An abnormal Ca(2+) response in mutant sarcomere protein-mediated familial hypertrophic cardiomyopathy.

Dominant-negative sarcomere protein gene mutations cause familial hypertrophic cardiomyopathy (FHC), a disease characterized by left-ventricular hypertrophy, angina, and dyspnea that can result in sudden death. We report here that a murine model of FHC bearing a cardiac myosin heavy-chain gene missense mutation (alphaMHC(403/+)), when treated with calcineurin inhibitors or a K(+)-channel agonist, developed accentuated hypertrophy, worsened histopathology, and was at risk for early death. Despite distinct pharmacologic targets, each agent augmented diastolic Ca(2+) concentrations in wild-type cardiac myocytes; alphaMHC(403/+) myocytes failed to respond. Pretreatment with a Ca(2+)-channel antagonist abrogated diastolic Ca(2+) changes in wild-type myocytes and prevented the exaggerated hypertrophic response of treated alphaMHC(403/+) mice. We conclude that FHC-causing sarcomere protein gene mutations cause abnormal Ca(2+) responses that initiate a hypertrophic response. These data define an important Ca(2+)-dependent step in the pathway by which mutant sarcomere proteins trigger myocyte growth and remodel the heart, provide definitive evidence that environment influences progression of FHC, and suggest a rational therapeutic approach to this prevalent human disease.

Neonatal cardiomyopathy in mice homozygous for the Arg403Gln mutation in the alpha cardiac myosin heavy chain gene.

Heterozygous mice bearing an Arg403Gln missense mutation in the alpha cardiac myosin heavy chain gene (alpha-MHC403/+) exhibit the histopathologic features of human familial hypertrophic cardiomyopathy. Surprisingly, homozygous alpha-MHC403/403 mice die by postnatal day 8. Here we report that neonatal lethality is caused by a fulminant dilated cardiomyopathy characterized by myocyte dysfunction and loss. Heart tissues from neonatal wild-type and alpha-MHC403/403 mice demonstrate equivalent switching of MHC isoforms; alpha isoforms in each increase from 30% at birth to 70% by day 6. Cardiac dimensions and function, studied for the first time in neonatal mice by high frequency (45 MHz) echocardiography, were normal at birth. Between days 4 and 6, alpha-MHC403/403 mice developed a rapidly progressive cardiomyopathy with left ventricular dilation, wall thinning, and reduced systolic contraction. Histopathology revealed myocardial necrosis with dystrophic calcification. Electron microscopy showed normal architecture intermixed with focal myofibrillar disarray. We conclude that 45-MHz echocardiography is an excellent tool for assessing cardiac physiology in neonatal mice and that the concentration of Gln403 alpha cardiac MHC in myocytes influences both cell function and cell viability. We speculate that variable incorporation of mutant and normal MHC into sarcomeres of heterozygotes may account for focal myocyte death in familial hypertrophic cardiomyopathy.

Dilated cardiomyopathy in homozygous myosin-binding protein-C mutant mice.

To elucidate the role of cardiac myosin-binding protein-C (MyBP-C) in myocardial structure and function, we have produced mice expressing altered forms of this sarcomere protein. The engineered mutations encode truncated forms of MyBP-C in which the cardiac myosin heavy chain-binding and titin-binding domain has been replaced with novel amino acid residues. Analogous heterozygous defects in humans cause hypertrophic cardiomyopathy. Mice that are homozygous for the mutated MyBP-C alleles express less than 10% of truncated protein in M-bands of otherwise normal sarcomeres. Homozygous mice bearing mutated MyBP-C alleles are viable but exhibit neonatal onset of a progressive dilated cardiomyopathy with prominent histopathology of myocyte hypertrophy, myofibrillar disarray, fibrosis, and dystrophic calcification. Echocardiography of homozygous mutant mice showed left ventricular dilation and reduced contractile function at birth; myocardial hypertrophy increased as the animals matured. Left-ventricular pressure-volume analyses in adult homozygous mutant mice demonstrated depressed systolic contractility with diastolic dysfunction. These data revise our understanding of the role that MyBP-C plays in myofibrillogenesis during cardiac development and indicate the importance of this protein for long-term sarcomere function and normal cardiac morphology. We also propose that mice bearing homozygous familial hypertrophic cardiomyopathy-causing mutations may provide useful tools for predicting the severity of disease that these mutations will cause in humans.

