Research Article
MRI in Tropical Endomyocardial Fibrosis
Prabha Nini Gupta*, Ruma Madhu, Sudheer MD, Dilip MN, Ankul Gupta and Krishna Kumar Bhaskara Pillai
Corresponding Author: Prabha Nini Gupta, Department of Cardiology, Medical College Hospital, Trivandrum, Kerala, India
Received: February 02, 2019; Revised: August 10, 2019; Accepted: March 20, 2019
Citation: Gupta PN, Madhu R, Sudheer MD, Dilip MN, Gupta A, et al., (2019) MRI in Tropical Endomyocardial Fibrosis. J Blood Transfusions Dis, 2(2): 57-68.
Copyrights: ©2019 Gupta PN, Madhu R, Sudheer MD, Dilip MN, Gupta A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Objective: To define the magnetic resonance imaging (MRI) features of tropical endomyocardial fibrosis (EMF) in Mocumbi criteria-positive cases of endomyocardial fibrosis. To date, the MRI features of only hypereosinophilia and Loefler’s myocarditis have been described. 

Methodology: This was an observational study performed in a tertiary teaching hospital in India (Medical College Hospital, Trivandrum). Seven consecutive patients with echocardiographic features of endomyocardial fibrosis defined by the Mocumbi scoring were included in the study and cardiac MRIs were performed on them.

Results: Two patients who were assumed to have endomyocardial fibrosis had normal MRIs. The remaining had: Diffuse subendocardial gadolinium enhancement involving the right or left ventricle (hyper enhancement) (5/5), apical thickening and obliteration of either ventricle was found in 5/5 patients, 2/5 had a right ventricular dimple, 1/5 had an intracardiac thrombus, seen as an “apical black signal.” 2/5 had a typical “three-layered appearance”, 3/5 had a pericardial effusion and 5/5 had an increased atrial size.

Conclusion: MRI appears to be more accurate in diagnosing endomyocardial fibrosis than echocardiography. Though echocardiography has been considered the gold standard for the diagnosis of endomyocardial fibrosis it appears to be time to reconsider this.

 

Keywords: Endomyocardial fibrosis, Hypereosinophilic syndrome, MRI

 

Abbreviations: MRI: Magnetic Resonance Imaging; EMF: Endomyocardial Fibrosis; LGE: Late Gadolinium Enhancement; CMR: Cardiac Magnetic Resonance Imaging; LV: Left Ventricle; FSE: Fast Spin Echo; SSFP: Steady State with Free Precession; DENSE: Displacement Encoding with Stimulated Echoes; SPAMM: Spatial Pre-Saturation Pulses or Spatial Modulation of Magnetization; 2D: 2 Dimensional; RV: Right Ventricle; Gd-DTPA: Gadolinium Diethylene Triamine Pentacetic Acid; CT: Computerized Tomography; ARVD/C: Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy; IMF: Idiopathic Myocardial Fibrosis; HCM: Hypertrophic Cardiomyopathy; T1W1: T1 Weighted Images; T2W1: T2 Weighted Images; VENC: Velocity Encoding Phase Contrast

WHAT IS ALREADY KNOWN ON THE SUBJECT?

There are many articles describing the features of hypereosinophilic syndrome and cardiac involvement by MRI but articles on the MRI features of tropical endomyocardial fibrosis are few. This study describes how to diagnose endomyocardial fibrosis by MRI.

WHAT DOES THIS STUDY ADD?

This describes how to diagnose tropical endomyocardial fibrosis from an MRI. This is especially useful when the echocardiographic findings are confusing. The presence of endocardial calcium, trilayer appearance and absence of contrast from the chambers of the heart (right or left ventricle) on contrast MRI signify endomyocardial fibrosis, not hypertrophic cardiomyopathy or other causes of left ventricular hypertrophy.

HOW MIGHT THIS PAPER IMPACT CLINICAL PRACTICE?

Left ventricular hypertrophy due to systemic hypertension or other causes does not need any special treatment. But the hypertrophied ventricles with endocardial calcium of endomyocardial fibrosis need chronic anticoagulation as it has been shown that anticoagulation reduces ischemic events (like stroke) in endomyocardial fibrosis. Further care has to be taken to maintain sinus rhythm in these patients as atrial fibrillation in endomyocardial fibrosis spells increased mortality. MRI data can also be used to plan surgical treatment though surgical treatment is not generally performed now-a-days for endomyocardial fibrosis.

