Atrial Myxoma

An atrial myxoma (AM) is a primary cardiac tumor located in one of the atria of the heart. This benign neoplasm most frequently affects the left atrium.

The disease is related to the following processes:  neoplastic and has an incidence of about  1 / 100.000.

Presentation

Symptoms manifest due to limited heart function or even heart failure and thus include orthopnea and dyspnea, paroxysmal nocturnal dyspnea, but also pulmonary edema, cough and hemoptysis. General fatigue is often reported in advanced cases. Fever and weight loss may be observed in one third of all cases. Abnormalities in blood count and blood chemistry do occur with a similar frequency and often affect patients with systemic symptoms. In this context, anemia, an increased sedimentation rate, globulinemia and an elevated level of C-reactive protein have been reported.

During clinical examination, a characteristic "tumor plop" heard in early diastole may point to the presence of a cardiac tumor [10]. Also, arrhythmias may be present and are possibly caused by invasion of the myocardium. This same process may reduce myocardial contractility or provoke heart block. Moreover, AM may cause pericardial effusion and possibly cardiac tamponade.

If non-cardiac tissues are affected either by invasion of the primary neoplasm or by development of metastases, additional symptoms may be observed. Symptoms may, for instance, mimic those present with bronchogenic carcinoma [11].

Tumor embolism is a frequent complication of AM and may lead to pulmonary embolism, cerebral infarction and other pathological conditions associated with embolism.

Workup

If patients present with the abovementioned symptoms or if other factors indicate the possibility of a cardiac tumor, an echocardiographic examination is usually realized. This non-invasive technique allows for the detection of cardiac tumors and for the determination of its location. Furthermore, heart action and blood flow can be assessed in an echocardiographic examination, which is of utmost importance due to the frequent mechanical complications arising with AM. It has been proposed that even the probability of tumor embolism may be predicted with echocardiography [12].

Of note, transesophageal echocardiograpy may be superior to transthoracic echocardiography and may reveal more conclusive results. Less intervening tissues may render the former technique more sensitive than the latter.

Although the findings obtained by echocardiography may hint at a certain type of tumor and thus its benignancy or malignancy, further diagnostic measures generally have to be taken in order to provide an accurate diagnosis. In this context, imaging techniques are most commonly applied. High resolution images of the heart may be obtained by magnetic resonance imaging as well as computed tomography. If available and not contraindicated, the former is often preferred because T1- and T2-weighted images may offer additional information regarding the structure and thus the type of the neoplasm. Positron emission tomography has also been successfully applied in cases of AM [13].

Whereas biopsies are standard operating procedures in other types of tumors, considerable risks are associated to transvenous biopsies of cardiac neoplasms. With regards to AM, the risk of tumor embolism may increase when a biopsy is conducted. Thus, if imaging techniques allow for a sufficiently certain diagnosis, AM do not usually require this type of confirmation. Other cardiac tumors may justify such procedures [14].

Treatment

According to current knowledge, there are no conservative treatment options for AM. Drug therapy is only applied to alleviate certain symptoms associated with the presence of a cardiac neoplasm, e.g. to treat arrhythmias.

The tumor has to be surgically resected. During surgery, the neoplasm has to be handled with utmost care in order to avoid detachment of cells and subsequent tumor embolism or development of metastases. If at all possible, the AM has to be resected entirely. Therefor, a wider safety margin should be considered when removing the peduncle of the myxoma. If necessary, defects to the atrial walls are subsequently closed with an adequate patch or with parietal pericardium. Of note, laser photocoagulation of tumor cells possibly present in close proximity to the resected peduncle may help to decrease the necessary safety margin. During surgery, the atrioventricular valves should be carefully examined. If the AM provoked damage to these anatomical structures, an annuloplasty or prosthetic valve replacement may be required. The other chambers should be checked for possible metastases. In order to be able to do this, a biatrial approach is sometimes recommended.

