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What is Atrioventricular (AV) Canal?
Michiaki Imamura, M.D., Ph.D. ; Pediatric Cardiac Surgeon, Arkansas Children’s Hospital; Assistant Professor of Surgery, University of Arkansas for Medical Sciences In patients with atrioventricular canal (AV canal), the central part of the heart is missing. AV canal is classified depending on the degree of the missing portion. Classification
In patients with complete AV canal, the central part of the heart is missing. The normal heart has two AV valves: the tricuspid valve and the mitral valve. However, the heart with complete AV canal has only one AV valve, called the common AV valve and atrial septal defect (ASD – a hole between two atriums) and ventricular septal defect (VSD – a hole between two ventricles). Partial AV Canal (Figure
3)
Transitional AV Canal (Figure
4) AV Canal Nomenclature
The mitral valve is sitting slightly higher than the tricuspid valve. The difference between these valves is called AV Septum (Figure 1). Because in the AV canal patient the right and left AV valves are sitting at the same level and AV septum is not present, AV canal also is called AV septal defect. In the case of an AV canal, additional intracardiac anomalies may occur, including pulmonary valve stenosis, pulmonary valve atresia, pulmonary artery stenosis, subpulmonary stenosis, aortic stenosis, left ventricular outflow tract obstruction, coarctation of the aorta, hypoplasia of the aortic arch, interrupted aortic arch, patent ductus arteriosus, tetralogy of Fallot, double outlet right ventricle, and hypoplasia of one ventricle.
Patients with Down syndrome make up 60 to 80 percent of complete AV canal cases. Among partial AV canal cases, only about 30 percent of patients have Down syndrome. Of all babies born with Down syndrome, 15 to 40 percent have complete AV canal. Signs and Symptoms Diagnosing Treatment
Surgical treatments include palliative surgery and complete repair. The palliative surgery is pulmonary artery banding placement. Complete repair involves closure of VSD and ASD and repair of the left AV valve. Currently, palliative surgery is performed when the patient is too small for complete repair or has contraindication for cardiopulmonary bypass. Otherwise, the complete repair is the surgical treatment of choice. In the patient with complete AV canal, operation usually is performed in early infancy. In partial AV canal cases, surgery is performed at the toddler stage. However, when symptoms are severe, surgical intervention may be instituted at an earlier age. Treatment Results
Extracorporeal Membrane Oxygenation in the Heart Center
Parthak Prodhan, M.D., Pediatric Cardiologist, Arkansas Children’s Hospital; Assistant Professor, Pediatrics, University of Arkansas for Medical Sciences Venovenous and Venoarterial Extracorporeal Membrane Oxygenation Support (ECMO) is a form of long-term heart-lung bypass used to treat neonates, infants, children and adults in cardiac and/or respiratory failure despite maximal medical therapy. ECMO may be indicated primarily for either intractable lung or cardiac disease. In neonates, primary pulmonary hypertension of the newborn, meconium aspiration syndrome, respiratory distress syndrome, group B streptococcal sepsis and congenital diaphragmatic hernia which do not respond to conventional medical management may require ECMO support. Older children and adults with acute respiratory distress syndrome (ARDS) unresponsive to conventional medical treatments may benefit from ECMO support as well. ECMO support may be required for low cardiac output resulting from heart failure due to intrinsic heart disease, following repair of a congenital heart defect or intractable cardiac arrhythmias; pulmonary vasoreactive crisis following repair of a congenital heart defect leading to severe hypoxemia and low cardiac output, or both. The purpose of ECMO is to allow time for intrinsic recovery of the lungs and heart. In cases of heart failure-supported ECMO, if recovery is not seen within a reasonable amount of time, ECMO is used to bridge the patient to ventricular devices or to heart transplantation.
To initiate ECMO, cannulae are placed in large blood vessels to provide access to the patient’s blood. The patient must be continuously anticoagulated (usually with heparin) to prevent blood clotting within the circuit. The ECMO machine continuously pumps blood from the patient through a “membrane oxygenator” that is responsible for exchanging both oxygen and carbon dioxide thus imitating the gas exchange process of the lungs. Oxygenated blood is then rewarmed prior to returning to the patient. Two forms of ECMO cannulation exist: venovenous (VV-ECMO) and venoarterial (VA-ECMO). In venovenous bypass, a double-lumen cannula is placed through the right jugular vein into the right atrium. Desaturated blood is withdrawn from the right atrium through the outer fenestrated venous catheter wall, and oxygenated blood is returned through the inner lumen of the catheter and is angled to direct blood towards the right ventricle. VA-ECMO requires placement of two cannulae by the surgeon. Commonly, a cannula is placed through the right jugular vein into the right atrium to withdraw desaturated blood into the ECMO circuit. Blood once oxygenated using the ECMO circuit is returned to the patient via another cannula placed via the carotid artery into the aorta. In rare instances, cannulation for ECMO may occur directly through an open chest after cardiac surgery or by cannulation of blood vessels in the groin. VV-ECMO is used in patients with primary respiratory failure while VA-ECMO is reserved for patients with cardiovascular instability to maintain an adequate cardiac output.