INTRODUCTION

Endomyocardial fibrosis (EMF) is a form of tropical endomyocardial disease that can result in restrictive cardiomyopathy with left- and/or right-sided heart failure [1-3]. EMF is known to involve the inflow and spare the outflow regions of the heart. Previously, involvement of these regions was identified by echocardiographic and angiographic studies. Now, however, magnetic resonance imaging (MRI) is likely to be an excellent tool to demonstrate the cavity obliteration, calcification, subendocardial hyper enhancement, pericardial effusion and the presence or absence of thrombi. Even in rheumatic mitral stenosis, MRI has been recommended to look for intracavitary thrombi in patients with poor echocardiographic windows, especially in those who cannot swallow adequately during transesophageal echocardiograms due to a recent stroke. In this article we have studied the MRIs of echocardiographically proven patients with EMF. There are only a few reports of MRI in tropical EMF.

A few words about MRI and the detection of myocardial fibrosis:

Presently, the most common contrast agent used in MRI is gadolinium. This contrast agent takes 15-30 s to reach the myocardium and undergoes a first pass in the cardiac chambers. Then, it diffuses into the extracellular space. At 10-15 min after an intravenous injection, it reaches a steady state with the extracellular areas. Late gadolinium enhancement is seen in this steady state. Myocardial perfusion images are viewed during the first pass of gadolinium [4]. The extracellular gadolinium causes the late gadolinium enhancement (LGE) and provides clues to the location of the interstitial spaces and pericardial cavity around the normal myocardium.

Cardiac MRI attempts to overcome the artefacts caused by cardiac motion, respiratory movements, and those due to blood flow. Cardiac MRI requires special electrocardiographic (ECG) leads, which are used for prospective ECG gating. Cine MRI uses retrospective gating to prevent interference with a flash artefact. To prevent artefacts, either a single-shot approach where the entire image is acquired for a short time, or a segmental approach where a certain part of the cardiac cycle is acquired, is used. Respiratory artefacts are avoided by triggering data acquisition to movements of the diaphragm. Some laboratories use the “breath hold” to prevent respiratory movements if the patient’s condition permits [4].

Cardiac MR (CMR) MRI typically uses two or three types of imaging, including “bright blood cine imaging or dark blood fast spin-echo (FSE) imaging to assess cardiac structures and morphology. Cine spin CMR has become the gold standard for quantifying left ventricular (LV) mass, volumes, and regional contractility. These volumes do not require assumptions about shape like the Todd formula for LV volume by echocardiography. The cine steady state with free precession (SSFP) gives the best type of image quality. A cine movie can be acquired at 35-45 ms with a breath hold of 10 s, so that the whole heart motion is captured in less than 5 min [4].

T1-weighted dark blood FSE imaging can show the following structures: morphology of the cardiac chambers, the aorta and the pulmonary arteries, the pericardium and any fat. Techniques such as displacement encoding with stimulated echoes (DENSE) and spatial pre-saturation pulses or spatial modulation of magnetisation (SPAMM) have been used to remove motion artefacts. Myocardial grid tagging and phase contrast velocity mapping have also been used to remove motion artefacts [4].

We have also used contrast MRI to give an indication of the cardiac chambers. EMF obliteration has been shown as a filling defect. Contrast MRI gives an idea about the cavity filling. Cavity obliteration is seen as a filling defect. Contrast MRI can prove the obliteration of the cavity. A bright hyperechoic image seen on echocardiography can be seen directly on MRI as fibrotic material that fills the right or left ventricular cavity.

T1-weighted images can detect the extracellular myocardial compartment and whether it is enlarged. This is expressed as LGE that is seen approximately 15 min after the injection of gadolinium (late) versus early (that occurs within 15 s). Thus, in myocardial infarction or during infiltration by some chemical or during fibrosis, the extracellular compartment enlarges and is seen as LGE, allowing the myocardial fibrosis in endomyocardial fibrosis to be seen directly on MRI. On echocardiography, the exact extent of fibrosis cannot be exactly viewed.

