Tetralogy of Fallot

Kamal K. Pourmoghadam, M.D.

Historical Background

First complete description of tetralogy of Fallot (TOF) credited to Etienne Fallot, published 1888
First surgical procedure, palliation, for TOF, Alfred Blalock & Vivien Thomas 1945, John Hopkins University
Numerous aortopulmonary shunts
First successful intracardiac repair, Dr. Lillehei & Varco at University of Minnesota, controlled cross circulation, 1954
First successful repair with cardiopulmonary bypass, Dr. Kirklin, 1955
First complete description of tetralogy of Fallot (TOF) credited to Etienne Fallot, published 1888
First surgical procedure, palliation, for TOF, Alfred Blalock & Vivien Thomas 1945, John Hopkins University
Numerous aortopulmonary shunts
First successful intracardiac repair, Dr. Lillehei & Varco at University of Minnesota, controlled cross circulation, 1954
First successful repair with cardiopulmonary bypass, Dr. Kirklin, 1955

Morphology

The classic “tetrad” of TOF
Ventricular Septal Defect
Aortic override
Right ventricular outflow tract obstruction
Right ventricular hypertrophy
Each results from anterior and leftward displacement of infundibular/conal septum with respect to the trabecular septum
Boundaries of the VSD
Anterior- Anterior limb of septal band
Posterior- Anteroseptal leaflet of TV
Inferior- Posterior limb of septal band
Superior- Conal septum
Pulmonary valve, bicuspid in 58% of patients
Rarely PV, smallest portion of RVOT
Pulmonary atresia, 7% of TOF patients
Multiple aortopulmonary collateral arteries (MAPCAs)
More likely to have peripheral pulmonary stenosis
Complete absence of pulmonary valve leaflets, 5% of TOF patients
Severe pulmonary insufficiency
Aneurysmal dilatation of MPA & PA branches
Compression of distal tracheobronchial tree
Origin of LAD from RCA, 3-5% of TOF patients
Dual distribution of LAD
Single right coronary, rare

Associated Defects

ASD
PDA
Complete atrioventricular canal defect
Multiple VSDs

Pathophysiology & Diagnosis

Initial manifestation depends on the degree of RVOT obstruction
Cyanosis is mild at birth, progressive with age
Cyanosis main physical finding in TOF
First heart sound is normal but second sound is often single
Inaudible pulmonary component
Systolic murmur results from RVOT obstruction
Murmur disappears during “tet spell”
Electrocardiographic characteristics consistent with right ventricular hypertrophy
Chest radiography
Heart size usually normal
Aortic arch is right-sided, 25%
“boot shaped” heart
Elevation of cardiac apex due to RV hypertrophy
Concave upper left heart border due to narrowing of MPA
Diagnosis
Established by echocardiography
Cardiac catheterization
Usually not necessary
Recommended
Concerns for coronary anatomy
Multiple VSDs
Determination of aortopulmonary collateral anatomy
Non-confluent pulmonary artery branches

Treatment
Medical Management
Progressive decrease in oxygen saturation usually due to fixed RVOT obstruction, does not respond to Med. Therapy
Hypoxemic spells may result from transient decrease in pulmonary blood flow
Medical Management Cont.
Sudden increase in RVOT obstruction & decrease in SVR
Results in sudden profound decrease in oxygen saturation
Dehydration
Anemia
Increased catecholamine levels
Acidosis
Decrease in SVR
Medical Management Cont.
Treatment
Oxygen
Sedation
Bicarbonate
Transfusion/volume resuscitation
Administration of α-agonist to increase SVR
Long-term  β-blocker may decrease myocardial contractility & decrease frequency and severity of spells
Indications for surgery
Usually asymptomatic at birth
Operative intervention is undertaken, once oxygen saturation is 75 to 80%
Occurrence of hypoxemic spells generally considered indication for surgery
In most institutions elective repair is undertaken at 3 to 6 months of age
Single stage complete repair, majority
Staged repair, preferred by few especially when
Pulmonary atresia with marked hypoplasia of PA branches
Severe associated non-cardiac anomalies
Systemic to pulmonary artery shunts designed to increase pulmonary blood flow in cyanotic children
Blalock-Taussing Shunt, Alfred Blalock,1944
Potts Shunt, Willis Potts, 1946
Waterston Shunt, David Waterston, 1962
Cooley Shunt, Denton Cooley, 1966
Modified Blalock-Taussing Shunt, Marc DeLeval, 1976
Complete repair
Closure of VSD
Relief of RVOT Obstruction
Pulmonary valve sparing vs. transannular patch (estimated RV/LV < 0.7)
Hypoplastic PA branches, rare
Considered present, McGoon ratio < 1.2 (diameter RPA + LPA/diameter of Ao at level of diaphragm)
Nakata index of approximately 70
Pulmonary atresia with MAPCAs
Usually associated with diminutive PA branches
Abnormal arborization
Peripheral PA stenosis
Higher operative mortality and complexity
Complete vs. staged repair
TOF with absent pulmonary valve
Urgent repair with placement of competent pulmonary valve and PA Branch plication
Early mortality is 21.4%
Preoperative mechanical ventilation, poorer outcome
TOF with complete AV canal defect (CAVCD)
Occurs in 2% of patients with TOF
Most common in patients with Down’s syndrome
Anatomy is that of CAVCD
Anterior bridging leaflet is always undivided & unattached to crest of the septum (Rastelli type C)
VSD has a large outlet component
Difficult to repair through atrial approach
Due to marked override of Ao valve, exposure is impeded
Valve in the pulmonic position is unnecessary unless marked branch PA hypoplasia

