By T. Tragak. Davis College.
The next most common variation is the left circumflex arising from the right coronary artery and coursing posterior to the pulmonary artery buy penegra overnight delivery androgen hormone x and hair, which is seen in about 20% of patients buy generic penegra 100 mg on-line prostate health essentials, usually with side-by-side great vessels (Fig. The coronary arteries also may be completely inverted, with the right coronary artery arising from a left anterior sinus and the left coronary artery arising from the right posterior sinus (Fig 32. The coronary vessels also may be partially inverted, with the left circumflex arising from the right posterior sinus and the left anterior P. Variants with single (8%) and intramural (5%) coronary arteries are not illustrated. Finally, various single coronary anomalies may occur, and intramural coursing of any of the variants may occur, usually with branches passing between the great vessels. These variations affect the planning and conduct of the arterial switch operation because they may make it difficult to move the coronary arterial origins to the neoaortic root without excessive tension. Tetralogy of Fallot About 40% of patients have an abnormally long, large conus artery that supplies a significant mass of myocardium. In 4% to 5%, the left anterior descending coronary artery arises from the right coronary artery and passes across the right ventricular outflow tract (see Fig. Occasionally, a single coronary artery comes from either the right or left sinus, and the major branch that crosses the heart may pass across the right ventricular outflow tract (see Fig. If major arteries cross the right ventricular outflow tract, it makes surgery with the traditional transannular incision more difficult. To avoid cutting the artery and infarcting part of the myocardium supplied by it (61), the surgeon may make incisions parallel to the artery, make incisions above and below the artery, tunnel underneath the artery, or bypass the stenotic region with a conduit (60). All these approaches interfere with the effectiveness of the surgery and in the small infant may lead to the decision to palliate rather than perform a total repair. These anomalies may be detected by echocardiography, and if the anatomy is uncertain, then aortic root angiography or selective coronary angiography is needed (60). Although the surgeon can usually see the anomalies, there are advantages in knowing about them in advance to plan the procedure more effectively. Furthermore, the anomalous arteries may not be visible if they are obscured by epicardial adhesions from previous surgery or if they run deep in the myocardium. Congenitally Corrected Transposition of the Great Arteries (l-Transposition) The aorta is anterior and to the left of the pulmonary artery, and the two main coronary arteries come from the facing sinuses as seen with d-transposition of the great arteries. Because of this anatomy, there is some confusion about naming coronary arteries that appear to arise from incorrect sinuses (59,62). Some describe the vessels as right or left sided, based on their sinus of origin (62), whereas others (63) describe the arteries based on their territory of supply, and this terminology will be used here. The left coronary artery supplies the left ventricle but arises in the right facing sinus. It passes in front of the pulmonary annulus and divides into left anterior descending and circumflex branches, the latter passing in front of the right atrial appendage in the atrioventricular groove. It arises from the left facing sinus and runs in the atrioventricular groove in front of the left atrial appendage to terminate as the posterior descending artery. The most common variant is a single coronary artery coming from the right facing sinus. Double-Inlet Left Ventricle (Univentricular Heart) Because there is no true ventricular septum, there is no typical interventricular groove, and the arterial branches that run along the borders of the rudimentary outlet chamber are referred to as delimiting arteries (33,64) rather than as anterior descending arteries. When the outlet chamber is anterior and to the right, the aorta and pulmonary artery are related as in a complete transposition. The right coronary artery arises from the right facing aortic sinus and runs along the right atrioventricular sulcus. The left main coronary artery comes from the left facing sinus and continues around the left atrioventricular groove as the circumflex artery. The left and right coronary arteries give off the left and right delimiting arteries, respectively. When the outlet chamber is anterior and to the left, the great vessels are related like those in congenitally corrected transposition. The right and left main coronary arteries arise from their respective facing sinuses, and the “anterior descending” coronary artery may come from the left or the right coronary arteries, or there may be two delimiting arteries that border the rudimentary outlet chamber (64). With any of these variants, there may be several large diagonal arterial branches that run parallel to the delimiting branches and cross the outflow tract of the right ventricle, making septation difficult. Double-Outlet Right Ventricle The coronary artery origins are usually normal in most forms of this group of anomalies, except that because the aortic sinuses are rotated clockwise, the right coronary artery arises anteriorly and the left coronary artery arises posteriorly (59). When the aorta is anterior and to the right, the coronary pattern is similar to that in complete transposition of the great arteries, with the right coronary artery arising from the right facing sinus. In 15% there may be a single coronary artery arising anteriorly or posteriorly (65). Occasionally, the left anterior descending coronary artery comes from the right coronary artery and crosses the right ventricular outflow tract, as in tetralogy of Fallot (65). Truncus Arteriosus The right and left coronary arteries usually arise normally from their appropriate sinuses (66). If, however, the valve has more than three cusps, conventional descriptions must be abandoned. What is most consistent is that the left main coronary artery arises from the posterior sinus. Major variants include unusually high ostia, closely approximated ostia, or a single ostium (66). Large diagonal branches of the right coronary artery may cross over the anterior surface of the right ventricle and contribute to flow to the ventricular septum and even part of the left ventricular free wall (66). Congenital Anomalies of the Aortic Root Aortic-Left Ventricular Defect (Tunnel) This