J. Daryl. Franklin and Marshall College.
It should be realized trusted premarin 0.625 mg, however order premarin online pills, that this terminology only is based on the temporal aspect of two waves of the differentiation of cardiomyocyte progenitors formed from the common mesodermal source (40) buy cheap premarin line. A: Shows a slightly modified reproduction of the results of classic labeling experiments by Maria de la Cruz in early chicken embryos order genuine premarin online, which have shown already in the 1970s that considerable parts of the venous and arterial poles (hatched green areas) of the primitive heart tube are formed by addition of the cells from outside the heart. Note that distance between colored dots does not change significantly (dashed arrows). B–D: Show the three independently performed studies, all published in 2001, which have confirmed the findings of the classic labeling experiments and led to rediscovery of the secondary heart field of cardiac progenitors. Labeling technique using a fluorescent marker demonstrated the addition of the cells adjacent to the Fgf8-expressing pharyngeal mesenchyme to the cardiac outflow tract (asterisk). Note that there is considerable length of the outflow tract lacking fluorescent labeling (star). Such an addition of cells from outside the heart resulted in the formation of the outflow tract (arrow) even after complete ablation of the primary heart fields (asterisks). Prior to outflow tract formation, the lacZ staining was observed in a discrete population of Fgf10-expressing pharyngeal mesodermal cells (arrowheads). Experimental study of the development of the truncus and the conus in the chick embryo. The arterial pole of the mouse heart forms from Fgf10-expressing cells in pharyngeal mesoderm. A: Depicts schematically the progression from cardiac crescent through the primitive heart tube toward the four-chambered heart. The secondary heart field is located dorsally from the forming heart derived from the primary field. The cells making up the secondary heart field encompass the dorsal pericardial wall, and are added at the venous and arterial poles of the definitive heart. B: Summarizes current knowledge about genetic regulation of proliferation, migration, and differentiation of cardiomyocytes derived from the second heart field. These signals both regulate and are regulated by transcription factors in the pharyngeal mesoderm and adjacent cells, including pharyngeal epithelia and neural crest–derived cells, as well as autocrine signals from pharyngeal mesoderm itself (88,89). Transcription factors such as Islet1 and Tbx1 play central roles in integrating the output of different signaling pathways during secondary heart field development (87,94). Islet1, named after its involvement in pancreatic development, is essential for proliferation and differentiation of secondary heart field cells (ref), but Islet1 expression is extinguished as soon as progenitor cells have differentiated into cardiomyocytes (Fig. As such, the pathways regulating the determination and differentiation of secondary heart field cells may provide the foundation for efforts to induce the cardiac lineage from progenitor cells. Furthermore, delineation of the factors that regulate the development of the secondary heart field has revealed differences as compared to the factors governing differentiation of the primary heart field. Chamber Formation and Ventricular Septation A fundamental question in cardiac development relates to the establishment of the correct disposition of the chambers and the conduction system (95,96). Whereas the primitive peristaltically contracting heart tube does not need valves, they are essential for the proper functioning of the synchronously contracting four-chambered heart to prevent backflow from a downstream compartment during relaxation and to an upstream compartment during contraction. In the early developing heart, it is not possible to histologically identify the components of the conduction system as one can in the postnatal heart. Despite the absence of a specialized conduction system and valves, the electrical configuration of the embryonic heart consisting of alternating slowly and rapidly contracting segments, as described below, allows the early chamber-forming heart to produce coordinated atrial and ventricular contractions effectively propelling blood forward (97). Because slow conduction is also a prerequisite for nodal function, it may not be coincidental that nodes in these areas have developed, as discussed in Chapter 18. Development of the Basic Building Plan of the Mammalian Heart The elongation of the primitive heart tube is followed by the process of looping, during which the ventral part of the tube deviates to the right while bulging more and more ventrally as the ventricular chambers start to develop. At the same time the atrial chambers develop dorsally to the right and left of the forming outflow tract, which leads to the definitive appearance of the human heart at the end of the 8th week of development, when the fetal period begins (Fig. Subsequent to looping of the primitive heart tube, it becomes possible to distinguish its outer and inner curvatures (Fig. At localized areas of the outer curvature, the primary