Position-triggered embolic events in cardiac myxoma: a description of two cases

Introduction

Cardiac myxomas are the most common type of primary benign neoplasms in the heart (1), and are more prevalent in females than males; the incidence in females has been reported to be approximately three times that in males (2,3). The average age of patients with cardiac myxoma is 40–60 years (1). Cardiac myxomas are commonly located in the left atrium, especially at the mitral annulus or near the interatrial septum (4). Most cardiac myxoma cases (i.e., around 90%) are sporadic, and only 5–10% of cases demonstrate familial inheritance patterns, primarily manifesting as the Carney complex (CNC) (5,6).

The clinical presentations of cardiac myxomas are non-specific, but primarily include cardiac hemodynamic disturbances, arterial embolism, and systemic manifestations. Cardiac myxomas vary significantly in size and shape, with diameters ranging from a few millimeters to several centimeters. Most cardiac myxomas are attached to the endocardium via a stalk, but some cases exhibit diffuse adhesion growth. The tumor surfaces may appear smooth or slightly irregular, and thrombotic attachments are observed occasionally. Myxomas are typically soft with a loosely organized structure, rendering them susceptible to detachment under the impact of blood flow, which may lead to embolic complications. Large myxomas can impede blood flow, potentially obstructing the pulmonary veins, mitral valve orifice, superior vena cava, or tricuspid valve orifice. Obstruction symptoms often occur when patients change their body positions (7).

Echocardiography is the preferred imaging examination for diagnosing myxomas, as it can effectively delineate the tumor’s shape, size, site of attachment, and movement between the atria and ventricles (8,9). Due to the risk of severe complications associated with cardiac myxomas, immediate surgical intervention is necessary following diagnosis (10).

This article describes two cases of cardiac myxoma patients and reviews the related literature. Notably, both patients experienced tumor detachment in the hospital when changing their body positions.

Case presentation

Case report 1

An 18-year-old male with no underlying diseases attended the Cardiology Outpatient Clinic of Shiyan Taihe Hospital complaining of chest discomfort. A physical examination revealed no suspicious signs. Cardiac auscultation revealed no pathological murmurs. Electrocardiogram showed sinus rhythm. The routine laboratory examination results showed no abnormalities.

Transthoracic echocardiography (TTE) revealed a moderately echogenic mass, approximately 86×65×49 mm in size, with a broad base attached to the lateral wall of the right ventricle (Figure 1A). One end of the mass swung back and forth across the tricuspid valve with the cardiac cycle, while the other end approached the right ventricular outflow tract. During the echocardiographic examination, the patient experienced an episode of chest discomfort and dyspnea when transitioning from a left lateral decubitus position to a supine position, and his heart rate increased from 93 to 117 beats per minute in this process. The echocardiographer suspected that the mass had detached, potentially causing a pulmonary artery embolism. Thus, the examination was immediately halted, and the patient was fast-tracked following the emergency protocol. Pulmonary artery computed tomography angiography (CTA) revealed a thrombotic occlusion in the right lower pulmonary artery (Figure 1B). The preoperative electrocardiogram showed an incomplete right bundle branch block (RBBB) (Figure 1C).

Figure 1 Imaging scans and electrocardiogram results of Case 1. (A) The TTE scan showed a huge mass floating in the right ventricle. (B) The CTA scan showed a thrombotic occlusion in the right lower pulmonary artery. (C) The electrocardiogram results showed an incomplete right bundle branch block. TTE, transthoracic echocardiography; CTA, computed tomography angiography.

The patient underwent emergency surgery to excise the occupying mass in the right ventricle and relieve the pulmonary artery thrombus (Figure 2A,2B). The pathological examination results confirmed that the right ventricular mass was a myxoma, and the pulmonary artery thrombus was a myxoma thrombus (Figure 2C,2D). The immunohistochemistry results were positive for CD31, CD34, ERG, and Calretinin (CR).

Figure 2 Macroscopic images and postoperative pathological sections of Case 1. (A) Macroscopic image of myxoma removed from the right ventricle. (B) Macroscopic image of myxoma thrombus removed from the right lower pulmonary artery. (C) Pathological sections of the tumor taken from the right ventricle. (D) Pathological sections of the emboli taken from the right lower pulmonary artery, which had microscopic findings identical with those of the cardiac myxoma (hematoxylin and eosin, ×200).

The patient was routinely followed up for one year after discharge, and no recurrence of myxoma was detected by echocardiography.