Cardiomyopathy in Irx4-deficient mice is preceded by abnormal ventricular gene expression.

To define the role of Irx4, a member of the Iroquois family of homeobox transcription factors in mammalian heart development and function, we disrupted the murine Irx4 gene. Cardiac morphology in Irx4-deficient mice (designated Irx4(Delta ex2/Delta ex2)) was normal during embryogenesis and in early postnatal life. Adult Irx4(Delta ex2/Delta ex2) mice developed a cardiomyopathy characterized by cardiac hypertrophy and impaired contractile function. Prior to the development of cardiomyopathy, Irx4(Delta ex2/Delta ex2) hearts had abnormal ventricular gene expression: Irx4-deficient embryos exhibited reduced ventricular expression of the basic helix-loop-helix transcription factor eHand (Hand1), increased Irx2 expression, and ventricular induction of an atrial chamber-specific transgene. In neonatal hearts, ventricular expression of atrial natriuretic factor and alpha-skeletal actin was markedly increased. Several weeks subsequent to these changes in embryonic and neonatal gene expression, increased expression of hypertrophic markers BNP and beta-myosin heavy chain accompanied adult-onset cardiac hypertrophy. Cardiac expression of Irx1, Irx2, and Irx5 may partially compensate for loss of Irx4 function. We conclude that Irx4 is not sufficient for ventricular chamber formation but is required for the establishment of some components of a ventricle-specific gene expression program. In the absence of genes under the control of Irx4, ventricular function deteriorates and cardiomyopathy ensues.

Adding dimension to cellular mechanotransduction: Advances in biomedical engineering of multiaxial cell-stretch systems and their application to cardiovascular biomechanics and mechano-signaling.

Hollow organs (e.g. heart) experience pressure-induced mechanical wall stress sensed by molecular mechano-biosensors, including mechanosensitive ion channels, to translate into intracellular signaling. For direct mechanistic studies, stretch devices to apply defined extensions to cells adhered to elastomeric membranes have stimulated mechanotransduction research. However, most engineered systems only exploit unilateral cellular stretch. In addition, it is often taken for granted that stretch applied by hardware translates 1:1 to the cell membrane. However, the latter crucially depends on the tightness of the cell-substrate junction by focal adhesion complexes and is often not calibrated for. In the heart, (increased) hemodynamic volume/pressure load is associated with (increased) multiaxial wall tension, stretching individual cardiomyocytes in multiple directions. To adequately study cellular models of chronic organ distension on a cellular level, biomedical engineering faces challenges to implement multiaxial cell stretch systems that allow observing cell reactions to stretch during live-cell imaging, and to calibrate for hardware-to-cell membrane stretch translation. Here, we review mechanotransduction, cell stretch technologies from uni-to multiaxial designs in cardio-vascular research, and the importance of the stretch substrate-cell membrane junction. We also present new results using our IsoStretcher to demonstrate mechanosensitivity of Piezo1 in HEK293 cells and stretch-induced Ca2+ entry in 3D-hydrogel-embedded cardiomyocytes.

Comparison of two murine models of familial hypertrophic cardiomyopathy.

Although sarcomere protein gene mutations cause familial hypertrophic cardiomyopathy (FHC), individuals bearing a mutant cardiac myosin binding protein C (MyBP-C) gene usually have a better prognosis than individuals bearing beta-cardiac myosin heavy chain (MHC) gene mutations. Heterozygous mice bearing a cardiac MHC missense mutation (alphaMHC(403/+) or a cardiac MyBP-C mutation (MyBP-C(t/+)) were constructed as murine FHC models using homologous recombination in embryonic stem cells. We have compared cardiac structure and function of these mouse strains by several methods to further define mechanisms that determine the severity of FHC. Both strains demonstrated progressive left ventricular (LV) hypertrophy; however, by age 30 weeks, alphaMHC(403/+) mice demonstrated considerably more LV hypertrophy than MyBP-C(t/+) mice. In older heterozygous mice, hypertrophy continued to be more severe in the alphaMHC(403/+) mice than in the MyBP-C(t/+) mice. Consistent with this finding, hearts from 50-week-old alphaMHC(403/+) mice demonstrated increased expression of molecular markers of cardiac hypertrophy, but MyBP-C(t/+) hearts did not demonstrate expression of these molecular markers until the mice were >125 weeks old. Electrophysiological evaluation indicated that MyBP-C(t/+) mice are not as likely to have inducible ventricular tachycardia as alphaMHC(403/+) mice. In addition, cardiac function of alphaMHC(403/+) mice is significantly impaired before the development of LV hypertrophy, whereas cardiac function of MyBP-C(t/+) mice is not impaired even after the development of cardiac hypertrophy. Because these murine FHC models mimic their human counterparts, we propose that similar murine models will be useful for predicting the clinical consequences of other FHC-causing mutations. These data suggest that both electrophysiological and cardiac function studies may enable more definitive risk stratification in FHC patients.