T2-weighted images show myocardial oedema [4]. Schmidt et al. [5] have quantified a heterogeneous peri-infarct zone that was found to be associated with increased monomorphic ventricular tachycardia inducibility and the need for an internal cardioverter defibrillator.

The fine-tuning possible with MRI shows that tissue characterisation by this modality is superior to that of two-dimensional (2D) echocardiography [6].

The extent of fibrosis in congestive heart failure has been directly studied by Iles and co-workers. Post contrast T1 times correlated histologically with fibrosis and were found to be shorter in patients with heart failure than in normal control subjects [7].

Invasive angiography has been described in detail in EMF. This modality can detect obliteration of the right ventricle (RV) apex or LV apices. When the whole of the apex is obliterated this has been referred to as the “mushroom sign” [8]. However, invasive angiography is not without risks. Embolism due to dislodgement of LV or RV thrombi, contrast reactions and hypotension are the complications that can occur after angiography. MRI is a less invasive and safer modality that yields equivalent results.

We looked for the following features of EMF on MRI in echocardiography proven cases of endomyocardial fibrosis:

1.       Diffuse subendocardial gadolinium enhancement involving either the RV or LV (hyperenhancement). Late gadolinium enhancement denotes fibrotic tissue and that the myocardial cells are damaged.

2.       Apical RV or LV thickening with obliteration of RV or LV apex. Obliteration of the ventricular apices appears as a hyperintense mass or a structure obscuring the apices of the affected ventricles. This has been found on histopathology to be fibrous tissue [9-11].

3.       An apical dark signal, showing no evidence of contrast on LGE images, signifying a thrombus. The thrombus is basically an inert structure; thus, contrast material does not penetrate it, causing it to appear as an apical dark signal without enhancement.

4.       Presence or absence of thrombus in the atria or ventricle. EMF is usually associated with dilated atria, with the atrial dilatation being out of proportion to the size of the ventricles. Any structure that is hypocontractile and dilated can form the nidus for intracavitary thrombi.

5.       Presence or absence of calcium. One hallmark of fibrotic tissue is its tendency to become calcified. In EMF, tissue in the endocardium, as well as intracavitary tissue, can become calcified. Further, the myocardium can become calcified. This calcification is usually seen along the line of demarcation of the endocardium and the myocardium and is distinctly different from the pericardial calcification outlining the cardiac silhouette that is seen in constrictive pericarditis. Amorphous, unformed large areas of calcification are the hallmark of EMF and these areas are found inside the cavity of the ventricles.

6.       Presence or absence of pericardial effusion. Pericardial effusion on MRI usually appears as a bright shadow around the heart. Unlike on echocardiography, where pericardial effusion appears black, on MRI it appears white, or bright. Classically, a transudate type of pericardial effusion has a signal void on black blood images and high signal intensity on SSFP and gradient echo images [12].

Hemorrhagic effusions have high signal intensity on T1-weighted spin images and low intensity on gradient echo images during MRI.

7.       Atrial dilatation

8.       Three-layered appearance of dark overlying thrombus, bright fibrotic endomyocardium and dark underlying myocardium. This appearance has been described as typical of EMF, regardless of the type, whether due to tropical EMF or due to hypereosinophilic syndrome. This is caused by the deepest layer of thrombus, followed by a thin or thick layer of endocardium and the underlying myocardium.

9.       Typical dimple at RV apex, the typical picture in RV EMF, as described by Vijayaraghavan [16] “the fibrotic retraction of the right ventricular apex produces the typical apical dimple in endomyocardial fibrosis.” He has described this dimple on echocardiography, and we show it on MRI. Basically, it is the typical shape seen on the outer border of the RV on echocardiogram or at autopsy.

10.    MRI can accurately quantify the degree of mitral regurgitation or tricuspid regurgitation, which can help in planning whether the patient needs mitral valve replacement.

AIM

We intend to report patients with echocardiogram-proven EMF and to find out how many of them have the typical MRI features of EMF.

