Professor, Florida International University Herbert Wertheim College of Medicine
These pulmonary arteriolar changes occur in both the obstructed and unobstructed lung muscle relaxant 503 purchase discount lioresal online. Manifestations Clinical Features Patients present with history of persistent tachypnea and recurrent pneumonia muscle relaxant without drowsiness order lioresal no prescription, ultimately progressing to rightsided heart failure muscle relaxant drugs z order lioresal 25 mg with amex. The physical examination is consistent with signs of pulmonary hypertension xanax muscle relaxant dosage order lioresal 25mg without a prescription, including a right ventricular heave and accentuation of the pulmonary component of the second heart sound. The reflective nature of the air in the lungs limits the ability of ultrasound to image more proximal portions of the pulmonary veins. When pulmonary venous obstruction or stenosis of individual pulmonary veins is in the differential diagnosis, identification of each pulmonary vein is necessary. Electrocardiographic Features Right ventricular hypertrophy is usual, and right atrial enlargement may be present. Radiologic Features the heart is not greatly enlarged but reflects right ventricular hypertrophy. The heart shifts toward the side of major involvement with pulmonary venous stenosis. Treatment Operative management of stenosis of the individual pulmonary veins is disappointing, which may be related to the coexistence or progression of obstruction into the intraparenchymal pulmonary vein (long-segment stenosis/hypoplasia). Several series have demonstrated effective short-term relief of stenosis with transcatheter techniques, but nearly universal recurrence of obstruction. Echocardiographic pattern of right ventricular diastolic volume overload in children. Anomalous left pulmonary venous drainage to the inferior vena cava and through the pericardiophrenic vein to the innominate vein: left-sided scimitar syndrome. Isolated partial anomalous pulmonary venous drainage associated with pulmonary vascular obstructive disease. Tetralogy of Fallot with anomalous pulmonary venous connections: a rare but clinically important association. Gadolinium-enhanced three-dimensional magnetic resonance angiography of pulmonary and systemic venous anomalies. Cardiac magnetic resonance imaging evaluation of sinus venosus defects: comparison to surgical findings. Surgical treatment of anomalous pulmonary venous connection (partial anomalous pulmonary venous drainage). Total anomalous pulmonary venous connection: report of 93 autopsied cases with emphasis on diagnostic and surgical considerations. Total anomalous pulmonary venous connection: morphology and outcome from an international population-based study. Partial and total anomalous pulmonary venous connection in the fetus: two-dimensional and Doppler echocardiographic findings. Cross sectional echocardiographic diagnosis of total anomalous pulmonary venous connection. Infant total anomalous pulmonary venous connection: factors influencing timing of presentation and operative outcome. A proposed pathogenesis of cor triatriatum: impingement of the left superior vena cava on the developing left atrium. Congenital stenosis of individual pulmonary veins: clinical spectrum and unsuccessful treatment by transvenous balloon dilation. The spectrum of systemic venous anomalies varies widely from minor asymptomatic anatomic variations to complex abnormalities that can lead to cyanosis or that might complicate surgical repair of congenital heart disease. Clinically significant abnormalities of the systemic veins are infrequent when visceroatrial situs is lateralized (either situs solitus or situs inversus). In contrast, the incidence of systemic venous anomalies in patients with heterotaxy syndrome exceeds 90% (1,2). Embryology There are three basic venous systems in the human embryo: (a) the cardinal veins and their tributaries, which form the superior and inferior caval systems; (b) the umbilical, vitelline, and omphalomesenteric veins, which carry the blood from the placenta, yolk sac, and intestine; and (c) the pulmonary veins, which return the blood from the lungs. The age of human embryos cannot be estimated reliably on the basis of their length, which may vary greatly (3), or on the number of somites, which are visible for only a limited time. In 1942, therefore, Streeter (4) proposed classifying human embryos into 25 age groups, or horizons, each representing 2 days of embryonic life. Normal Development of the Cardinal and Umbilicovitelline Venous Systems the sinus venosus, that is, the cavity into which all veins eventually drain, develops by enlargement of the confluence of the umbilical veins and joins the atrial segment of the heart through a slit-like opening, the sinoatrial foramen. The three main paired venous systems of the embryo-the cardinal, the umbilical, and the vitelline veins-drain into the ipsilateral horns of the sinus venosus. It will connect with the sinus venosus through the right hepatocardiac channel, which drains into the right horn of the sinus venosus and with the yolk sac via the left omphalomesenteric vein. They drain blood from the fused neural folds that form the central nervous system. They join the anterior cardinals to form the right and left common cardinals (ducts of Cuvier) and drain together with the umbilical and vitelline veins into the right and left horns of the sinus venosus. As the transverse segment of the sinus venosus shifts rightward, it pulls the left horn of the sinus venosus along the posterior atrioventricular groove. The left horn of the sinus venosus and the adjacent part of the common cardinal vein receive the cardiac veins and form the coronary sinus. The mode of formation of the coronary sinus is responsible for the following anatomic P. The ventricular part of the heart is removed at the atrioventricular junction (A-V Jct.
