume intake required to gain weight. Often, caloric density of formula is increased to decrease the volume needed for growth and supplemental gavage feedings may be needed to complete volume.  
A bedside clinical feeding assessment by a speech language pathologist of the infant's oral-motor function, coordination of sucking, swallowing and breathing will provide valuable information regarding the ability and safety during feeding and allow development of an individualized bedside feeding plan. Heart rate, oxygen saturations, respiratory rate, breathing pattern at rest and during feeding are important physiologic factors to consider. Tachypnea may lead to decreased coordination of sucking, swallowing and breathing. Without intervention, this may lead to swallowing dysfunction. Giving the infant imposed breathing breaks offers the opportunity to pause, swallow and re-organize breathing before proceeding with the feeding task. 

Other associated factors may impact feeding skills. Vocal fold injury can be a post-operative problem and may be one potential source for post-operative swallowing dysfunction. Vocal fold dysfunction may influence or prohibit total oral feeding. Vocal quality should be monitored. Gastrointestinal motility, including gastroesophageal reflux, can further complicate an infant's overall feeding pattern.  Infants with associated conditions such as Trisomy 21, DiGeorge Syndrome and CHARGE syndrome may have additional complications impeding feeding success. 
Investigators at the University of Pennsylvania currently are measuring feeding performance and energy expenditures over the first year of life in infants who have undergone cardiac surgery in the first month of life. This study proposes to "establish which aspects of feeding performance (suck, swallow, breathe coordination, temporal patterning of sucking with meals, suck pressure generation, adaptation to variation of flow rate) are most subject to disruption in CHD infants after corrective or palliative surgery. The results of this investigation could prove useful in determining feeding methods and techniques as well as to further define why infants with CHD have feeding difficulties. 

FISH testing for 22q11 deletion often is used indice of feeding issues as many patients with this deletion have abnormal palates that can contribute to feeding problems. Therapeutic techniques including nipple changes, positioning, oral stimulation and/or environmental modifications may maximize efficiency of feeding and safety of swallowing. Ultimate success in oral feeding is best met by a child centered team approach including the family, primary physician, cardiologist, nurse practitioner, speech language pathologist and dietitian. Consistency in following the established feeding plan by this core group of caregivers may contribute to a more timely attainment of oral
feeding.

The Hacienda tube

L. Eliot May, PA-C, physician assistant, Herma Heart Center, Children's Hospital of Wisconsin.

The Hacienda tube, also known as the Norwood tube is a unique type of chest tube utilized for blood evacuation in patients who have excessive postoperative bleeding despite maximization of hemostasis techniques. The Hacienda tube is designed for rapid drainage of blood and fluids from the mediastinum. Unlike standard closed-system pleurivac drainage systems, the Hacienda tube is an open system.

This open-system tube is designed as a tube within a tube. The inner-most tube is connected to wall suction. This tube has a single opening at the very end. The outer tube has multiple perforations so blood can drain into its lumen. The concept of the Hacienda tube is that atmospheric air is entrained through a special air filter (to prevent bacteria from entering the system). The air enters the outer tube at the non-patient end and is quickly swept upward to the patient end. Blood seeps through the perforations in the outer tube and is rapidly carried by this current of air to the opening at the tip of the smaller inner-most tube. Blood then is removed to the wall suction canister. The advantage of this system is that blood quickly is evacuated to prevent collection and clotting within the mediastinum.

Ideally, postoperative bleeding should be kept to a minimum, but when circumstances arise that make this goal unattainable (severe postoperative coagulopathy), the Hacienda tube can be helpful to prevent tamponade while measures to correct the cause of the bleeding are instituted.

Herma Heart Center satellite clinics

Matt Groninger, manager, Herma Heart Center, Children's Hospital of Wisconsin.

Herma Heart Center satellite clinics provide a unique opportunity for the strengths and advantages of the larger main campus to be available closer to the patients' homes. It also allows the referring doctors to get to know the pediatric specialists on a more personal level. Herma Heart Center currently provides satellite clinics to several cities within a 100 mile radius of the city of Milwaukee.  Pamela Cava, DO, is available to see patients in Gurnee, Ill., and Kenosha and Racine, Wis. Raymond Fedderly, MD, sees patients in Sheboygan and Neenah, Wis. David Friedberg, MD, sees patients in Two Rivers and Burlington, Wis. Janette Strasburger, MD, sees patients in Neenah, Wis., and John Thomas, MD, has appointments available in Appleton, Wis. All pediatric cardiologists are part of the Herma Heart Center and on the faculty at the Medical College of Wisconsin. Cava and Strasburger have their primary offices at the satellite clinics along with full-time pediatric cardiac nurse practitioners.

Our goal is to provide outpatient care at these locations that is on a par with that found at the main campus in Milwaukee. Some services such as complex sedated echocardiograms and specialized exercise stress testing with pulmonary function evaluation still will require a visit to the main campus. 
Appointments are available for both new and established patients who do not need a specialized test. Fetal cardiac evaluation is available at the Neenah and Gurnee sites. We also are available for outside echocardiogram and EKG interpretation or other cardiac-related questions as they arise.

We currently are in the process of examining other sites within our area to create new satellite clinics. One of our main goals is to ensure a seamless coordination between our satellite sites and main campus facility in regards to information technology and patient records.