Introduction

Human cystic echinococcosis (CE), also known as hydatid disease, is a tissue infestation, which is endemic in many sheep-farming areas of the world, notably Mediterranean countries, the Middle East, South America, and Australia [1, 2]. Echinococcosis is a common health problem in low- and middle-income countries [3], and the European Registry of CE found it a neglected health problem in these countries [4]. CE has a considerable economic impact, with the cost of the disease approximated at 0.03% of the country’s gross domestic product in Iran [5]. CE occurs mainly as a result of infection with the larvae of Echinococcus granulosus. Most often, dogs and other carnivores are the primary hosts and sheep are intermediate hosts, whereas humans are accidental hosts of the parasite. Humans usually become infected by ingesting food, milk, or water contaminated by dog feces containing the ova of the parasite [6, 7]. The most common sites of CE involvement are the liver and lung [8]; however, it can affect other organs in the body such as the heart, too [9]. Cardiac CE is a relatively rare manifestation of Echinococcus infection, which represents 0.5 to 2% of CE cases [10,11,12] Despite the multiple studies regarding the features of cardiac CE [13, 14], there was no systematic review of the literature on this topic, therefore this study aimed to determine the characteristics of cardiac CE disease based on available evidence.

Methods

This study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) 2020 statement [15].

Eligibility criteria

Case-series studies which presented the features of cardiac CE were considered for inclusion in this systematic review. Non-English studies, case reports, conference abstracts, review articles, letters, and commentaries were excluded.

Literature search

Medline via PubMed and EMBASE databases were searched systematically from inception to March 2022 with the following keywords: ((Echinococc* OR Hydatid*) AND (Heart OR cardi*)) OR Cardiac Hydatid in title, abstract, and author keywords. During the search, no restrictions on language and type of study were applied. Also, forward and backward searches from references and cited studies of included studies were performed for a comprehensive coverage of the published studies.

Study selection and data collection

Two authors separately reviewed the full-texts of the studies after being primarily screened based on title/abstract. The data from the included studies were extracted into a Microsoft Excel table. Information from eligible studies, including the name of the first author, publication year, study setting, patients’ demographics, the site of the heart’s involvement, the involvement of other organs, clinical manifestations, Electrocardiogram (ECG) findings, echocardiography, Chest X-ray (CXR) or magnetic resonance imaging, laboratory findings, management, final outcome, and follow-up, is extracted by two authors and cross-checked. Disagreements between authors were solved by the third author.

Risk of bias assessment

The potential for risk of bias in the studies was assessed by The Joanna Briggs Institute (JBI) Critical Appraisal tool for Case Series. The validity and reliability of condition evaluation, the contiguous recruitment of participants, the reporting of patient demographic and clinical data, clinical management, and follow-up are the sources of bias that being evaluated by this checklist.

Results

Search and selection process

Electronic searches in the databases results in 3985 records and finally, 37 studies met our criteria for inclusion in this systematic review. The details of the selection process are presented in Fig. 1.

Fig. 1
figure 1

PRISMA 2020 flow diagram

Full size image

Study characteristics

Seventeen studies were conducted in Turkey and the setting in other studies were Tunisia (5 studies), Iraq (3 studies), Spain, Syria, China, Greece (2 studies for each), Saudi Arabia, Kyrgyzstan, India, and France (1 study for each). The sample of cardiac CE in the studies varies between 2 and 62.

Risk of bias in studies

Figure 2 is a summary of the risk of bias assessments based on The JBI Critical Appraisal tool for Case Series. The details are reported in supplementary material 1. Based on our assessments, the most common possible sources of bias in the included studies were regarding the consecutive and complete inclusion of participants and statistical analysis, which were not reported in a clear form for a conclusive judgment. Inappropriate reporting of the demographics was also another source of bias in the studies.

Fig. 2
figure 2

Summary of risk of bias assessments based on The Joanna Briggs Institute Critical Appraisal tool for Case Series

Q1: Were there clear criteria for inclusion in the case series?

Q2: Was the condition measured in a standard, reliable way for all participants included in the case series?

Q3: Were valid methods used for identification of the condition for all participants included in the case series?

Q4: Did the case series have consecutive inclusion of participants?

Q5: Did the case series have complete inclusion of participants?

Q6: Was there clear reporting of the demographics of the participants in the study?

Q7: Was there clear reporting of clinical information of the participants?

Q8: Were the outcomes or follow up results of cases clearly reported?

Q9: Was there clear reporting of the presenting site(s)/clinic(s) demographic information?

Q10: Was statistical analysis appropriate?

