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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Pediatric Cardiology

Diagnosis and Imaging: Making Sense of the Scans

At a Glance

Echocardiograms, CT scans, and MRIs are essential tools used to map a child's heart after a Tetralogy of Fallot (ToF) diagnosis. These scans measure critical details like the pulmonary valve Z-score and coronary artery placement, which guide surgeons in planning the safest, most effective repair.

When a child is diagnosed with Tetralogy of Fallot (ToF), the medical team uses a variety of advanced “pictures” to map out the heart’s unique structure. These scans are not just for diagnosis; they are the blueprints the surgical team uses to plan your child’s repair.

The First Look: Echocardiograms

The echocardiogram (or “echo”) is an ultrasound of the heart. It is the most common tool used to monitor ToF because it is safe, does not use radiation, and provides a clear view of blood flow [1].

  • Fetal Echo: Many cases of ToF are found before birth. A fetal echo allows doctors to plan for the baby’s delivery and immediate care [2]. However, because a baby’s circulation changes dramatically after their first breath, some details—like the exact size of the pulmonary valve—might look different after birth [3][4].
  • Postnatal Echo: After birth, this scan confirms the diagnosis and measures the pressures inside the heart to help determine if the baby needs surgery sooner or later [5][6].

Understanding “Z-Scores”

During an echo, you will likely hear the doctors talk about Z-scores. A Z-score is a way to describe how much a part of the heart (like the pulmonary valve) differs from the “average” size for a baby of your child’s height and weight [7][8].

  • Positive Z-score: The structure is larger than average.
  • Negative Z-score: The structure is smaller than average.

In ToF, the pulmonary valve Z-score is critical. If the valve is only slightly small (a Z-score of -1 or -2), surgeons may be able to “save” the valve (valve-sparing repair) [8]. If the valve is very small (a Z-score lower than -3), the surgeon may need to use a transannular patch to widen the opening, which helps blood flow but may cause some leaking later in life [7][9]. (Learn more about what this means in Surgical Treatment Options).

Advanced Imaging: MRI and CT

Sometimes, an echo doesn’t show the whole picture, especially the blood vessels outside the heart.

  • Cardiac CT: This is often used before surgery to get a detailed 3D map of the coronary arteries (the small vessels that provide blood to the heart muscle itself) [4][10]. About 10% of children with ToF have an “anomalous” coronary artery that crosses right over where the surgeon needs to work [11]. Knowing this ahead of time is vital for a safe surgery [11].
  • Cardiac MRI (CMR): While less common in newborns, MRI is the “gold standard” for older children and adults who have already had ToF surgery [12]. It provides incredibly accurate measurements of the heart’s size and how well it is pumping, helping doctors decide when a leaky valve might need to be replaced [13][14].

Looking for Variations

No two hearts with ToF are exactly the same. Doctors look for specific variations that might change the “plan of attack”:

  • Right-Sided Aortic Arch: In about 10-25% of ToF cases, the main artery (aorta) curves to the right instead of the left [15][16].
  • MAPCAs: Some babies develop extra “collateral” arteries to get blood to the lungs because the main path is so narrow [17].
  • Additional Holes: Doctors check for extra holes in the wall between the chambers (VSDs) that might need to be closed during surgery [1].

By using these scans, the care team moves from a general diagnosis to a precise surgical plan tailored specifically to your child’s heart.

Common questions in this guide

What does a pulmonary valve Z-score mean in ToF?
A Z-score describes how your child's pulmonary valve size compares to the average for a baby of their height and weight. A slightly small valve may allow for a valve-sparing repair, while a very small valve typically means the surgeon will need to use a transannular patch to widen the opening.
Why might my child need a cardiac CT scan for Tetralogy of Fallot?
A cardiac CT scan provides a detailed 3D map of the heart's coronary arteries. This is crucial because about 10% of children with ToF have an atypical coronary artery that crosses the surgical area, and surgeons need this map to plan a safe operation.
How does a fetal echo compare to an echo after birth?
A fetal echo allows doctors to diagnose ToF before birth and safely plan for delivery. However, because a baby's circulation changes dramatically after taking their first breath, an echocardiogram after birth is required to confirm the exact size of heart structures.
What does it mean to have a right-sided aortic arch?
In a typical heart, the main artery (aorta) curves to the left. In 10 to 25 percent of Tetralogy of Fallot cases, the aorta curves to the right instead. This is a common structural variation that doctors look for when creating your child's specific surgical plan.
Will my child need a cardiac MRI before their first ToF surgery?
Cardiac MRIs are less commonly used in newborns and are usually reserved for older children and adults who have already had ToF surgery. They provide highly accurate measurements of heart function to help doctors decide if a leaky valve needs replacement later in life.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is my child's pulmonary valve Z-score, and how does that influence the decision between a valve-sparing repair and a transannular patch?
  2. 2.Have you been able to clearly see the coronary arteries on the echo, or do we need a CT scan to be sure they don't cross the area where you'll be operating?
  3. 3.Does my child have a right-sided aortic arch or any major aortopulmonary collateral arteries (MAPCAs)?
  4. 4.If we are doing a staged repair, what specifically are we looking for on future scans to know it's time for the complete repair?
  5. 5.Will my child need a cardiac MRI before their first surgery, or is that typically reserved for later in life?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (17)
  1. 1

    Cardiovascular imaging approach in pre and postoperative tetralogy of Fallot.

