Congenital absence of the pericardium

Article written and reviewed by Dr Luca Moretti

Congenital absence of the pericardium, or pericardial agenesis, is a developmental anomaly in which part or all of the sac fails to form. It may involve the left side, which is more frequently described, the right side, or both. Classification should specify location, extent, and residual margins, because a generic definition of an absent pericardium does not convey functional risk.

Many extensive forms are recognized incidentally and are well tolerated. Some partial defects may instead allow a portion of the heart to herniate through a relatively rigid margin, causing compression, ischemia, or strangulation. Risk therefore does not simply increase with the amount of missing pericardium.

Diagnosis integrates cardiac position, mobility, lung interposition, and visualization of the sac by echocardiography, computed tomography, and magnetic resonance imaging. Treatment is often conservative; surgery is considered for high-risk anatomy or disabling symptoms plausibly related to the defect. Evidence derives predominantly from cases and small series, requiring caution when interpreting complication rates.

Embryology, classification, and associated anomalies

During development, the pleuropericardial membranes contribute to separating the pleural cavities from the pericardial cavity. A defect in their formation or fusion may leave a communication of variable extent. Proposed embryological explanations include premature involution of cardinal venous structures involved in supplying the membrane, with greater vulnerability of the left side. This is an interpretive model of the malformation, not a mechanism that can be demonstrated retrospectively in every patient with current clinical examinations.

The distinction between complete absence and partial absence requires terminological care. Complete may refer to absence of the entire pericardium or to complete absence of one of its lateral components; the report should make explicit which meaning is intended. An extensive left-sided defect is not necessarily equivalent to bilateral agenesis. The description should specify which segments remain present, whether there is a margin capable of incarcerating structures, and how the heart, diaphragm, pleura, and great vessels are arranged.

Partial forms include openings of different sizes and locations. The heart may remain largely within the sac while an atrial appendage or a ventricular portion protrudes beyond the margin. An opening small enough to constrict tissue but large enough to allow it to pass through may be more dangerous than a very extensive defect. This anatomical relationship explains why assessment cannot be based solely on the side involved or on a linear measurement of the opening.

Reported associated congenital heart diseases include atrial septal defects, anomalous pulmonary venous return, patent ductus arteriosus, and other malformations. Thoracic or diaphragmatic anomalies are also possible. They should be sought carefully, especially in pediatric patients and when cardiac position and echocardiographic windows make examination difficult. The presence of agenesis does not automatically explain chamber overload: a true shunt or valvular lesion may coexist and require independent treatment.

Acquired absence after surgery and traumatic pericardial rupture are distinct diagnoses. They may cause mobility or herniation, but their chronology, tissues, and risk differ from those of the congenital malformation. A history of pericardiectomy, lung resection, or trauma is therefore essential before classifying a finding as agenesis. A defect discovered during surgery should be described anatomically without assigning an unproven origin, particularly when scarring or altered tissue planes are present.

Prevalence is not precisely defined: silent forms may go undetected, whereas complicated cases are more likely to be published. The systematic review of 247 cases collected from the literature broadens the descriptive picture but is not a population cohort. Frequencies of symptoms, associated anomalies, and deaths are affected by selection and do not represent individual risks transferable to a newly identified asymptomatic patient. Rarity and heterogeneity make accurate anatomical and clinical documentation of cases particularly important.

Pathophysiology of mobility and partial defects

The pericardium helps maintain cardiac position and limit sudden displacement and distension. When an extensive segment is absent, the heart may rotate and shift toward the left hemithorax, with a more lateral and posterior apex. The change in geometry alters imaging appearances and the relationship with the chest wall without necessarily implying functional impairment. Loss of external restraint should not be confused with cardiomyopathy or true chamber dilatation.

Hypermobility may become more pronounced with posture and the cardiac cycle, producing the appearance described as a swinging heart. Traction on attachments and changes in anatomical relationships may contribute to pain or heightened awareness of the heartbeat in some patients. These mechanisms are plausible but do not prove that every symptom results from the anomaly. A substantial proportion of extensive forms remain clinically silent, suggesting that anatomical adaptation can be effective and that increased mobility does not in itself imply dangerous instability.

In limited defects, the residual margin may compress a portion that herniates through the opening. The left atrial appendage is one of the structures described, but other parts of the heart may be involved. Compression may impede local venous return, deform the myocardium, or interfere with epicardial vessels. Simple protrusion does not prove strangulation: narrowing at the neck, perfusion, function, and signs of tissue compromise must be assessed to distinguish stable anatomy from an acute complication.

