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SCA 2011 PBLD Complex Congenital Cardiac Case: Tetralogy of Fallot Cesar A Rodriguez-Diaz, MD Assistant Professor Department of Anesthesiology Mt Sinai Medical Center New York, NY James A. DiNardo, MD, FAAP Chief, Division of Cardiac Anesthesia Children’s Hospital Boston Professor of Anaesthesia Harvard Medical School Boston, MA Objectives: At the conclusion of this PBLD the attendees will be able to: 1 Discuss the spectrum of common anatomy variants referred as Tetralogy of Fallot, as well as their clinical manifestations. 2 Understand the physiology involved in medical management. 3 Recognize the various palliative and corrective surgical procedures available. 4 Develop a safe anesthetic plan when presented with a Tetralogy of Fallot patient. CASE PRESENTATION A 28 year-old male born with Tetralogy of Fallot (TOF) palliated with a Blalock-Taussig shunt at 2 weeks of age, followed by a transannular patch at 2 years of age is scheduled for a pulmonary artery plasty and pulmonic valve replacement. He complains of shortness of breath on moderate exercise. 1 Which anomalies constitute TOF? 2 What is the spectrum of pulmonic stenosis found in TOF? 3 What other cardiac anomalies may be found in TOF patients? 4 Which palliative procedures exist for TOF patients? 5 Which repair procedures exist for TOF patients? 6 Is there a benefit for palliation before repair? 7 Why do you think this patient has reduced exercise tolerance? 8 Is there a genetic predisposition for TOF? 9 What are major aortopulmonary collaterals (MAPCAs)? Preoperative evaluation reveals: Meds: Sotalol Allergies: none, Surgeries: BT shunt, Transannular patch. Airway: MP 1, Review of systems: history of ventricular tachycardia, otherwise non contributory. EKG: Right Bundle Branch block, Premature ventricular contractions. Right ventricular hypertrophy. HR 98, BP 120/80, RR 20, SpaO2 97% Wt 56kg, Ht 142cm, left sternal pansystolic murmur Labs: Htc 32%, Plt 162, INR 1.3, PTT 36, Cre 0.8 Transthoracic echocardiography reveals a very dilated right ventricle with moderate systolic dysfunction, moderate tricuspid regurgitation, severe pulmonic insufficiency, normal left ventricular systolic function, trace mitral regurgitation, trace aortic insufficiency, no residual ventricular septal defect, no atrial septal defect or patent foramen ovale. Main pulmonic artery severely dilated. 10 Why are dysrhythmias common in TOF? 11 What monitoring would you use? PA catheter? Pre/Post induction arterial line? Right or left ? 12 How would you induce anesthesia in this patient? 13 Does this procedure require aortic cross clamping? 14 What non surgical alternative is available for pulmonic insufficiency? Why is it not being used in this patient? 15 Would you use a lysine analogue antifibrinolytic? Why? 16 Is a tricuspid ring indicated? 17 What kind of valve, mechanical or bioprosthetic, should be placed? Surgeon is finished with the pulmonary artery plasty and pulmonic valve replacement. You are getting ready to wean the patient off cardiopulmonary bypass. 18 Which drips would you start, if any? Why? 19 If pacing is needed, which mode will you prefer? 20 Is there any benefit to justify early extubation? Discussion Described by Etienne Fallot in 1888, Tetralogy of Fallot syndrome is composed of 1) an overriding aorta, 2) right ventricular hypertrophy, 3) ventricular septal defect, and 4) pulmonic stenosis. It is the most common congenital cyanotic disease with an incidence of 32 per 100,000 live births. There are two schools of thought on the origin of Tetralogy of Fallot that explain the anteriorly malaligned conal septum and ventricular septal defect. Van Praagh et al. believe it is due to an underdevelopment of the distal pulmonary conus. Becker and Anderson believe it results from lack of normal rotation and unequal partitioning of the distal bulbus. Broadly classified, there are 3 subtypes of TOF: TOF with pulmonary stenosis (TOF/PS), TOF with pulmonary atresia (TOF/PA), and TOF with absent pulmonary valve (TOF/APV). TOF/PS is associated with varying degrees of valvular PS. At one end of the spectrum of TOF/PS the pulmonary valve may be mildly hypoplastic (reduced annulus size) with minimal fusion of the pulmonary valve leaflets. The pulmonary valve is almost always bileaflet. At the other end of the spectrum the pulmonary annulus may be very small with near fusion of the valve leaflets. It is important to point out that the valvular obstruction is a fixed obstruction while the subvalvular obstruction is dynamic. While the baseline level of arterial oxygenation (pink or blue tets) is determined by the extent of pulmonary stenosis, “tet” or hypercyanotic spells are always associated with changes in the dynamic component of RVOT obstruction. In TOF/PA there is infundibular and pulmonary valve atresia with varying degrees of main pulmonary arterial atresia. In the mildest forms the main pulmonary and branch pulmonary arteries are of normal caliber and pulmonary blood flow is supplied by a tortuous PDA or by major aortopulmonary collaterals (MAPCAs). In the most severe forms the branch pulmonary arteries are discontinuous and all pulmonary blood flow is supplied by MAPCAs. Associated defects include right aortic arch (25%), persistent left superior vena cava (10%), anomalous coronaries (5%), aberrant subclavian artery (10%), atrial septal defects, complete atrioventricular canal, patent ductus arteriosus, and bicuspid pulmonic valve. Palliative procedures include the original Blalock Taussig, where the subclavian artery is cut and anastomosed to the pulmonary artery. It not commonly performed anymore due to underdevelopment of the arm involved. Instead, the modified Blalock Taussig shunt (MBTS) is preformed; a Gore Tex tube typically 3 to 4 mm in diameter is placed between the innominate artery and the right pulmonary artery. Central shunts, such as the Potts shunt (descending aorta to left pulmonary artery) and Waterston shunt (ascending aorta to right pulmonary artery) are no longer performed but may encountered in older patients. Currently, most patients with TOF/PS have an elective full correction between the ages of 2 to 10 months