rare lesion is a vascular connection between the aorta and the left ventricle (Fig. Some describe it as a tunnel that begins above the right coronary ostium, usually separated from it by a ridge, and passes behind the right ventricular infundibulum and through the anterior upper part of the ventricular septum to enter the left ventricle just below the right and left aortic cusps (67). Others (68) have considered the lesion to be a congenital defect associated with the thinned-out anterior wall of the left ventricular outflow tract where the right aortic sinus meets the membranous septum. They have signs resembling marked aortic valve regurgitation: A wide pulse pressure with a low diastolic blood pressure, a hyperactive dilated left ventricle and enlarged left atrium, and a loud to-and-fro murmur at the base. The electrocardiogram shows varying degrees of left ventricular and atrial hypertrophy. The chest radiograph shows variable cardiomegaly, possibly signs of congestive heart failure, but in all patients there is a dilated ascending aorta and in some a bulge of the enlarged right aortic sinus. Echocardiography with Doppler color flow mapping and aortography serve to separate this lesion from aortic valve regurgitation by the absence of retrograde flow through the aortic valve; from a coronary artery–left ventricular fistula by the finding of normal right and left main coronary arteries; from an associated ventricular septal defect by the absence of a left-to-right shunt through the defect; and from a ruptured sinus of Valsalva by the anterior position of the tunnel and the absence of a dilated sinus of Valsalva (69). Treatment has been surgical, but there is a high incidence of aortic incompetence after surgery. Alternative treatment options include transcatheter occluders in selected patients. Sagittal section showing the tunnel burrowing through the septal wall to enter the left ventricle. Aneurysms of the Sinus of Valsalva A localized weakness of the wall of a sinus of Valsalva, a relatively rare lesion reported in the 19th century (70), leads to aneurysmal bulging and even rupture. It is to be distinguished from diffuse dilation of all the sinuses in Marfan syndrome. The localized aneurysms are usually congenital, with thinning just above the annulus at the leaflet hinge owing to the absence of normal elastic and muscular tissue (71).
Even today quality 50 mg penegra prostate cancer 6 months to live, clamps can be placed bypass buy cheap penegra 50 mg online mens health 10k edinburgh, hypothermia provided an important safety element. Conduct of Cardiopulmonary Bypass 189 Improved Myocardial Protection Hypothermia reduces complete cessation of bypass, i. Although local myocardial hypothermia of perfusion fow rate evolved slowly and somewhat surrep- can be attained through infusion of cold cardioplegia solu- titiously entered into clinical cardiac surgical practice. One tion, the temperature of the pump perfusate has an important of the most important reasons for the slow acceptance of effect on the rate of rewarming of the heart between car- reduced fow rate with hypothermic bypass is a consequence dioplegia infusions (Fig. Even when there is total cardiopulmonary bypass with separate caval cannulas and • Improved intracardiac exposure. Many patients tourniquets, the temperature of retrocardiac tissues in par- with congenital cardiac anomalies, particularly ticular will be determined by perfusate temperature and will those which result in cyanosis, will develop mul- affect the rate of myocardial rewarming. Although multiple tiple profuse collateral vessels which increase the infusions of cardioplegia solution are well tolerated beyond left heart return. This blood fow usually returns infancy, many studies have suggested that in the neonate and to the left atrium through the pulmonary veins, younger infant, multiple reinfusions of cardioplegia result in but when the pulmonary artery is open it will also less good myocardial protection, most likely because of myo- result in continuous back bleeding from the pulmo- cardial edema. When excellent intracardiac expo- sure is necessary, it is often important to reduce the Decreased Metabolic Rate Allows Reduced Flow Rate: amount of left heart return temporarily. This can be Advantages Although it was recognized early in the his- achieved very effectively by reducing the perfusion tory of cardiac surgery that hypothermia would allow fow rate. Although left heart venting systems are available, it is often diffcult in the very small heart to achieve excellent exposure by venting all the left 35 heart return back to the pump circuit. As noted above, hypothermia per se reduces the infammatory effects of bypass, includ- ing both cellular activation and reduced activation of many humoral cascades. Although it has not 20 been well documented, it seems probable that an increased perfusion fow rate results in a greater degree of activation of both the cellular components of blood, as well as humoral cascades. The fgure fore highly probable that the use of a reduced fow illustrates mean cardiac septal temperature in neonatal pigs. J Thorac ies have demonstrated that the number of gaseous Cardiovasc Surg 1988;86:414–22. Because fat has a Membrane oxygenators can also produce multiple relatively poor blood supply, obese patients require longer gaseous microemboli if air is being entrained by the periods of cooling and rewarming than patients with a lean venous cannula and this effect is worse at high fow body mass. The higher ratio of surface area to body sible for most of the particles introduced into the mass in babies optimizes the effectiveness of water and air bypass circuit. Babies necessitate greater volumes of cardiotomy return also tend to be relatively low in total adipose tissue relative during open extracardiac procedures. A longer duration of cardiopulmonary bypass will result in a greater aggregation of the deleterious effects of cardio- Decreased Metabolic Rate Allows Reduced Flow Rate: pulmonary bypass, almost all of which are time related in Disadvantages The principal disadvantage of low fow their degree of severity. In their landmark textbook, Kirklin and Bleeding Barratt-Boyes attempted to develop a nomogram which It is generally considered that use of hypothermic bypass broadly indicates fow rates that may be safe at specifc tem- increases the probability of postoperative bleeding. The different effects of normothermic and for monitoring the safety of cardiopulmonary bypass both in hypothermic bypass on platelet function have not been well the past and currently remain quite inadequate. Furthermore, use of aprotinin and antifbri- patient