Coronary compression may cause ischemia even in the absence of significant atherosclerosis. An indentation or fold of the ventricle at the margin indicates a mechanical interaction that warrants specialist assessment. If compatible symptoms are present, coronary imaging and, in selected cases, ischemia testing may clarify its significance. Not every contour abnormality is pathognomonic: the finding should be reproducible and consistent with the location of the defect, avoiding assignment of absolute prognostic value to an isolated image.

Lung interposition between the aorta and pulmonary artery or between the cardiac base and diaphragm results from spaces that are normally restricted by the sac becoming available. It is an important diagnostic clue, particularly when associated with rotation and absence of the pericardial lining. Interposed lung may also alter ultrasound transmission. Abnormal geometry may create apparent right-sided dilatation or unusual septal motion, which should be distinguished from true hemodynamic overload through appropriate acquisitions and overall assessment.

Anatomical risk stratification therefore considers extent, herniation, ventricular deformation, and coronary relationships. These are findings used in pathways proposed in the literature and imaging documents, not components of a universally validated prognostic score. Their value lies in identifying a plausible mechanism of injury. Clinical decisions should integrate symptoms, function, and operative risk, keeping an extensive unconstricted form distinct from a partial defect that exerts actual compression.

Clinical presentation, history, and physical examination

The finding may be incidental during radiography, CT, MRI, or surgery performed for other reasons. In some patients, the first clue is an echocardiogram that is difficult to interpret because of displaced windows and unusual geometry. Timely diagnosis avoids repeated investigations for presumed chamber abnormalities that result only from rotation. The finding should nevertheless be completed with an assessment sufficient to distinguish an extensive form from a partial defect and to identify any associated congenital heart disease.

Chest pain may be intermittent, stabbing, or related to position and is not necessarily exertional. Clinical series describe presentations capable of mimicking coronary disease, but this similarity does not justify omitting ischemic assessment when indicated by age, risk, or characteristics of the episode. Prolonged or severe pain, or pain associated with instability, requires consideration of a complication of the defect as well as other thoracic emergencies. Knowledge of the agenesis modifies clinical reasoning without replacing general assessment.

Postural dyspnea, sometimes more prominent in one lateral decubitus position, may reflect changes in cardiac relationships. Palpitations, a sensation of a very prominent heartbeat, and reduced exercise tolerance are additional reported presentations. These symptoms remain nonspecific and should be correlated with function, rhythm, and anatomy. Major limitation should not automatically be explained by hypermobility: anemia, respiratory disease, a shunt, valvular disease, or ventricular dysfunction may provide an independent or additional explanation.

Syncope warrants a higher level of concern, particularly when associated with pain or palpitations and a partial defect. Arrhythmias, ischemia due to compression, and unrelated causes should be considered. Electrocardiographic monitoring is selected according to the frequency and characteristics of episodes; a normal tracing between events does not resolve the question. Signs of acute compromise require an urgent pathway without waiting for elective demonstration of every anatomical detail before cardiac surgical assessment.

The physical examination may show a displaced or broader apical impulse, altered transmission of heart sounds, and changes with posture, but no finding is sufficiently specific. The electrocardiogram may show axis deviation, incomplete right bundle branch block, or poor R-wave progression, also because of the different orientation of the heart. These abnormalities do not diagnose agenesis and should not be considered benign without clinical interpretation, because true electrical or structural disease may coexist.

A targeted history reconstructs development, known heart disease, procedures, trauma, and previous imaging. In an asymptomatic adult with an incidental finding, extensive genetic screening is not automatically indicated; the presence of additional malformations may instead justify dedicated assessment. It is useful to establish which symptom prompted the examination and whether it was already present before the finding. This prevents the rare diagnosis from becoming a general explanation for new symptoms, limitations, or concerns unsupported by a documented clinical mechanism.

Multimodality diagnosis and definition of anatomical risk

Chest radiography may show leftward displacement, elongation of the cardiac silhouette, loss of the normal right cardiac border, and interposition of lung in unusual locations. The profile sometimes called the Snoopy sign is suggestive but not sufficient on its own. Patient rotation, chest-wall deformities, lung abnormalities, and other causes of cardiac displacement may mimic some findings. A radiographic suspicion should be clarified with imaging that directly or indirectly defines the sac and its relationships.

Echocardiography requires adaptation of imaging windows to the actual position of the heart. Off-axis images, apparent right-sided dilatation, unusual septal motion, and marked posterior-wall excursion may occur. Before diagnosing overload or cardiomyopathy, reliable planes should be obtained and volumes, flows, and function assessed. The examination also looks for septal defects, valvular abnormalities, and signs of herniation. Failure to visualize the pericardium directly, which is very thin under normal conditions, does not by itself prove absence.