Familial dilated cardiomyopathy locus maps to chromosome 2q31.

BACKGROUND: Inherited gene defects are an important cause of dilated cardiomyopathy. Although the chromosome locations of some defects and 1 disease gene (actin) have been identified, the genetic etiologies of most cases of familial dilated cardiomyopathy remain unknown. METHODS AND RESULTS: We clinically evaluated 3 generations of a kindred with autosomal dominant transmission of dilated cardiomyopathy. Nine surviving and affected individuals had early-onset disease (ventricular chamber dilation during the teenage years and congestive heart failure during the third decade of life). The disease was nonpenetrant in 2 obligate carriers. To identify the causal gene defect, linkage studies were performed. A new dilated cardiomyopathy locus was identified on chromosome 2 between loci GCG and D2S72 (maximum logarithm of odds [LOD] score=4.86 at theta=0). Because the massive gene encoding titin, a cytoskeletal muscle protein, resides in this disease interval, sequences encoding 900 amino acid residues of the cardiac-specific (N2-B) domain were analyzed. Five sequence variants were identified, but none segregated with disease in this family. CONCLUSIONS: A dilated cardiomyopathy locus (designated CMD1G) is located on chromosome 2q31 and causes early-onset congestive heart failure. Although titin remains an intriguing candidate gene for this disorder, a disease-causing mutation is not present in its cardiac-specific N2-B domain.

Dilated cardiomyopathy and sensorineural hearing loss: a heritable syndrome that maps to 6q23-24.

BACKGROUND: Dilated cardiomyopathy (DCM) and sensorineural hearing loss (SNHL) are prevalent disorders that occur alone or as components of complex multisystem syndromes. Multiple genetic loci have been identified that, when mutated, cause DCM or SNHL. However, the isolated coinheritance of these phenotypes has not been previously recognized. METHODS AND RESULTS: Clinical evaluations of 2 kindreds demonstrated autosomal-dominant transmission and age-related penetrance of both SNHL and DCM in the absence of other disorders. Moderate-to-severe hearing loss was evident by late adolescence, whereas ventricular dysfunction produced progressive congestive heart failure after the fourth decade. DNA samples from the larger kindred (29 individuals) were used to perform a genome-wide linkage study. Polymorphic loci on chromosome 6q23 to 24 were coinherited with the disease (maximum logarithm of odds score, 4.88 at locus D6S2411). The disease locus must lie within a 2.8 cM interval between loci D6S975 and D6S292, a location that overlaps an SNHL disease locus (DFNA10). However, DFNA10 does not cause cardiomyopathy. The epicardin gene, which encodes a transcription factor expressed in the myocardium and cochlea, was assessed as a candidate gene by nucleotide sequence analysis; no mutations were identified. CONCLUSIONS: A syndrome of juvenile-onset SNHL and adult-onset DCM is caused by a mutation at 6q23 to 24 (locus designated CMD1J). Recognition of this cardioauditory disorder allows for the identification of young adults at risk for serious heart disease, thereby enabling early intervention. Definition of the molecular cause of this syndrome may provide new information about important cell physiology common to both the ear and heart.

Relations between left atrial appendage blood flow velocity, spontaneous echocardiographic contrast and thromboembolic risk in vivo.