This is almost always caused predominantly by a ring of tissue present at the level where the pulmonary valve leaflets would be expected muscle relaxant g 2011 lioresal 10mg cheap, rather than by infundibular stenosis (118 muscle relaxant starting with b discount lioresal 25 mg with mastercard,119) spasms in colon order lioresal 25 mg. The authors suggested that their findings might explain why some patients continue to experience respiratory problems muscle relaxant during pregnancy generic 10 mg lioresal with mastercard, despite relief of compression of the main stem bronchus by surgical repair (119). Most are initially cyanotic, but this usually becomes less apparent during the first week of life (119). The chest x-ray of these patients is distinctive and is characterized by a moderately enlarged cardiac silhouette that has a prominent bulge at the upper left cardiac border, caused by the massively dilated proximal pulmonary arteries, and usually normal peripheral vascular markings. Although there is probably a spectrum of disease, general consensus divides patients into two groups: those who exhibit severe respiratory problems early in life and those who do not. Patients who present with severe respiratory compromise immediately after birth or in the first weeks of life will generally require urgent intervention and have a worse outcome than those who escape early intervention with relatively minor respiratory involvement. Otherwise, these patients usually require prompt intubation and positive airway pressure ventilation to maintain their airway. It is clear from early surgical series that infants who present with severe respiratory distress and require preoperative ventilation have the highest surgical mortality (125). However, modern surgical strategies and improvements in intensive care management may have improved outcomes in this group. The pulmonary arteries can be reduced in size by removal of tissue from either their anterior or posterior walls. Even after complete surgical repair with apparent relief of airway obstruction, patients may suffer long-term problems such as recurrent respiratory tract infection, wheezing, and reactive airways disease; some require reintervention for such symptoms (125). The authors reported that the presence of associated chromosomal abnormalities or severe extracardiac abnormalities were factors that determined parental choice (134). Patients with tetralogy and pulmonary atresia usually present as a cyanotic newborn. The infant may do well for a day or two, as long as there is substantial blood flow through a patent ductus arteriosus, but then becomes increasingly hypoxemic as the ductus constricts. Use of prostaglandin E1 is critical in the early neonatal period to maintain ductal patency and stabilize the patient prior to surgery. On rare occasions, an infant may have heart failure and signs of increased pulmonary blood flow. This may be difficult to control medically, and surgical intervention may be necessary. In the group of patients with large collateral vessels, however, the true pulmonary arteries frequently are hypoplastic with arborization abnormalities making definitive correction more difficult. It is usually possible to diagnose a right-sided aortic arch from the chest x-ray by absence of the usual left-sided aortic knuckle, a bulge to the right of the upper mediastinum, and an impression to the right of the trachea (145). In most patients, all of the salient features of the anatomy and physiology can be obtained from a transthoracic echocardiogram so that other imaging modalities are unnecessary. When performed as a primary diagnostic procedure a large-field radiographic format using biplane angiocardiography is advantageous. In addition, a detailed analysis of the systemic arterial collateral blood supply to the pulmonary arterial tree, which includes identification of the degree of intercommunication among the various vascular pathways, must be done. Historically, an initial aortogram was necessary to demonstrate the number and location of the systemic-to-pulmonary collateral arteries. Thus, nonselective injections now more frequently are performed later in a catheterization, if the pulmonary segmental arterial anatomy has not been defined completely by selective injections. Such collateral injections can be enhanced by selective balloon occlusion techniques (146). This allows detection of discrete stenoses or tubular hypoplasia involving the pulmonary arteries as well as the degree to which the central and peripheral pulmonary arteries communicate (147). Some patients with complex patterns of pulmonary blood supply may require multiple injections of contrast material before the pulmonary vascular supply is documented. Because these patients often are hypoxemic and polycythemic, a total dose of not more than 5 to 6 mL of contrast material per kilogram of body weight should not, ideally, be exceeded during any single procedure. Opacification of a pulmonary artery confluence by contrast medium indicates