Thrombus associated with mitral valve calcification. A possible mechanism for embolic stroke

Stroke and Noninfective Native Valvular Disease

PURPOSE OF REVIEW

Embolic stroke of undetermined source is a challenging clinical entity. While less common than atrial fibrillation and endocarditis, many noninfective heart valve lesions have been associated with stroke and may be considered as culprits for cerebral infarcts when other more common causes are excluded. This review discusses the epidemiology, pathophysiology, and management of noninfective valvular diseases that are commonly associated with stroke.

RECENT FINDINGS

Calcific debris from degenerating aortic and mitral valves may embolize to the cerebral vasculature causing small- or large-vessel ischemia. Thrombus which may be adherent to calcified valvular structures or left-sided cardiac tumors may also embolize resulting in stroke. Tumors themselves, most commonly myxomas and papillary fibroelastomas, may fragment and travel to the cerebral vasculature. Despite this broad differential, many types of valve diseases are highly comorbid with atrial fibrillation and vascular atheromatous disease. Thus, a high index of suspicion for more common causes of stroke is needed, especially given that treatment for valvular lesions typically involves cardiac surgery whereas secondary prevention of stroke due to occult atrial fibrillation is readily accomplished with anticoagulation.

Mobile thrombus originating from densely calcified mitral annulus with cerebral embolism

Mitral annular calcification (MAC) has been considered a predisposition and an association of thrombo-embolic disease. Superimposed thrombus on MAC is under-appreciated as a potential cause of systemic thrombo-embolism. This report describes an elderly gentleman, who had recurrent cerebral embolism and in one of the episodes, a large mobile thrombus was detected on the ventricular surface of calcified mitral annulus. The thrombus disappeared after initiation of anti-coagulation.

Nonstenotic carotid plaque on CT angiography in patients with cryptogenic stroke

OBJECTIVE

To determine whether large (≥3 mm thick) but nonstenotic (<50%) carotid artery atherosclerotic plaque predominantly occurs ipsilateral rather than contralateral to cryptogenic stroke.

METHODS

This was a cross-sectional observational study. Using a stroke registry, we identified consecutive patients with anterior circulation embolic stroke of undetermined source (ESUS). Using CT angiography, we measured carotid plaque size (thickness, mm) and carotid artery stenosis (North American Symptomatic Carotid Endarterectomy Trial method) for each patient. We dichotomized plaque size at several predefined thresholds and calculated the frequency of plaque size above each threshold ipsilateral vs contralateral to stroke.

RESULTS

We included 85 patients with ESUS. Plaque with thickness ≥5 mm was present ipsilateral to stroke in 11% of patients, and contralateral in 1% (9/85 vs 1/85; p = 0.008). Plaque with thickness ≥4 mm was present ipsilateral to stroke in 19% of patients, and contralateral in 5% (16/85 vs 4/85; p = 0.002). Plaque with thickness ≥3 mm was present ipsilateral to stroke in 35% of patients, and contralateral in 15% (30/85 vs 13/85; p = 0.001). There was no difference in percentage stenosis ipsilateral vs contralateral to stroke (p = 0.98), and weak correlation between plaque size and stenosis (R(2) = 0.26, p < 0.001).

CONCLUSIONS

Large but nonstenotic carotid artery plaque is considerably more common ipsilateral than contralateral to cryptogenic stroke, suggesting that nonstenotic plaque is an underrecognized cause of stroke. We measured plaque size using CT angiography, a method that could be easily implemented in clinical practice.