Cardiac magnetic resonance imaging is particularly useful for confirming anatomy and studying dynamics. It combines assessment of the pericardial lining, fat distribution, interposed lung, and cardiac motion. In patients with little adipose tissue, distinguishing the pericardial layer may be difficult even without a defect; several concordant signs are therefore needed. Cine acquisitions allow assessment of protrusions and deformation and distinction of hypermobility from dysfunction. The examination should explicitly state the observable extent and any residual margins.

Cardiac CT provides high spatial resolution for margins, interposed lung, and relationships with the coronary arteries and great vessels. An appropriate protocol can clarify compression of a vessel or narrowing of a herniated structure. Choice between CT and MRI depends on the clinical question, availability, and the patient's condition, taking radiation and contrast into account. An already available chest scan may contain decisive information and should be reviewed before repeating an examination that would add no concrete benefit.

Warning findings include herniation with narrowing, myocardial folding or indentation at the defect margin, coronary compression, and ischemia consistent with the defect. If ischemic suspicion warrants it and the patient is stable, a selected perfusion test may contribute to the decision. This does not mean performing a stress test in every asymptomatic patient. In acute presentations, anatomical demonstration of compromise and surgical assessment take priority over elective functional testing.

The differential diagnosis includes acquired defects, dextroposition or levoposition due to pulmonary disease, chest-wall deformities, and other congenital anomalies. A prominent cardiac portion may mimic a mass, while rotation can alter interpretation of chamber volumes. Integration of imaging techniques avoids basing the diagnosis on a single sign and permits a description useful for treatment. Diagnostic pneumothorax and other historical invasive maneuvers are unnecessary: modern imaging allows much safer definition of anatomical relationships.

Conservative treatment and indications for correction

In extensive asymptomatic forms, without compression or other concerning features, management is frequently conservative. There is no need to reconstruct the pericardium solely because it is absent, nor is there a pharmacological therapy capable of restoring it. The decision requires a sufficiently secure anatomical diagnosis and assessment of associated congenital heart disease. Observation should not automatically be extended to a poorly defined partial defect, because absence of symptoms at the time of examination does not by itself describe the risk posed by the residual margin.

In partial defects, herniation, coronary compression, myocardial compromise, or attributable symptoms may favor surgery. Prophylactic intervention in an asymptomatic patient is discussed when the anatomy appears susceptible to incarceration, but evidence is limited and does not support a single rule for every opening. The decision should be shared by specialists experienced in imaging and cardiac surgery, considering expected benefits, technical feasibility, and individual risk. The report should enable this assessment rather than being limited to a generic diagnostic label.

Pericardioplasty reconstructs a barrier using appropriate tissue or materials, with the aim of preventing protrusion and stabilizing problematic relationships. In other anatomical configurations, enlarging the defect or removing a constricting margin may be preferable, transforming a dangerous opening into a broad communication. These approaches address different mechanisms and are not interchangeable without anatomical assessment. The proximity of the phrenic nerve, coronary arteries, and herniated structures requires careful planning.

Complicated herniation, with suspected ischemia or strangulation, is an urgent problem. Treatment aims to release the compromised structure and correct the mechanism while arrhythmias and circulatory failure are managed. Antianginal therapy does not remove significant mechanical compression and should not delay surgical assessment. If other malformations require correction, the operative plan should consider how changes in cardiac volumes and position may interact with the pericardial defect.

Disabling symptoms in the absence of a clear anatomical complication require a more cautious discussion. Surgery may be considered in selected cases, but the probability of benefit depends on the plausibility of a relationship with hypermobility or traction. Alternative causes should be assessed and symptom severity documented before surgery. Published experience does not allow a promise that pain or palpitations will resolve, particularly when rhythm, perfusion, and function are normal.

Management of physical activity is individualized. A well-tolerated extensive form does not automatically require a general prohibition, whereas symptoms, ischemia, or high-risk anatomy may require restrictions until the management pathway is defined. Anticoagulation, antibiotic prophylaxis, or antiarrhythmic therapy are not indicated by agenesis alone; they are prescribed for appropriate concomitant conditions. The patient should receive a clear description of the anatomy and the reasons for observation or intervention so that future decisions are not based merely on the label of a rare malformation.