cardiomyocytes start to proliferate and initiate a genetic program governing their differentiation toward the working myocardium phenotype, which is characterized by the expression of fast-conducting gap-junctional proteins and atrial natriuretic factor P. Morphologically this differentiation can be recognized by the rapid expansion of the atrial chambers dorsally and the trabeculated ventricular chambers ventrally, a process that has been called ballooning (98,99). In the human-developing heart, this process was nicely illustrated by Streeter already in the 1940s (100). He demonstrated that the remnants of the smooth-walled primary heart tube persist as a continuous space in between the expanding trabeculated cardiac chambers. This space provides from the very beginning direct communications not only between the developing atria and the respective ventricles, but also between two developing ventricles and the outflow tract (Fig. After initiation of chamber formation, a new myocardial structure, the systemic venous sinus, is formed at the inflow region of the heart (102,103). Similar to the myocardium of the primary heart tube, the myocardium of the venous sinus initially escapes further differentiation, does not express fast- conducting connexins, and is characterized by high intrinsic automaticity, ensuring dominant pacemaker activity at the inflow of the heart (102,103,104,105,106). The panels show ventral views of the hearts after removal of the ventral body wall. A: Depicts the prototypic linear heart tube as seen in ventral and right lateral views. The primary myocardium is indicated in gray, the secondary myocardium of the atrial chambers ballooning at the dorsal aspect of the heart tube (arrows) is indicated in blue, and the myocardium of the ventricular chambers growing ventrally along the outer curvature of the heart tube (arrows) is indicated in red. The chamber myocardium is first seen locally at the stage of looping and does not involve the entire circumference of the tube. D: Shows the separation of the blood flow streams within the chamber-forming heart, even without completed septation. This enigma was solved by careful analysis of the expression pattern of a neural tissue antigen Gln2 in the developing human heart. A, A*: Show that at 30 to 34 days of development, a single ring of Gln2-staining tissue (brown staining on the sections) can be identified. Immunohistochemical analysis of the distribution of the neural tissue antigen Gln2 in the embryonic human heart. Green arrows indicate positive regulation and red lines suppression for differentiation toward the working phenotype or retention of the more primitive phenotype. Discovery of the secondary heart field led to a reinterpretation of the findings in mice lacking critical regulatory proteins and in transgenic mice harboring enhancers of genes expressed in the heart (117) (Fig. This observation further supported the concept that separable regulatory pathways control the development of the ventricles. Right ventricular hypoplasia in mice lacking transcription factor Mef2c, now a known target of Isl1, Gata4, Foxh1, and Tbx20 in the secondary heart field, may, similar to the Hand2 disruption, represent a defect of secondary heart field development (121,122). Many of the central transcriptional regulators of cardiac development in the primary heart field, including Nkx2–5 and Gata4, are also found to play an important role in the secondary heart field development (124). The secondary field of cardiac progenitors of zebrafish is, similar to mammals, positive for the analogous transcription factors Islet1, Tbx1, and Mef2c and essential for proper development of its two- chambered heart (125,126,127). This reflects the evolutionary changes in the expanded contribution of the secondary mesodermal pool of cardiac progenitors that occurred in higher vertebrates possessing four cardiac chambers. Epigenetic factors, such as the chromatin remodeling, may also contribute to cardiomyocyte differentiation and chamber morphogenesis (128). Furthermore, a direct role for several histone deacetylases in cardiac development was also demonstrated by a failure of ventricular growth in compound mutant mice lacking the isoforms 5 and 9 of P. Red dashed line in (B) demarcates the position of the developing ventricular septum. D: Depicts the distinct genetic regulatory pathways of the differentiation of the left versus right ventricular cardiomyocytes. Green arrows indicate positive regulation and red lines suppression of the particular genes. Chamber-specific cardiac expression of Tbx5 and heart defects in Holt–Oram syndrome. The right ventricle, outflow tract, and ventricular septum comprise a restricted expression domain within the secondary heart field. It is tempting to speculate, therefore, that impairment of this contribution to the ventricle may result in left ventricular hypoplasia. Soon after starting of ballooning, the developing ventricular chambers acquire initially tiny, but rapidly elongating trabeculations at their inner surface. The trabeculations within both ventricles express the rapid conduction connexins 40 and 43 and provide the precursor cells for the Purkinje network of the ventricular conduction system (56,73,111), as described in Chapter 18. During normal heart development, proliferation ceases in the trabeculations soon after their formation, while the outer ventricular wall becomes highly proliferative to form the compact myocardial layer (73,77,134), thus meeting the increasing demand to produce more powerful contractions. Unlike the trabecular myocardium, the newly formed compact layer of the ventricular wall does not express connexin 40.
