Introduction

Hydatid cyst disease results from a parasitic infection with Echinococcus granulosus. Hydatidosis is still endemic in some countries, including Turkey. Although domestic dogs and cats are the most commonly affected species, humans may become infected after ingestion of viable E. granulosus ova because of poor food hygiene (1). Hydatid cysts may occur in many organ systems; however, in humans, they are most commonly found in the liver (55%-70%) and lungs (20%-30%) (1). Cardiac involvement is rare, presenting in only 0.5%-2% of all cases of hydatidosis, and can occur either as a part of a broader systemic infection or more rarely as the only organ system affected. The most commonly affected cardiac structures are the left ventricle (LV) in 50%-60%, interventricular septum in 10%-20%, and right ventricle (RV) in 5%-15% of patients with cardiac hydatidosis. Less commonly, cysts have been reported in the pericardium (7%), pulmonary artery (6%), and right or left atrium (5%-8%) (2-5). Most patients with cardiac hydatid cyst disease develop symptoms very late, because cardiac cysts grow very slowly. Symptoms of cardiac hydatid cyst include chest pain, dyspnea, syncope, and palpitation, and symptom severity correlates with the size of the cyst and the affected cardiac structures (2-6). On diagnosis of a cardiac hydatid disease cyst, because of the likely involvement of other organ systems, whole body screening should be performed. The main treatment of hydatid disease is surgery with complete removal of the cyst (7). Medical therapies may include albendazole or mebendazole, given before and after surgery (2). This study aimed to present a single tertiary center experience of cardiac hydatid cyst disease and describe the general characteristics, management, imaging findings, range of organ involvement, and follow-up in cases of cardiac hydatid disease.

Methods

Patients diagnosed with cardiac hydatid cyst with extracardiac organ involvement and presented to the cardiology and radiology departments between December 2007 and December 2019 were enrolled retrospectively in this study. Patient data were extracted from a detailed clinical database of all patients diagnosed with hydatid cyst disease. Details extracted included demographic information, such as age and sex, and other relevant medical history. Clinical symptoms on admission including chest pain, dyspnea, palpitation, syncope, and headache were also evaluated. From each patient, other information obtained included cardiac structures affected by the hydatid cysts, all extracardiac organ system involvement, surgical and medical treatment, preoperative complications, and postoperative follow-up of at least 12 months.

All patients underwent basal electrocardiography, chest X-ray imaging, and echocardiography. Transthoracic echocardiography (TTE) images were obtained for each patient using a Vivid 7 ultrasound system (GE Medical System, Horten, Norway). When hydatid cysts were found in the heart, patients underwent cranial, thoracic, and abdominal computed tomography (CT) and/or magnetic resonance imaging (MRI) to detect the involvement of other organ systems. Cardiac MRI was performed in selected cases using a 3-T Philips MRI unit (Philips Achieva Intera Release, Eindhoven, Netherlands). Non-contrast and contrast-enhanced CT was performed with a 64-channel multidetector CT scanner (Aquilion 64; Toshiba Medical Systems, Tokyo, Japan). Survival and disease status was obtained from the hospital records or, if necessary, by direct communication with the patient or their families.

The study was approved by the Kocaeli University Faculty of Medicine Ethic Committee (approval number: KU-GOKAEK-2020/37). Given the retrospective nature of the study, no specific individual informed consent was required. All patients had given informed consent for the treatment procedure.

Statistical Analysis

Statistical analysis was performed using SPSS 22.0 software (IBM Corp., Armonk, NY, USA). Continuous data are shown as mean ± standard deviation and categorical variables as numbers and percentages.

Results

In 12 years, 22 (13 males: 59.1%) patients were diagnosed with cardiac hydatid cyst after cardiac examination, and these patients were initially admitted for various cardiac symptoms, including chest pain, dyspnea, palpitation, syncope, and headache. The mean age was 43.1±18.2 years. The baseline demographic, clinical, treatment, follow-up characteristics and imaging findings of patients with hydatid cyst disease are shown in Table 1.

All patients underwent non-contrast and contrast-enhanced CT, while 14 (63.6%) patients underwent cardiac MRI. Twenty (90.9%) patients had a single cardiac hydatid cyst, while the remaining two (9.1%) had two cardiac cysts. Cardiac hydatid cysts were found in the following cardiac regions: LV (n=10, 41.7%), RV (n=5, 20.8%), interventricular septum (n=5, 20.8%), and pericardium (n=4, 16.7%). Common symptoms at admission included chest pain (n=13, 59.1%), dyspnea (n=7, 31.8%), and palpitations (n=5, 22.7%). In addition, one patient (4.5%) presented with syncope due to a complete atrioventricular (AV) block and one (4.5%) was admitted for complaint of headache due to brain hydatid cysts. Finally, one patient presented without symptoms, and the cyst was found incidentally at checkup with chest X-ray imaging.