Atrial fibrillation burden and atrial fibrillation type: Clinical significance and impact on the risk of stroke and decision making for long-term anticoagulation

Atrial fibrillation (AF) is a common arrhythmia increasing the risk of morbidity and adverse outcomes (stroke, heart failure, death). AF is found in 1-2% of the general population, with increasing prevalence with aging. Its exact epidemiological profile is incomplete and underestimated, because 10-40% of AF patients (particularly the elderly) can be asymptomatic ("clinically silent or subclinical AF"), with occasional electrocardiographic diagnosis. The research interest on silent AF has increased by the evidence that its outcome is no less severe, in terms of risks of stroke and death, than that for symptomatic patients. Data collected from more than 18,000 patients indicate that cardiac implantable electrical devices (CIEDs) are validated tools for detecting silent AF and measuring the time spent in AF, defined as "AF burden." A maximum daily AF burden of ≥5-6min, but particularly ≥1h, is associated with a significant increase in the risk of stroke, and may be clinically relevant to improve current risk stratification based on risk scores and for "personalizing" prescription of oral anticoagulants. An in-depth study of the temporal relationship between AF and ischemic stroke showed that data from CIEDs reveal a complex scenario, by which AF is certainly a risk factor for cardioembolic stroke, with a cause-effect relationship related to atrial thrombi, but can also be a simple "marker of risk," with a noncausal association with stroke. In such cases, stroke is possibly related to atheroemboli from the aorta, the carotid arteries, or other sources.

Embolic strokes of undetermined source: the case for a new clinical construct

Cryptogenic (of unknown cause) ischaemic strokes are now thought to comprise about 25% of all ischaemic strokes. Advances in imaging techniques and improved understanding of stroke pathophysiology have prompted a reassessment of cryptogenic stroke. There is persuasive evidence that most cryptogenic strokes are thromboembolic. The thrombus is thought to originate from any of several well established potential embolic sources, including minor-risk or covert cardiac sources, veins via paradoxical embolism, and non-occlusive atherosclerotic plaques in the aortic arch, cervical, or cerebral arteries. Accordingly, we propose that embolic strokes of undetermined source are a therapeutically relevant entity, which are defined as a non-lacunar brain infarct without proximal arterial stenosis or cardioembolic sources, with a clear indication for anticoagulation. Because emboli consist mainly of thrombus, anticoagulants are likely to reduce recurrent brain ischaemia more effectively than are antiplatelet drugs. Randomised trials testing direct-acting oral anticoagulants for secondary prevention of embolic strokes of undetermined source are warranted.

AF burden is important - fact or fiction?

Asymptomatic atrial fibrillation (AF) is common and in view of its prognostic impact (the same as of clinically overt AF) knowledge of the overall AF burden (defined as the amount of time spent in AF) appears to be important, both for scientific and clinical reasons. Data collected on more than 12,000 patients indicate that cardiac implantable electrical devices (CIEDs) are validated tools for measuring AF burden and that AF burden is associated with an increased risk of stroke. A maximum daily AF burden of ≥ 1 h carries important negative prognostic implications and may be a clinically relevant parameter for improving risk stratification for stroke. Decision-making should primarily consider the context in which asymptomatic, subclinical arrhythmias are detected (i.e. primary or secondary prevention of stroke and systemic embolism) and the risk profile of every individual patient with regard to thromboembolic and haemorrhagic risk, as well as patient preferences and values. Continuous monitoring using CIEDs with extensive data storage capabilities allow in-depth study of the temporal relationship between AF and ischaemic stroke. The relationships between AF and stroke are complex. AF is certainly a risk factor for cardioembolic stroke, with a cause-effect relationship between the arrhythmia and a thromboembolic event, the latter being related to atrial thrombi. However, AF can also be a simple 'marker of risk', with a non-causal association between the arrhythmia and stroke, the latter being possibly related to atheroemboli from the aorta, the carotid arteries or from other sources.

Caseous necrosis of mitral annulus: a rare cause of stroke

The current report describes a rare case of a caseous necrosis presenting as a pseudotumor in ventricle, revealed by stroke. Cerebral MRI, showing multiples lacunes, evocates a cardioembolic mechanism. Transthoracic and transesophageal echocardiography demonstrate a large hyperechogenic mass fixed to the posterior mitral valve and annulus while thoracic tomography revealed a fully calcified lesion, at the mitral annulus, evocative of caseus necrosis. Medical therapy was preferred (anticoagulation), because of her age and the decaying nature of surgery.