Pulmonary valve replacement in patients with tetralogy of Fallot and pulmonary regurgitation: early surgery similar to optimal timing of surgery? Magnetic resonance imaging to assess the hemodynamic effects of pulmonary valve replacement in adults late after repair of tetralogy of fallot 0.625mg premarin for sale. Optimal timing for pulmonary valve replacement in adults after tetralogy of Fallot repair cheap 0.625 mg premarin mastercard. Ventricular fibrosis suggested by cardiovascular magnetic resonance in adults with repaired tetralogy of fallot and its relationship to adverse markers of clinical outcome buy premarin online from canada. Histopathology of the right ventricular outflow tract and its relationship to clinical outcomes and arrhythmias in patients with tetralogy of Fallot discount premarin 0.625 mg without a prescription. Corrected tetralogy of Fallot: delayed enhancement in right ventricular outflow tract. Effects of regional dysfunction and late gadolinium enhancement on global right ventricular function and exercise capacity in patients with repaired tetralogy of Fallot. Diffuse myocardial fibrosis following tetralogy of Fallot repair: a T1 mapping cardiac magnetic resonance study. Mechanoelectrical interaction in tetralogy of fallot: qrs prolongation relates to right ventricular size and predicts malignant ventricular arrhythmias and sudden death. Characterization of right ventricular diastolic performance after complete repair of tetralogy of Fallot. Acute right ventricular restrictive physiology after repair of tetralogy of Fallot: association with myocardial injury and oxidative stress. Impact of restrictive physiology on intrinsic diastolic right ventricular function and lusitropy in children and adolescents after repair of tetralogy of Fallot. Does restrictive right ventricular physiology in the early postoperative period predict subsequent right ventricular restriction after repair of tetralogy of Fallot? Right ventricular diastolic function in children with pulmonary regurgitation after repair of tetralogy of Fallot: volumetric evaluation by magnetic resonance velocity mapping. Relationship between type of outflow tract repair and postoperative right ventricular diastolic physiology in tetralogy of fallot: implications for long-term outcome. The impact of pulmonary valve replacement after tetralogy of Fallot repair: a matched comparison. Pulmonary valve replacement in tetralogy of fallot: impact on survival and ventricular tachycardia. Preoperative thresholds for pulmonary valve replacement in patients with corrected tetralogy of Fallot using cardiovascular magnetic resonance. Pulmonary valve replacement in adults late after repair of tetralogy of fallot: Are we operating too late? Outcomes after late reoperation in patients with repaired tetralogy of Fallot: the impact of arrhythmia and arrhythmia surgery. Impact of pulmonary valve replacement on arrhythmia propensity late after repair of tetralogy of Fallot. Left heart function in children with tetralogy of Fallot before and after palliative or corrective surgery. Total correction of tetralogy of Fallot in infancy, Postoperative hemodynamic evaluation. Left ventricular function after repair of tetralogy of fallot and its relationship to age at surgery. Left ventricular contractile state after surgical correction of tetralogy of Fallot: risk factors for late left ventricular dysfunction. Left ventricular dysfunction on exercise long term after total repair of tetralogy of fallot. Left ventricular dysfunction is a risk factor for sudden cardiac death in adults late after repair of tetralogy of Fallot. Factors associated with impaired clinical status in long-term survivors of tetralogy of Fallot repair evaluated by magnetic resonance imaging. Anatomy and myoarchitecture of the left ventricular wall in normal and in disease. Influence of right ventricular filling pressure on left ventricular pressure and dimension. Effects of diastolic transseptal pressure gradient on ventricular septal position and motion. Right ventricular function in adults with repaired tetralogy of Fallot assessed with cardiovascular magnetic resonance imaging: detrimental role of right ventricular outflow aneurysms or akinesia and adverse right-to-left ventricular interaction. The left heart after pulmonary valve replacement in adults late after tetralogy of Fallot repair. Structural abnormalities of great arterial walls in congenital heart disease: light and electron microscopic analyses. Aortic root dilation and aortic elastic properties in children after repair of tetralogy of Fallot. Prevalence and optimal management strategy for aortic regurgitation in tetralogy of Fallot. Aortic valve replacement after repair of pulmonary atresia and ventricular septal defect of tetralogy of Fallot. Massive aortic aneurysm and dissection in repaired tetralogy of