22 June 2022: Review Articles
A Review of the Role of Transthoracic and Transesophageal Echocardiography, Computed Tomography, and Magnetic Resonance Imaging in Cardioembolic StrokeSergiu Florin Arnautu 123ABCDEFG, Diana Aurora Arnautu4BCF, Ana Lascu567BE, Andrei A. Hajevschi2B, Ciprian Ilie Ilie Rosca 8910D, Abhinav Sharma 41011AF*, Dragos Catalin Jianu123EF
Med Sci Monit 2022; 28:e936365
ABSTRACT: Stroke is a major source of morbidity and mortality worldwide, accounting for the second largest cause of mortality and the third greatest cause of disability. Stroke is frequently preceded by a transient ischemic attack (TIA). The etiologies of 20-30% of ischemic strokes are unknown, and thus are termed “cryptogenic strokes”. About 25% of ischemic strokes are cardioembolic. Strokes occur at a rate of around 2% per year in individuals with heart failure with reduced ejection fraction (HFrEF), with a strong correlation between stroke risk and the degree of ventricular impairment. Furthermore, stroke risk is augmented in the absence of anticoagulation therapy. Cardioembolic strokes, when treated inadequately, have a greater predilection for recurrences than atherothrombotic strokes, both early and late in life. The role of a patent foramen ovale in strokes, specifically in “cryptogenic strokes”, is a matter of concern that deserves due attention. The use of tissue-engineered heart valves and aspirin for minimizing the risk of stroke is recommended. Transthoracic echocardiography (TTE) is advantageous for assessing heart function in the acute phase of ischemic stroke. Transesophageal echocardiography (TEE) is considered the criterion standard procedure for detecting LAA thrombi. Computed tomography (CT) scans are good imaging modalities for identifying and excluding bleeding. Magnetic resonance imaging (MRI) images are by far the most effective imaging technique available for assessing the brain parenchymal state. We conducted a thorough review of the literature on the use of imaging modalities, highlighting the important contribution of TTE, TEE, CT, and MRI in the evaluation of cardioembolic stroke.
Keywords: Atrial Fibrillation, embolic stroke, Echocardiography, Transesophageal, Heart Failure, Humans, Magnetic Resonance Imaging, Stroke, Stroke Volume, Tomography, X-Ray Computed
Stroke is a major source of morbidity and mortality worldwide, accounting for the second largest cause of death and the third greatest cause of disability-adjusted life years (DALYs), as shown in the World Health Organization (WHO) Report on Mortality and Global Health estimates . Frequently, it is preceded by transient ischemic attacks (TIAs). Since the etiologies of 20–30% of ischemic strokes are unknown, they are classified as cryptogenic . However, using novel diagnostic procedures, the cause of 30% of the cryptogenic strokes can be attributed to the cardioembolic events of silent atrial fibrillation (AF) . The most common sustained cardiac arrhythmia is AF, with a prevalence of 2–4% in adults and 5–15% in the elderly . The yearly absolute risk of occurrence of stroke in AF is 3–4% [4–7]. This risk is amplified in patients with asymptomatic and paroxysmal atrial fibrillation (PAF), as these patients are vulnerable due to inadequate use of anticoagulants. Around 15% of TIAs can be attributed to silent PAF . Although Holter monitoring is commonly used for diagnosing PAF, its efficiency is limited by the sporadic nature of PAF and the inability of patients to identify it. Long-term monitoring is only feasible by the use of insertable loop recorders, but their invasive implantation is expensive and thus cannot be achieved in most stroke patients . Situations become even more complex when cardioembolic stroke is distinguished from extracranial and intracranial atherosclerotic strokes, which can be caused by a variety of diverse processes, including in situ thromboembolic obstruction, artery-to-artery embolism, branch occlusion, and circulatory insufficiency .
About 25% of ischemic strokes are cardioembolic. Strokes caused by cardioembolic thrombosis are typically more severe than those caused by atherothrombotic thrombosis. Furthermore, they have a greater proclivity for relapses, both earlier and late in life. Therefore, we conducted this review to elucidate the role of transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), magnetic resonance imaging (MRI), and computed tomography (CT) in diagnosing cardioembolic stroke. The following cardioembolic stroke risk factors are among the most common ones.
Cardioembolic Stroke Risk Factors
Clinical Characteristics of Cardioembolic Stroke
Cardioembolic stroke is characterized by the following characteristics: sudden deterioration of mental state, presence of neurological impairments, and modification of level of consciousness. Cardiac abnormalities can manifest themselves in the following ways: In the recent past, the patient may have had an arrhythmia (atrial fibrillation), a cardiac murmur, signs of congestive heart failure, acute myocardial infarction, or acute infective endocarditis.
Cardiovascular Assessment Methods
It is only effective for detecting continuing arrhythmias. Additionally, it can offer important information on the myocardial state of the ventricles (evidence of ventricular hypertrophy) and previous cardiac ischemia events. However, transitory arrhythmias can be overlooked, most notably paroxysmal atrial fibrillation.
It is now routinely used on all suspected cardioembolic stroke patients. While it is fundamentally identical to an electrocardiogram, it has the limitation of examining the conduction system for just 24 h.