OBJECTIVES: The aim of this study was to determine the relations between spontaneous echo contrast, left atrial appendage blood flow velocity and thromboembolism. BACKGROUND: Left atrial thrombus and spontaneous echo contrast, a putative marker of thromboembolic risk, are frequently located in the left atrial appendage. Measurement of left atrial appendage outflow Doppler velocity by transesophageal echocardiography is a recent technique for assessment of left atrial appendage function, which may be important in thrombus formation. METHODS: Transthoracic and transesophageal echocardiographic studies were performed in 140 patients with atrial fibrillation (chronic in 80 patients, paroxysmal in 50 patients, first episode < 2 weeks in 10 patients). The left atrium and appendage were inspected for thrombus and spontaneous echo contrast, which was graded from 0 (none) to 4+ (severe). Outflow velocity profiles were obtained by pulsed wave Doppler at the orifice of the left atrial appendage. RESULTS: Left atrial spontaneous echo contrast was present in 78 patients (56%). In multivariate logistic regression analysis, spontaneous echo contrast was the only significant correlate of left atrial thrombus and was present in 14 (93%) of 15 patients. Spontaneous echo contrast and age were associated positively, and anticoagulant therapy was associated negatively, with previous thromboembolic events. Increasing grades of spontaneous echo contrast were associated with decreasing left atrial appendage blood velocity. The velocity in patients with thrombus was not significantly different from that in patients with 4+ spontaneous echo contrast. In multivariate linear regression analysis, the grade of spontaneous echo contrast was significantly and negatively associated with left atrial appendage velocity (p = -0.0001) and mitral regurgitation (p = -0.0002) and significantly and positively associated with left atrial area (p = 0.0005). The odds ratio for spontaneous echo contrast was 28:1 for low left atrial appendage blood flow velocity (< 35 cm/s) and 96:1 for low velocity and the absence of mitral regurgitation. CONCLUSIONS: Spontaneous echo contrast is the cardiac factor most strongly associated with left atrial appendage thrombus and embolic events. Spontaneous echo contrast formation is promoted by reduced blood flow velocity and increased left atrial size but is diminished by mitral regurgitation.

Percutaneous balloon mitral valvotomy with the Inoue single-balloon catheter: commissural morphology as a determinant of outcome.

OBJECTIVES: The aim of this study was to determine the importance to outcome and the predictability of commissural splitting in patients undergoing percutaneous mitral valvotomy with the Inoue single-balloon catheter. BACKGROUND: Echocardiographic scoring systems devised to predict mitral valvotomy outcome are based on assessment of leaflet and subvalvular morphology, but the specific importance of commissural morphology has not been examined. METHODS: In 30 consecutive patients, commissural splitting was predicted on the basis of the two-dimensional echocardiographic commissural morphology: the extent of fusion, fibrosis or calcification of each commissure. Valve morphology also was evaluated according to a previously described echocardiographic scoring system. RESULTS: Splitting of one or both commissures occurred in 24 patients (80%) and was associated with a significantly greater mean increase in valve area (85%) than if neither commissure was split (13%). A good outcome from valvotomy (defined as valve area > 1.5 cm2 and increase in valve area > 25%) was achieved in 96% of those in whom one or both commissures split, but in none of the patients in whom neither commissure split. Whether or not splitting of at least one commissure would occur was predicted accurately in 28 (93%) of the 30 patients. Consequently, the prediction that one or both commissures would split was associated with a good outcome in 23 (89%) of 26 patients, whereas the prediction that neither commissure would split was not associated with a good outcome in any patient. There was no significant difference in the increase in mitral valve area between those with a mitral echocardiographic score < 8 and those with a score > or = 8. New or worsening mitral regurgitation occurred in nine patients, most commonly as a jet directed through a split commissure. CONCLUSIONS: Commissural splitting is the dominant mechanism by which mitral valve area is increased with the Inoue balloon technique, and it can be predicted by echocardiographic assessment of commissural morphology. Commissural morphology is a better predictor of outcome than is the mitral echocardiographic score.

Transesophageal echocardiography before and during direct current cardioversion of atrial fibrillation: evidence for "atrial stunning" as a mechanism of thromboembolic complications.