Fallot; diagnosis by cardiovascular magnetic resonance imaging. Choosing the best contraceptive method for the adult with congenital heart disease. Dearani Persistent truncus arteriosus is an uncommon congenital cardiovascular malformation. There is no striking gender difference in frequency, although most series contained more male than female subjects. Truncus arteriosus usually occurs as an isolated cardiovascular malformation, although it has been reported in association with anomalies of other systems, particularly the DiGeorge or velocardiofacial syndrome (microdeletion chromosome 22q11. The anomaly has occurred in dizygotic twins (5) and siblings, and there is an increased incidence of cardiac malformations in relatives of children with this lesion (6,7,8). Because corrective operation for this malformation was first performed more than 30 years ago (9) ever-increasing numbers of postoperative patients are now reaching adolescence and adulthood. Patients who have had truncus arteriosus corrected need continued follow-up care throughout life. During the last 30 years, surgical correction of truncus arteriosus during infancy has become routine (10,11). Embryology The embryonic truncus arteriosus lies between the conus cordis proximally and the aortic sac and aortic arch system distally. Partitioning of the truncus arteriosus, which is intimately associated with conal and aortopulmonary septation, was reviewed by Van Mierop et al. Truncus swellings, similar in appearance to endocardial cushions, divide the truncal lumen into two channels: the proximal ascending aorta and the pulmonary trunk. As the proximal portion of this truncal septum fuses with the developing conal septum (derived from conal swellings), the right ventricular origin of the pulmonary trunk and the left ventricular origin of the aorta are established. Valve swellings develop from truncal tissue at this line of fusion, and the excavation of these swellings leads to formation of the aortic and pulmonary valves in their respective sinuses. Along the aortic sac, the paired sixth aortic arches (primitive pulmonary arteries) migrate leftward, and the paired fourth aortic arches shift rightward. Invagination of the aortic sac roof thereby forms an aortopulmonary septum that eventually fuses with the distal extent of the truncal septum. Accordingly, the right and left pulmonary arteries originate from the pulmonary trunk, and the aortic arch emanates from the ascending aorta. The spiral course of the truncoaortic partition produces the normal intertwinement of the great arteries. When conotruncal or truncoaortic septation does not proceed normally, various congenital ventriculoarterial anomalies may result (12). One of these anomalies is truncus arteriosus, in which a single arterial trunk exits from the heart. Also, either deficiency or absence of the conal (infundibular) septum produces a large ventricular septal defect. Because the conal septum also contributes to the development of the anterior tricuspid leaflet and the medial tricuspid papillary muscle, these structures may be malformed. The single truncal valve may be deformed and functionally insufficient or, less commonly, stenotic (14).
Even if the stenosis is relieved order premarin without prescription, right-to-left atrial shunting and cyanosis often persist P cheap premarin online american express. Manifestations Clinical Features Most patients with valvar pulmonary stenosis are asymptomatic premarin 0.625mg without prescription, and the diagnosis usually is made when a pathologic murmur is detected on routine examination purchase generic premarin on-line. Symptoms are rarely present in childhood but become more common with increasing age in patients with moderate to severe stenosis. Occasionally, patients with moderate to severe stenosis may experience chest pain, syncope, and even sudden death with strenuous exercise. Decreased myocardial perfusion caused by inadequate cardiac output during exercise, leading to ischemia and ventricular arrhythmias, is thought to be the mechanism for these events. Children with valvar pulmonary stenosis usually exhibit normal growth and development regardless of the severity of obstruction. If squatting is present, other diagnoses, especially tetralogy of Fallot, should be sought. Infants with critical pulmonary stenosis are cyanotic at birth, and the cyanosis may be severe enough to be life threatening (15). Although the right ventricular cavity is often relatively hypoplastic, the atrial communication is usually large enough to maintain cardiac output and prevent right heart failure at the expense of cyanosis. Symptoms of right-sided heart failure may be seen in some newborns with significant tricuspid regurgitation or may develop in untreated infants if the atrial communication becomes inadequate with growth. The auscultatory findings in valvar pulmonary stenosis are quite distinctive, often allowing the diagnosis to be made based only on the physical examination (Fig. The first heart sound is normal, and in patients with mild or moderate stenosis, it is followed by a pulmonary ejection click. The click corresponds to the time when the doming pulmonary valve reaches its open position. The more severe the stenosis, the earlier in systole the click