Quadricuspid Pulmonary Valve on CT: A Rare Incidental Finding in a 43-Year-Old Woman With Sudden Epigastric Pain
A radiologist’s approach to quadricuspid pulmonary valve: CT diagnosis, four-cusp morphology, differential diagnosis, pulmonary regurgitation, pulmonary artery aneurysm, multimodality imaging, management, and prognosis.
Introduction
A 43-year-old woman presented with sudden epigastric pain radiating to the back.
That clinical description immediately raises an important diagnostic concern. Sudden severe upper abdominal or epigastric pain extending toward the back can represent acute aortic syndrome (AAS), including aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, or aortic rupture. In an emergency setting, these potentially fatal conditions must be excluded rapidly.
CT angiography was therefore performed.
The aorta was unremarkable for an acute aortic catastrophe. There was no convincing aortic dissection, penetrating atherosclerotic ulcer, intramural hematoma, rupture, or pericardial effusion.
However, the examination contained an unexpected finding.
At the level of the pulmonary valve, four valve cusps were identified instead of the normal three.
The finding was consistent with a quadricuspid pulmonary valve (QPV).
This is more than an interesting anatomical curiosity.
The real diagnostic challenge is determining whether a four-cusp pulmonary valve is simply an incidental congenital anatomical variant or whether it is associated with clinically relevant pulmonary regurgitation, pulmonary stenosis, pulmonary artery dilatation, pulmonary artery aneurysm, right ventricular remodeling, or another congenital cardiac abnormality.
That distinction is where imaging interpretation becomes clinically meaningful.
1. What Is a Quadricuspid Pulmonary Valve?
The normal pulmonary valve is a tricuspid semilunar valve, consisting of three cusps. During right ventricular systole, the valve opens to permit blood flow into the pulmonary artery. During diastole, the cusps coapt and prevent significant retrograde flow into the right ventricle.
A quadricuspid pulmonary valve, also termed a quadricuspid pulmonic valve, is a congenital valvular anomaly in which the pulmonary valve contains four cusps rather than three. The abbreviation QPV is commonly used.
The morphology is not necessarily symmetrical.
The four cusps may be:
approximately equal in size,
composed of one relatively large and one smaller cusp,
characterized by two intermediate-sized cusps,
or demonstrate other combinations of cusp dimensions.
The classical Hurwitz-Roberts classification describes semilunar valve morphology according to the relative size of the cusps, with QPV configurations categorized into several morphological types. Recent imaging work has drawn particular attention to the type D configuration, characterized by one large cusp, two intermediate cusps, and one small cusp.
The critical point is that the presence of four cusps does not automatically mean that the valve is functionally abnormal.
2. Rare Does Not Mean Dangerous
Historically, QPV has been considered an exceptionally uncommon congenital cardiac anomaly.
Older autopsy series reported frequencies approximately in the range of 1 in 400 to 1 in 2,000, although these figures should not be interpreted as a reliable estimate of contemporary population prevalence. A 2023 review summarized historical autopsy data with an estimated range of approximately 0.02%–0.41%.
The difficulty in establishing prevalence is understandable.
The pulmonary valve is anatomically small and highly mobile. Conventional transthoracic echocardiography may not always provide an optimal visualization of all pulmonary valve cusps. Modern ECG-gated cardiac CT and cardiac MRI have substantially improved the ability to recognize subtle pulmonary valve abnormalities in living patients.
This creates an important conceptual distinction:
QPV is rare, but rarity itself does not establish clinical significance.
Some patients have a morphologically abnormal pulmonary valve with preserved function and remain asymptomatic.
Others develop clinically important pulmonary regurgitation, pulmonary stenosis, pulmonary artery enlargement or aneurysm, and right ventricular enlargement.
Therefore, the diagnostic task should not end after counting the cusps.
3. Why Does a Four-Cusp Pulmonary Valve Develop?
The precise embryological mechanism of QPV remains incompletely understood.