Lesions were assessed according to Gharbi classification (1). This revealed that 8/24 (33.3%) cases were type 1, 5/24 (20.8%) were type 2, 1/4 (4.2%) was type 3, 3/24 (12.5%) were type 4, and 7/24 (29.2%) were type 5. MRI was performed in 14 patients. In patients who underwent MRI, 4 lesions were hyperintense and 10 lesions were hypointense on T1-weighted images, and 10 lesions were hyperintense and 4 lesions were hypointense in T2-weighted images. CT and TTE were performed in all 22 patients. On CT, 9/24 (37.5%) lesions were mildly hypodense and 14/24 (58.3%) lesions were hypodense. A calcification component was observed on CT examination in seven patients, all with Gharbi type 5 cardiac hydatid cyst. On TTE, 5/24 (20.8%) lesions were hyperechoic, 7/24 (29.1%) lesions were anechoic, and 11/24 (45.8%) lesions were hypoechoic. In patient 2, CT, MRI, and TTE showed LV aneurysmatic dilatation due to a ruptured cardiac hydatid cyst. Imaging findings of cardiac hydatid cysts are shown in Figure 1, 2, 3, 4, 5, 6, 7.

There was no extracardiac hydatid disease organ involvement in 8/22 (36.4%) patients. The remaining 14 patients had hydatid organ system involvement, as follows: Liver in 10/22 (45.4%), lung in 5/22 (22.7%), brain in 2/22 (9.09%), and spleen hydatid cysts in 2/22 (9.09%) patients.

Of the 8 patients with hydatid disease only affecting the heart, 7/8 (87.5%) underwent open-heart surgery and the eighth patient had medical therapy only. Of those undergoing open-heart surgery, one died intraoperatively because of generalized anaphylaxis (patient 5), while another patient (patient 3) died of pulmonary embolism due to hydatid cyst rupture while being prepared for surgery. A 12 year old male patient (patient 2) had concomitant cardiac and brain surgery for hydatid cyst disease without any postoperative complication. Open-heart surgery and puncture, aspiration, injection, and reaspiration (PAIR) for treatment of cysts in the liver were performed in 5 of 10 patients with cardiac and liver cysts, without any complication, while 4 more of them (18.1%) underwent successful open-heart and liver surgery for cysts. Complete removal of lung hydatid cysts were successfully achieved in four of the five patients with concomitant lung and cardiac involvement, in addition to surgical removal of cardiac cysts. Surgical removal of spleen cysts was successful in two patients. A 21 year old female patient (patient 14) had successful open cardiac and brain surgery with PAIR for the liver. Two patients did not undergo surgery because of comorbidities (patients 18 and 22), which included pulmonary embolism, pulmonary atelectasis, and vascular embolism that occurred preoperatively. Preoperative treatment of 400 mg albendazole or mebendazole was given to all patients and continued for 12 months after surgery. On follow-up, the remaining 20 patients continued to have good health status, without any further complications. In addition, there was no cardiac reinfestation in 18 patients, while in the two patients who were on medical therapy alone, cardiac cysts were stable at 1 year follow-up.

Discussion

Cardiac hydatid cysts are rare and account for 0.5%-2% of all cases of hydatidosis. When cardiac hydatid cysts are present, extracardiac organ system involvement is reported to range from 38% to 100% of cases (7-9). In hydatid cyst disease with extracardiac involvement, cardiac hydatid cyst may occur as single or multiple cysts and affect a single or multiple organ systems (10). Cardiac involvement has several possible mechanisms: 1) Infection of the myocardium via coronary arterial supply, 2) infestation as a result of echinococcal cyst rupture into a pulmonary vein, and 3) direct tissue-to-tissue contact with cysts in the liver or lungs (11).

The most common symptom in patients with cardiac hydatid cyst disease is chest pain. However, patients may present with dyspnea, palpitations, and/or syncope, depending on the location and size of the cyst. Angina pectoris may occur if the cyst impedes coronary artery function (2-4). Cardiac conduction impairment, such as AV block or nodal rhythm abnormality, may occur if the cysts compress the AV node or bundle of His (6).

Complications of cardiac hydatid cysts can be severe and fatal, so prompt and accurate diagnosis is important. Cyst rupture is the most dangerous complication, which may cause cardiac tamponade, anaphylactic shock, systemic embolism or combined pulmonary and systemic embolisms, and arrhythmias (11-14). In the present series, one patient died from anaphylactic shock and the other from pulmonary embolism.