occurs, until it merges with the first heart sound and becomes inaudible. The intensity of the click varies with respiration, decreasing during inspiration and increasing during expiration. The systolic murmur of valvar pulmonary stenosis is ejection in quality and maximal at the upper left sternal border. It may radiate over the entire precordium and neck, but characteristically is heard in the back. In general, the intensity of the murmur increases with the severity of obstruction. Mild stenosis is associated with murmurs of grade 3 or lower, and moderate to severe stenosis with grade 4 or louder. Patients with severe stenosis and right heart failure may have an unusually soft murmur because of low cardiac output. The length of the murmur is proportionately related to the duration of right ventricular ejection, which is determined primarily by the severity of obstruction. In mild stenosis, the murmur is relatively short and peaks at or before midsystole (Fig. In moderate stenosis, the murmur ends at or slightly after the aortic component of the second heart sound, which remains audible. With severe obstruction, the murmur extends beyond the aortic closure sound, which may become inaudible. A soft, early diastolic murmur of mild pulmonary insufficiency is rarely heard and usually results from progressive pulmonary trunk dilation. Patients with mild pulmonary valve stenosis have normal “a” waves and therefore normal jugular venous pulsations. With more severe obstruction, the “a” wave becomes progressively larger, and abnormal pulsations may be felt both in the jugular venous pulse and in the liver. In infants and children, jugular venous pulsations are often difficult to appreciate, even in the presence of large “a” waves. Auscultatory and phonocardiographic assessment of pulmonary stenosis with intact ventricular septum. Typically, the thrill is located at the second to third intercostal space, but it may also be felt at the suprasternal notch. The thrill may be absent in young infants with severe stenosis and in patients with congestive heart failure and low cardiac output. The second heart sound in pulmonary stenosis is usually split, and the degree of splitting is proportional to the degree of stenosis. The split may become fixed in severe stenosis as a result of a fixed stroke volume. The intensity of the pulmonary component of the second heart sound typically decreases with increasing obstruction, which may make the splitting difficult to appreciate. Occasionally, in mild stenosis, the pulmonary closure sound is louder than normal because of marked dilation of the pulmonary artery trunk. A fourth heart sound often is heard at the lower left sternal border in patients with severe stenosis. When a third heart sound is heard, the presence of an atrial septal defect should be suspected. The cardiac examination in infants with critical pulmonary stenosis may differ from that of older patients with severe obstruction. The systolic murmur of pulmonary stenosis may be deceptively soft as a result of decreased flow across the pulmonary valve in the presence of an atrial right-to-left shunt. Significant cardiomegaly may be detected by precordial palpation, most commonly due to right atrial enlargement. Electrocardiographic Features The electrocardiogram can be somewhat useful in assessing the severity of obstruction in patients with pulmonary valve stenosis. As many as 40% to 50% of patients with mild stenosis have a normal electrocardiogram. In moderate pulmonary stenosis, the electrocardiogram is almost always abnormal, with only 10% of patients having a normal tracing. The T waves in the right precordial leads are upright in approximately 50% of patients. The T waves may be upright or inverted in the right precordial leads, and the P waves are abnormally tall and peaked in lead 2 and in the right precordial leads, indicating right atrial enlargement. It is possible to estimate the right ventricular pressure in patients between 2 and 20 years of age if a pure R wave is present in lead V4R or V1. The height of the R wave in millimeters, multiplied by 5, approximates the right ventricular systolic pressure in millimeters of mercury (14). A superior axis, sometimes accompanied by a conduction abnormality of the left bundle, also has been described in some patients with pulmonary stenosis. There may be a correlation between these findings and Noonan syndrome, with its associated cardiomyopathy. This finding is present in 80% to 90% of cases, but it may be absent in infants, in patients with dysplastic pulmonary valve, and in cases of rubella syndrome. The right atrial segment may be prominent, more commonly in patients with associated P. The pulmonary vascularity is diminished as a result of right-to-left shunting at the atrial level. Heart size and pulmonary vascularity are usually normal in patients with mild to moderate stenosis. In the absence of right ventricular failure, even with severe obstruction, only mild cardio megaly is seen. When heart failure develops, marked cardiomegaly results due to right atrial and right ventricular enlargement, and pulmonary vascularity is decreased as a result of a reduction in pulmonary flow. Cardiomegaly is commonly present in infants with severe or critical pulmonary stenosis, and pulmonary vascularity is severely reduced because of the large atrial right-to-left shunt (Fig. Two-Dimensional Echocardiography The 2-D echocardiogram clearly demonstrates the typical features of the stenotic pulmonary valve from the standard and high parasternal short-axis and long-axis views as well as the subcostal sagittal views (Fig. Systolic motion is restricted, with inward curving of the tips of the leaflets, known as doming. Associated features, such as poststenotic dilation of the main and branch pulmonary arteries, also are easily recognized.
