Partial Agenesis of the Pericardium: A Rare Cause of Palpitations in a Young Adult

ABSTRACT

Partial agenesis of the pericardium is a rare congenital anomaly in which part of the fibroelastic pericardial membrane is absent. Many patients remain asymptomatic, while others present with nonspecific symptoms such as palpitations, chest pain, or dyspnea. The rarity and variable presentation often delay diagnosis. We report a case of a male in his 30s who presented with intermittent palpitations, more pronounced during moderate exertion. Laboratory tests were largely unremarkable except for elevated triglycerides. Electrocardiogram (ECG) showed sinus rhythm with incomplete right bundle branch block. Chest radiography demonstrated leftward cardiac displacement and lucent areas suggestive of absent pericardium. Transthoracic echocardiography revealed normal ventricular function with paradoxical septal motion. Cardiac computed tomography confirmed partial absence of the pericardium, sparing a thin rim at the right antero‐inferior aspect, with interposition of lung tissue between the aorta and pulmonary artery. A patient presenting with palpitations as the only symptom highlights the importance to consider pericardial agenesis in the differential diagnosis of unexplained palpitations. Awareness of its characteristic imaging features can prevent misdiagnosis, guide appropriate management, and reduce the risk of complications such as cardiac herniation.

Key Clinical Message

Partial pericardial agenesis, though rare and often asymptomatic, can present with palpitations and subtle cardiac displacement. Awareness of its imaging features on computed tomography and magnetic resonance imaging is essential for accurate diagnosis, appropriate management, and prevention of complications such as cardiac herniation.

Abbreviations

CMR

Cardiac Magnetic resonance

CT

Computed tomography

ECG

Electrocardiogram

MRI

Magnetic resonance imaging

1. Case Report

A 34‐year‐old male soldier presented to the cardiology department with a 20–30‐day history of intermittent palpitation. It was more pronounced after moderate physical exertion like his daily exercise, which previously did not trouble him. He described the feeling as a sense of self‐awareness of forceful heart pounding, associated with a sense of panic. The episodes were no more than 30 to 40 s and resolved spontaneously after some rest without the need for any external intervention. The patient had no problems performing his daily activities that required no extra effort.

Notably, the patient had a few similar episodes of palpitations about 7–8 years ago during military training, without any other associated symptoms at the time. This episode resolved spontaneously, and the patient did not seek medical attention. His past medical history was unremarkable for any cardiovascular or thyroid disorders. Family history was insignificant for any coronary artery disease or sudden cardiac death. The patient seldom drank coffee, was a non‐smoker, and did not drink alcohol. His vital parameters were within normal limits at the time of presentation, and clinical assessment was insignificant.

1.1. Initial Investigations and Differential Diagnosis

The patient underwent a series of tests. The initial laboratory results were normal except for the triglyceride level of 730 mg per deciliter (mg/dl), which was significantly raised (Normal reference range: < 150 mg/dL>).

Electrocardiogram of the heart showed a sinus rhythm and incomplete right bundle branch block, evident by the RSR’ pattern in leads V2‐V4, and a normal QRS duration. (Figure 1). Chest X‐ray showed obscuration of the right border of the heart and leftward shift of the cardiac silhouette. Notably, there is a presence of a lucent area between both the aorta and pulmonary artery, and between the lower border of the heart and the left hemidiaphragm. The elongation of the left cardiac silhouette can also be noted (Figure 2). 24‐h ambulatory Holter monitoring showed sinus bradycardia with an average day time heart rate of 54 beats per minute and an average night time heart rate of 46 beats per minute. The maximum heart rate was 103 beats per minute and minimum heart rate of 38 beats per minute. A total of 17 ventricular ectopic beats were noted which accounted for 0.03% of total beats. The Holter recording did not reveal any sustained supraventricular or ventricular arrhythmias. Given the brief and intermittent nature of the patient's palpitations (30–40 s, self‐resolving), and the lack of a symptom diary or real‐time correlation during monitoring, no arrhythmic events were directly captured during symptomatic episodes. The very low ventricular ectopic burden (0.03%) suggests that the sensations were likely related to heightened awareness of cardiac motion or transient mechanical effects rather than frequent or complex arrhythmias.

