Download A Complex Congenital Case

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
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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
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lifetime strategy for patients with congenital heart disease. Netherland Heart J. 2007
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