MATERIALS AND METHODS

Patients diagnosed with EMF using echocardiograms were included in the study and underwent cardiac MRIs if they were willing. The MRI was performed with a 1.5 Tesla machine. The findings in five cases are listed in Table 1 and the protocol used is explained in Table 2. Informed written consent was obtained in all the cases. This was part of a postgraduate thesis so was shown to both the institutional review board and the Medical College ethics committee and approved. The study was carried out in the Medical College Hospital Trivandrum (otherwise called Government Medical College Trivandrum).

RESULTS

Seven of our patients had MRI for suspected EMF. Two patients did not have findings of endomyocardial fibrosis on MRI. The MRIs of the remaining five patients are included in Table 1 and were analysed in detail (Figures 1-5). The techniques used are summarized in Table 2.

Five of the seven patients included in the study were women, whose ages were 47, 85, 55, 40, 48 years, respectively. The MRIs of patient 4 have already been published and are reproduced with permission [9]. All the patients satisfied the Mocumbi criteria of diagnosis of EMF on echocardiography [1]. Patient 5 was a case of suspected mitral stenosis with atrial fibrillation that had a cerebrovascular accident and was assessed both by echocardiography and MRI. Patient 7 was a 75 year old man who presented with systemic hypertension and atrial fibrillation. On initial echocardiogram, it was thought that he had LV EMF. But by the time he had an MRI, the findings for EMF were negative. He only had concentric LV hypertrophy. The images of patient number 6 were normal so we excluded her from the study. Her history briefly: We performed a radiofrequency ablation for atrioventricular node re-entry tachycardia (AVNRT); but we did not preserve her MRIs, as they were normal. The MRI features of the patients are given in Table 1. The Figures 1-5 show the MRI features of the various patients.

The clinical details of the patients

Patient 1 was a 47 year old woman with typical angina, who on echocardiogram had obliteration of her RV apex and mild tricuspid regurgitation. She was diagnosed with EMF and her antianginal medications were stopped. It is of interest that she had a distinct demarcation between her myocardium and endocardium, possibly early EMF that can be scored out at surgery [10,11]. However, we did not consider surgery, as previous surgeries for right-sided EMF had poor outcomes (Figures 3 and 4) [10].

Our second patient was an 85 year old woman who presented with acute palpitations and giddiness. On examination, her heart rate was 100 bpm and irregular; her blood pressure was 130/80. Her jugular venous pressure was elevated to 8 cm and her V-wave was prominent. This later reverted to sinus rhythm. Her apex beat was not palpable; she had no left parasternal heave; her first heart sound was varying in intensity, her second heart sound was loud and she had no third or fourth heart sound and no murmurs. She was thought to have new-onset atrial fibrillation either due to systemic hypertension or mild rheumatic mitral stenosis. But her echocardiogram demonstrated right atrium dilation and apical obliteration of her RV apex and mild tricuspid regurgitation. By Mocumbi echocardiographic criteria, her score was -8 (Figures 1 and 2).

Patient 3 presented with atrial fibrillation and a fast ventricular rate. She was put on a combination of beta-blocker and Ramipril and after a period of 6 months she reverted to sinus rhythm. She has continued with the same drugs and still comes for follow-up. She is also taking warfarin (Figures 5 and 6).

This patient’s image is already published in Indian Heart Journal. This is a different image of the same patient.

Patient 4 was a long-time female patient of the Department of Cardiology. Her MRIs were obtained when she was 40 years old [9]. She had dominant RV EMF. Her MRI can be described as late EMF. Her MRI showed a right atrial thrombus, filling defect on contrast MRI at the RV apex, LGE and the typical trilayer of subendocardial LGE, with a layer of dark myocardium below and then a pericardial effusion [9].

Patient 5 was a 51 year old woman who presented with hemiparesis and was clinically thought to have mitral stenosis. An echocardiogram showed biventricular, dominant left endomyocardial fibrosis. The MRI allowed her to be placed on medical follow-up and not be sent for closed mitral valvotomy/balloon mitral valvotomy or valve replacement (Figure 7).

DISCUSSION

EMF is a rare disease that has fascinated cardiologists and pathologists for ages. The most amazing feature of this disease is that patients survive relatively long periods in spite of having a grossly distorted heart [3,13,14]. Recent reports have shown that the population of EMF patients is aging [15,16].