    Apostolopoulou SC, Manginas A, Kelekis NL, Noutsias M

    BMC cardiovascular disorders 2019; (19(1)):7 doi:10.1186/s12872-018-0996-9.

    PMID: 30616556
  2. 2

    [Factors associated with survival at one year of life in neonates with severe congenital cardiopathy in A National Hospital in Peru].

    Torres-Romucho CE, Uriondo-Ore VG, Ramirez-Palomino AJ, et al.

    Revista peruana de medicina experimental y salud publica 2019; (36(3)):433-441 doi:10.17843/rpmesp.2019.363.4166.

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    Prenatal diagnosis of tetralogy of Fallot associated with pulmonary artery sling: Two case reports.

    Li T, Han J, Gao S, et al.

    Echocardiography (Mount Kisco, N.Y.) 2019; (36(11)):2114-2117 doi:10.1111/echo.14513.

    PMID: 31705550
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    Coronary artery anomalies in tetralogy of Fallot patients evaluated by multi slice computed tomography; myocardial bridge is not a rare finding.

    Romeih S, Kaoud A, Shaaban M, et al.

    Medicine 2021; (100(7)):e24325 doi:10.1097/MD.0000000000024325.

    PMID: 33607768
  5. 5

    2-Year Outcomes After Complete or Staged Procedure for Tetralogy of Fallot in Neonates.

    Savla JJ, Faerber JA, Huang YV, et al.

    Journal of the American College of Cardiology 2019; (74(12)):1570-1579 doi:10.1016/j.jacc.2019.05.057.

    PMID: 31537267
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    Tetralogy of Fallot: Everything you wanted to know but were afraid to ask.

    Wise-Faberowski L, Asija R, McElhinney DB

    Paediatric anaesthesia 2019; (29(5)):475-482 doi:10.1111/pan.13569.

    PMID: 30592107
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    Validity of Pulmonary Valve Z-Scores in Predicting Valve-Sparing Tetralogy Repairs-Systematic Review †.

    Sinha R, Gooty V, Jang S, et al.

    Children (Basel, Switzerland) 2019; (6(5)) doi:10.3390/children6050067.

    PMID: 31060236
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    Pulmonary valve preservation during tetralogy of Fallot repair: midterm functional outcomes and risk factors for pulmonary regurgitation.

    Guariento A, Schiena CA, Cattapan C, et al.

    European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery 2022; (62(2)) doi:10.1093/ejcts/ezac365.

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    Fate of the Right Ventricular Outflow Tract Following Valve-Sparing Repair of Tetralogy of Fallot.

    Toubat O, Wells WJ, Starnes VA, Kumar SR

    Seminars in thoracic and cardiovascular surgery 2024; (36(2)):242-249 doi:10.1053/j.semtcvs.2022.12.002.

    PMID: 36567048
  10. 10

    Coronary artery anomalies on preoperative cardiac CT in children with tetralogy of Fallot or Fallot type of double outlet right ventricle: comparison with surgical findings.

    Goo HW

    The international journal of cardiovascular imaging 2018; (34(12)):1997-2009 doi:10.1007/s10554-018-1422-1.

    PMID: 30051301
  11. 11

    Coronary anomalies in tetralogy of Fallot - A meta-analysis.

    Koppel CJ, Jongbloed MRM, Kiès P, et al.

    International journal of cardiology 2020; (306()):78-85 doi:10.1016/j.ijcard.2020.02.037.

    PMID: 32156463
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    High Variability of Right Ventricular Volumes and Function in Adults with Severe Pulmonary Regurgitation Late After Tetralogy of Fallot Repair.

    Greutmann M, Ruperti J, Schwitz F, et al.

    The American journal of cardiology 2022; (166()):88-96 doi:10.1016/j.amjcard.2021.11.022.

    PMID: 34949470
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    Utility of Cardiac Magnetic Resonance Imaging in Predicting Atrial Arrhythmias in Repaired Tetralogy of Fallot.

    Pinsker BL, Serfas JD, Awerbach JD, et al.

    The American journal of cardiology 2022; (174()):151-157 doi:10.1016/j.amjcard.2022.03.043.

    PMID: 35473783
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    Repaired Tetralogy of Fallot: Have We Understood the Right Timing of PVR?

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    Journal of clinical medicine 2024; (13(9)) doi:10.3390/jcm13092682.

    PMID: 38731211
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    The aortic arch in tetralogy of Fallot: types of branching and clinical implications.

    Prabhu S, Kasturi S, Mehra S, et al.

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    Right Aortic Arch with Bicarotid Trunk and Isolated Left Subclavian Artery: Hitherto Unreported Pattern.

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  17. 17

    Partial anomalous pulmonary venous connection in a patient with tetralogy of Fallot: Infrequent, but not inconsequential.

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    PMID: 32557816

This page provides educational information on imaging and diagnostic tools for Tetralogy of Fallot. Always consult your pediatric cardiologist to interpret your child's specific echo and scan results.

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