that a direct communication exists between the pulmonary artery confluence and the systemic collateral. Note stream of unopacified blood (arrow) washing out contrast medium in right pulmonary artery, an indication of competitive blood flow from a connecting vessel. In many centers, a move toward earlier corrective surgery has obviated the need for medical management in this condition. However, in some circumstances, a limited period of medical management may still be appropriate and, in the instance of an acute hypercyanotic spells, medical management can be lifesaving. Those who develop heart failure usually derive some benefit from pharmacotherapy (149,150,151), and caloric supplementation with nasogastric tube feeds allows continued weight gain (152). In contrast, infants who develop hypercyanotic spells usually do respond to medical therapy, both for acute treatment and for prophylaxis, although many would consider that even a single hypercyanotic spell is an indication for surgery. As discussed above, the pathophysiology of hypercyanotic spells should be thought of as an acute imbalance between systemic and pulmonary blood flow resulting from a vicious spiral of changes in inotropy secondary to endogenous catecholamine release, increased P. The aim of therapy is to redress this imbalance and disrupt the pathophysiologic spiral by relieving pain and anxiety (to reduce heart rate and systemic oxygen consumption), increase systemic vascular resistance, and increase pulmonary blood flow. Since most hypercyanotic spells are provoked, or worsened, by crying the infant should be picked up and comforted as soon as an episode begins, ideally while being held in a position of flexed knees and hips that kinks or compresses the femoral arteries and increases peripheral systemic vascular resistance. If no improvement is seen within a few minutes, oxygen should be administered and intravenous access obtained. The following measures (in order of increasing intensity of intervention) can then be tried, any of which may terminate the spell (153): An intravenous bolus of colloid or crystalloid fluid will increase intravascular volume, maximize preload, and improve cardiac output (thereby increasing mixed venous O2 content) and may help prevent hypotension caused by other therapeutic interventions below. Beta-receptor antagonists lower heart rate and improve diastolic ventricular filling thus increasing preload and probably also act acutely to increase systemic vascular resistance. Intravenous sodium bicarbonate (1 mEq/kg) may be required if there is evidence of worsening acidosis despite the measures above.
In an older child 2410 muscle relaxant cheap 25mg lioresal otc, when pulmonary vascular obstructive disease is suspected muscle relaxant football commercial purchase online lioresal, there is a role for determining pulmonary vascular resistance muscle relaxant in anesthesia cheap 10mg lioresal free shipping. Cardiac catheterization reveals increased oxygen saturation at both the right atrial and the right ventricular levels muscle relaxant hydrochloride buy lioresal 25mg with visa. Pulmonary blood flow is increased as a result of left-to-right shunting at both atrial and ventricular sites, and the degree of shunting depends upon the relationship of pulmonary to systemic vascular resistance. The timing of surgical intervention must account for development of pulmonary vascular disease in these patients at an early age. Children with associated Down syndrome may require surgical intervention at an earlier age due to their propensity to develop pulmonary vascular obstructive changes. In contrast, splenic anomalies and abnormalities of sidedness (situs) are rare in patients with Down syndrome. Others (55,56) have suggested that children with Down syndrome have pulmonary parenchyma hypoplasia and develop pulmonary vascular obstructive disease earlier than patients with normal chromosomes. These factors contribute to carbon dioxide retention, relative hypoxia, and elevated pulmonary vascular resistance. Patients with Down syndrome have a higher ratio of pulmonary to systemic resistance than patients without Down syndrome (57). This difference resolves with administration of 100% oxygen, suggesting that apparent hypoxia and hypoventilation are factors that can be corrected during hemodynamic evaluation. Fixed and elevated pulmonary vascular resistance has been demonstrated in 11% of Down syndrome patients <1 year of age (57). These objectives can be accomplished by careful approximation of the edges of the valve cleft with interrupted nonabsorbable sutures. On occasion, it is necessary to add eccentric annuloplasty sutures, typically in the area of the commissures to correct persistent central leaks. The repair is completed by closure of the interatrial communication (usually with an autologous or bovine pericardial patch), avoiding injury to the conduction tissue (59). However, the morphologic concepts and surgical methods, favored by Carpentier (60) and Piccoli et al. In