The pulmonary valve develops as part of the complex remodeling of the cardiac outflow tract during embryogenesis. A developmental variation in the formation or partitioning of valvular tissue may result in the presence of an additional cusp.
From an imaging perspective, however, the exact embryological mechanism is less important than recognizing the resulting anatomy.
The morphology can vary considerably.
A radiologist should therefore avoid expecting four perfectly identical triangular leaflets.
One cusp may be substantially smaller than the others, and partial cusp fusion may make the valve appear deceptively similar to other semilunar valve configurations. Recent imaging data have reported cusp fusion in approximately one-quarter of QPV cases.
This is one reason why multiplanar imaging is essential.
4. The Pathophysiological Question: Is the Valve Functionally Competent?
The most clinically important distinction is between:
morphological QPV
and
functionally significant QPV.
If the four cusps coapt adequately, pulmonary valve function may remain normal.
If cusp geometry is abnormal or coaptation is incomplete, however, blood may flow backward from the pulmonary artery into the right ventricle during diastole.
The resulting sequence can be conceptualized as:
QPV → abnormal cusp coaptation → pulmonary regurgitation → chronic RV volume overload → RV dilatation → RV dysfunction
Over time, significant pulmonary regurgitation can contribute to exercise intolerance, dyspnea, fatigue, palpitations, and, in advanced cases, right-sided heart failure.
This is why the number four is only the beginning of the diagnosis.
5. The Clinical Presentation: Usually Silent
Most patients with QPV are asymptomatic.
The anomaly may be discovered incidentally during:
transthoracic echocardiography,
transesophageal echocardiography,
cardiac CT,
cardiac MRI,
or postmortem examination.
When functional abnormalities are present, possible manifestations include:
exertional dyspnea,
chest discomfort,
fatigue,
reduced exercise capacity,
palpitations,
occasional syncope,
or symptoms related to right ventricular dysfunction.
There is, however, an important clinical trap in the present case.
Sudden epigastric pain radiating to the back should not be automatically attributed to QPV.
The patient's acute symptom pattern justified an initial search for acute aortic syndrome.
The QPV was discovered during that investigation, but there is no basis for assuming that the four-cusp valve caused the acute pain.
This distinction between an imaging finding and a symptom-producing diagnosis is fundamental to responsible radiological interpretation.
6. CT Diagnosis: Count the Cusps, but Do Not Count Them on One Image
The central CT finding is straightforward:
Normal pulmonary valve → 3 cusps
QPV → 4 cusps
But the practical diagnosis is more difficult than the simple numbers suggest.
The pulmonary valve is:
thin,
mobile,
small,
and affected by cardiac motion.
Motion artifact and partial-volume averaging can therefore alter the apparent number or configuration of cusps.
For that reason:
Never diagnose QPV solely from a single axial CT image when multiplanar data are available.
The four-cusp configuration should be confirmed using multiple planes.
Figure 1. Multiplanar CT demonstration of a quadricuspid pulmonary valve
(A) Axial reconstruction
At the pulmonary valve level, four distinct cusp structures are identified rather than the normal three-cusp configuration.
Key imaging point: a reproducible four-leaflet configuration strongly supports QPV.
(B) Oblique reconstruction
The oblique reconstruction improves visualization of the spatial relationship between the cusps and helps distinguish true valvular anatomy from partial-volume or motion-related artifact.
(C) Sagittal reconstruction
The sagittal plane allows assessment of the pulmonary valve together with the right ventricular outflow tract and main pulmonary artery.
The accompanying case material specifically identifies axial, oblique, and sagittal CT reconstructions as the key imaging views for establishing the diagnosis and assessing the adjacent pulmonary artery and right ventricular outflow tract.
7. What Should Be Evaluated After QPV Is Identified?
Once four cusps have been confirmed, the CT examination should immediately move to the next level of analysis.