Newly developed mobile mass superimposed on mitral annulus calcification in patient with cerebral infarction: Documentation of a unique embolic source

Mitral annulus calcification (MAC) has been recognized as a potent risk factor to cause cerebral infarction. There has been suggested possible linkage between mass on MAC and systemic embolic events. We report a case of cerebral infarction with newly developed mobile mass superimposed on MAC.

Spontaneous fistulization of a caseous calcification of the mitral annulus: an exceptional cause of stroke

We present the case of a caseous calcification of the mitral annulus, responsible for two strokes, in a 72-year-old female patient. The brain computed tomography (CT) scan confirmed the presence of a calcific embolus. The echocardiography showed a liquidy, pseudotumoral mass combined with numerous calcifications located in the posterior part of the mitral annulus and extending toward the inferior surface of the left ventricle. During surgery, we found a direct communication between the caseous necrosis and the lumen of the left ventricle at the level of its inferior wall. We performed a valve repair procedure and excision of the caseous necrosis, combined with injection of bioglue into the cavity, to avoid recurrence. Six months after the procedure, the patient was in good health, and had no recurrence of stroke with a satisfactory echocardiography. This is the first description of spontaneous fistulization of a caseous necrosis in the lumen of the left ventricle, explaining a new mechanism for cerebral embolism during the course of calcifying diseases of the mitral annulus.

Tumors and tumor-like lesions of the heart valves

Valvular tumors and tumor-like lesions may have similar morphological and clinical characteristics, and may place the patients at a high risk of stroke in different ways. From January 2004 to June 2008, 11 patients underwent surgery for a suspected valvular tumor. Valvular tumor and tumor-like lesions accounted for 0.32% of adult cardiac operations. Five (45.5%) valvular lesions were papillary fibroelastomas, one (9.1%) was myxoma, 2 (18.2%) were organized thrombi, and 3 (27.3%) were calcification lesions. There was a total of 5 (45.5%) atrioventricular valve lesions, 4 arising from the atrial side of the leaflets, and one from the ventricular side. All 5 (45.5%) semilunar valvular lesions were from the aortic valve. One (9.1%) lesion originated from the chorda tendinea of the mitral valve. All leaflet lesions were resected by a simple shave technique, and all the patients recovered favorably. Valvular tumor and tumor-like lesions are rare. Pre-operative differential diagnoses among these valvular lesions pose important clinical implications for appropriate treatment for the underlying diseases. Prompt therapeutic measures in view of the underlying diseases of the valvular lesions are essential to prevent potential embolic events.

Association between mitral annular calcification and stroke

It remains controversial as to whether mitral annular calcification (MAC) is an independent predictor of stroke. The aim of this study was to investigate whether there is an association between the presence of MAC and stroke or whether MAC is one of the predictive factors of carotid atheroma and therefore is a secondary risk for stroke. Fifty-six patients who had MAC demonstrated by echocardiography underwent carotid artery duplex sonography and computed brain tomography with various causes were enrolled in the study. They were compared with 58 control patients without MAC. MAC was defined as a dense, localized, highly reflective area larger than 5 mm at the junction of the atrioventricular groove and posterior mitral valve leaflet. Carotid artery stenosis was defined as lumen diameter narrowing exceeding 60%. Cerebral ischemia was detected by spiral tomography and was classified as infarction and lacunae. A significant association was found between the presence of MAC and carotid atheroma (P = 0.011), MAC and hyperechogen plaque (P = 0.034), and MAC and stenosis (P = 0.008). There was an association between the presence of carotid atheroma and cerebral infarction (P = 0.007). Logistic regression analysis revealed hypertension and diabetes mellitus were independent risk factors (P = 0.030, P = 0.034, respectively) for developing carotid atheroma. MAC was an independent factor for carotid stenosis (P = 0.029). MAC may not be a significant causative factor for stroke, but may be a secondary risk factor. A significant association between the presence of MAC and carotid artery atherosclerotic disease may explain the high prevalence of stroke in patients with MAC.