temperature, pH and hematocrit have a strong infu- nolytic agents can be effective in reversing the deleterious ence on safe minimum fow rate as will be discussed later in effects of bypass and hypothermia on platelet function and this chapter. Disadvantages of Hypothermia Prolongation of Cardiopulmonary Bypass Infection Use of a more severe degree of hypothermia, i. The exact duration of cooling and well documented that transient exposure to hypothermic rewarming is determined both by the temperature gradients bypass results in a greater incidence of postoperative infec- employed between the water and the heat exchanger, blood tion relative to the use of normothermic bypass. The crosses mark appropriate clinical perfusion fow rates which allow a reasonable margin of safety for the indicated tempera- ture. Proteins provide most of the bypass often results in patients returning to the intensive body’s buffering capacity. It is the imidazole moi- care unit with a considerable heat debt and they often ety, which is found in the amino acid histidine, that is the principal buffer group of proteins. It has been well documented that this prolongs the duration of intubation, as is widely found in plasma proteins and importantly well as total recovery time, in the intensive care unit. Thus red cells, as well as plasma, neonates and infants who can be more effectively warmed have an essential buffering function that is reduced by surface means than adults and who appear in general to by hemodilution. However, just as is the Normal Physiology of Carbon Dioxide and pH case with imidazole, red cells also play an important role in bicarbonate buffering. They achieve this by Vasomotor Effects: Systemic Vasodilation, containing carbonic anhydrase. Carbonic anhydrase Pulmonary Vasoconstriction facilitates conversion of carbonic acid to carbon Carbon dioxide is a powerful systemic vasodilator and dioxide and water thereby preventing accumulation conversely alkalosis and a low carbon dioxide level cause of carbonic acid through subsequent exhalation of systemic vasoconstriction. Patients suffering an acute anxiety attack through respiratory changes and bicarbonate levels through can hyperventilate to the point that their carbon dioxide level renal excretion, the bicarbonate buffer is a critically impor- falls so low that cerebral vasoconstriction results. This situation can be remedied by rebreathing in a paper bag Carbon Dioxide and pH during to raise the patient’s carbon dioxide level, thereby restor- Cardiopulmonary Bypass ing adequate cerebral blood fow. The interpretation of the Cardiopulmonary bypass places the control of acid-base direct vasomotor effects of carbon dioxide is complicated by in the hands of the perfusion team and overrides the many the sympathetic response that results from hypercarbia and homeostatic mechanisms that function during normal physi- respiratory acidosis, which may cause sympathetic vasocon- ology. It is also important to remember that the effects an important impact on acid-base balance. Thus if Flow Rate there are connections between the systemic and pulmonary Tissue acidosis with a subsequent fall in blood pH will result circulation, such as aortopulmonary collaterals or a systemic if the fow rate is inadequate to maintain tissue oxygenation. It is important to remember that this the distribution of fow between the systemic and pulmonary is between a half and two thirds of a normal physiological vascular beds. Acid-Base Balance Dilution Maintenance of a stable intracellular pH at close to the pH The contribution to buffering of the nonbicarbonate buf- of neutrality of water (pN) is essential for optimal enzyme fers (the imidazole groups of the proteins contained within function. In order to maintain ity expressed as the titration of a specifc amount of acid intracellular pH at this point, extracellular pH is maintained or alkali added to a closed system and causing a change in humans between 7. The unit of this measurement is called the the actions of a number of buffer systems. If a crystalloid solution is used N as the bypass prime, the consequent dilution of the patient’s H+ blood will result in a signifcant reduction in the nonbicar- 7. Erythrocyte dilution to a hematocrit of 20%, associated with the same degree of plasma dilution, results in a decrease in buffer strength of approximately 61 7. If the hematocrit is reduced to between 24 and 28% dur- ing bypass, this will result in a 20% reduction in nonbi- carbonate buffering. Hypothermia Phosphate As noted earlier in this chapter, the pH of water increases 6. Another way of expressing this fact is that the pH of neutrality (pN) rises with hypothermia. The pH which is read from the machine can be temperature corrected to a 0 10 20 30 40 body temperature of X°C by the formula: Temperature (°C) pHxºC = –pH37°C + (37 – x)(0. Because the imidazole moiety It is interesting to note that the fact that the slope of the of the amino acid histidine in proteins performs the bulk of buffer- change in pH with temperature of whole blood is similar to ing in blood, the slope of the dissociation constant for blood is simi- that for neutral water refects the dominant role of imidazole lar to the slope of the dissociation constant for water. The importance of acid-base man- stant (pK) for imidazole is very similar to the dissociation agement for cardiac and cerebral preservation during open heart constant for water (Fig. The pH of neutrality of blood retains during Cardiopulmonary Bypass its usual alkalinity relative to intracellular pH so that there Ectothermic (“cold-blooded”) animals and hibernating mam- is a constant hydrogen ion concentration gradient between mals have provided an opportunity for study of the alternative the intracellular and extracellular environments both at nor- methods whereby different species adjust their physiology mothermia and hypothermia. Interestingly dif- temperature allows these animals to maintain a constant ratio ferent strategies have evolved for species that must remain of hydrogen to hydrogen ions across a wide range of tempera- active while hypothermic versus those that hibernate. They are faced with the problem “alpha”) of dissociated to nondissociated imidazole groups of needing to be able to mobilize energy stores effciently remains constant with this strategy.