Case report 2

A 62-year-old male with a longstanding history of hypertension presented at our Cardiology Outpatient Department, complaining of palpitations for a week. His blood pressure was 159/93 mmHg. A distinctive plop sound was audible in the mitral valve auscultation area. The electrocardiogram showed sinus rhythm. The routine laboratory examination results revealed no significant abnormalities.

The TTE examination showed a mass within the left atrium, approximately 82 mm × 42 mm × 29 mm in size, with a loose surface texture, anchored by a pedicle to the midsection of the interatrial septum (Figure 3A). This mass demonstrated dynamic movement through the mitral valve orifice following the cardiac cycle. This patient was initially scheduled for surgical excision of the left atrial mass the day after admission. However, on the evening of his admission to hospital, he unexpectedly suffered from dizziness and intense abdominal pain. This occurred when he moved from lying down in the bed to standing up, changing from a supine posture to an upright posture.

Figure 3 Imaging scans and electrocardiogram results of Case 2. (A) The first echocardiographic image revealed a huge mass (82 mm × 42 mm × 29 mm). (B) The second echocardiographic image revealed that the size of the mass was decreasing (45 mm × 30 mm × 22 mm). (C) The abdominal aortic Doppler ultrasound scan showed a thrombus in the abdominal aorta. (D) The electrocardiogram results showed an ST-segment elevation (V2–5). SMA, superior mesenteric artery; AAO, abdominal aorta.

Echocardiography showed a significant reduction in the size of the left atrial mass, which now measured about 45 mm × 30 mm × 22 mm (Figure 3B). Abdominal aortic Doppler ultrasound identified a thrombus in the abdominal aorta (Figure 3C). The electrocardiogram showed alterations in the ST-segment, with a dome-shaped elevation of 0.4 mV in leads V2–5 (Figure 3D). Magnetic resonance imaging of the brain showed multiple foci of high signal on diffusion weighted imaging (DWI) in the left temporal, parietal, and occipital lobes, bilateral basal ganglia, and the centrum semiovale leading to a diagnosis of multiple acute cerebral infarction (Figure 4A). Aortic CTA showed a mass in the left atrium, and the formation of thrombi in the distal segment of the abdominal aorta, bilateral common iliac arteries, internal and external iliac arteries, proximal segments of the inferior mesenteric artery, and proximal segments of the femoral arteries, coupled with bilateral renal infarctions (Figure 4B-4D).

Figure 4 Imaging scans of Case 2. (A) Multiple foci of high signal on DWI seen in the left occipital lobe and right basal ganglia. (B) A three-dimensional modeling image of aortic CTA showing the formation of thrombi in the distal segment of the abdominal aorta, bilateral common iliac arteries, internal and external iliac arteries, proximal segments of the inferior mesenteric artery, and proximal segments of the femoral arteries. (C) Aortic CTA showing left renal infarction. (D) Aortic CTA showing right renal infarction. DWI, diffusion weighted imaging; CTA, computed tomography angiography.

The routine laboratory examination results showed that the patient’s myoglobin concentration exceeded 1,000.0 ng/L, increased cardiac troponin I of 15.02 µg/L, elevated creatine kinase isoenzyme of 573 IU/L, and increased creatinine of 171.9 µmol/L. These results suggested the embolization of the left atrial mass, which can lead to widespread systemic organ embolism.

The patient underwent an emergency percutaneous thrombectomy of the abdominal aorta (Figure 5A). A histopathological examination of the surgical specimen confirmed the diagnosis of a myxoma thrombus (Figure 5B). Follow-up medical treatments included anticoagulation therapy, thrombolysis, continuous renal replacement therapy, anti-hypertensive treatment, and fluid resuscitation, which facilitated the normalization of the electrocardiographic findings and ameliorated renal function. Two weeks later, the patient underwent excision of the left atrial mass, and histopathology of the excised mass revealed a hemorrhagic myxoma (Figure 5C,5D). The immunohistochemistry results were positive for vimentin, CD34, and CR.

Figure 5 Postoperative pathological sections from Case 2. (A) Macroscopic image of the myxoma thrombus removed from the abdominal aorta. (B) Pathological sections of the emboli taken from the abdominal aorta. (C) Macroscopic image of the myxoma removed from the left atrium. (D) Pathological sections of the tumor taken from the left atrium, which had microscopic findings identical with those of the embolus (hematoxylin and eosin, ×200).

At the six-month follow up after discharge, no significant sequelae that could be attributed to thromboembolism were observed.