The procedure is considered a safe surgery, with post-operative mortality amounting to about 2%. One in three patients that underwent AM resection presents atrial fibrillation after surgery [15]. Recurrences are rare and are generally associated with incomplete resection or rough handling of the tumor during surgery.

Follow-ups consist in biannual transthoracic echocardiographic examinations and mainly aim at detecting possible recurrences.

Complications arising with AM, e.g. pulmonary embolism and stroke, require the respective, adequate treatment.

Prognosis

Although AM are benign tumors, they may, however, cause mechanical interference with heart function and/or tumor embolism. Furthermore, neoplastic cells may reach other chambers of the heart or other organ systems and metastases may develop. In order to prevent these complications as well as sudden cardiac death, the AM needs to be surgically removed.

Upon successful tumor resection, the overall prognosis is very good. Risks of recurrence are augmented in patients showing familial AM and consequent genetic predisposition as well as in cases of inadequate resection or malignant degeneration [8].

Long-time survival has been estimated to be about 90% [9].

Etiology

The majority of cases of AM is of unknown etiology. There is, however, a smaller share (less than 10%) of AM that occur with an increased incidence in certain families. This predisposition for AM is inherited with an autosomal dominant trait. Some patients suffering from familial AM show an increased overall risk for neoplasms, particularly for myxomas and endocrine tumors, and also present a spotty pigmentation of the skin. This symptom complex is known as Carney's complex [1] [2].

Epidemiology

Primary cardiac tumors are rare. The overall prevalence of benign and malignant primary heart tumors has been estimated to range between 0.001% and 0.03% [3]. Other studies have reported prevalences of up to 0.3% [4]. Nevertheless, those studies agree in that benign primary cardiac tumors can be found more frequently than malignant neoplasms. Three out of four primary cardiac neoplasms are benign. Among benign tumors, myxomas are by far the most common ones and account for about 50% of the cases. Of note, these numbers refer to adults. In children, myxomas only account for about 15% of primary heart tumors. A genetic predisposition for cardiac myxomas can be detected in less than 10% of all cases. A cardiac myxoma may be the only clinical manifestation of such a genetic disorder, but this kind of tumor may also develop as one of several symptoms of more complex heritable diseases [4].

AM more frequently affect the left atrium, but can also be found in the right atrium. Myxomas may also develop in the ventricles, but the incidence of ventricular myxomas is considerably lower than the incidence of AM. With regards to ventricular myxomas, they are more frequently detected in the right ventricle.

For AM, the female-to-male ratio is 3:1 [5]. The majority of patients diagnosed with AM are between 40 and 60 years of age. These data have been confirmed in several studies, although there is one report from India that suggests the incidence of myxomas to peak before the age of 40 [6].

Sex distribution
Age distribution

Pathophysiology

As has been mentioned before, most cases of AM are sporadic. The tumor does mainly affect the left atrium and only about 20% are detected in the right atrium. An AM is usually pedunculated and most patients develop solitary myxomas. However, multiple myxomas are often found in patients presenting a genetical predisposition to develop neoplasms. In these cases, myxomas can also more frequently be detected in the heart's ventricles.

AM are of gelatinous consistency and are composed of scattered mesenchymal cells within a mucopolysaccharide stroma. They are round, oval or polypoid, of white or yellowish to brown color and present a smooth, villous or friable surface. These neoplasms originate from the endocardium and although they can develop at different parts of the atrial wall, they are most commonly attached to the fossa ovalis of the atrial septum. AM may be of different size, but tumors measuring up to 15 cm in diameter have been described. Tumor growth is enhanced by cytokines and growth factors released by tumor cells themselves. The release of vascular endothelial growth factor, for instance, does promote angiogenesis and thus nutrient supply and growth of the AM [7]. There are, however, no reliable data regarding the growth rate of AM.

AM do mechanically interfere with cardiac function. Patients with AM manifest symptoms when tumors reach a certain size. Atrial fibrillation has been observed in a significant share of patients with large AM. For AM located in the left atrium, a diameter of 5 cm and a weight of about 70 g have been proposed as possible limits for asymptomatic cases. With regards to AM affecting the right atrium, symptoms develop even later.