of age. In some centers surgery is delayed as long as possible within this time interval with the precise timing of repair dictated by the onset of cyanotic episodes. Placement of a palliative MBTS prior to definite repair is an increasing uncommon approach. Definitive repair for TOF/PS is being accomplished in neonates in some centers if favorable anatomy is present. Complete repair involves closure of the ventricular septal defect and relief of RVOT obstruction. During cardiopulmonary bypass, and rarely deep hypothermic circulatory arrest in small neonates, the right ventricular outflow tract is divided exposing the VSD and the pulmonic valve. If there are infundibular septal bands they are resected. The pulmonic valve is measured with Hegar dilators and if found to be less than 3 Z scores it is transected and a transannular patch placed. The pulmonary arteries are inspected and if found to be stenotic they can be also patch augmented. In all cases an effort is made to limit the size of the ventriculotomy. In many cases, a transatrial and supravalvar approach may provide adequate visualization for the surgeon to close the VSD and address the stenosis. If a transannular patch is required, the patient will end with free pulmonic insufficiency that, over time leads to RV dilation and progressive biventricular dysfunction despite being symptomatically well tolerated for decades. Another technique employed for repair is the right ventricle to pulmonic artery conduit. This is typically performed when the patient has anomalous coronaries. In a small percentage of patients the LAD courses over the RVOT and prevents the use of a transannular patch. Unfortunately, the development of both conduit stenosis and regurgitation over time necessitates surgical reintervention for conduit replacements typically non valved, but there are some with a monocusp valve, and can lead to RV dilation due to free pulmonic insufficiency. These conduits tend to stenose overtime due to neo intimal growth, inflammation and calcification, requiring replacement about every 10 years. When the child finishes growing a valved conduit can be placed. In TOF/PA, the surgeon must establish continuity from the right ventricle to the pulmonary arteries with a conduit. MAPCAs that provide pulmonary blood flow to segments of lung not supplied by native pulmonary arteries must be unifocalized to the proximal pulmonary circulation. This involves removal of the collateral vessels from the aorta with subsequent reanastomosis to the conduit or a proximal pulmonary artery branch. In the most severe forms of this disease this process requires a staged procedure, often with unifocalization of MAPCAs to a central shunt as an initial procedure. The patient in this case had a transannular patch repair. These patients typically do well for a few decades despite pulmonary regurgitation. Chronic pulmonary insufficiency has been associated with RV dysfunction, ventricular dysrhythmias, and exercise intolerance. Predictors of long term outcome after Tetralogy of Fallot repair include, RV and LV size and function, degree of pulmonic stenosis, degree of tricuspid stenosis, and a QRS duration > 180ms. A pulmonary valve implantation might be indicated if the patient develops right ventricular dilation or dysfunction. Recently, percutaneous stentless valves have been deployed successfully in the pulmonary position. An RVOT diameter larger than 22mm and a prior transannular patch render the patient a poor candidate for this procedure. Open surgical implantation of a pulmonic valve remains the most feasible approach for most patients. Usual anesthetic measures should be taken for any re-do sternotomy. High flow intravenous lines and external defibrillator pads should be placed. Pulses should be examined prior to placing an arterial line especially in patients who had a palliative shunt due to the possibility of hypoperfusion to the arm. Pre-induction arterial line placement after intravenous sedation should be considered. Transesophageal echocardiography is recommended to assess ventricular function, tricuspid regurgitation and valve function and leaks after repair. A PA catheter could be placed but practically speaking this is rarely done. It should be kept in mind that might prove difficult to advance a PA catheter in the presence of TR and PI. Use of a lysine analogue antifibrinolytic is recommended. Valve replacement is done under cardiopulmonary bypass. Cross clamping the aorta is not necessary if no atrial or ventricular communications are present since the risk of systemic air embolism is minimized. Milrinone is commonly the drip of choice coming off bypass when ventricular dysfunction is present. Dobutamine or epinephrine are other choices, but must be balanced against the risk of arrhythmia. A pacing, AV pacing and lastly V pacing are recommended in that order to improve cardiac output if bradycardia is present. Early extubation can be considered but the benefits of this approach are largely institution dependent. References Jonas RA, ed. Tetralogy of Fallot with pulmonary atresia. Comprehensive surgical management of congenital heart disease. London: Arnold, 2004:440–456. Jonas RA, ed. Tetralogy of Fallot with pulmonary stenosis. Comprehensive surgical management of congenital heart disease. London: Arnold, 2004:279–300. Knauth, A.L.Ventricular size and function assessed by cardiac MRI predict major adverse clinical outcomes late after tetralogy of Fallot repair. Heart 2008;94:211-216 Stulak, J.M. The Increasing Use of Mechanical Pulmonary Valve Replacement Over a 40-Year Period. Ann. Thorac. Surg., December 1, 2010; 90(6): 2009 - 2015. Mulder, B.J.M. Percutaneous pulmonary valve replacement: a new development in the lifetime strategy for patients with congenital heart disease. Netherland Heart J. 2007 January; 15(1): 3–4. Abdullah, A. Early Extubation after Pediatric Cardiac Surgery: Systematic Review, Meta-analysis, and Evidence-Based Recommendations. Journal of Cardiac Surgery Vol 25, Issue 5, Sept 2010, Pages 586–595 Geva T: Indications and timing of pulmonary valve replacement after tetralogy of Fallot repair. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 2006: 11-22