OBJECTIVES: The purpose of this study was to evaluate the usefulness of transesophageal echocardiography before electrical cardioversion in patients with atrial fibrillation and to determine the mechanism of thromboembolism after cardioversion. BACKGROUND: Thromboembolic complications after electrical cardioversion of atrial fibrillation have been attributed to the dislodgment of preexistent left atrial thrombus during the resumption of atrial contraction. Transesophageal echocardiography has been proposed as a method of screening patients for left atrial thrombus before cardioversion. METHODS: Seventy transesophageal echocardiographic studies were performed in 66 patients, predominantly with nonvalvular atrial fibrillation, before direct current cardioversion. In addition, transesophageal echocardiography was performed during the cardioversion procedure in 15 patients and immediately after in 1 patient. RESULTS: Left atrial thrombus was detected in one patient (1.4%), and cardioversion was cancelled. Thromboembolic complications occurred in 4 patients, none of whom had evidence of left atrial thrombus before cardioversion. Within 10 s of successful cardioversion, left atrial spontaneous echo contrast appeared in five patients, increased in one patient and was unchanged in nine patients. Patients with new or increased spontaneous echo contrast had more impaired atrial contraction and slower initial heart rates after cardioversion than those without. Left ventricular contraction was also impaired transiently by cardioversion. CONCLUSIONS: Transesophageal echocardiographic detection of left atrial thrombus before direct current cardioversion is important but infrequent in patients with predominantly nonvalvular atrial fibrillation. The occurrence of thromboembolic complications in the absence of demonstrable left atrial thrombus and the new development of spontaneous echo contrast in association with the transient atrial dysfunction ("stunning") caused by cardioversion suggest that cardioversion may promote new thrombus formation, in which case all patients should receive full anticoagulant therapy at the time of cardioversion.

Hematologic correlates of spontaneous echo contrast in patients with atrial fibrillation and implications for thromboembolic risk.

Spontaneous echo contrast has been observed in conditions of low blood flow velocity, such as rheumatic mitral stenosis and atrial fibrillation (AF). The phenomenon has been attributed to increased echogenicity due to aggregation of blood cells at low shear rates. The aim of this study was to determine whether abnormalities of blood composition also might contribute to spontaneous echo contrast formation by promoting cellular aggregation. Transesophageal echocardiography was performed in 185 patients with AF (31 with valvular and 154 with nonvalvular AF). The left atrium was examined for thrombus and spontaneous echo contrast, which was graded from 0 (nil) to 4+ (severe) by 2 independent observers. Forty milliliters of venous blood was obtained from each patient for hematologic analysis. Spontaneous echo contrast was observed in 46% of patients (74% with valvular and 41% with nonvalvular AF). In linear regression analysis, positive correlations were found between grade of spontaneous echo contrast and erythrocyte sedimentation rate (p < 0.001), low-shear blood viscosity (p < 0.001) and anticardiolipin antibody (p = 0.02) in the total study population, and in patients with nonvalvular AF. Spontaneous echo contrast correlated with mitral valve area (p < 0.01) and gradient (p = 0.03), but not with hematologic parameters in patients with valvular AF. Left atrial thrombus was present in 6 patients, all of whom had spontaneous echo contrast. Age (< 0.01), spontaneous echo contrast (p = 0.03) and the fibrinogen concentration (p = 0.03) correlated with previous embolic events.(ABSTRACT TRUNCATED AT 250 WORDS)

Familial hypertrophic cardiomyopathy and atrial fibrillation caused by Arg663His beta-cardiac myosin heavy chain mutation.

More than 40 different beta-cardiac myosin heavy chain (beta-MHC) missense mutations have been identified that cause familial hypertrophic cardiomyopathy (FHC). Some of these are recognized to have important clinical manifestations, such as an increased incidence of sudden death. We report that the beta-MHC missense mutation Arg663His causes predominant cardiac morphology and atrial fibrillation. Longitudinal clinical evaluations were performed in a kindred with FHC. The nucleotide sequence of the beta-MHC gene was analyzed to define the causal mutation. A missense mutation in the beta-MHC gene, Arg663His, was identified in 24 individuals. Clinical studies demonstrated modest left ventricular hypertrophy in affected individuals, predominantly localized in the proximal segment of the interventricular septum, which increased (average = 40 +/- 8%) during 7 years of follow-up. Results showed that 47% of Arg663His adults (age > 16 years) with ventricular hypertrophy developed atrial fibrillation, significantly more (p <0.001) than observed in ungenotyped FHC populations. Survival of affected individuals remained near normal. The beta-MHC missense mutation Arg663His causes a characteristic pattern of ventricular hypertrophy. Arg663His individuals have a markedly higher prevalence of atrial fibrillation, compared with a population with ungenotyped hypertrophic cardiomyopathy. The demonstration of phenotype as a direct consequence of genotype further extends the utility of molecular data in clinical medicine. Early identification of Arg663His individuals has the potential to minimize the serious sequelae of this arrhythmia in this FHC group.

Direct effects of DC cardioversion on blood echogenicity: an in vitro study.