This sequence is more clinically useful than simply reporting:
“Quadricuspid pulmonary valve.”
A better radiological interpretation would communicate the potential clinical implications:
“Quadricuspid pulmonary valve is identified. Correlation with echocardiography or cardiac MRI may be considered to assess pulmonary regurgitation, right ventricular size/function, and associated pulmonary arterial abnormalities.”
8. QPV and Pulmonary Artery Dilatation: The Finding You Should Not Miss
The main pulmonary artery deserves particular attention.
QPV has been reported in association with pulmonary artery dilatation and pulmonary artery aneurysm. Previous multimodality reports demonstrated that echocardiography and ECG-gated CT can complement each other in evaluating both valve morphology and pulmonary artery anatomy.
This association becomes particularly relevant when interpreting contemporary imaging data.
A 2026 multimodality study cited in the case material evaluated 1,367,280 cardiac CT and MR examinations and identified 16 patients with QPV. The mean age was approximately 43 years. In that cohort, congenital heart disease was reported in 38%, moderate-or-greater pulmonary regurgitation in 69%, pulmonary artery aneurysm in 50%, and approximately 31% underwent surgery during follow-up.
These numbers are striking, but they must be interpreted correctly.
This was a small, single-center retrospective cohort of identified QPV cases, not a population-based prevalence study.
Therefore, these percentages should not be interpreted as the expected risk for every person with incidentally discovered QPV.
Nevertheless, they provide an important imaging message:
Once QPV is identified, pulmonary artery morphology and valve function deserve deliberate assessment.
9. Differential Diagnosis
9.1 Bicuspid Pulmonary Valve
The most direct anatomical differential is a bicuspid pulmonary valve.
The distinction is numerical:
| Valve | Number of cusps |
|---|---|
| Normal pulmonary valve | 3 |
| Bicuspid pulmonary valve | 2 |
| Quadricuspid pulmonary valve | 4 |
A small fourth cusp or partial cusp fusion can make the anatomy difficult to interpret, particularly on limited CT datasets.
9.2 Cardiac Motion Artifact
This is perhaps the most realistic imaging pitfall.
A moving pulmonary valve can generate apparent additional lines or split a cusp into structures that resemble separate leaflets.
The solution is simple but important:
Check multiple planes.
If the same four anatomical structures are reproducible on axial, sagittal, coronal, and oblique reconstructions, a true congenital valve anomaly becomes much more likely.
9.3 Partial Cusp Fusion
QPV does not necessarily appear as four completely separated cusps.
Partial fusion may obscure one commissure and make the valve appear morphologically atypical.
This is why the diagnosis should be based on the overall three-dimensional valve architecture rather than on a simplistic requirement for four identical leaflets.
10. Which Imaging Modality Is Best?
There is no single “best” modality for every question.
| Modality | Primary role | Major strength | Main limitation |
|---|---|---|---|
| TTE | Hemodynamics, pulmonary regurgitation, RV function | Noninvasive and accessible | Pulmonary valve morphology may be limited |
| TEE | Valve anatomy | High spatial resolution | Invasive |
| ECG-gated cardiac CT | Cusp number, valve morphology, pulmonary artery anatomy | Excellent spatial resolution | Radiation and iodinated contrast |
| Cardiac MRI | Regurgitant volume, RV volume and function | Excellent quantitative functional assessment | Longer examination and lower spatial resolution than CT |
The case material emphasizes that ECG-gated cardiac CT is particularly powerful for morphological diagnosis, whereas cardiac MRI is especially valuable for quantifying pulmonary regurgitation and evaluating right ventricular volume and function.
This creates a logical multimodality workflow:
CT answers:
“What does the valve look like?”
Echocardiography answers:
“How does the valve function?”
MRI answers:
“How much regurgitation is occurring, and what has happened to the right ventricle?”
11. Treatment: Does Every QPV Require Surgery?
No.