Diagnostic methods for cardiac cysts include non-invasive imaging techniques such as those used in this series (TTE, CT, and MRI) and serological tests (15). Serologic tests are more sensitive and specific for liver involvement than for cardiac hydatid disease, although these tests are not capable of positively identifying the organ(s) involved (11). Serological testing, using an enzyme-linked immunosorbent assay, is the most sensitive (94%) and specific (90%) test for most hydatid cyst locations (11). TTE is the first-line imaging modality of choice being widely available, easy to use, and with good sensitivity for cardiac hydatid cyst diagnosis (16). CT is a good second-line modality for cardiac cysts and shows cyst wall calcification well in type 5 cysts. However, cardiac motion artifacts are an important limitation of CT. MRI is excellent at identifying the exact anatomic location of cysts and provides information concerning cystic internal and external structures, thus allowing cysts to be differentiated from other masses and tumors. Hydatid cysts have a characteristic appearance on MRI, usually as a hypointense and hyperintense oval lesion on T1- and T2-weighted images, respectively. In addition, T2-weighted images may show a hypointense peripheral ring caused by the formation of a pericyst consisting of host tissues deposited as a result of the inflammatory response to the cyst (5,15). On suspicion of a hydatid cyst, positive identification of the cystic wall and peripheral contrast enhancement are crucial to distinguishing the cyst from other cardiac masses. Cardiac hydatid disease occurs more often in the LV because of its large myocardial mass and abundant blood supply (2,15). Thus, the LV was the most commonly affected cardiac region in our series.

The definite treatment for hydatid cyst disease is surgery, and an open-heart surgery for cardiac cysts is known as cystopericystectomy. Rarely, partial pericystectomy can be performed to preserve organ function (11). In our study, majority (19/22) of the patients underwent total cystopericystectomy during open-heart surgery with cardiopulmonary bypass. Different approaches for cystectomy during open-heart surgery have been described. Birincioğlu et al. (17) suggested that subepicardial cysts can be resected without cardiopulmonary bypass. By contrast, Abhishek and Avinash (11) suggested that cardiopulmonary bypass is still required for optimal safety. Gentle handling of the heart during cardiopulmonary bypass minimizes operative risks and complications, such as cyst rupture (18). Unfortunately, cyst rupture occurred in a 17-year-old female patient (patient 5) in our series, resulting in intraoperative anaphylaxis and death.

Previous reports from small series have indicated extracardiac organ involvement in approximately one-third of all patients (7-9). In our series, an incidence of 63.7% falls at the middle of this range. Thus, given the high likelihood of extracardiac involvement in patients initially diagnosed with cardiac hydatid cyst, we suggest that all patients undergo systemic screening to identify other affected organ systems. In patients with hepatic involvement, the gold standard treatment is complete removal with open surgery, such as through percutaneous, minimally invasive surgery and PAIR (19). In our series, PAIR was successfully performed in four patients with liver hydatid cysts. The two remaining patients with liver disease underwent open surgery without any postoperative complication. For all patients with cardiac hydatid disease, medical therapy with albendazole or mebendazole should be implemented to reduce repeated infections and minimize perioperative complications. This treatment should be started 14 days before surgery and continued for at least 1 year following surgery (6,11,14,20).

Study Limitations

This study has some limitations. First, this is a single-center retrospective study, with inherent biases. Second, the sample size was small; however, cardiac hydatid cyst is a very rare disease, which also led to the long duration of the study period, a further limitation. This led to some missing data and inevitable variation in clinical management and treatment strategy because of the lack of standard guidelines. Prospective, randomized, and multicenter study is the ideal study design for collection of data concerning cardiac hydatid cyst disease, but this is difficult, given the rarity of the condition.

Conclusion

Cardiac hydatid cyst is a very rare condition, and majority of the cases have left ventricular involvement. The most common presenting symptom is chest pain. TTE is the first-line imaging modality of choice, while CT and MRI provide valuable additional findings for the diagnosis of cardiac hydatid disease, including the exact anatomic location. In our cohort, more than two-thirds of patients had extracardiac organ system involvement; thus, all patients should be screened for other cyst locations, especially the liver, lung, and brain. In addition, multisystem involvement is common, so patients presenting with non-cardiac hydatid disease should also undergo cardiac imaging. Surgery is the main treatment modality with adjunctive medical therapy using either albendazole or mebendazole therapy. Given the rarity of the condition, there is little data about the clinical course and outcomes in patients with cardiac hydatid cyst, so further studies are necessary.

Acknowledgment

The authors are grateful to Mr. Jeremy Jones of the Academic Writing Department of Kocaeli University, İzmit, Turkey, for his assistance in editing the English used and for his help and advice concerning the contents of this article.

Ethics Committee Approval: The study was approved by the Kocaeli University Faculty of Medicine Ethic Committee (approval number: KÜ-GOKAEK-2020/37).

Informed Consent: All patients had given informed consent for the treatment procedure.

Peer-review: Externally and internally peer-reviewed.

Authorship Contributions: Surgical and Medical Practices - K.K., İ.K., O.O., E.Ç.; Concept - İ.Ç., K.K., İ.K., A.Y., Ö.Ç., O.O., E.Ç., Y.A.; Design - İ.Ç., K.K., T.Ö., Ö.Ç., O.O., E.Ç., T.Ş.; Data Collection or Processing - İ.Ç., K.K., İ.K., T.Ö., Ö.Ç., O.O.; Analysis or Interpretation - İ.Ç., K.K., İ.K., A.Y., H.C., B.E.G., E.Ç., T.Ş., Y.A.; Literature Search - İ.Ç., T.Ö., A.Y., H.C., B.E.G., Y.A.; Writing - İ.Ç., K.K., A.Y., H.C., B.E.G., E.Ç., Y.A.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.