FIGURE 1.

Electrocardiogram of the patient showing an incomplete right bundle branch.

FIGURE 2.

Chest X‐ray showing lucent area between the aorta and pulmonary artery (white arrow), and lucent area between the lower border of the heart and left hemidiaphragm (black arrow).

Transthoracic echocardiography was performed, which revealed normal left ventricular systolic and diastolic function with an ejection fraction of 64%. The heart appeared to be displaced towards the left side, and a paradoxical movement of the interventricular septum was also seen. The right atrium and right ventricle looked more prominent in the apical view, likely due to pseudodilation caused by the abnormal orientation of the heart (Figure 3). NT‐proBNP level of patient was 610 pg/mL (Normal reference level: < 300 pg/mL).

FIGURE 3.

Transthoracic echocardiography of the patient showing heart chambers in parasternal long axis view and apical four chamber view obtained from different acoustic windows.

No exercise treadmill test or stress testing was performed. The patient's symptoms were brief, self‐limiting, and not accompanied by syncope, chest pain, dyspnea on maximal exertion, or features suggestive of inducible ischemia or high‐grade arrhythmias. With normal left ventricular function (ejection fraction 64%) on echocardiography and characteristic imaging findings already confirming the diagnosis, additional stress testing was not deemed necessary.

1.2. Diagnostic Imaging and Differential Diagnosis

Further evaluation with cardiac CT, performed before and after intravenous contrast administration, confirmed partial agenesis of the pericardium (Figure 4). The CT showed the near complete absence of pericardium, except for a thin pericardium noted near the right ventricular region of the heart. Lung tissue was also noted between the aorta and the pulmonary artery. The cardiac chambers were normal in size and morphology, with no septal defects noted. CT also revealed rotation of the cardiac axis towards the left side.

FIGURE 4.

(A, B): Axial section of cardiac CT at the level of the aorta (A) and at the mid‐ventricular level (B) showing non‐visualization of the pericardium involving almost all of the heart and visualization of lung tissue between the aorta and pulmonary artery (green and white arrow), Panel B also demonstrates leftward deviation of heart.

A similar pattern of clinical and imaging findings can also be observed in other structural or functional cardiac abnormalities, such as arrhythmogenic right ventricular cardiomyopathy or dilated cardiomyopathy. However, the patient had no history of syncope, exercise intolerance, or family history of sudden cardiac death. Additionally, echocardiography and cardiac CT revealed no structural defects or ventricular dysfunction, effectively ruling out these conditions.

2. Treatment and Follow Up

The patient was advised to take metoprolol, a cardioselective beta‐blocker that has improved his symptoms. The episodes of palpitation have subsided, and the patient has been able to perform the activities that previously provoked his symptoms. The patient was advised to follow up in 6 months [1, 2].

3. Discussion

The pericardium develops from the fusion of the pleuropericardial membranes in embryonic life. Failure of the fusion leads to partial or complete pericardial agenesis [3, 4]. The incidence is less than 1 in 10,000 [5] and is more common in males [4], as in our case. As many cases remain asymptomatic and identified incidentally, the described incidence and gender distribution may underestimate the true prevalence [6].

Agenesis can cause excess heart motility, contacting nearby structures and potentially triggering extra systoles and arrhythmias. This mechanism could account for the intermittent palpitations that the patient was experiencing during exertion. In this case, the absence of sustained arrhythmias on Holter monitoring aligns with a primarily mechanical etiology for the palpitations, likely from excessive cardiac mobility and paradoxical septal motion rather than primary arrhythmogenesis.

The partial form of agenesis is linked with increased risk of complications, including atrial septal defect, type A aortic dissection, and patent ductus arteriosus. It has also been reported in patients with Marfan syndrome, diaphragmatic hernia, VACTERL (Vertebrae‐Anus‐Cardiac‐Trachea‐Esophagus‐Renal, Limb) syndrome, and Pallister‐Killian syndrome [7, 8]. Due to the rarity of its incidence, it is difficult to decide whether the association is true or spurious.

