Cystic hydatid disease is a parasitic infestation by helminthes of Echinococcus species, that is, Echinococcus granulosus
and less frequently Echinococcus multilocularis
. Human (intermediate host) infection results from accidental ingestion of their ova in the form of food or water contaminated with canine (definitive host) feces. The larvae hatch in the duodenum and from there reaches to liver, lungs, heart and systemic circulation1
and develop into hydatid cysts. The cyst grows slowly but continuously at a rate of 1 to 5 cm a year. The cysts of E granulosus
have an outer hyaline ectocyst and inner endocyst. The endocyst is the germinal layer that produces ectocyst, hydatid fluid and brood capsules. Several protoscolices develop in the brood capsule. Sometimes, the cysts may be sterile. In contrast, the hydatid cyst of E multilocularis
is multilocular and lacks hyaline membrane with little or no hydatid fluid. The cysts are generally sterile in humans.
Cardiac hydatidosis accounts for 0.5% to 2% of all hydatid diseases.2
The reason for this rare occurrence appears to be the cardiac contractions that provide resistance to the presence of viable cysts.3
It can occur in any part of the heart, left ventricle being the most common site (75%), followed by the RV (15%), inter ventricular septum (5–9%) left atrium (8%), pericardium (8%), pulmonary artery (7%) and right atrium (3–4%).4
Clinical manifestations are seen in less than 10% of the cases and, if present, depend on the location, size and integrity of the cyst.1
Chest pain is the most common symptom.1
IVS cysts (very rare) may present with arrhythmias, conduction blocks or ventricular outflow tract obstruction. Other manifestations include ACS, valvular dysfunction and so on.1 5 6
There are very few case reports of hydatid cyst presenting as an ACS. Most of them are either pericardial cysts compressing coronaries or ruptured cysts.7 8
The case reported here is of particular interest because its presentation as an ACS may misdirect diagnosis and its recognition, which is important in planning therapeutic strategies. Treating the patient with inappropriate medication may expose him to life-threatening complications like rupture of the cyst leading to anaphylaxis, embolisation of cyst contents in to pulmonary or systemic circulation, pericardial tamponade, sudden cardiac death and so on.
The chest radiograph can often appear normal, as was the condition in the present case.
Electrocardiographic changes also depend on location, size and integrity of the cyst. These include ischemic changes (ST depressions and T wave inversions) and conduction disturbances (atrioventricular nodal blocks, bundle branch blocks) as observed in the present case. Other changes include arrhythmias and sudden cardiac arrest.6 9 10
However, none of the above changes is characteristic of hydatid cyst. Therefore, a cautious interpretation of electrocardiographic changes always with the aid of a bedside echocardiography is necessary, especially in the setting of a stable ACS.
Echocardiography is the diagnostic investigation of choice for all cases of cardiac hydatid cysts.1 10
Apart from its non-invasive nature, widespread availability, cost-effectiveness, easy bedside assessment, its potential advantages include accurate differentiation of a solid mass from a cystic lesion; determination of number, location, size and integrity of cysts; and demonstration of thin membranes of daughter cysts and hydatid sand in a multiloculated cystic lesion. It also helps to determine the haemodynamic effects of cysts on the heart.10 11
The present case scenario highlights how an early echocardiography unmasked a very rare disease like hydatid cyst, which is a tough clinical diagnosis to make out in a patient presenting with most commonly encountered disease, that is, ACS. Therefore, in the setting of an ACS, an early echocardiography, apart from assessment of LV function, will also help us recognize rare entities like cardiac tumours, aneurysms, cysts (hydatid cysts) and so on.
CT and MRI are the other non-invasive diagnostic modalities but are not superior to echocardiography due to the presence of cardiac-motion artefacts and lack of bedside assessment.11
Nevertheless, CT is helpful in determining polyvisceral involvement, especially when lung parenchyma is involved.
Coronary angiography (conventional/CT) studies should be carried out to evaluate the coronary vessels in all patients with symptoms or when electrocardiographic abnormalities are present as in our case.12
Even though serological tests like Casoni's intradermal test and ELISA are available, accuracy of these tests depends on several factors, including type and quality of antigen used. Many false-positive and false-negative results were observed in the past. Therefore, their role is limited to supplement the radiological diagnosis.13
Once the diagnosis of cardiac hydatidosis is made, surgery is the definitive mode of treatment to prevent complications. A preoperative albendazole therapy was initiated in our patient to prepare for possible cyst rupture and dissemination of daughter cysts during the surgical procedure. Intraoperative echocardiography gives a definitive diagnosis and can help in planning the surgery by aiding identification of the cannulation site and in making decisions such as whether to use CPB or to perform the surgery on a beating heart or under cross-clamp.12
In the present case, we performed the surgery under CPB. We can never be careful enough because complications may arise during surgery from rupture of cystone and one must be prepared to handle them.
- In the setting of an acute coronary syndrome, apart from ECG, an early bedside echocardiography may help in recognising rare etiological entities like cardiac cysts and tumours.
- A polyvisceral involvement in the setting of multiple cardiac cysts is always suggestive of cardiac hydatidosis
- In cardiac hydatidosis coronary angiography (conventional/CT) studies should be carried out to evaluate the coronary vessels in all patients with symptoms or when electrocardiographic abnormalities are present
- Surgery is the definitive mode of treatment for cardiac hydatidosis