For example proven 50 mg penegra prostate cancer 90 year old man, a male patient with neutropenia should be assessed for Barth syndrome (55) purchase penegra american express prostate 101. Genetic testing is also frequently performed for patients without a clear etiology and is recommended in specific contexts by many organizations including the International Society for Heart and Lung Transplantation and the Heart Failure Society of America (56,57). The endomyocardial biopsy can help in establishing the underlying disorder and may be particularly helpful in challenging cases. In one study of adults with a diagnosis of new-onset heart failure undergoing endomyocardial biopsy, the biopsy revealed the underlying disease in 25% of the cases (35% if symptoms were <2 weeks of duration) and clinical management was changed in 23% of the patients based on the results (39). The risk of any type of invasive procedure must obviously be weighed against the potential benefit of the study, but in experienced centers, endomyocardial biopsies can be performed safely even in small, critically ill children (60,61,62). If there is no evidence of disease in the family members, it is recommended that clinical screening be continued at intermittent intervals, the frequency of which depends on whether an underlying disease-causing mutation is found (Table 53. Interestingly, there is considerable debate surrounding the utility of immunomodulatory agents in cases where myocarditis is suspected (63,64,65,66,67,68,69,70,71). Pediatric versus adult cardiomyopathy and heart failure-related hospitalizations: a value-based analysis. In comparison to adult cardiomyopathy patients, pediatric cardiomyopathy patients have greater mortality, length of stay, and hospital charges when hospitalized with heart failure (73). It is important to note that every age group of pediatric patients has longer length of stay and greater charges than every age group of adults, including adults >70 years old (Fig. Additionally, pediatric patients aged ≤10 years have greater mortality compared to every age group of adult patients, including those >70 years old (73). A useful method for categorizing patients with heart failure symptoms, described by Grady et al. The ideal patient has adequate perfusion (warm) and no symptoms of congestion (dry). Symptomatic patients can have evidence of decreased perfusion (cold) and/or congestion (wet). For the less common profile of low output without congestion, the letter L was chosen rather than the letter D to avoid the implication that this profile necessarily follows profile C or is a less desirable profile than C. Team management of patients with heart failure: a statement for healthcare professionals from The Cardiovascular Nursing Council of the American Heart Association. Diuretics and vasodilators are important first-line agents which can result in rapid improvements in symptoms (76). Furosemide is often utilized as the first-line diuretic, either as a continuous infusion or bolus doses (77,78,79). Limited pediatric data suggest the medication is safe and possibly effective in selected children with acute heart failure; however, a large randomized trial in adult heart failure patients did not demonstrate efficacy of nesiritide over standard heart failure therapy (80,81,82,83). There are data from multiple studies among adult heart failure patients, including randomized controlled trials and large registries, linking the use of inotropic agents to increased mortality and other adverse events in heart failure patients (84,85,86,87). There are limited data in pediatric heart failure admissions, though inotropic agents have also been associated with worse outcomes in some studies (54,88). Chronic heart failure medications can be initiated or modified during these hospital admissions. Patients with Poor Perfusion; “Cold and Wet” and “Cold and Dry” Patients with congestion and poor perfusion represent a significant group of children presenting with heart failure (19,88). These patients are generally admitted to an intensive care unit and their management depends on the degree of circulatory compromise. Some patients can be stabilized with inotropic medications while others may warrant urgent or emergent mechanical circulatory support. Commonly utilized inotropic medications include milrinone, dopamine, and epinephrine (72,88). There are multiple short-term and durable ventricular assist devices that have been utilized successfully in pediatric patients with refractory heart failure (89,90,91,92). The utilization of implantable continuous flow devices has allowed some pediatric patients to be discharged from the hospital while on device support. Most of these patients will be bridged on the device to heart transplantation, although there has been some use of these devices as destination therapy (implantation of the device with no plan for heart transplantation) in selected patients, such as those with neuromuscular disease (91,100,101,102,103,104). However, many patients can remain free from symptoms with medical management and some will have significant and even complete recovery of systolic function (29,106,110). Due to the complex nature of this chronic disease with often multiple comorbidities, we and others advocate for a multidisciplinary team approach (111). Treating symptoms of congestion and low perfusion is critical to the medical management of heart failure, in both acute and chronic settings (85). Guidelines for the treatment of heart failure in pediatric patients, mostly based on data extrapolated from studies in adult patients, have recently been published by the International Society for Heart and Lung Transplantation (56) and the Canadian Cardiovascular Society (Fig. Presentation, diagnosis, and medical management of heart failure in children: Canadian Cardiovascular Society guidelines. Multiple, prospective, randomized trials of different medications within this class demonstrated improved symptoms, decreased progression of heart failure, and decreased hospitalizations in addition to the beneficial effect on mortality (113,114,115,116,117,118). In addition to the upregulation of the renin–angiotensin–aldosterone system, the sympathetic nervous system is activated in heart failure with resulting detrimental effects on cardiac structure and function (122,123,124). As such, beta-adrenergic receptor (beta)-blockers have been extensively studied in adult patients with heart failure with multiple randomized controlled trails demonstrating benefits in symptoms, heart function, hospitalizations, and survival (123,124,125,126,127,128). Data on beta-blocker use in pediatric heart failure are limited, though a large, multicenter randomized controlled trial failed to find a benefit for carvedilol on ventricular function among a mixed group of patients with cardiomyopathies and congenital heart disease (129). However, there was a 30% decrease in the risk of death at 24 months in patients randomized to receive