A typical feature of RV EMF has been described as the “heart of Africa” or the right-ventricular dimple. This feature has been shown on both chest radiograph and on echocardiography [13]. The “heart of Africa” is supposed to be the dilated heart in RV EMF that has the shape of the map of Africa. Severe RV EMF has been considered to have a Fontan-like circulation [17]. The disease was recently reviewed [18-20]. The angiographic findings in EMF have been described by Krishnamoorty [8]. EMF has been studied at autopsy, during echocardiography, and by angiography.

What are the MRI features of EMF?

1.       One feature described is diffuse subendocardial gadolinium enhancement involving either RV or LV (hyperenhancement) and apical RV or LV obliteration. Another MRI feature described is the “apical dark signal” that shows no evidence of contrast in LGE images, signifying an inert structure, a thrombus. A thrombus in the LV or RV shows neither early nor late enhancement. As we mention below, MRI usually overestimates the size of left atrial appendage thrombi [21,22].

2.       EMF classically presents with calcification, which can be endocardial calcification, myocardial calcification, or a calcified thrombus. These features can all be accurately delineated by MRI, improving on the image obtained by echocardiography.

3.       Pericardial effusion can be seen on echocardiography, but sometimes what appears to be a pericardial effusion can actually be a pericardial lipomatosis. On MRI, however, even small quantities of pericardial effusion and loculated pericardial effusions can be accurately distinguished. Epicardial fat and pericardial effusion (thin rim) both appear dark on echocardiography and cannot be accurately distinguished. But on MRI, the transudate type of pericardial effusion has a white or bright appearance on T1-weighted images and a signal void on black blood images. A hemorrhagic effusion can also be identified. A transudate type of pericardial effusion has a signal void on black blood images and high signal intensity on SSFP and gradient echo images. Hemorrhagic effusions have high signal intensity on T1-weighted spin images and low intensity on gradient echo images on MRI. These findings are not possible with pure echocardiographic imaging:

A “three-layered appearance” describes a dark overlying thrombus, bright fibrotic endomyocardium, and dark underlying myocardium. Another sign that has been described in hypereosinophilic syndrome is the V sign [21,22].

 

Recent publications on MRI and hypereosinophilic syndrome

Caudrona et al. [21] describes the MRI findings in hypereosinophilic syndrome.

Syed et al. [22] have described the MRI features of hypereosinophilic syndrome. They used contrast-enhanced CMR to demonstrate thrombus, endocardial fibrosis and inflammation. The typical appearance they described was the “three-layered appearance.” This consists of one layer of normal myocardium, a second layer of the thickened and fibrotic endocardium with inflammatory infiltrate, and the third layer, the thrombus. It is believed that MRI precludes the need for an open biopsy (earlier studies have biopsy data).

Kharabish and Haroun [23] had a patient with rheumatoid arthritis and dyspnoea who on inversion recovery (IR), delayed enhancement and cine SSFP found that their patient had EMF with fibrosis, apical ventricular hypertrophy and LV thrombus. They believed the MRI was more useful than echocardiography in detecting EMF due to hypereosinophilia. They used the cine SSFP images and dark blood sequences T1 and T2 turbo-spin echo images before and after contrast. They also used inversion recovery images after gadolinium, administered intravenously to detect LGE. They also used velocity-encoding phase contrast (VENC). Their Figure 4 is very much like our Figure 5.

MRI gives an idea about the tissue characterisation and has a good histological correlation [24]. Subendocardial hyper enhancement after 0.2 mmol/kg body weight of intravenous gadolinium on inversion recovery technique suggested fibrosis or irreversible myocardial necrosis. Their patient was a Venezuelan woman who at biopsy was proved to have EMF.

Delayed enhancement MRI allows detection of subendocardial fibrosis non-invasively.

Genee et al. [25] have described the MRI characteristics of an intracavitary thrombus in a suspected case of hypereosinophilia. A delayed hyperenhancement showed the “subendocardium” within 10 min of intravenous infusion with gadolinum diethylene triamine pentacetic acid (Gd-DTPA). The thrombus was demonstrated by “no evidence of early or late hyperenhancement.”

Salanitri [26] also described the MRI features of intracardiac thrombi in hypereosinophilic syndrome.