Complications, prognosis, and follow-up

Prognosis is often good in complete or extensive forms without complications. Reports of sudden death mainly concern selected situations and do not define an annual risk for all affected individuals. Reviews of published cases overrepresent unusual and severe presentations and include patients with other diseases. It is therefore incorrect to turn the proportion of deaths collected in the literature into an individual probability for an asymptomatic adult with favorable anatomy and preserved function.

The most concerning complications are incarceration and strangulation of herniated structures, coronary compression, and ischemia, with possible electrical or circulatory instability. Their plausibility depends on the relationship between the opening and tissue, not solely on the extent of the defect. Persistent pain, syncope, or new ischemic signs require prompt reassessment. A previously reassuring examination does not remove the need to investigate a clinical change, particularly if the morphology was partial or incompletely defined.

Increased mobility may make anatomical relationships unusual during trauma or thoracic procedures. The malformation should be reported to those planning procedures because cardiac position and absence of the normal barrier influence access and protection of structures. This does not imply that every procedure is contraindicated. Clear anatomical documentation reduces intraoperative surprises and allows management to be adapted to the actual condition, distinguishing congenital forms from surgically created defects.

Clinical follow-up is proportionate to the type of defect, symptoms, and associated heart disease. There is no imaging interval validated for everyone. In stable, well-characterized cases, non-intensive surveillance may be sufficient, whereas uncertain or potentially compressive findings require closer follow-up. Repeated CT without a new clinical question should be avoided when other modalities provide adequate answers. The aim is to identify changes relevant to management, not to periodically demonstrate an already defined malformation.

After surgical correction, cardiac position and function, absence of new compression, and the course of symptoms are assessed. Pleural complications, bleeding, nerve injury, and possible effects of reconstructive material should be considered. Follow-up is adapted to the technique and to any associated repairs. Persistent pain does not automatically demonstrate anatomical failure: postoperative recovery, musculoskeletal disorders, ischemia, and other conditions that may have contributed to the initial presentation should be distinguished.

Continuity of care requires the patient to have access to the complete report and, when useful, the key images. Communication should specify side, extent, any risk features, and the reason for the chosen strategy. New dyspnea, syncope, significant pain, or sustained palpitations require assessment consistent with their severity, without automatic reassurance or indiscriminate attribution to agenesis. In the absence of problems, the aim is to maintain a life compatible with actual function while avoiding medicalization and restrictions unsupported by anatomy or the available evidence.

References
1. Schulz-Menger J et al. 2025 ESC Guidelines for the management of myocarditis and pericarditis. European Heart Journal. 2025;46(40):3952-4041.
2. Klein AL et al. Pericardial Diseases: International Position Statement on New Concepts and Advances in Multimodality Cardiac Imaging. JACC: Cardiovascular Imaging. 2024;17(8):937-988.
3. Adler Y et al. 2015 ESC Guidelines for the diagnosis and management of pericardial diseases: The Task Force for the Diagnosis and Management of Pericardial Diseases of the European Society of Cardiology (ESC). Endorsed by: The European Association for Cardio-Thoracic Surgery (EACTS). European Heart Journal. 2015;36(42):2921-2964.
4. Parmar YJ, Shah AB, Poon M, Kronzon I. Congenital Abnormalities of the Pericardium. Cardiology Clinics. 2017;35(4):601-614.
5. Shah AB, Kronzon I. Congenital defects of the pericardium: a review. European Heart Journal - Cardiovascular Imaging. 2015;16(8):821-827.
6. Khayata M et al. Case series, contemporary review and imaging guided diagnostic and management approach of congenital pericardial defects. Open Heart. 2020;7(1):e001103.
7. Gatzoulis MA et al. Isolated congenital absence of the pericardium: clinical presentation, diagnosis, and management. Annals of Thoracic Surgery. 2000;69(4):1209-1215.
8. Xu B, Betancor J, Asher C, Rosario A, Klein A. Congenital Absence of the Pericardium: A Systematic Approach to Diagnosis and Management. Cardiology. 2017;136(4):270-278.
9. Marzullo R et al. Congenital Absence of Pericardium: The Swinging Heart. Journal of Imaging. 2024;10(8):199.
10. Bassareo PP et al. Congenital Absence of Pericardium: The Largest Systematic Review in the Field on 247 Worldwide Cases (1977-Now). Congenital Heart Disease. 2023;18(6):595-610.
11. Cosyns B et al. European Association of Cardiovascular Imaging (EACVI) position paper: Multimodality imaging in pericardial disease. European Heart Journal - Cardiovascular Imaging. 2015;16(1):12-31.
12. Roberts WC. Pericardial heart disease: its morphologic features and its causes. Proceedings (Baylor University Medical Center). 2005;18(1):38-55.