- Donate
- Understanding Rare Disease
- Living with a Rare Disease
- Community Support
- Advancing Research
- Driving Policy
- Get Involved
- Rare Disease News
- Resource Library
- About Us
- For Clinicians & Researchers
- For Patient Organizations
Last updated: 1/16/2025
Years published: 1986, 1994, 2003, 2025
NORD gratefully acknowledges Gioconda Alyea, MD (FMG), MS, National Organization for Rare Disorders, for assistance in the preparation of this report.
Cor triatriatum is an extremely rare congenital (present at birth) heart defect where a thin membrane divides one of the heart upper chambers (atrium) into two parts resulting in three atrium chambers instead of two.
Normally, the human heart has four chambers of which two are the atria. These two are separated from each other by a partition (septum) called the atrial septum. The other two chambers, known as ventricles, are also separated by a septum.
Cor triatriatum can be classified into 2 subtypes:
Symptoms, severity and onset vary based on the affected chamber and the size and number of openings in the membrane.
Treatment includes surgical correction of the associated defects.
Cor triatriatum is a rare heart condition where a thin membrane divides one of the upper chambers of the heart (atrium), disrupting normal blood flow. Symptoms, severity and onset vary based on the affected chamber and the size and number of openings in the membrane.
Signs and symptoms often appear early in life and may include:
Based on the affected chamber the specific signs and symptoms may include:
Cor triatriatum sinister
This condition affects the left atrium and is classified based on the size and number of openings in the membrane:
In infants and children smaller or no openings are more common, leading to early symptoms like rapid breathing, fluid retention and heart enlargement. In adults, larger openings are more typical and symptoms may not appear until the membrane thickens or calcifies, narrowing the opening and worsening blood flow.
As the condition progresses the symptoms may include:
Cor triatriatum dexter
This form affects the right atrium and symptoms depend on the degree of obstruction:
Across both forms, symptoms vary based on the size of the membrane opening and any related heart conditions. Common signs of both subtypes may include:
A doctor may detect a heart murmur during a routine checkup or identify the condition during heart imaging performed for another reason. Diagnostic tests can confirm the presence of the membrane and its effects on blood flow.
Depending on the severity of the obstruction and other complications the following signs and symptoms may include:
Cor triatriatum is a rare heart condition where a thin membrane divides one of the heart’s upper chambers (atria) into two compartments. It can affect the left atrium (cor triatriatum sinistrum) or the right atrium (cor triatriatum dextrum).
In cor triatriatum sinister, a membrane divides the left atrium, likely due to incomplete incorporation of the pulmonary veins during early heart development (malincorporation theory). This leaves a narrow opening and disrupts normal blood flow.
In cor triatriatum dexter, a membrane divides the right atrium due to incomplete regression of the right sinus valve during fetal development. Normally, a fetal structure called the Chiari network disappears before birth. If it persists with small openings and a web-like appearance, it forms cor triatriatum dexter.
Both forms arise from abnormal fetal heart development and disrupt normal blood flow through the heart.
Cor triatriatum is an extremely rare congenital heart defect that affects males and females equally. In the United States, it accounts for only 0.1% to 0.4% of all infants born with congenital heart disease.
Several imaging studies are used to diagnose and evaluate cor triatriatum:
For people with cor triatriatum, treatment depends on symptoms:
When the affected person does not have symptoms, no specific treatment is required but regular monitoring is recommended to detect any new symptoms. Symptomatic people need surgical treatment. Preoperative medical treatment may include stabilizing fluid overload and pulmonary edema and managing atrial fibrillation with rate and rhythm control and anticoagulation therapy, as well as preventing complications like deep vein thrombosis, pulmonary embolism and stroke using anticoagulation medications.
The American Heart Association advises that adults with cor triatriatum should be screened for other congenital defects, especially atrial sept defects, ventricular sept defects, and pulmonary vein abnormalities. Surgical repair is indicated for those with symptoms of pulmonary vein obstruction or a high-pressure gradient across the restrictive membrane.
Surgery is the definitive treatment for cor triatriatum and involves removing the abnormal membrane in the atrium:
Post-surgery and echocardiography are used to confirm the success of the repair. The 10-year survival rate after surgery is about 83%, though people with additional heart defects may face higher risks and lower survival rates.
Because people with cor triatriatum are susceptible to bacterial infection of the membranes that surround the heart (endocarditis), any respiratory infection should be treated vigorously and early. Affected individuals should also be given antibiotics before invasive dental procedures (i.e., root canal or extractions) or other surgical procedures to help prevent potentially life-threatening infections.
Cor triatriatum is a rare but treatable condition. With timely diagnosis, proper management, and surgical intervention when needed, many patients achieve good outcomes. Regular follow-ups and tailored care are essential for ensuring long-term health and quality of life.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:
https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/
For information about clinical trials sponsored by private sources, contact: www.centerwatch.com
For information about clinical trials conducted in Europe, contact: https://www.clinicaltrialsregister.eu/
Ather B, Meredith A, Siddiqui WJ. Cor Triatriatum. [Updated 2024 Jul 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534243/ Accessed Jan 8, 2025.
Shirani J. Cor Triatriatum. December 18, 2020. Medscape Reference. https://emedicine.medscape.com/article/154168-overview Accessed Jan 8, 2025.
NORD strives to open new assistance programs as funding allows. If we don’t have a program for you now, please continue to check back with us.
NORD and MedicAlert Foundation have teamed up on a new program to provide protection to rare disease patients in emergency situations.
Learn more https://rarediseases.org/patient-assistance-programs/medicalert-assistance-program/Ensuring that patients and caregivers are armed with the tools they need to live their best lives while managing their rare condition is a vital part of NORD’s mission.
Learn more https://rarediseases.org/patient-assistance-programs/rare-disease-educational-support/This first-of-its-kind assistance program is designed for caregivers of a child or adult diagnosed with a rare disorder.
Learn more https://rarediseases.org/patient-assistance-programs/caregiver-respite/The information provided on this page is for informational purposes only. The National Organization for Rare Disorders (NORD) does not endorse the information presented. The content has been gathered in partnership with the MONDO Disease Ontology. Please consult with a healthcare professional for medical advice and treatment.
Show Your Stripes® this Rare Disease Day® with a gift to NORD
Your donation will help more than 30 million Americans with a rare disease navigate their diagnosis, receive financial assistance, and access the care and support they deserve. Make your tax-deductible gift today!