All procedures performed in this study were in accordance with the ethical standards of the Ethics Committee of Shiyan Taihe Hospital (No. 2024KS68) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patients for publication of this article and accompanying images. Copies of the written consent forms are available for review by the editorial office of this journal.

Discussion

Primary cardiac tumors are rare clinical entities, with an incidence of approximately 1,380 cases per 100 million individuals (11). Among these cases, about 75% are benign tumors, and nearly half are cardiac myxomas (12). Myxomas occur more frequently in adults, with the peak incidence generally reported in the thirty to sixth decades of life (1); however, they can occur in individuals of all ages (13). Myxomas are more prevalent in females than males, and some studies have reported a female-to-male ratio of approximately 3:1 (2,3).

In the two cases we reported, both patients were male, and one patient was aged 18 years, and the other was aged 66 years. The incidence of cardiac myxomas is also reported to be higher in certain individuals, particularly those with genetic predispositions such as the CNC (6). Myxomas can occur in any cardiac region, but they predominantly occur in the left atrium (75% of cases occur in the left atrium) (1). More specifically, myxomas most commonly occur in the left atrial side of the fossa ovalis on the interatrial septum, but may also occur in the right atrium (15–20%), and right and left ventricles (3–4%) (14). There have been occasional reports of myxomas in locations such as the mitral valve, aortic valve, inferior vena cava, and pulmonary vessels (15).

Cardiac myxomas are intriguing because of their diverse clinical manifestations. Symptoms depend on the size, location, and mobility of the tumor. While often asymptomatic, patients can present with diverse symptoms ranging from subtle constitutional signs to severe, life-threatening complications like embolic strokes. Common symptoms include breathing difficulties, heart palpitations, fainting, and chest pain (16). Such variability in the presentation of symptoms leads to diagnostic challenges; however, a diagnosis of myxomas should be considered, especially in cases of unexplained embolic events.

Debate continues as to the histogenesis of cardiac myxomas, but existing research suggests that myxomas may originate from subendothelial cells or pluripotent mesenchymal stem cells, which are capable of neural and endothelial differentiation (17). In pathological terms, cardiac myxomas are categorized as Type I or Type II. Type I myxomas have an irregular surface, a loose internal structure, and a softer consistency. While Type II myxomas have a more regular appearance, a smoother surface and a harder texture. Research suggests that Type I myxomas are more prone to hemodynamic shear stress, which may result in tumor emboli and vascular embolization. Moreover, the irregular surface topology of Type I myxomas increases the propensity for thrombogenesis (18).

The two cardiac myxomas cases we describe were characterized by irregular surface morphology and a heterogeneous internal architecture, both fitting the Type I criteria.

From a morphological perspective, tumors with long villi on their surface are prone to detachment, as polypoid tumors have a higher incidence of systemic embolism than spherical tumors (19). In relation to the mechanism of vascular embolism events caused by cardiac myxomas, current research suggests that there may be two sources: (I) thrombi may form on the surface of the neoplasm, subsequently detaching and entering the systemic or pulmonary circulation; or (II) the intrinsic characteristics of myxomas, specifically their loose architecture and soft yet fragile consistency, may lead to the partial or extensive dislodgement of tumor tissue (20).

The symptoms of embolism depend on the location of the embolism. Myxomas in the left cardiac system often cause systemic circulation embolisms, of which cerebral vascular embolism is the most common. Clinical symptoms can include stroke or cerebral ischemic attacks. Embolisms may also occur in the coronary, splenic, renal, and peripheral arteries, leading to clinical symptoms such as angina pectoris, Raynaud’s phenomenon, abdominal pain, diarrhea, and acute limb ischemia. In the right cardiac system, myxomas are more likely to cause pulmonary embolisms, resulting in clinical symptoms such as dyspnea, thoracic pain, and hemoptysis (21).

The diagnosis of cardiac myxomas often relies on imaging modalities, of which TTE is the primary tool (8). TTE provides a non-invasive imaging modality for observing intracardiac myxomas, and enables the visualization of intracardiac myxoma masses, their mobility, and the attachment site of the tumor pedicle. This technique also facilitates the assessment of the tumor’s impact on hemodynamics (9). In addition, pulsed-wave tissue Doppler imaging can accurately measure the peak antegrade velocity of cardiac myxomas, and thus quantify their embolic potential, which may provide useful prognostic information for patients with cardiac myxomas (22).