The primary advantages of VV-ECMO are reduced risk of embolization of blood clots into the arterial system. The second advantage is that it does not require ligation of the carotid artery while placing the arterial cannula. The carotid artery is one of the blood vessels which supplies blood to the brain, and its ligation may result in neurological injury. The main advantage of VA-ECMO is that this method gives excellent support for the heart in addition to the lungs. Therefore, if the heart function is a concern, VA-ECMO will be used. However, VA-ECMO requires major arterial access. Other disadvantages include reduced pulmonary blood flow, potential for arterial discharge of emboli and circulatory dependence on an extracorporeal circuit. If cardiac function improves, the patient may be converted from VA- to VV-ECMO. Any child who requires either VA- or VV-ECMO therapy is very ill and usually will die without it. However, there are major risks associated with this procedure which include major bleeding, increased risk of infection, risk associated with the need for blood transfusion and mechanical malfunction of the ECMO circuit. The duration of ECMO support required for a particular patient will depend on the age of the child and his/her original diagnosis. The duration of ECMO support may vary from a few days to many weeks depending upon the type of lung or heart disease, the amount of damage to the lungs before ECMO and complications that may occur during ECMO. In summary, despite significant risks associated with ECMO, it provides cardio-pulmonary support to critically ill patients with significant heart or lung disease refractory to conventional medical management and is associated with good clinical outcomes. The decision on whether VV- or VA-ECMO support is required is dictated by the patient’s clinical diagnoses, and the management of a patient on ECMO requires a coordinated team effort in order to have good clinical outcomes. ECMO support has been available at Arkansas Children’s Hospital since 1989. At this institution a dedicated group of health personnel’s with extensive experience are equipped to manage children of all ages while on ECMO. The outcomes and track record of providing this type of support is among the best in the country. The hospital is one of the few in the country, uniquely equipped to provide ECMO support while on transport
Family-Centered Care: An Evolving Process for the Heart Center at Arkansas Children's Hospital
Sherry Pye, M.N.Sc., A.P.N.,
C.C.R.N. ; Advanced Practice Nurse,
Cardiology, Arkansas Children’s Hospital Historically, visiting routines and parent-child interactions in an intensive care environment have occurred under a strict, controlled atmosphere. The focus was on the clinical condition of the child, and the parent was treated as a visitor with restricted involvement. It was recognized in the late 1950s that the child and family experienced emotional distress and trauma under these conditions. Parental interaction and participation was limited, which led to feelings of loss of control, anxiety and despair. In addition, there was poor, limited communication between the child, family and medical team that led to disruption of family structure and dynamics. Children experienced separation anxiety and physical and emotional distress that negatively affected the recovery process. The process of change and transition has been slow. In the early 1990s, family centered care terminology
evolved. This was defined as “an approach to the planning, delivery and evaluation of health care that is grounded in mutually beneficial partnerships among health care providers, patients and families” which recognizes the vital role that families play in the recovery process of sick children. Nine elements were delineated as being essential to successfully promoting family centered care. They are as follows.
As a leader in pediatric health care, Arkansas Children’s Hospital strives to meet these goals. The newly opened Pediatric Intensive Care Unit (PICU) provided for structural and policy changes that were centered on 24/7 family presence at the bedside. The Heart Center has evolved to Family Centered Care with no restriction on visitation, improved team communication and future expansion planning. Currently, there are no restrictions on family presence at the child’s bedside. Parental interaction is encouraged during rounds, procedures, and patient care. Special support is provided by the medical team as families progress through their stay in the intensive care unit (ICU). Additional resources available to families include the departments of Social Work, Child Life and Pastoral Care. Space limitations prevent parental sleeping accommodations in the current ICU, but planning for future structural changes will alleviate this barrier and separation. We, as a unit and team, are striving to facilitate a greater degree of congruence between theory and reality. Parents of children with congenital heart disease are integral partners and participants in their child’s care.
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Elizabeth Lawson, B.S.N., R.N.; Electrophysiology Specialty Nurse, Arkansas Children's Hospital; University of Arkansas for Medical Sciences Syncope is never a funny condition to experience, although many a good laugh has come out of the common occurrence. Incidents of syncope often make their way to America’s Funniest Home Videos, a popular TV show with real life recordings of the funny and not so funny occurrences of everyday life. Typically, the funny side of syncope happens while the groom awaiting his bride passes out at the altar, or the robed choir member singing an emotional song gets all attention as she falls to the floor. I’m never sure if the person “falling out” thinks things are so funny at the time, though. When this happens, the patients feel terribly drained, confused, scared and often embarrassed. Syncope is defined as the abrupt and transient loss of consciousness associated with the loss of postural tone, typically followed by rapid recovery. Because syncope as an isolated event has so many causes, its occurrence can never be downplayed. There are about 30 different causes of syncope which symptomatically represent neurological, metabolic, psychiatric or cardiovascular disorders. When the patient presents, often to an emergency room, the primary physician must carefully determine the history, physical findings and objective findings to accurately diagnosis and treat syncope. This often leads to a cardiology consult, and rightly so. Cardiovascular pathology leading to syncope can be either electrical or mechanical. Most common causes include arrhythmia, Long QT Syndrome, ischemia, aortic stenosis, cardiomyopathy, or other congenital/familial diseases. These provoking causes should be evaluated immediately by a cardiologist to provide appropriate intervention and follow up.