In the setting of acute rheumatic aortic regurgitation purchase premarin 0.625 mg with visa, the aortic valve may appear normal or show mild prolapse by 2-D echocardiographic imaging purchase premarin from india. The severity of mitral and/or aortic regurgitation should be evaluated using a combination of methods (240) discount 0.625mg premarin with visa. Although a single report did not find evidence of cardiac involvement in the absence of clinical findings (225) order 0.625mg premarin with amex, there are now multiple reports of such subclinical or “silent” cardiac involvement in patients with either isolated polyarthritis or “pure” chorea at the time of presentation (244,248,252,253). It is well known that the severity of cardiac involvement ranges from very mild to severe. In the current era with diminished auscultatory skills (254), this is likely to be an even more frequent occurrence. Further support for the existence of subclinical echocardiographic evidence of cardiac involvement comes from the fact that some series have described a subset of patients with initially “silent” subclinical evidence of carditis who subsequently developed murmurs of mitral and/or aortic regurgitation (253,255). Indirect evidence in support of “silent” subclinical carditis comes from natural history studies. Despite evidence in support of these findings, there has appropriately been concern over creating “iatrogenic” disease since a significant percentage of normal individuals have very small amounts of “physiologic,” Doppler- detected valvular regurgitation (mostly tricuspid, pulmonary, and mitral), especially with advances in ultrasound technology. To avoid labeling such normal findings as abnormal, strict criteria should be used to differentiate pathologic mitral and aortic regurgitation from the Doppler signals seen in normal individuals. The New Zealand and Australian Guidelines for diagnosis have gone a step further, with the New Zealand Guideline including subclinical carditis as a major diagnostic criterion (169), and the Australia Guideline including subclinical carditis as a major criterion in high-risk patients (171). It is important to note that if carditis is not found at presentation and initial evaluation, it may appear within 2 to 4 weeks. Therefore, consideration should be given to repeating a negative or equivocal echocardiogram in 2 to 4 weeks. Rheumatic fever diagnosis, management, and secondary prevention: a New Zealand guideline. Australian Guideline for Prevention, Diagnosis, and Management of Acute Rheumatic Fever and Rheumatic Heart Disease. Two-dimensional echocardiographic images from parasternal long axis (A) and apical four chamber (B) showing a posterolaterally directed jet of mitral regurgitation extending into the left atrium well beyond the mitral valve leaflets. Cardiac Catheterization Catheterization and angiography are rarely necessary for the management of patients with acute rheumatic valvular disease, including those who ultimately require surgery. Catheterization should be reserved for those in whom symptoms, clinical findings, and noninvasive imaging are discrepant, when measurement of pulmonary artery pressure and pulmonary vascular resistance is important in decision-making, and when balloon valvuloplasty for mitral stenosis is being contemplated (241,258). The cardiac silhouette may be enlarged due to valvular regurgitation and chamber enlargement and/or due to an associated pericardial effusion. In contrast to the chordal elongation and annular dilation that occur with acute rheumatic mitral valvulitis and regurgitation, leaflet shortening, rigidity, deformation, and retraction, often associated with chordal fusion and shortening result in abnormal leaflet coaptation and chronic rheumatic mitral regurgitation. Chronic mitral regurgitation results in compensatory dilation of the left ventricle, allowing for an increased total stroke volume that maintains forward flow. The combination of compensatory dilation of the left ventricle and the left atrium initially prevents a rise in left ventricular filling, left atrial, and pulmonary venous pressures. Although patients may remain asymptomatic for years with this compensation, the mitral regurgitation may progress over time (262). Severe chronic mitral regurgitation may eventually result in left ventricular dysfunction with decreased ejection fraction, elevated end-systolic volume, and elevated left heart filling pressures (27). Symptoms, most commonly exertional dyspnea or decreased exercise tolerance, may develop prior to, or with the onset of ventricular dysfunction (241,263,264). In the setting of chronic mitral regurgitation, precordial activity is increased and