Infarctus cérébral par embolie calcaire : complication spontanée révélatrice d’un rétrécissement aortique calcifié

Calcified aortic stenosis (CAS) is an unusual cause of cerebral infarct. The presence of cerebral intra-vascular or intra-parenchymatous calcifications, symptomatic or not, is suggestive of the diagnosis of CAS. We report two patients who experienced stroke induced by spontaneous calcic emboli from a calcified aortic valve and underline the importance of brain CT scan.

Mobile components associated with rapidly developing mitral annulus calcification in patients with chronic renal failure: review of mobile elements associated with mitral annulus calcification

Mitral annulus calcification may directly cause cerebrovascular accidents by serving as a source of calcific or thrombotic emboli. This hypothesis has been supported by recent reports of mobile components associated with mitral annulus calcification detected by echocardiography. Cardiovascular calcifications, including mitral annulus calcification, are common in end-stage renal disease and may develop and progress over a short period of time. We report two patients with mobile components associated with mitral annulus calcification and end-stage renal disease. Serial echocardiography documented that the mitral annulus calcification in these two patients had developed rapidly. Follow-up echocardiography in one patient demonstrated resolution of the mobile elements.

Mitral annulus calcification with a mobile component as a possible source of embolism

Mitral annulus calcification has been associated with embolic events, but the precise pathophysiology has not been elucidated. The authors describe four patients who experienced embolic events whose transesophageal echocardiograms showed a mitral annulus calcification, with a mobile component that exhibited the same echogenicity as the calcification. Three patients had no other conditions known to be associated with embolism. On follow-up transesophageal echocardiography, the mobile component of the mitral annulus calcification had disappeared in three patients. These findings support the hypothesis that mitral annulus calcification not only is associated with but also is possibly a direct cause of embolic events in some patients.

Embolization of calcific thrombi after tissue plasminogen activator treatment

BACKGROUND AND PURPOSE

Embolic stroke has been reported after thrombolysis in cardiac patients but has not yet been documented after thrombolytic therapy for acute ischemic stroke.

DESCRIPTION OF CASES

Patient 1 had a calcific embolus in the right M1 region on head computed tomography (CT) scan when treated with tissue plasminogen activator (tPA). Repeat imaging within hours showed distal migration of calcific fragments into the M2 region. Patient 2 had a calcific embolus in the right M1 region, as well as distal calcific emboli in multiple vascular distributions on initial head CT scan. She was treated with intravenous tPA but became unresponsive within 2 hours. Repeat imaging showed new calcium-density signal in the basilar artery.

CONCLUSIONS

We present 2 cases of radiographically evident, calcific embolization after tPA therapy for acute ischemic stroke. Emboli with a calcific component may lyse with tPA, but such patients should be carefully monitored for distal or recurrent embolization.

Epidemiology and natural history of atrial fibrillation: clinical implications

With a substantial impact on morbidity and mortality, the growing "epidemic" of atrial fibrillation (AF) intersects with a number of conditions, including aging, thromboembolism, hemorrhage, hypertension and left ventricular dysfunction. Currently, the epidemiology and natural history of AF govern all aspects of its clinical management. The ongoing global investigative efforts toward understanding AF are also driven by epidemiologic findings. New developments, by affecting the natural history of the disease, could eventually alter the nature of decision making in patients with AF. The crucial issue of rate versus rhythm control awaits completion of the AF Follow-up Investigation of Rhythm Management trial. The processes of electrical and structural remodeling that perpetuate AF appear to be reversible. In the era of functional genomics, the molecular basis of this ubiquitous arrhythmia is in the process of being defined. Unraveling the molecular genetics of AF might provide new insights into the structural and electrical phenotypes resulting from genetic mutations and, as such, new approaches to treatment of this arrhythmia at the ion channel and cellular levels. Thus, current adverse trends are superimposed on a background of a rapidly developing knowledge base and potentially exciting new therapeutic options. Consequently, an understanding of the epidemiology and natural history of AF is crucial to the future allocation of resources and the utilization of an expanding range of therapies aimed at reducing the impact of this disease on a changing patient population.