This is perhaps the most important management principle.
The presence of four pulmonary valve cusps alone is not an indication for surgery.
Management should be based on the functional and structural consequences of the anomaly.
Observation may be appropriate when the patient has:
no relevant symptoms,
no significant pulmonary regurgitation,
no significant pulmonary stenosis,
no right ventricular enlargement or dysfunction,
no major pulmonary artery enlargement,
and no clinically important associated congenital heart disease.
Potential management strategies include:
periodic echocardiographic surveillance,
cardiac MRI for quantitative assessment,
ECG-gated CT when anatomical reassessment is necessary,
pulmonary valve surgery,
pulmonary valve replacement,
and surgical treatment of an associated pulmonary artery aneurysm or other congenital cardiac lesion.
The correct principle is therefore:
Treat the consequence, not the cusp count.
12. What Happens if Significant Pulmonary Regurgitation Is Missed?
The principal concern is chronic right ventricular volume overload.
Severe pulmonary regurgitation can progressively enlarge the right ventricle. Persistent volume overload may eventually lead to impaired right ventricular systolic function and reduced exercise capacity.
If pulmonary artery dilatation or aneurysm is also present, the patient has an additional structural abnormality requiring dedicated cardiovascular evaluation.
This is why an apparently incidental QPV can become clinically relevant even when the patient initially has no cardiac symptoms.
13. Prognosis
The prognosis of an isolated, functionally normal QPV is generally favorable.
Historical and pathological literature has not established QPV itself as a common direct cause of death, particularly when significant associated cardiac disease is absent.
However, the newer multimodality literature suggests that the simplistic statement
“QPV is always benign”
is no longer adequate.
The 2026 cohort reported moderate-or-greater pulmonary regurgitation in 69% and pulmonary artery aneurysm in 50% of its 16 identified patients, with approximately 31% undergoing surgery during follow-up. Importantly, there were no deaths during follow-up.
Again, these findings should not be extrapolated directly to the general population.
But they reinforce a clinically important concept:
The prognosis of QPV depends less on the presence of four cusps than on what those four cusps are doing.
14. The 43-Year-Old Woman: What Is the Real Diagnosis?
The most important aspect of this case is not simply the rare valve anomaly.
It is the diagnostic reasoning pathway.
The patient presented with sudden epigastric pain radiating to the back.
The first priority was therefore to exclude potentially fatal acute aortic pathology.
The CTA showed no convincing evidence of:
aortic dissection,
intramural hematoma,
penetrating atherosclerotic ulcer,
rupture,
or significant pericardial effusion.
Only after the life-threatening diagnosis had been addressed did the unexpected pulmonary valve abnormality become the focus of attention.
This sequence matters.
The QPV should not be retroactively declared the cause of the patient's abdominal and back pain simply because it was the most unusual finding on the CT.
The more defensible interpretation is that the QPV represents an incidental congenital anatomical abnormality, unless independent clinical and functional evidence demonstrates otherwise.
15. A Radiologist's Seven-Step CT Checklist
When a QPV is suspected, I recommend a structured approach.
STEP 1 — Confirm four cusps
Do not rely on a single axial image.
Use multiplanar reconstruction.
STEP 2 — Evaluate cusp morphology
Determine whether the cusps are:
equal in size,
asymmetric,
partially fused,
or associated with an unusual configuration.
STEP 3 — Look for stenosis
Assess the pulmonary valve and right ventricular outflow tract for evidence of obstructive physiology.
STEP 4 — Consider pulmonary regurgitation
CT can suggest abnormal morphology, but functional assessment should be performed with echocardiography or cardiac MRI when clinically indicated.
STEP 5 — Examine the main pulmonary artery
Look specifically for:
dilatation,
aneurysmal enlargement,
or other pulmonary arterial abnormalities.
STEP 6 — Assess the right ventricle
Look for:
RV enlargement,
remodeling,
or evidence of functional impairment.