spironolactone. Eplerenone, a selective mineralocorticoid receptor antagonist, was studied in adult patients with heart failure after myocardial infarction and also demonstrated an improvement in mortality, with the decrease in cardiovascular mortality being driven mostly by a reduction in sudden death (130). Hyperkalemia, especially in the setting of renal insufficiency, is more common in patients treated with mineralocorticoid receptor antagonists and needs to be followed closely (130,131,132,133). Although these are the most commonly used agents in the long-term management of heart failure patients, studies demonstrating long-term benefits are lacking and higher doses have been associated with increases in the activation of the renin– angiotensin–aldosterone system and mortality in adult patients (134,135). Digoxin, one of the oldest medications used for treating heart failure symptoms, is still commonly utilized. Digoxin inhibits cardiac Na–K channels in the cardiac myocyte, leading to increased contractility (136). While digoxin is effective in alleviating symptoms of heart failure (137), it has not been shown to improve mortality (138), and higher doses are associated with an increase in mortality (139). Retrospective data from the hospital for sick children in Toronto did not find an improvement in outcomes with the use of these medications (107). There are multiple possible reasons for these differences between pediatric and adult patients with cardiomyopathy and heart failure including challenges in study design in pediatric diseases, differences in pharmacokinetics and pharmacodynamics, and differing underlying diseases and response to heart failure (140,141,142,143). Cardiac Resynchronization Therapy and Implantable Cardioverter Defibrillators In adult patients with heart failure, intraventricular conduction abnormalities are common and lead to dyssynchronous ventricular contraction (150). This pattern is typically of a left bundle branch block in adults, a pattern seen less commonly in children. In the Pediatric Cardiomyopathy Registry, the transplant-free survival at 5 years was only 50% (Fig.
It provides a reliable window in the older patient who has had prior surgery and has a limited transthoracic window discount penegra 100 mg mastercard prostate cancer 911. Earlier studies documented the advantages and disadvantages of transesophageal echocardiography (52 discount penegra 50mg with visa mens health 10k glasgow 2013,53). Studies to date have shown good correlation with other modalities in terms of functional evaluation and have confirmed the concerns regarding systemic right ventricular function (56,57,58,59,60). Catheterization remains part of the assessment of left ventricular hemodynamics in patients undergoing left ventricular retraining prior to anatomic repair (64). Thus, it is always important to have available a system for emergent transvenous pacing. Interventional cardiac catheterization is largely reserved for the postoperative patient with important stenosis or regurgitation of surgically placed conduits that may be amenable to stenting or transcatheter pulmonary valve insertion or those patients with atrial baffle obstruction or leak (65). These modes of imaging should establish the diagnosis and also should indicate the relative topography of the ventricular septum. These observations are important to the determination of the axial projection for angiocardiography. The pulmonary arteries and their bifurcation are best imaged by a selective injection of contrast into the pulmonary arteries with craniocaudal angulation. The aorta and the coronary arteries can be profiled by aortography, filmed in the frontal and lateral projections. The coronary arteries originate from the posterior-facing sinuses, and selective coronary angiography may be necessary to obtain adequate demonstration of the anatomy. Natural History and Management Congenitally corrected transposition is a complex and unusual form of congenital heart disease. As such, it takes time to accumulate experience, and then meaningfully study the natural history, surgical outcomes, and results of changes in surgical management. There is however, a very high frequency of associated lesions, which, in their turn, tend to have quite different pathophysiologic effects on systemic right ventricular function. The complex interactions of these anatomic and physiologic variables complicate outcome analysis. Medical Management The neonate with ductal-dependent pulmonary blood flow requires immediate institution of intravenous prostaglandin to maintain patency of the arterial duct until such time that a stable source of blood supply to the lungs can be surgically constructed. Similar management is required for the infant who has severe coarctation of the aorta or interruption of the aortic arch. The medical management of the associated lesions thereafter dominates early medical management. The appropriate use of diuretics along with afterload reduction and beta-blockade may be required. Pacing A significant proportion of patients will develop spontaneous or postoperative complete heart block. The technical aspects of the procedure can be hindered by either an inaccessible coronary sinus or underdeveloped tributary cardiac veins. Unoperated Natural History Early natural history is impacted significantly by the severity of associated lesions and surgical management. A few investigators who have tried to separate natural history from associated lesions and surgical outcomes suggest a different set of probabilities. However, frequently severe valve dysplasia, along with surgical series showing recurrent or progressive regurgitation after repair, suggests that valve replacement is the preferred option when possible. For patients with poor systemic ventricular function, cardiac transplantation or mechanical circulatory support may be required (78). Many series assessing the long-term outcomes of conventional surgical approaches and factors thought to determine outcome have been reported (48,79,80,81,82,83,84,85). Immediate surgical results have improved with surgical mortality in the range of 3% to 10%. In a retrospective analysis of 46 patients, preoperative systemic ventricular ejection fraction as assessed by echocardiography was an independent predictor of ventricular function at ≥1 year after operation. Complications of these complex procedures can be expected to include those of the atrial switch (sinus node dysfunction, supraventricular dysrhythmias, baffle obstructions, and baffle leaks), the Rastelli (subaortic obstruction, aortic regurgitation, conduit obstruction, or regurgitation), and/or the arterial switch (coronary artery obstructions, aortic valve incompetence, pulmonary arterial obstruction, or aortic root dilation). Surgical series have been encouraging overall with surgical mortality of 0% to 10% (65,73,97,98). The adequacy of banding can be assessed intraoperatively with echocardiography or with the use of conductance catheters to assess pressure–volume relationships. To compare the outcomes of patients following physiologic versus anatomic repair, Alghamdi et al. Age at surgery ranged from 3 months to 55 years with 41% of patients undergoing definitive surgery prior to 1995. Surgery included 33 patients with physiologic repair, 69 Rastelli-type anatomic repair, and 25 with anatomic repair including arterial switch. Patients who had undergone anatomic repair as well as their parents or proxies reported similar quality of life to those in the nonanatomic repair group. One area of difference was in the domain of school performance with the anatomic repair group self-reporting a significantly lower score. However, when rated by parents, school performance was not different between the two groups. Prolonged hospital stay and need for pacing were possible risk factors for lower quality of life in this study. The rate of cesarean section was 12%, lower than the rate in the general population. Another group reported a miscarriage rate of 27% in 19 women with 45 pregnancies, and maternal cyanosis was a risk factor (106). Cardiovascular complications occurred in five patients (26% of mothers), with congestive heart failure in three, worsening cyanosis in one, and a cerebrovascular accident in one. Pregnancy was successful in 19/20 (95%) pregnancies in 13 women with cardiovascular complications occurring in 3 patients. The etiology, morphogenesis, and morphology are complex and fascinating to consider. The clinical picture is dominated by the pathophysiology of associated cardiac anomalies. Midterm results may be promising, but associated late postoperative complications are also emerging and the final assessment of the evidence requires further long-term follow-up. Acknowledgments The authors would like to acknowledge the contribution of 3-D echo still frames and 2-D echo loops by Dr. An embryologic explanation for the corrected transposition of the great vessels: additional description of the main anatomic features of this malformation and its varieties. Corrected transposition of the great arteries without associated defects in adult patients: clinical profile and follow up.
For patients who present in shock with suspected ductal1 closure or a restrictive duct cheap penegra online mastercard androgen hormone x for hair, initial dosing will range from 0 buy penegra 100mg cheap man health report garcinia. Once ductal patency is ensured, the infusion rate can be decreased to an effective dose as low as 0. Initiation of intravenous caffeine with a loading dose of 20 mg/kg followed by a maintenance dose of 5 to 10 mg/kg/day has been effective in reducing the need for mechanical ventilation preoperatively. Patients who received aminophylline had a decreased incidence of apnea and did not require intubation when compared with the placebo group of whom 35% required intubation (225). Respiratory Support and Inspired Gases In the preoperative patient without anatomic limitation to pulmonary blood flow, mechanical ventilation and medical gas manipulation of pulmonary arteriolar resistance are sometimes necessary and beneficial. Controlled positive-pressure ventilation with care taken to avoid hyperventilation can limit pulmonary blood flow. Clinical experience supports the use of hypoxia as a means to attenuate an elevated Qp/Qs (196,227). Hypoxic gas mixtures are achieved through blending nitrogen and oxygen to achieve inspired subatmospheric fiO of 0. The use of inspired gases in humans has been2 best studied in an acute model by Tabbutt et al. Although both strategies were successful in acutely reducing SaO and2 2 2 Qp/Qs, only hypercarbia improved systemic oxygen delivery (199). Furthermore, whereas hypercarbia improved cerebral oxygenation, hypoxia provided no benefit to cerebral saturation (228). In patients who have severely restrictive or absent atrial septal defect, supplemental oxygen and other medical therapies are ineffective in treating the severe arterial desaturation, prompting emergency intervention with balloon atrial septostomy, atrial septal balloon dilation and/or stent, surgical septectomy, or immediate stage 1 palliation. Vasoactive Medications The need for preoperative inotropic support is variable and directed by clinical presentation and echocardiographic features. Patients who present in cardiogenic shock most commonly benefit from inotropic support as do patients with significantly reduced right ventricular function. The neonate with progressive metabolic acidosis, or cerebral or somatic hypoxia approaching the anaerobic threshold may require mechanical ventilation, and benefit from earlier surgical intervention (229,230). Other Adjunctive Therapies The hypoxic patient with inefficient single-ventricle physiology benefits from increased oxygen carrying capacity. Other means to improve systemic perfusion include therapies that can attenuate sympathetic vascular tone, and low-dose dexmedetomidine may be cautiously applied. Parenteral nutrition is provided with volume administration that is consistent with gestational age, birth weight, and postnatal age. For the term infant who is greater than 2,500 g, our recommendations for fluid requirements during the first day of life are 70 to 80 cc/kg/day with escalation to 100 cc/kg/day on day of life 3, then, 120 to 140 cc/kg/day infants 4 days of age and older. The preterm infant requires more fluid due to higher transdermal insensible losses at a lower weight. Diuretic therapy is reserved for those patients who demonstrate respiratory insufficiency from increased interstitial lung edema related to either pulmonary overcirculation or restrictive pulmonary venous return. Any of the proposed preoperative management strategies can be used in isolation or combination to balance pulmonary-to-systemic flow, optimize systemic perfusion, and preserve organ function. Physiologically based preoperative supportive care is associated with improved outcome (125,202) including the timing of surgical intervention (231). When preoperative stabilization is inadequate to preserve extracardiac organ function particularly in neonates who present in cardiogenic shock, branch pulmonary artery banding should be considered to improved systemic perfusion and allow further organ recovery prior to traditional staged palliation (232,233). Recognition of such