Transesophageal echocardiography for the evaluation and management of patients with cerebral ischemia

To prevent recurrent strokes and transient ischemic attacks, considerable attention is devoted to investigating the etiology of acute cerebral ischemia in the large subpopulation of patients without an easily identifiable cause. In general, transthoracic echocardiography is an insensitive tool for the evaluation of patients with cerebral ischemia, unless clinical signs and/or symptoms of cardiac disease are present. Transesophageal echocardiography (TEE), because of its increased sensitivity for aortic arch atheromata, atrial septal pathology, left atrial thrombi, and valvular abnormalities, is the preferred cardiac imaging modality, especially in young patients, older patients with hypertension or systemic atherosclerosis, and patients with prosthetic heart valves. This paper reviews the prognostic and therapeutic impact of TEE in patients with cerebral ischemia, specifically focusing on the ability of information obtained by this technique to alter patient management and improve risk stratification.

Coronary artery erosion and dissection: an unusual complication of mitral annular calcification

This article describes a 42-year-old male patient with a longstanding history of insulin-dependent diabetes mellitus, systemic arterial hypertension, and chronic renal failure. The patient had severe mitral annular calcification (MAC) identified at autopsy. This MAC was of an amorphous, caseous-appearing type; it displaced the posterior mitral valve leaflet and extruded into the myocardium of the lateral and posterolateral left ventricle to involve the epicardial surface. The MAC produced extramural erosion of the wall, and dissection into the media, of the first left/obtuse marginal coronary artery. This coronary artery involvement by, and other complications of, MAC are discussed.

Cardiac changes in stroke patients and controls evaluated with transoesophageal echocardiography

In stroke patients several cardiac changes associated with embolism can be detected with transoesophageal echocardiography. Potential major cardiac embolic sources (e.g. atrial fibrillation, thrombi of left ventricle/atrium, vegetation, myxoma, dilated cardiomyopathy) have a causal relationship to embolism. Other changes with no certain causal relationship are regarded as potential minor cardiac embolic sources (e.g. atrial septal aneurysm, patent foramen ovale, mitral annular calcification, mitral valve prolapse, protruding atheroma of the aorta). We compared the prevalences of major and minor potential cardiac embolic sources in a stroke population with that in controls. One hundred and twenty-one patients with first-ever stroke were compared with 68 randomly selected controls. All subjects underwent magnetic resonance imaging of the brain, carotid ultrasound and transthoracic/transoesophageal echocardiography. The patients were slightly older (mean age 70.7 +/- 10.3 years) than the controls (65.5 +/- 15.5 years) (p < 0.05). Potential major cardiac embolic sources were found in 27% of the patients and in 4% of the controls (p < 0.001). The most common major potential embolic source was atrial fibrillation, detected in 22/121 patients. Fifteen of these also had spontaneous echocontrast in the left atrium. Eleven left atrial thrombi were found (four of these patients had atrial fibrillation and seven had sinus rhythm). A history of heart disease was more common in patients with a potential major cardiac embolic source or a carotid artery stenosis (77%) than in those patients without (44%) (p < 0.01). After excluding subjects with a major potential cardiac embolic source and/or carotid artery stenosis, no differences in the prevalence of minor potential cardiac embolic sources were found between patients (55%) and control subjects (47%) (p = NS). Even when subjects without a major potential cardiac embolic source or a carotid artery stenosis were categorized into three age groups (35-54, 55-74 and > 74 years) the prevalence of potential minor cardiac embolic sources did not differ between patients and controls. To conclude, major potential cardiac embolic sources are more common in an older population with first-ever stroke than in a comparable control group. However, potential minor cardiac embolic sources did not differ in prevalence in the patients compared with controls. Certain changes (e.g. atrial septal aneurysm) might have a potential embolic role in younger stroke patients but in our study no difference was found between older stroke patients and controls.

Possible association of thrombotic, nonbacterial vegetations of the mitral ring-mitral annular calcium and stroke

Although numerous studies have shown an increased risk of stroke associated with mitral annular calcification, a direct link has rarely been demonstrated. We report the occurrence of long, pedunculated thrombi attached to the calcified mitral annulus in 3 patients who suffered from stroke, with resolution after anticoagulant and antithrombotic therapy.