Results
Early hospital mortality, 1 to 5% (3.7%)
Repair within first year of life, does not influence early outcome
Improvement in intraoperative technique
Avoidance of excessive RVOT muscle resection
CPB management
Refinement in postoperative care

Long-term survival from University of Alabama at Birmingham, postoperative
1 month-93%
1 year-92%
5 years-92%
20 years-87%

Effect of pulmonary valve insufficiency (PI)
Long standing PI appears to have certain deleterious effects on ventricular function & exercise capacity
Particularly true if additional lesions
Peripheral pulmonary stenosis
Residual VSD
In a series of 20 asymptomatic patients, 9 years post-op., significantly lower  RV & LV EFs were  found compared to a group with competent PV
When symptoms develop, PV insertion improves functional status & ventricular function

Effect of pulmonary valve insufficiency (PI) cont.
Indications for pulmonary valve replacement in absence of CHF & exercise intolerance is not well defined
Pulmonary valve replacement should be considered when there is
Poor ventricular function
Tricuspid valve insufficiency
Progressive RV dilatation
Effect of pulmonary valve insufficiency (PI) cont.
Early operation for asymptomatic RV dysfunction improves likelihood of full recovery of ventricular function & decreases prevalence of ventricular arrhythmias
Operative risk, 1.1%
Functional status post-op. was NYHA I for 90% of patients
10 year survival, 95%

Conclusion
The results of surgical repair of TOF have continued to steadily improve due to
Enhanced myocardial preservation techniques
More attentive RVOT reconstruction
Improved postoperative care
These refinements have decreased, but have not eliminated the long-term sequalae of pulmonary valve insufficiency, RV dysfunction, and ventricular arrhythmias
A more aggressive approach to implantation of a competent pulmonary valve, in TOF patients with progressive  RV dilatation, TV insufficiency, or poor ventricular function improves the likelihood of full recovery of RV function & decreases the prevalence of ventricular arrhythmias.

About Dr. Kamal K. Pourmoghadam

Kamal Pourmoghadam, MD, is a pediatric cardiac surgeon at The Heart Center at Arnold Palmer Hospital for Children. He is board certified in general surgery, cardiothoracic surgery and congenital cardiac surgery.

Dr. Pourmoghadam earned his bachelor’s degree from University of California, Berkeley, and his medical degree from Albany Medical College in New York. He trained for adult cardiac surgery at the University of Miami, Jackson Memorial Hospital in Miami, and for congenital cardiac surgery at the University of Washington, Seattle Children’s Hospital in Seattle.

Dr. Pourmoghadam is a professor of surgery at the University of Central Florida College of Medicine, practicing congenital cardiac surgery for over twenty years and has been active in clinical research. He has extensive experience in neonatal and infant cardiac surgery and has special interest in the repair of single ventricle physiology patients and research in univentricular hearts.
References:

Website: https://kamalpourmoghadam.com
Blog: https://drpourmoghadam.home.blog/
News: https://hippocratesguild.com/dr-kamal-pourmoghadam
News: https://medicogazette.com/dr-kamal-pourmoghadam#425f92ce-0ccc-4fe2-8c31-56cf497704f4
News: https://hype.news/dr-kamal-pourmoghadam/
News report about Dr. Pourmoghadam: http://www.tiogapublishing.com/features/the_marketplace/covington-tot-returns-home-to-pennsylvania-after-lengthy-oklahoma-hospital/article_04865c00-0ae5-11e1-aec8-001cc4c002e0.html
Linkedin: https://www.linkedin.com/in/kamal-pourmoghadam-9a796157/

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