The clinical course is highly variable, ranging from asymptomatic to symptoms like chest pain, palpitations, and shortness of breath. Patients with partial agenesis report more symptoms than patients with complete agenesis, including trepopnea [9]. The patient presented primarily with exertional palpitations, which have been rarely reported as the sole initial symptom. The mechanism is thought to involve excessive mobility of the heart within the thoracic cavity, predisposing to arrhythmias. The incidental markedly elevated triglycerides (730 mg/dL) were unrelated to the partial pericardial agenesis and were treated with fenofibrate 160 mg once daily for 6 weeks, along with lifestyle counseling, as no secondary causes were identified.

The diagnosis often presents difficulty. Electrocardiogram in patients with partial agenesis can be essentially normal, in contrast to patients with complete agenesis, who might reveal right axis deviation and right bundle branch block. In a leftward‐displaced heart, poor R‐wave progression is often noted in precordial leads, and electrical alternans of the QRS complex is also seen, which might be due to excess motility of the heart. This is in contrast to the finding in our patient, whose ECG revealed incomplete right bundle branch block in the partial form of pericardial agenesis. A chest X‐ray is also helpful in identifying some peculiarities that might aid in the diagnosis. Visualization of the lucent area between the aorta and the main pulmonary artery, or in between the heart's underside and the diaphragm, as in our case, can be done, reflecting the absence of pericardium in the respective area. Leftward rotation of the heart and elongation of the left cardiac silhouette, described as “Snoopy sign” in a few literatures, can also be seen, which might prompt further investigations [7, 9]. The Snoopy sign can also be appreciated on the patient's chest X‐ray.

The confirmation of diagnosis typically requires advanced imaging modalities such as cardiac magnetic resonance imaging (CMR) or cardiac computed tomography (CCT), which also help to exclude associated anomalies and complications. An ECG‐gated CCT with contrast administration can clearly delineate the pericardium, which appears bright and well defined against the low attenuation of adipose tissue. Cardiac CT of the patient demonstrated near‐complete absence of the pericardium with interposition of lung tissue, which was diagnostic. CT also revealed leftward deviation of the heart, whereas normally approximately two‐thirds of the heart is present on the left side and the rest on the right. Although CMR is regarded as the gold standard, it was not pursued in this patient, as CCT provided sufficient diagnostic clarity and additional imaging would have imposed an unnecessary financial burden.

The management depends upon the extent of agenesis and the associated complications and anomalies. In partial agenesis, such defects carry a higher risk of herniation and cardiac strangulation whereas in cases of complete pericardial agenesis, such defects have apparently less lethal complications. As such, patients with complete agenesis are often asymptomatic and require no treatment except for long‐term follow‐up [10, 11]. The treatment of symptomatic patients with a partial defect can consist of symptomatic management, patch closure of the defect, and enlargement of the defect for incarceration prevention. Complications are more common in the partial form of the defect. Herniation of the heart, which is a likely complication, can be managed surgically by pericardiectomy or pericardioplasty. The patient had palpitations as the sole symptom, which improved with medical management; therefore, the surgical procedure was deferred on clinical grounds. However, the optimal management of asymptomatic and uncomplicated defects remains debated at present [9].

4. Conclusions

The case highlights the importance of recognizing partial pericardial agenesis in patients with unexplained palpitations and utilizing appropriate imaging for diagnosis. Symptomatic management, close follow‐up, and awareness of potential complications are essential. Further studies are needed to establish standardized strategies for monitoring and managing this rare congenital anomaly.

Author Contributions

Parag Karki: conceptualization, methodology, project administration, writing – original draft, writing – review and editing. Sunischit Chandra Neupane: conceptualization, project administration, resources, writing – original draft, writing – review and editing. Sulav Neupane: conceptualization, methodology, resources, writing – original draft, writing – review and editing. Nishan Uprety: conceptualization, data curation, methodology, project administration, resources, supervision, writing – original draft, writing – review and editing.

Funding

The authors have nothing to report.

Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

Data sharing does not apply to this article, as no datasets were generated or analyzed during the current study.