that series, there was one surgical death, and the remaining patients had excellent palliation. Once the patch is sutured into place, the bridging leaflets are resuspended to the patch. Two-patch technique was used in 72% of cases, single-patch technique in 18%, and the Australian repair in 10%. Surgeons at many North American centers prefer to utilize a two-patch technique thereby avoiding division of the bridging leaflets (71). In an Australian report, the cleft was completely closed in 43%, partially closed in 20%, and left open in 36%. The bridging leaflets are sutured directly to the crest of the ventricular septum. Current recommendations are to close the zone of apposition, partially or completely, to reduce postoperative regurgitation. This will leave mild valve stenosis, which is usually well tolerated and may improve with time (75). Right or Left Ventricular Hypoplasia these anomalies may be severe enough to preclude septation. The only option for definitive surgical palliation is the Fontan procedure preceded by adequate pulmonary artery banding in infancy (78). In tetralogy of Fallot, there is obstruction of the right ventricular outflow tract. These cyanotic infants often initially are treated with a systemic-to-pulmonary artery shunt and then with "complete repair" at 2 to 4 years of age. The intracardiac repair of these hearts is best accomplished through a combined right atrial and right ventricular approach (51). Subaortic Stenosis If discovered at the time of initial preoperative evaluation, subaortic stenosis tends to be of the fibromuscular membrane type and should be treated by appropriate resection during surgical repair. The obstruction usually is due to the formation of endocardial fibrous tags and fibromuscular ridges. Usually it can be treated by local resection, although in some patients a modified Konno procedure may be necessary (79,80,81,82). Repeat valve repair is possible if the dysplasia is not severe or when the mechanism of regurgitation is through a residual cleft. In rare circumstances, the new larger prosthesis is sewn into the left atrium in a supra-annular position. Others have described alternative approaches, including reconstruction of the deficient inlet septum, septal myectomy, and apical-aortic conduits (79,80,81,82). It occurs in the presence of pulmonary hypertension or in association with tetralogy of Fallot with right ventricular dysfunction and pulmonary valve regurgitation or stenosis. The patch (arrow) is attached to the right side of the atrial septum and the right atrioventricular valve to avoid damage to the conduction tissue and left atrioventricular valve. However, there are limited data in pediatric patients regarding the utility and feasibility of 3-D color Doppler quantitative assessment of regurgitation in these patients. In that setting, the echocardiographer should use indirect techniques such as assessment of ventricular septal flattening or bowing, right ventricular size and function, and Doppler interrogation of the pulmonary regurgitation velocity waveforms to assess pulmonary artery diastolic pressure. Note the tear in the leaflet (white arrow) just posterior to the repaired cleft (black dashed line). The larger jet (dashed black arrow) is through the tear just posterior to the repaired cleft and central to the cleft.
Clinical Features and Diagnostic Methods Symptoms With the exception of severe aortic stenosis in a neonate or infant muscle relaxant herbs cheap lioresal, obstruction of the left ventricular outflow tract is generally a gradually progressive disease which produces symptoms only late in the disease course muscle relaxant recreational use best order for lioresal. The most common symptoms in patients with moderate to severe aortic stenosis are fatigue muscle relaxant 4211 purchase 10mg lioresal free shipping, exertional dyspnea muscle relaxant ointment 10mg lioresal free shipping, angina, and syncope (33). In one large published series, exertional dyspnea was present in all patients with a left ventricular outflow tract gradient of at least 70 mm Hg, but was also described in <20% of patients with a lower gradient (33). Angina and syncope are likewise increasingly common with increasing disease severity, and a complaint of dyspnea, angina, or syncope in a patient with known or suspected aortic stenosis warrants urgent evaluation. Unlike the gradually progressive course of aortic stenosis in older children and adults, critical. Symptoms will include poor feeding and lethargy with eventual cardiovascular collapse. In cases of severe but noncritical aortic stenosis in older infants, symptoms of heart failure may develop more rapidly than in older children or adults (9). Physical Examination Findings On physical examination, vital signs are generally normal, though tachycardia and tachypnea will likely be present in infants with severe disease or older patients who have progressed to left ventricular failure. In cases of supravalvar aortic stenosis, there may be a discrepancy in