Shapiro et al. [11] described an early case of EMF that had a shiny collagenous, gelatinous material, similar to an intracardiac tumour that could be scored out in surgery. This was actually the fibrosed endocardium.

In his article on surgery in EMF, Valiathan et al. [10] describes how in some cases he was able to score out the endocardium and remove it from the ventricle. This is seen on MRI in our patient 1. We believe this is true for early cases of EMF. 

Why should an MRI be done in EMF?

The first reason is the history of EMF in Kerala. The first case of EMF was diagnosed at autopsy in a patient who had been mistakenly operated on for closed mitral valvotomy and then died during surgery. On autopsy, it was found that the patient had obliteration of the LV, tethering of the posterior mitral leaflet and a large left atrial thrombus.

In those days, MRIs were not available. Invasive angiography was a new technology. Any thrombus would have embolized if a left ventriculogram had been performed with a pressure injector.

Secondly, an MRI can demarcate and denote different types of tissues. Pericardial effusion, fat, calcification, the pericardial thickness, the myocardium and any thickened endocardium can be clearly seen. The valves can be distinguished, and any cavity obliteration can be seen directly.

The MRI would be useful in the accurate staging of the patient. Shaper et al. [2] was the first person to describe the types of EMF. The exact Shaper types can be determined by MRI. For example, patient 3 has obliteration of both her RV and LV, so she has types R3 and L3. Further, this diagnosis is by a non-invasive investigation and not by autopsy, as was done in Shaper original series.

MRI helps in the differential diagnosis of EMF. 

MRI features of mitral stenosis

MRI can quantify the severity of mitral stenosis by planimetry or by pressure half time. For planimetry, the mitral valve is assessed by the gated SSFP mode, which is a series of short axis cuts of the ventricle. The planimetry is then done at the tips of the mitral leaflets. The white blood parts of the image should be included and the calcified leaflets should be excluded.

Pressure half time mitral valve area is performed by using special software that makes a graph of the blood flow across the mitral valve.

Djavidani et al. [27] have studied 22 cases of suspected mitral stenosis. The MRI evaluated mitral valve area correlated with the catheterisation-measured mitral valve area. MRI slightly overestimates the mitral valve area compared to the echocardiographic or the catheterisation methods. However, it can be very useful in patients who have poor echo windows and who cannot cooperate with a transoesophageal echocardiogram (such as stroke patients).

MRI features of constrictive pericarditis

The initial evaluation of a case of constrictive pericarditis is usually an echocardiogram. Computed tomography (CT) scans show the thickened pericardium but not the hemodynamics [28]. A thickened pericardium of greater than 4 mm signifies pericardial thickening suggestive of constrictive pericarditis. CT is superior in identifying calcification, but calcification can occur without constriction. CMR or MRI is better that CT and echo imaging in that it can detect small pericardial effusions, has better temporal resolution and may reveal ongoing pericardial inflammation. A septal bounce can be seen on cine MRI as can the respire-phasic variations in the septal motion.

MRI can provide a few specific findings of constriction that are not available with CT scan, as follows: pericardial myocardial adherence and abrupt cessation of myocardial filling in diastole, by SSFP cine images. Phase encoding velocimetry provides similar information as Doppler echocardiography. Thus, if the patient has a non-diagnostic echocardiogram and is suspected of having constriction, MRI should be preferred to CT imaging of the heart.

MRI features of Ebstein’s anomaly

Nakamura et al. [29] have displayed classical images of the MRI in Ebstein’s anomaly. They showed thick pericardial fat on the free wall of the RV, small circumferential pericardial effusion, a huge right atrium and apical displacement of the tricuspid leaflets. The atrialized ventricular wall was thinner than the distal functional RV wall. LGE was observed in the atrialized ventricular wall.

Left dominant arrhythmogenic dysplasia

The MRI diagnosis of ARVD/C depends on the demonstration of fibro-fatty change by MRI. However, MRI is not very sensitive for this syndrome. Sen-Choudhry et al. [30] have gone a step further. They have characterised by MRI a left-dominant arrhythmogenic cardiomyopathy.