The length of the tumor's peduncle determines its mobility. When mobile AM reach a certain size, they can prolapse into the respective ventricle. This is more frequently the case with polypoid tumors and may cause significant damage to the mitral or tricuspid valve structures. Further complications may arise from tumor embolism. Due to AM being an intravascular neoplasm, embolism occurs quite frequently. It has been estimated that tumor embolism occurs in up to 40% of all patients suffering from AM whereby the site of embolism varies with the location of the myxoma. Similar to what has been said about a possible prolapse into the ventricle, tumor embolism is more common with polypoid tumors. Also, AM with a villous or friable surface are said to provoke more frequent embolism [5]. Hemorrhages may occur, but have been reported less frequently.

Prevention

Preventive measures can only be recommended to those suffering from known genetic predisposition for AM. These patients should be regularly examined in order to detect possible neoplasms early. Family members may benefit from genetic testing. Only if genetic mutations were inherited, routine screenings are necessary. No preventive measures are known for sporadic cases of AM.

Summary

Among primary cardiac neoplasms, benign tumors occur more frequently and myxoma account for approximately half of those benign tumors. Although they may develop in each of the four chambers of the heart, they are more often found in the atria, particularly in the left atrium.

Patients usually do not present any symptoms until the neoplasm reaches a critical size. At this point, the atrial myxoma (AM) will interfere significantly with the heart function and cause symptoms typically manifested in cases of heart failure, e.g. dyspnea, pulmonary edema and cough. Electrocardiographic exams are generally combined with imaging techniques to diagnose an AM. Biopsies are usually not required to confirm the diagnosis, since considerable risks are associated with the respective procedure. In cases of AM, these risks outweigh the possible benefits.

AM have to be surgically resected, conservative treatment is not an option. Drug therapy is limited to the treatment of complications arising from the presence of an intracardiac mass. Upon successful surgical removal, the prognosis is very good. Prognosis may, however, deteriorate when complications such as tumor embolism, formation of metastases and invasion of adjacent tissues occur.

Patient Information

An atrial myxoma (AM) is a benign tumor that originates from the endocardium, the inner layer of the heart. It develops in either one of the two atria which, in turn, constitute two of the four chambers of the heart.

Causes

An AM is a primary cardiac tumor, i.e. this neoplasm originates from cardiac tissue and is not a metastasis of other tumors. Whereas in some cases, AM may be attributed to genetic disorders that predispose affected patients for developing myxomas and/or other types of tumors, most cases of AM are sporadic. With regards to sporadic AM, no direct causes can be associated with the development of the tumor.

Symptoms

Initially, AM do not cause any symptoms. However, as soon as they reach a certain size, they may considerably interfere with heart function. Patients may then suffer from breathing difficulties, may even wake from breathing difficulties at night. In some cases, these respiratory problems only occur during exercise, in other cases they are present at rest. Cough and chest tightness may also be observed and go along with a blue discoloration of the skin and soft tissue swelling. Overall fatigue, fever and loss of weight are also possible manifestations of AM.

Diagnosis

The physician may suspect the presence of an AM if the patient presents with the abovementioned symptoms and if he or she detects further hints upon auscultation, i.e. when he or she is listening to the heart's action with the stethoscope. Initial diagnosis is usually based on the results of an echocardiographic examination. This non-invasive technique allows for the detection of cardiac tumors and also enables the physician to assess possible obstructions of cardiovascular structures. Additional diagnostic imaging, e.g. magnetic resonance imaging, computed tomography, angiography or combinations thereof, may be required to confirm the suspected diagnosis. If needed, blood tests will also be done.

Treatment

The tumor has to be surgically removed. This surgery is considered a safe procedure and allows for an in situ evaluation of certain cardiac structures that may be damaged by the AM. If such damage is detected, it will be surgically repaired. Additional drug therapy may be required to alleviate symptoms associated with the AM. Recurrences are uncommon if the tumor can be removed completely.

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References

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