The primary risk associated with cardiac myxomas is embolism, where parts of the tumor break off and travel through the bloodstream, potentially causing blockages in blood vessels. This can lead to serious complications such as stroke or heart attack. Other risks include obstruction of blood flow in the heart and interference with the heart valve function. Therefore, once a diagnosis of cardiac myxomas is confirmed, immediate open-heart surgery should be performed to excise the cardiac myxoma (10,23). The surgical excision of myxomas can significantly improve patient prognosis, and the risk of recurrence is very low, ranging from 1–5% (24). If preoperative vascular embolic events occur, they can affect the patient’s postoperative quality of life and survival rate, necessitating a multidisciplinary treatment approach. Thus, early diagnosis and prompt treatment are of great importance (25). Regular follow up is also important after treatment to monitor the signs of recurrence. In cases in which surgery is not possible or is too risky, close monitoring and symptomatic treatment may be necessary.

The first case reported in this article was of a male student who had been in good health previously. TTE revealed a huge mass floating in the right ventricle. During the echocardiographic examination, as the patient transitioned from a left lateral decubitus to a supine position to assist the ultrasound doctor, a tumor detachment occurred, leading to acute embolism in the right lower pulmonary artery. The preoperative electrocardiogram for this patient revealed an incomplete RBBB. In acute pulmonary embolism, the incidence of incomplete RBBB is approximately 29% (26). Studies have reported that a newly emerged RBBB may be an indicator of complete occlusion of the main pulmonary artery (27). This symptom is typically transient, subsiding gradually with the normalization of hemodynamic parameters, but it has the potential to persist indefinitely (26,27). A positive correlation has been reported between the wall shear stress (WSS) in arterial aneurysms and hemodynamic velocity, which suggests that an increase in blood flow velocity results in a corresponding increase in WSS (28). Thus, we hypothesized that rapid changes in body position can induce instantaneous variations in the WSS around the tumor, resulting in the detachment of the friable tumor tissue.

The second case involved an elderly male with a history of chronic hypertension. TTE suggested a left atrial mass. The patient experienced myxoma detachment while transitioning from a horizontal position to a standing position, which led to embolic occlusion extending from the abdominal aorta to the bilateral femoral arteries’ proximal segments, extensive acute myocardial infarction of the anterior wall, bilateral renal infarctions, and multiple acute cerebral infarctions. Such systemic multi-organ embolic events might also be associated with the abrupt positional change. Systemic multi-organ embolic events are typically associated with a poor prognosis, but this patient was exceptionally fortunate, as the medical team promptly identified the embolic symptoms and administered immediate treatment, thereby preventing any significant residual sequelae.

Despite the considerable age disparity and myxoma location differences between these two patients, both cases experienced embolic events related to positional changes. Myxomas are like “ticking time bombs” in the heart that can potentially detach at any moment and cause embolism in vital organs. Due to their loose, friable, and easily detachable tissue, myxomas, are more prone to embolic complications than other cardiac tumors. Myxomas exhibit significant oscillatory movement in response to cardiac systole and diastole. The effect of blood flow can lead to the dislodgement of myxoma fragments. In conditions of heightened hemodynamics, these detached fragments can disseminate throughout the circulatory system, leading to widespread vascular embolisms.

Both patients described in this article experienced myxoma detachment caused by abrupt postural changes, which suggests that positional alterations may expedite the fragmentation of myxomas. In addition, the two myxomas were large, which might have contributed to their detachment. A study reported an approximate 1.25% risk of embolic mortality in the interim between myxoma diagnosis and surgical intervention (29). This highlights the necessity of vigilant monitoring of cardiac myxoma patients before surgery. Patients need to be placed on a regimen of bed rest, stringent activity restriction, and abrupt postural shift avoidance to mitigate risks of syncope and sudden cardiac death. Moreover, judiciously implementing anticoagulation therapy could also be crucial in averting embolic occurrences.

In conclusion, these two cases show the importance of the preoperative position management of patients with friable cardiac myxomas. Our findings emphasize the necessity of minimizing preoperative position movement, and closely monitoring clinical symptoms to avert severe complications like embolism or obstruction. The expeditious scheduling of surgical resection following the diagnosis of cardiac myxomas is crucial, as it plays a pivotal role in ensuring patient safety.

Acknowledgments

Funding: This study was supported by funding from the National Natural Science Foundation of China (Nos. 81800266 and 81872698), and the Cultivating Project for Young Scholars at Hubei University of Medicine (No. 2017QDJZR04).

Footnote

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-1003/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the Ethics Committee of Shiyan Taihe Hospital (No. 2024KS68) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patients for publication of this article and accompanying images. Copies of the written consent forms are available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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