physiologic necessities drove the development of numerous surgical approaches (234,235). The staged approach ultimately leads the patient on a pathway to a single-ventricle in-series circulation, usually culminating in a Fontan operation with the final result similar to patients with tricuspid atresia and hypoplastic right heart syndrome (238,239). Most commonly, stage 1 palliation consists of reconstruction of the aortic arch into the right ventricular outflow, separation of branch pulmonary arteries from the right ventricle, and creation of a restrictive source of pulmonary blood flow from a systemic artery or directly from the single ventricle (237,240). Stage 2 palliation unloads the single ventricle by replacing the systemic-to-pulmonary shunt with a superior cavopulmonary anastomosis (241). Stage 1 Palliation Surgical Approaches The goals of stage 1 palliation include relief of ductal-dependent systemic flow, provision of unrestricted coronary artery flow, creation of a nonrestrictive atrial septal defect to prevent pulmonary venous hypertension, and provision of a reliable but restricted source of pulmonary blood flow (Fig. A connection is created between the smaller ascending aorta and the pulmonary root for provision of coronary blood flow. Variations in surgical techniques include resection of ductal tissue or coarctectomy as opposed to patching of the region of ductal insertion. The aim of stage 1 palliation is to create a stable anatomy that permits growth and maturation of the pulmonary vasculature so that it can accommodate subsequent single-ventricle palliation. It is important that successful surgical strategies have a low incidence of recurrent or residual lesions because these are a source of interstage mortality and can limit suitability for subsequent stages of single-ventricle palliation. Development of a restrictive atrial septal defect rarely complicates the interstage course (247). The observation that smaller ascending aortic size and the presence of aortic atresia are risk factors for mortality is an indication that coronary insufficiency is a cause of death following stage 1 palliation, and strategies that target creation of a large ascending aorta-to- pulmonary root anastomosis are likely to result in improved outcome (248,249,250,251). Arch reconstruction strategies that include coarctectomy appear to have a lower incidence of late arch obstruction (85,248). A modification of the systemic-to-pulmonary artery shunt developed by Blalock, Thomas, and Taussig has historically been the source of pulmonary blood flow following stage 1 palliation (252). Both the diameter and length of this shunt are relevant to determining its flow-resistive characteristics (203). The resulting anatomy ideally provides enough resistance to pulmonary blood flow to avoid destabilization from excessive pulmonary blood flow P. Physiologic limitations result from the inherent Qp/Qs mismatch of the parallel circulation and diastolic aortic runoff to the pulmonary circulation with risk of aortocoronary flow impairment (253,254). Additionally, competition between cerebral and pulmonary circulations for blood flow is possible if the shunt originates from the innominate artery (211). Furthermore, the systemic-to-pulmonary artery shunt is susceptible to occlusion owing to thrombosis or thromboembolism (247,255). The shunt originates from the innominate artery and inserts into the central pulmonary artery. A larger 5- or 6-mm graft is placed between the right ventricle and the central pulmonary artery. Pulmonary blood flow is restricted with branch pulmonary artery bands, and the ductal patency is maintained by placement of a stent. In this modification pulmonary blood flow is supplied by conduit, generally a Gore-Tex tube graft, from the right ventricle to the pulmonary artery (256). Use of this approach has also been reported in the rare neonate who cannot be stabilized by medical interventions because of excessive pulmonary blood flow (232,277). The hybrid approach uses surgical branch pulmonary artery banding combined with transcatheter ductal stenting (243,244,245,278). Intervention to provide a reliable atrial septal communication is also necessary and may include a balloon septostomy and/or stent placement within the atrial septum (279).
Each cusp moves in undulating fashion toward its arterial sinus during ventricular systole and then back toward the center of the arterial lumen during ventricular diastole as retrograde blood flow fills each valve pocket proven penegra 50mg prostate cancer after surgery. Pulmonary Valve The pulmonary valve lies closest to the chest wall order generic penegra on-line prostate meaning, near the upper left sternal border, and its orifice is directed toward the left shoulder. Because right ventricular myocardium extends onto the pulmonary sinuses, the valve appears partially submerged within a crater of infundibular muscle. The anterosuperior limb of the septal band extends onto the left pulmonary sinus, and trabeculations parallel to the parietal band insert onto the right pulmonary sinus. In the setting of pulmonary atresia with an intact ventricular septum, failure to recognize these features has resulted in burrowing into the pericardial sac rather than into the pulmonary artery during closed operations (Brock procedure). Although this procedure is no longer performed, it is important to remember this potential complication during cardiac catheter manipulations. Aortic Valve The annulus of the aortic valve is a midline structure, and its orifice is directed toward the right shoulder. Consequently, its systolic murmurs are best heard along the upper right sternal border and radiate toward the neck. Although the valve cusps are similar in size, in only about 10% of hearts are they truly equal in size. Thus, a minor degree of inequality is the rule, and in two-thirds of hearts, either the right or the posterior cusp is larger than the other two. By virtue of its central position, the aortic valve and its sinuses contact all four cardiac chambers, an important consideration in evaluating aortic sinus aneurysms of congenital or infectious origin. The right aortic sinus abuts the basal ventricular septum and right ventricular parietal band and is covered in part by the right atrial appendage. In contrast, the left aortic sinus rests against the anterior left ventricular free wall and a portion of the anterior mitral leaflet, abuts the left atrial free wall, and is covered in part by the main pulmonary artery and left atrial appendage. Finally, the posterior aortic sinus overlies the basal ventricular septum and a part of the anterior mitral leaflet, forms part