Full size image

Results of individual studies

The evidence regarding the site of involvement, other organ involvement, signs and symptoms, ECG findings, echocardiography or CXR findings, laboratory findings, management, outcome, and follow-up are summarized and presented in Table 1. Cardiac CE can infect people of any age in both males and females. LV is reported as the most common site of infection. Studies suggested that cardiac CE can be secondary to other site infections, such as lung, liver, and spleen; however, cases of cardiac involvement without other organ involvement are also documented. The most commonly reported symptoms were chest pain, dyspnea, and palpitation and normal sinus rhythm (NSR) was the most common declared ECG feature. Regarding the laboratory findings, serological tests such as echinococcus indirect hemagglutination (EIHA) and enzyme-linked immunosorbent assay (ELISA), as well as eosinophilia, and positive casoni were the most commonly reported findings. A combination of surgical methods, such as cardiopulmonary bypass, and pharmacological management were reported in the studies; which were associated with appropriate outcomes, so the rate of mortality and recurrence were not considerable.

Table 1 – summary of included studies
Full size table

Discussion

This study is the first systematic review to summarize the evidence regarding the features of cardiac CE. Cardiac involvement occurs mainly by invasion of myocardium from the coronary arteries or pulmonary veins as a result of rupture of pulmonary echinococcal cysts [16]. Various locations of the heart can be infected with CE; however, LV is the most common site [17,18,19,20,21,22] and it can be presented in the pericardium as well as the myocardium layer, too [23, 24]. The main reason for higher rate of LV involvement can be the dominance of the left coronary artery [13, 25].

The clinical presentation of CE ranges from asymptomatic to life-threatening conditions and sudden death. Symptoms depend on location, size, compression, or involvement of abutting structures. The most frequent symptoms of CE are dyspnea, chest pain, and palpitation. The stretch of pericardium and/or compression of coronary vessels can be an explanation for this [11, 26, 27]. Also, the NSR is the most common ECG finding in CE patients, which suggested a crucial role of imaging and laboratory methods in the detection of cardiac CE.

Cardiac CE can affect almost everyone in each age group in the endemic areas; however, non-specific signs and ECG changes, make it a diagnostic challenge. Transthoracic echocardiogram (TTE) is suggested to be sensitive and specific in the diagnosis of cardiac CE [28, 29]. Classic cystic CE lesions appear as well-defined echo-lucent structures on echocardiographic images, whereas those that have become solidified, calcified, or degenerated can be hyper-echogenic and, thus, mimic semi-solid or solid mass lesions [30]. In a case series 6/16 (37.5%) of increased cardiothoracic ratio was reported [24]. Also, 5 cases of pericardial effusion were reported in the included studies [31,32,33]; which suggested that these features can be sign of cardiac CE, too. Cardiac CE infection is predominantly secondary to more commonly involved organs such as the liver and lung [34], therefore, in patients with CE in other organs, imaging and blood tests can help detect the cardiac form of the disease. Serological methods such as EIHA and ELISA are suggested as highly sensitive and specific tests for CE [14, 35]; however, the diagnostic accuracy of these blood tests, specifically in the cardiac form of the disease is not investigated. Most of the included studies reported a considerable rate of positive EIHA in patients with cardia CE; however, there is a need for future diagnostic accuracy studies of EIHA in cardiac CE, for clinical recommendation.

Cardiac CE is an uncommon but serious condition; however, it is not associated with a high rate of mortality in case of timely diagnosis and appropriate surgical and non-surgical management [36]. Overall, there was no significant cardiac CE-related mortality in the included studies. Rupture of the cyst during surgery, pulmonary embolism, and multi-organ failure was the cause of mortality in cardiac CE patients [17, 37, 38]. Also, pharmacotherapy with mebendazole or albendazole for 6–24 months postoperatively, is recommended for prevention of the recurrence of the disease [39].

Systematic and predefined approach of the review and a comprehensive database search as well as hand searching for full coverage of the published evidence were the main strengths of this study. The exclusion of non-English papers was the main limitation of this study. Future multi-center studies with larger sample sizes and comprehensive reports of the characteristics of the disease can strengthen the evidence in this regard and help appropriate management in cardiac CE patients. Also, it is recommended to report more details of cardiac CE patients in future studies.

Conclusion

Cardiac involvement is an uncommon presentation of CE which is associated with some non-specific signs and symptoms such as dyspnea, chest pain, palpitation, and fatigue. In the case of diagnosed CE in other organs such as the lungs and liver, cardiac CE, should be considered by clinicians. Non-specific signs and symptoms make cardiac CE a diagnostic challenge; however, imaging methods such as TTE as well as serological tests, can help diagnosis of the disease. Cardiac CE is not associated with considerable mortality in the case of timely diagnosis and appropriate management.