the apical impulse is displaced because of ventricular dilation. The first heart sound is often softer than normal and the second heart sound may be widely split due to shortened left ventricular ejection and earlier aortic valve closure. If there is associated pulmonary hypertension, the pulmonary component of the second heart sound (P2) may be increased. A regurgitant systolic murmur is best heard at the apex; more subtle mitral regurgitant murmurs may be heard at end-expiration with the patient in the left lateral decubitus position. When the regurgitant jet is posterolaterally directed, the murmur radiates to the left axilla. Medially directed jets may result in radiation of the murmur toward the base of the heart. For chronic mitral regurgitation, the intensity of the murmur correlates with the severity of regurgitation. When the regurgitant volume is significant, an apical diastolic flow rumble may be heard in the absence of mitral stenosis. The chest radiograph is usually normal in patients with mild mitral regurgitation. With moderate-to-severe mitral regurgitation, left atrial and left ventricular enlargement occur, resulting in a straight left heart border and cardiomegaly. Pulmonary venous congestion and interstitial edema may be evident with severe, decompensated mitral regurgitation and heart failure. Right ventricular hypertrophy may be evident in cases with secondary pulmonary hypertension. Atrial fibrillation is rare in children, but may be seen in adults with chronic rheumatic mitral valve disease (27). On echocardiography, the mitral valve leaflets are thickened and often echogenic with variably decreased mobility. In some cases, the anterior leaflet tip prolapse seen with acute carditis persists as chronic rheumatic mitral regurgitation. In other cases, the combination of a retracted, relatively immobile posterior (mural) leaflet with a more mobile anterior leaflet can give the impression of anterior prolapse even though the free edge of the anterior leaflet remains in the annular plane during systole. Such a combination, termed “pseudoprolapse,” also results in poor leaflet coaptation and significant regurgitation (see Fig. Aortic Regurgitation Chronic rheumatic aortic regurgitation occurs due to leaflet thickening, fibrosis and leaflet contracture, resulting in abnormal leaflet coaptation and a regurgitant orifice. This regurgitation leads to both volume and pressure overload of the left ventricle. During a compensatory phase, ventricular dilation occurs to maintain forward stroke volume and cardiac output, and ejection fraction remains normal. Similar to patients with chronic mitral regurgitation, patients with chronic severe aortic regurgitation may remain asymptomatic for years (241,265). Over time, decompensation may occur, resulting in decreased left ventricular function and/or symptoms, most commonly dyspnea on exertion or decreased exercise tolerance. On examination, significant chronic aortic regurgitation results in a wide pulse pressure (elevated systolic and low diastolic pressures) and bounding pulses. Precordial activity is increased, and the apical impulse is displaced laterally due to the dilated left ventricle. The typical diastolic murmur of aortic regurgitation is relatively high pitched, decrescendo, and heard best along the left sternal border with the patient leaning forward at end-expiration. The duration of the murmur rather than the intensity correlates with the severity of regurgitation. A short systolic ejection murmur may be heard at the mid-left or upper right sternal border from increased flow across the left ventricular outflow tract or associated aortic valve stenosis. In patients with moderate-to-severe aortic regurgitation, a low-pitched mid-to-late diastolic rumbling murmur may be audible at the apex in the absence of organic mitral stenosis (“Austin Flint” murmur). The chest radiograph is usually normal in mild aortic regurgitation and shows progressive cardiomegaly with increasing severity of aortic valve incompetence. On echocardiography, the aortic valve leaflets may show thickening, retraction, and variable commissural fusion. Three- dimensional (3-D) echocardiography may provide images allowing better understanding of the mechanism(s) of aortic regurgitation (266). The severity of the aortic regurgitation should be assessed (240) along with documentation of associated lesions, in particular mitral valve stenosis or regurgitation. Left ventricular size and function should be assessed in all patients with aortic regurgitation. In contrast, symptomatic rheumatic mitral stenosis may occur as early as the second decade of life in children from developing countries of the world (27,29,32,38,267). Mitral stenosis may occur as the dominant lesion, with insignificant amounts of associated regurgitation (“pure” mitral stenosis), or in combination with significant mitral regurgitation (268). A combination of leaflet thickening, fusion of commissures, cusps and chordae, and chordal shortening result in a funnel- shaped, stenotic mitral valve orifice. The process is usually continuous and slowly progressive (at least in industrialized countries), eventually resulting in left ventricular inflow obstruction and a diastolic gradient between the left atrium P.