of the transverse sinus, abuts the atrial septum, and indents both atrial free walls as the torus aorticus (aortic bulge). Comparison of Semilunar Valves The semilunar valves are named according to the great artery into which they empty, not the ventricle from which they arise. During fetal development and infancy, the aortic and pulmonary valves are virtually identical. However, during childhood, the aortic cusps begin to thicken and become more opaque than the pulmonary cusps as a result of higher left-sided pressures. The annular dimensions of the aortic and pulmonary valves are similar from birth through the first four decades of life, but beyond the age of 40 years, the rate of age-related annular dilation is greater for the aortic valve than for the pulmonary valve. It also contains the fibrous cardiac skeleton, the purpose of which is to weld together the valvular annuli, to fuse together but also electrically separate the atria and the ventricles, and to provide a firm foundation against which the ventricles can contract. The cardiac skeleton contains not only the four major valve annuli but also their intervalvular fibrous attachments (the right, left, and intervalvular fibrous trigones and the conus ligament). A: The aortic valve is located centrally and abuts the other three cardiac valves. B: The cardiac skeleton, shown schematically, consists of four valvular annuli, three fibrous trigones, a membranous septum, and the tendon of Todaro. The intervalvular fibrous trigone is interposed between the left-posterior aortic commissure and the anterior mitral leaflet, and the left and right fibrous trigones project from each side and attach to the remainder of the anterior mitral leaflet. Thus, the left, intervalvular, and right fibrous trigones provide the anatomic substrate for direct mitral–aortic valvular continuity. The membranous septum, in conjunction with the right fibrous trigone, fuses the right posterior aortic commissure to the anteroseptal tricuspid commissure. Therefore, the right fibrous trigone (also known as the central fibrous body) welds together the aortic, mitral, and tricuspid valves and forms the largest and strongest component of the cardiac skeleton. Even in the setting of a membranous ventricular septal defect, this connection is maintained, so that the region of mitral–tricuspid continuity forms the posterior wall of the defect. Near the right–left aortic commissure is a diminutive connection between the aortic and pulmonary valves, the conus ligament (or ligament of Krehl). Thus, each aortic valve commissure is fused to one of the other three valves: left-posterior commissure to mitral valve, right-posterior commissure to tricuspid valve, and right–left commissure to pulmonary valve. Although schematic drawings of the cardiac base generally show the four valves in the same plane, they actually do not lie in the same plane or even in parallel planes. Because of the intertwining of the great arteries, the aortic and pulmonary valves are skewed 60 to 90 degrees as the valvular orifices are directed toward opposite shoulders. Moreover, the tricuspid and mitral valves are skewed 10 to 15 degrees, such that their annuluses approach one another at the membranous septum and diverge along the inferior wall as the coronary sinus is interposed between them. Great Arteries General Features The great arteries include the aorta, pulmonary arteries, and ductus arteriosus. Although the aorta and pulmonary artery represent elastic vessels, the ductus arteriosus has a unique microscopic appearance that changes during fetal and neonatal life. In the fetus and neonate, the aorta and pulmonary arteries are similar in thickness and in the number of elastic laminae within their medial layers. During the first several months of life, and consequent to the postnatal decrease in pulmonary artery pressure and resistance, the mediastinal pulmonary arteries attenuate and decrease in thickness and their elastic fibers become irregular and fragmented. Beyond the first year of life, the thickness of the main pulmonary artery is normally less than half that of the adjacent ascending aorta, although the diameters of the two great arteries remain similar. Interestingly, for patients with persistent pulmonary artery hypertension after birth (as with unrepaired large ventricular septal defects), the medial thickness and elastic pattern in the pulmonary arteries remain similar to those in the aorta. In contrast, in patients who develop primary pulmonary hypertension later in life, their pulmonary arteries become thickened and the medial elastic layers retain the appearance of a pulmonary artery rather than that of an aorta. Pulmonary Arteries The main pulmonary artery emanates from the right ventricle and travels to the left of the ascending aorta in the general direction of the left shoulder. As it bifurcates, the left pulmonary artery continues as a smooth arch and courses over the left bronchus, whereas the right pulmonary artery arises at a right angle and travels beneath the aortic arch and behind the superior vena cava. Creation of a Glenn anastomosis between the superior vena cava and right pulmonary artery takes advantage of the close proximity of these two vessels. The main and left pulmonary arteries contribute to the upper left border of the radiographic frontal cardiac silhouette (Fig. Because the pulmonary arteries do not exhibit bilateral mirror-image symmetry, the spatial relationship of the main and lobar arteries to their adjacent bronchi differs between the right and left lungs and can be used to determine pulmonary morphology and sidedness (Fig. During childhood, the tracheobronchial cartilage is pliable and may be compressed by hypertensive pulmonary arteries. Chronic compression of the left main and right middle lobe bronchi may contribute to the development of recurrent bronchopneumonia or P. Furthermore, rightward displacement of the aortic arch by a dilated and hypertensive pulmonary trunk can produce tracheal indentation, which may be detected radiographically, and hoarseness owing to compression of the left recurrent laryngeal nerve. A: The right and left pulmonary arteries are not mirror-image structures, and neither are the right and left bronchial trees. B: Bronchial arteries usually arise from the descending thoracic aorta at the level of the carina, but they vary in number. Within the human lung, pulmonary arteries travel with their corresponding airways and pulmonary veins course within the interlobular septa (not septae) (22). Because the pulmonary circulation represents a low-pressure and low-resistance system, its arteries and veins are normally thin walled.