Exacerbation of left atrial spontaneous echo contrast (SEC) after cardioversion of atrial fibrillation has been attributed to left atrial mechanical dysfunction induced by the procedure ("atrial stunning"). An in vitro model was devised to determine whether electrically induced changes in blood properties might contribute to SEC formation after cardioversion. Human blood echogenicity was examined quantitatively by videodensitometry before and after shocks of 1, 2, 5, and 20 J. Changes in blood cell numbers, cell morphology, and erythrocyte sedimentation rate were determined by haematological analysis. Immediately following electrical discharges, transient and dose-related, highly echogenic microbubbles were noted, but shocks of increasing intensity did not induce SEC at high blood velocity or alter the severity of SEC at low blood velocity. No quantitative or qualitative changes in haematological parameters were observed. These results suggest that direct effects of electrical shock on blood do not contribute to SEC after cardioversion. Systemic haematological responses to electric shock that might indirectly promote red cell aggregation in vivo cannot be excluded by this in vitro study.

Quantification of blood echogenicity: evaluation of a semiquantitative method of grading spontaneous echo contrast.

Spontaneous echo contrast (SEC) is an echogenic, swirling pattern of blood flow which may be observed by transesophageal echocardiography (TEE) in the left atrium in low flow states, such as atrial fibrillation (AF). The presence of SEC has been proposed as a marker of increased thromboembolic risk. Evaluation of the severity of SEC might be useful in stratification of thromboembolic risk. The aim of this study was to validate a semiquantitative method of grading SEC against quantitative videodensitometric analysis. TEE studies were performed in 50 patients with AF. The severity of left atrial SEC was graded by three independent observers and by videodensitometry. There was a strong, positive correlation between the semiquantitative grades of SEC and quantitative videodensitometric scores (r = 0.85, P < 0.0001). Inter- and intraobserver correlations in the grading of SEC were very high (observer 1 vs. 2: r = 0.98, P = 0.0001; observer 1 vs. 3: r = 0.93, P = 0.0001; observer 1 vs. 1: r = 0.97, P = 0.0001). Semiquantitative grading of SEC can be performed rapidly and reliably by experienced observers. These results support the use of semiquantitative grading in studies of the pathogenesis and prognostic implications of SEC.

Mutation of the LUNATIC FRINGE gene in humans causes spondylocostal dysostosis with a severe vertebral phenotype.

The spondylocostal dysostoses (SCDs) are a heterogeneous group of vertebral malsegmentation disorders that arise during embryonic development by a disruption of somitogenesis. Previously, we had identified two genes that cause a subset of autosomal recessive forms of this disease: DLL3 (SCD1) and MESP2 (SCD2). These genes are important components of the Notch signaling pathway, which has multiple roles in development and disease. Here, we have used a candidate-gene approach to identify a mutation in a third Notch pathway gene, LUNATIC FRINGE (LFNG), in a family with autosomal recessive SCD. LFNG encodes a glycosyltransferase that modifies the Notch family of cell-surface receptors, a key step in the regulation of this signaling pathway. A missense mutation was identified in a highly conserved phenylalanine close to the active site of the enzyme. Functional analysis revealed that the mutant LFNG was not localized to the correct compartment of the cell, was unable to modulate Notch signaling in a cell-based assay, and was enzymatically inactive. This represents the first known mutation in the human LFNG gene and reinforces the hypothesis that proper regulation of the Notch signaling pathway is an absolute requirement for the correct patterning of the axial skeleton.

Stratification of thromboembolic risk of atrial fibrillation by transthoracic echocardiography and transesophageal echocardiography: the relative role of left atrial appendage function, mitral valve disease, and spontaneous echocardiographic contrast.

The role of transesophageal echocardiography (TEE) in thromboembolic risk stratification in atrial fibrillation (AF) has not been established. Left atrial appendage contractile dysfunction in patients with AF predisposes to thrombus formation. The extent of blood stasis and propensity for thrombus can be assessed during TEE by measurement of the peak Doppler velocity of blood outflow from the appendage. Spontaneous echocardiographic contrast (SEC) is a swirling pattern of blood echogenicity that may be detected by TEE in the left atrium in patients with AF. The presence of SEC reflects left atrial blood stasis and a prothrombotic state. SEC is associated with an increased risk of systemic thromboembolic events. Parameters derived from TEE may provide additional prognostic data to clinical history and transthoracic echocardiography in thromboembolic risk stratification in AF.