History is extremely important in diagnosing neurocardiogenic syncope. The situation surrounding the event, the timing of the event, patient activity and position, along with family history are all important points to evaluate. On the basis of history, the physician can have a good idea of the diagnosis in about 50 percent of patients. When the cause of syncope is not clear, screening for the differential diagnosis includes electrocardiography, stress testing, nuclear imaging, echocardiography and Holter monitoring. If neurocardiogenic syncope is suspected, a head-up-tilt test (HUT) is performed. This is a common provocative test that helps to reproduce a patient’s symptoms with tilt testing. When the patient is tilted from supine to 70 degrees, as the blood pools in the legs, a sympathetic response is provoked that initiates increased cardiac contracting, withdrawal of peripheral sympathetic tone and enhancement of vagal tone. In cases where positioning alone does not provoke the sympathetic response, carotid massage is performed with the patient in an upright position. If there still is no response, isoproteronol is administered as an infusion while tilted, with slow titration of the dose. A HUT is considered positive if the original symptoms are reproduced along with an abrupt decrease in blood pressure (vasodepressor), heart rate (cardioinhibitory), or both(vasovagal). There are several approaches to treating neurocardiogenic syncope. The first and easiest treatment is to teach the patient to increase fluid and salt intake so that blood volume expansion can be achieved. The patient should drink about a liter of water, electrolyte replacement beverages and fruit juices each day to achieve this balance. The patient should be advised to avoid caffeinated drinks, prevent dehydration, avoid alcohol consumption and prolonged standing. When this alone is not effective, fludrocortisone (Florinef) is started. Fludrocortisone acts to increase sodium retention therefore increasing intravascular volume. It may also increase the vasoconstrictive peripheral vascular response. Patients on fludrocortisone need to be monitored for electrolyte imbalance and blood pressure. Beta blockers such as atenolol or metoprolol are effective in reducing the affects of catecholamines. The patient needs to be monitored to potential side effects such as bradycardia, fatigue or depression. Selective serotonin reuptake inhibitors such as Paxil or Zoloft have also been found useful in the treatment and prevention of neurocardiogenic syncope. Pacemakers rarely are indicated for neurocardiogenic syncope. Recurrent syncope resulting from carotid sinus stimulation with minimal pressure that induces ventricular asystole is a class I indication for pacemaker implantation. Neurocardiogenic syncope with severe bradycardia that is reproduced during HUT is a class IIb indication. Pacemakers generally are more useful in patients with cardioinhibitory rather than vasodepressor type syncope. Therapy generally is guided by symptom recurrence and pharmacologic profile. Neurocardiogenic syncope is generally considered benign, although frequent or recurrent events can self limit the patient. Patients need teaching and reassurance as to the pathophysiology and management of neurocardiogenic syncope. Education is the mainstay of treatment. Implementing simple lifestyle changes can prevent syncope and help the patient avoid pharmacological treatments. Click here for references CPR for Family and Friends in The Heart Center
The Heart Center offers a program to teach our families CPR (Cardiopulmonary Resuscitation). Parents with children who have Congenital Heart Defects (CHD) require extra teaching. Here at the ACH Heart Center, we encourage all parents to take CPR training prior to their child’s discharge. This course is designed to teach the families how to give CPR to an adult, child or infant. CPR is important! Studies show that if you can receive effective CPR right away it improves your chances for survival after cardiac arrest. Cardiac arrest usually occurs when the patient is at home with family members. The course teaches the basics of CPR through a book and video. A nurse from the Heart Center who is a certified CPR instructor meets with families individually at the bedside or in the playroom to review CPR and evaluate their skills. Families are instructed in adult, child and infant CPR, as well as adult, child and infant choking. The instructors also provide an introduction to Automated External Defibrillators (AEDs). Parents are encouraged to notify a staff member for further information.
Spotlight on the Heart Center Picnic: The Beat Goes On!
The Heart Center teamed up with the Little Rock Zoo recently to allow its young patients a day of fun in the sun. Dozens of families and children who have faced congenital heart defects turned out for the Second Annual Heart Center Picnic. Patients visited with their doctors and nurses through the bright and warm afternoon, while also checking out exhibits and even taking rides on the camels! Everyone entered a contest for chances to win door prizes, too! The afternoon was a success and the Heart Center staff was pleased to see so many of its patients happy and healthy on this day. Stay tuned for details about next year’s event.
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