blood pressure between arms, with the right arm often demonstrating a systolic pressure 15 to 20 mm Hg higher than the left. This finding is thought to be related to streaming of blood due to the Coanda effect, a phenomenon in fluid dynamics in which a jet stream adheres to a boundary wall (150). Patients with supravalvar stenosis may also present with systolic hypertension and a widened pulse pressure due to reduced elasticity of the aorta (149). In patients with more than moderate stenosis, palpation of the precordium will likely reveal a laterally displaced left ventricular impulse and a systolic thrill over the base of the heart (33,48). A thrill over the suprasternal notch may be felt in even mild valvar aortic stenosis. The second heart sound will be single or narrowly split in up to 50% of patients with aortic stenosis due to delayed closure of the aortic valve (33), and physiologic splitting of S2 is the most reliable examination finding to exclude the presence of severe aortic stenosis (151). In cases of severe stenosis, the pulmonary valve may close prior to the aortic valve during expiration, with S2 becoming single during inspiration, a phenomenon referred to as "paradoxical splitting" (33,152). S3 and S4 gallops are relatively common in pediatric patients with left ventricular outflow tract obstruction, P. In patients greater than 12 years old, however, the presence of an S4 gallop suggests severe obstruction and left ventricular diastolic dysfunction (33). In the case of valvar and supravalvar stenosis, the murmur is generally loudest at the right upper sternal border, while subvalvar stenosis may result in a murmur better heard at the left mid sternal border. Regardless of the location of obstruction, the ejection murmur of aortic stenosis often radiates to the carotid arteries. If there is aortic insufficiency in addition to stenosis, an early diastolic decrescendo murmur may also be appreciated along the left lower sternal border. An important clue to help distinguish valvar aortic stenosis from supravalvar or subvalvar disease is the presence of a midsystolic ejection click. An aortic click, best heard at the apex of the heart, is present in most cases of dysplastic or bicuspid aortic valves, regardless of degree of stenosis. Unlike a pulmonary click which is louder with expiration, an aortic valve click is constant throughout the respiratory cycle. With severe left ventricular outflow tract obstruction, peripheral pulses are diminished and slightly delayed in relation to the second heart sound, the classic "parvus et tardus" pulses of aortic stenosis. In severe disease that has progressed to heart failure, findings including tachycardia, tachypnea, and hepatomegaly may be present in young children, while teenage and young adult patients may display typical signs of systemic venous congestion (hepatomegaly and jugular venous distension) and pulmonary venous congestion (tachypnea, pulmonary rales). On the other hand, 24% of patients with only mild stenosis demonstrated voltage criteria for left ventricular hypertrophy, with a strain pattern present in greater than 10%. Radiography Most patients with aortic stenosis will have a largely unremarkable chest x-ray with normal heart size (159). One exception is in cases of critical aortic stenosis in the neonate and severe aortic stenosis in infants (9). These patients will commonly demonstrate significant cardiomegaly on chest x-ray with enlargement of the left ventricular and left atrial borders. Echocardiography Echocardiography can provide an enormous quantity of information about the aortic valve and left ventricular outflow tract, offering crucial anatomic and physiologic data for any type of left ventricular outflow tract obstruction (160,161,162,163). Echocardiography is also integral in the monitoring of disease progression once a diagnosis of aortic stenosis has been made. While a detailed overview of pediatric echocardiography is beyond the scope of this chapter (see Chapter 12 for a comprehensive description), a complete echocardiographic evaluation including careful two-dimensional imaging and Doppler interrogation is necessary in the evaluation of left heart obstruction. Imaging of the left ventricular outflow tract from multiple planes will generally provide accurate information on the site(s) of obstruction. The parasternal long axis is the preferred view for measurement of the aortic valve annulus and aortic root dimensions, while the parasternal short axis provides optimal assessment of aortic valve morphology. Parasternal, subcostal, and apical two-dimensional imaging will likely provide accurate assessment of the location and mechanism of valvar and subvalvar aortic stenosis (164). Supravalvar stenosis is somewhat more difficult to fully evaluate by transthoracic echocardiography (163), but adequate assessment of the aortic root and ascending aorta can often be achieved with thorough parasternal and suprasternal imaging (161).
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