During MRI of a suspected case of ARVD/C, there are three differential diagnosis have to be excluded. First to diagnose whether it is ARVD/C, whether it is a biventricular or a left dominant ARVC/D or a case of idiopathic myocardial fibrosis (IMF), which is also associated with sudden death. In IMF the fibrosis has a predilection for the inferior wall. Echocardiography cannot distinguish between these 3 conditions.

Unlike myocardial infarction, the LGE is mid-myocardial or subepicardial and not subendocardial. These MRI features would help distinguish LV ARVD/C from LV EMF.  

Right-sided ARVD/C is classically diagnosed by the detection of fat in the RV free wall, but this is subject to errors. Fat-suppressed LGE imaging of the RV with short inversion times (<150 ms) shows a high correlation with ARVD/C and the presence of arrhythmias. Sen-Choudhry et al. [30] showed that CMR has a sensitivity of 96% and a sensitivity of 78% in detecting ARVD/C. This modality detected early disease not detected by the Task Force criteria [4].

Myocarditis

CMR shows myocardial edema on T2-weighted images. Myocarditis usually involves the subepicardial region. The myocardial injury and regional hyperaemia and capillary leak can be detected by early gadolinium enhancement (EGE) ratio or myocardial necrosis or fibrosis by LGE. It has been found that if LGE persists beyond week 4 on MRI, this is a poor prognostic sign [4].

Hypertrophic cardiomyopathy

Maron [31] has indeed described the different types of HCM by echocardiography.

MRI in HCM has been described by Chan et al. [32]. Peterson et al. [33] found that the basal myocardial blood flow in control subjects and in people with HCM was not significantly different, but the blood flow at maximum hyperaemia was much less in patients with HCM. This microvascular dysfunction had prognostic implications for sudden death.

On multivariate Cox regression analysis, a LGE of greater than 20% of the myocardium was associated with an increased risk of sudden death [32].

MRI in HCM detects 6% more hypertrophy when compared to echocardiography. Echocardiography underestimated the LV hypertrophy.

MRI for pericardial effusion

Compared with echocardiography, MRI can show small, localised pockets of pericardial effusion more easily [34]. Pericardial effusions have a signal void on black blood images and high signal intensity on SSFP images. Complex effusions such as exudative and hemorrhagic fluids have a high signal intensity on T1-weighted images and an intermediate signal on T2-weighted spin echo images. On SSFP images, fibrin strands or coagulated blood can be seen.

MRI for thrombi

The visualisation of a thrombus on MRI varies with whether the thrombus is in the atrium or in the left ventricle [35]. Thrombi are identified as low signal intensity filling defects. Thrombi by MRI are smaller than those seen on transoesophageal echocardiography. For thrombi, 2D perfusion imaging and 3D turbo-FLASH low-angle shots are useful. Contrast-enhanced MRI is useful for LV thrombi; but for the atrial appendage thrombi, non-contrast imaging is superior.

How does performing an MRI help in the clinical management of EMF?

We have not restarted performing surgery for EMF. But authors from New York, in the USA, illustrate a very interesting patient where they have performed both an MRI and 3D echocardiograms. They have used these investigations to mark out fibrosis in the cavities of their patient. They do not see much EMF, but they decided to score out this thick fibrous material, which they thought was a cardiac tumor. They meticulously removed this material and studied it by histopathology. The tissue turned out to be only fibrous tissue [11]. Thus, MRI would aid in planning endocardial resection in the surgical treatment of EMF.

Confirmation of a thrombus by the three-layer appearance would be an indication to anticoagulate the patient, even in sinus rhythm, preventing strokes.

MRI is better than echocardiography for delineating left ventricular thrombi; this would lead to early anticoagulation and prevention of stroke.

Finally, having the correct diagnosis always leads to better management, treatment and follow-up. An MRI can document a disease for better patient treatment. Grimaldi reviews tropical endomyocardial fibrosis in 2016 [36].

CONCLUSION

MRI in EMF can evaluate the extent of cavity obliteration, and the presence of intracardiac thrombi and myocardial calcium. These findings are found both in tropical EMF and in eosinophilic EMF [36].

Reports of the MRI findings in tropical EMF are few. This report summarizes the findings and may be a first until larger studies are published. MRI changes the treatment plan in 2 of 7 (28.57%) patients with suspected EMF. 

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