IMPLANTABLE LOOP RECORDERS (ILRS):
They can maintain a 3-year record of activities. As a result, their clinical value continues to grow, and their use has aided identification of numerous cases of “missing” atrial fibrillation.
Imaging Methods for Assessment of Structural and Functional Cardiac Abnormalities
Risk Evaluation and Treatment
LA enlargement is a strong predictor of newly diagnosed atrial fibrillation and embolic events in individuals with atrial fibrillation. Echocardiographic abnormalities, such as LA indexed volume, are related to the diagnosis of AF in patients with cardiac embolic stroke of unknown cause [22,45,46].
The pulsed-wave Doppler transmitral inflow (TMF) pattern is another previously described predictor of AF. TMF is composed of 2 components: early diastole filling induced by the left atrioventricular pressure gradient (E wave) and late diastole filling induced by atrial contraction (A wave). Around the age of 60 years, a decline in E velocity occurs, followed by an increase in compensatory age-related A velocity due to left ventricular diastolic failure, and reversal of the E/A ratio. This change happened regardless of age in response to an increase in blood pressure, even during the acute phase of stroke. Individuals with AF did not exhibit an increase in the velocity of their A-waves [47,48]. Meanwhile, LA stunning is another factor that contributes to patients with atrial fibrillation having a low A wave velocity . Anticoagulation for subclinical device-detected AF is debatable, as short-term AF has not been demonstrated to warrant it .
Neurological Imaging Methods
Evaluation of the Cerebral Parenchyma
COMPUTED TOMOGRAPHY (CT) SCANS: This is a good imaging modality for identifying and excluding bleeding. Rapid imaging and simplicity of reporting, especially in environments with minimal information, continue to be its main benefits. Nonetheless, it demonstrates low sensitivity for detecting infarcts early in their evolution. Subtle symptoms such as sulcal effacement or “the hyperdense middle cerebral artery (MCA) sign” can be present in large infarcts, although they are inconsistent and often ignored (Figure 3).
MAGNETIC RESONANCE IMAGING (MRI) SCANS: This is by far the best imaging modality available for assessing the brain parenchymal state. Numerous imaging sequences aid in not only delineating the infarcted region but also in providing a chronological context in cases when the history is not well known. By selecting the right b-value, diffusion-weighted imaging (DWI) (Figure 4), MRI can assist in identifying even hyper-acute infarcts. Cortical stroke in various vascular areas raises the possibility of a cardioembolic origin. The presence of an infarct in the fluid-attenuated inversion recovery (FLAIR) sequence implies that the infarct formed partially over 6 h ago. Using susceptibility-weighted imaging (SWI), MRI scans can also correctly detect hemorrhagic infarcts.
MAGNETIC RESONANCE ANGIOGRAPHY:
This is an advantageous imaging modality, especially in patients with renal impairment, because it does not involve administration of intravenous contrast medium. A disadvantage is that it is susceptible to a variety of errors, including overestimation of stenotic lesions.
This is the criterion standard for examining the cerebral vasculature, but has the disadvantage of not being suitable in individuals with renal impairment.
Complications of Cardioembolic Strokes
Cardioembolic strokes, when not treated adequately, have a greater proclivity for early and late recurrences than athero-thrombotic strokes. Hemorrhagic events, both spontaneous and as a result of anticoagulant treatment, are potentially fatal complications of this illness. Long-term impairment and consequences such as internal cranial hypertension can emerge, although their degree and extent of deterioration corresponds to the severity and depth of the neuro-deficiency .
Due to the high likelihood of recurrence and death associated with cardioembolic stroke, cardioembolic embolism should be suspected and evaluated in all patients presenting with stroke. Owing mostly to the increasing prevalence of AF with age, the incidence of cardioembolic stroke is predicted to rise in the future. Both 2-D TTE and 2-D TEE are critical in detecting cardioembolic causes of stroke. These imaging modalities give critical and additional data that can be utilized for secondary prevention and determining the therapeutic plan for stroke patients. However, the novel technological innovation, known as the RT3DE, provides better insight into the pathogenesis of cardioembolic stroke.
FiguresFigure 1. Transesophageal echocardiography. Vegetations of the mitral valve (indicated by yellow arrow). The image was acquired using a VIVID5S, General Electrics phased array ultrasonoscope (Tirat Carmel, Israel). LV – left ventricle; LA – left atrium. Figure 2. Transthoracic echocardiography. Thrombus in the left ventricle (indicated by yellow arrow). The image was acquired using a VIVID5S, General Electrics phased array ultrasonoscope (Tirat Carmel, Israel). LV – left ventricle. Figure 3. CT scan. Ischemic stroke in left superficial MCA territory (indicated by yellow arrow). The image was acquired using GE REVOLUTION EVO 128 SLICE computed tomograph produced by General Electric Healthcare Japan Corporation – Japan. CT – computed tomography; MCA – middle cerebral artery, R – right; L – left. Figure 4. MRI in DWI. Recent ischemic stroke in superficial left MCA (indicated by yellow arrow). The image was acquired using GE SIGNA EXPLORER 1.5T magnetic resonance imaging device produced by General Electric Healthcare Japan Corporation – Japan. MRI – magnetic resonance imaging; DWI – diffusion-weighted imaging; R – right; L – left.
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