STEP 7 — Search for associated congenital heart disease
Potential associated abnormalities include:
atrial septal defect,
ventricular septal defect,
patent ductus arteriosus,
and other congenital valvular abnormalities.
The case material similarly recommends moving from cusp confirmation to valve function, pulmonary artery size, right ventricular assessment, and associated congenital heart disease.
16. Why This Case Matters Beyond QPV
This case teaches a broader lesson about CT interpretation.
A radiologist does not simply answer the clinical question written on the examination request.
The indication tells us where to begin.
It does not tell us where to stop.
For suspected acute aortic syndrome, the aorta deserves immediate and systematic evaluation.
But once the aorta has been adequately assessed, the radiologist must continue to review the remainder of the acquired anatomy.
That includes:
heart → pulmonary artery → pulmonary valve → coronary arteries → mediastinal structures → lungs → other included anatomy
This is particularly important with modern high-resolution CT, because increasingly subtle cardiovascular abnormalities can be recognized even when they were never part of the original clinical question.
17. Key Clinical and Imaging Takeaways
| Question | Practical answer |
|---|---|
| What is QPV? | A congenital pulmonary valve anomaly with four cusps instead of three |
| Is it always symptomatic? | No; many cases are incidental |
| Is four cusps alone an indication for surgery? | No |
| What is the key CT finding? | Reproducible four-cusp morphology |
| What is the major CT pitfall? | Motion and partial-volume artifact |
| What should be assessed next? | Valve function, pulmonary artery, RV, associated CHD |
| Which modality best defines morphology? | ECG-gated cardiac CT |
| Which modality best quantifies regurgitation/RV remodeling? | Cardiac MRI |
| Major potential complication | Significant pulmonary regurgitation |
| Other important complication | Pulmonary artery dilatation/aneurysm |
| Does QPV explain acute epigastric pain automatically? | No |
| Is prognosis always benign? | Isolated, functionally normal QPV is generally favorable, but significant associated abnormalities require evaluation |
The central message is therefore simple:
Do not stop at “four cusps.”
Conclusion: In CT Interpretation, Recognition Is Only the Beginning
A quadricuspid pulmonary valve is an uncommon congenital cardiac anomaly, but modern cardiac CT makes it increasingly possible to recognize this subtle anatomical variation during routine clinical imaging.
The 43-year-old woman in this case illustrates why the finding is important.
Her sudden epigastric pain radiating to the back appropriately prompted evaluation for acute aortic syndrome. The dangerous aortic diagnoses were not identified. Instead, careful CT review revealed an unexpected four-cusp pulmonary valve.
The correct interpretation is not to sensationalize the rare finding.
It is to characterize it properly.
First, confirm that four pulmonary valve cusps are genuinely present.
Second, assess their morphology using multiplanar CT.
Third, determine whether pulmonary stenosis or regurgitation is present.
Fourth, examine the main pulmonary artery for dilatation or aneurysm.
Fifth, evaluate the right ventricle.
Finally, determine whether associated congenital heart disease exists.
The contemporary imaging perspective is therefore much more sophisticated than simply labeling QPV as either “benign” or “dangerous.”
QPV is a morphological diagnosis. Its clinical significance is determined by function and associated cardiovascular abnormalities.
And there is one final lesson from this case that extends well beyond pulmonary valve anomalies:
A good CT interpretation is not simply the ability to name an unusual finding. It is the ability to understand why the examination was performed, exclude the most dangerous diagnosis first, recognize unexpected abnormalities, and then determine whether those abnormalities actually matter to the patient.
That is where imaging interpretation becomes clinical medicine.
Medical Disclaimer
This article is intended for medical education and informational purposes only. It does not replace professional medical diagnosis, treatment, or individualized clinical decision-making. Patients with suspected cardiovascular disease or abnormal imaging findings should be evaluated by an appropriately qualified physician.
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