With any clinical deterioration in the early postoperative period buy 20 mg erectafil mastercard impotence at 75, evaluation of and treatment for rejection as the potential cause should be considered buy erectafil cheap online impotence vacuum pump demonstration. This need for noninvasive diagnosis of rejection has stimulated the ongoing search for biohumoral markers purchase cheap erectafil on-line erectile dysfunction and diabetes a study in primary care, such as B-type natriuretic peptide. Although there appears to be some correlation between biomarkers and rejection, the sensitivity and specificity of all biomarkers suffers from the same issues as echocardiographic parameters. Thus, the clinical role of these markers remains to be defined (167,168,169,170,171). Clinical evaluation for rejection is important but can be misleading, particularly in pediatric patients in whom infectious issues can mimic the presence of rejection. The characteristic infiltration of the donor heart by lymphocytes leads to the diagnosis of rejection on endomyocardial biopsy (172). Histologically, cardiac allograft rejection and lymphocytic myocarditis can be very similar. The surface electrocardiogram may suggest atrial flutter or atrioventricular dissociation, but this observation may be attributed to the fact that the recipient atrial tissue contracts independently of the donor atrial tissue, and there may be two P waves present on the surface electrocardiogram that are not synchronous. Pathologically, this form is characterized by a lack of significant cellular rejection on endomyocardial biopsy with characteristic histologic and/or immunohistochemical findings (177,178). It is often accompanied by left ventricular dysfunction and detection of donor-specific antibodies in the recipient serum. The vast majority of initial rejection episodes can be successfully reversed by high-dose corticosteroids alone or in conjunction with anti–T-cell antibodies. Corticosteroids as either intravenous methylprednisolone (10 to 30 mg/kg every 12 hours) or oral prednisone are the first line in rejection therapy. Fluid shifts, calcium and other electrolyte flux, and systemic reactions to blood products used for plasma replacement are other risks related to plasmapheresis and/or exchange transfusion. Immune apheresis (immunoadsorption) is another modality to specifically remove circulating antibodies and immune complexes. New therapies, including the use of bortezomib, are constantly being sought since the current methods are not universally successful (181,182,183). Immunosuppressive Medications Drugs that inhibit T-cell activation, specifically calcineurin inhibitors, remain the mainstay of immunosuppressive therapy. Cyclosporine was the first drug of this class to reach clinical utility in the early 1980s and in effect ushered in the modern era of solid organ transplantation. When oral medications can be tolerated, the usual starting dose is approximately three times the intravenous dose divided every 12 hours in older children, although higher doses are usually required in infants. Trough blood levels of cyclosporine must be monitored to insure efficacy and avoid toxicity. The therapeutic range for blood levels for the active compound, cyclosporine A, range from 100 to 350 ng/mL. Higher plasma levels are usually maintained early after transplantation, then are tapered over time, depending on the clinical course. The bioavailability of cyclosporine is variable particularly in children, although the microemulsion preparations have improved bioavailability (184). Studies comparing cyclosporine with tacrolimus have suggested possible benefit of tacrolimus over cyclosporine in terms of reducing the incidence of rejection or improving outcomes, although tacrolimus is now more widely used in pediatric heart transplantation than cyclosporine (4,78,185,186). The dosing and monitoring of sirolimus in pediatric patients is still being defined. Use in pediatric heart transplantation has been growing and has been positive for allowing reduction in calcineurin dose and in stabilizing and/or improving renal function (147,154,156). They should be carefully evaluated when starting new drugs, including even antibiotics or foods such as grapefruit. Antiproliferative Agents In the past, the most commonly used agent to block immune cell proliferation had been azathioprine. The improved selectivity compared to azathioprine may provide more effective immunosuppression (196). The value of blood levels is controversial, and monitoring of trough levels has been abandoned in many centers. Methotrexate and cyclophosphamide have also been used in transplant recipients as adjunctive therapy for chronic or recurrent rejection (198,199). Nonspecific Immunosuppression Corticosteroids are potent immunosuppressive agents and are the first line of rejection therapy. Some centers continue to use corticosteroids as part of routine immunosuppression, although most programs attempt to discontinue routine oral steroids (200,201). The favorable experience in pediatric heart transplant with a corticosteroid-free maintenance protocol has led to its use with other pediatric solid organ transplant recipients. For significant rejection, methylprednisolone is usually given in a dose of 10 to 30 mg/kg every 12 hours intravenously for six to eight doses. A tapering dose may then be used to return to usual maintenance oral doses of prednisone or discontinued depending on the policy of each individual program. All the current immunosuppressive medications do not lead to tolerance in humans, although they can lead to tolerance in experimental models. In order to reduce the burden of immunosuppressive drugs, the drive to develop tolerizing protocols for infants and children is pressing. Late Follow-Up The number of pediatric heart transplants performed worldwide markedly increased in the late 1980s and has since somewhat plateaued (4). Since 1982, more than 10,800 pediatric heart transplantations have been successfully completed around the world (4). The median survival time period for adolescents undergoing heart transplantation was 12. These data indicate that the majority of the transplant recipients are surviving into their late adolescence and early adulthood. Given the improved health outcomes of the pediatric transplant recipients, recent attention has begun to focus on growth, development (cognitive and psychosocial), and quality of life. The median conditional graft half-life was >20 years for childhood recipients, and 16. In addition to immunologic factors that may provide an advantage for transplantation in the first year of life (203), reduced compliance to therapies in adolescent age patients may play a key role in determining these results. Many centers have reported that incomplete adherence with immunosuppressive therapy is the leading cause of late death in the adolescents (204,205). Adolescent transplant recipients appear to be at particular risk for nonadherence for multiple reasons. First, adolescence itself is a risk factor for nonadherence due to increased need during this period to fit in with their peer group and suppress any qualities that make them appear different (206). Additionally, body image becomes very important during this period as it is associated with peer acceptance, and the negative impact immunosuppressant therapy can have on physical appearance may cause adolescents, especially girls, to stop taking the medication (206). Third, parents may expect adolescents to be more responsible for their own medical management and provide less supervision than they would with younger children (207). Fourth, there are data from pediatric cancer and the adult transplant literature that suggest patients become less adherent to medical regimen over time, which connotes increased rates for adolescence, given that many of them were transplanted as infants or younger children (208,209). Finally, the normal stressors that occur during adolescence can interact with the stressors that are a result of the chronic illness to create psychological distress, which also increases the risk of nonadherence.
Hypoplastic left heart syndrome: natural history in a geographically defined population cheap generic erectafil uk what causes erectile dysfunction cure. Prevalence erectafil 20 mg overnight delivery erectile dysfunction treatment exercises, treatment discount erectafil 20 mg fast delivery impotence medical definition, and outcome of heart disease in live-born children: a prospective analysis of 91,823 live-born children. The determinants of five-year survival of infants with critical congenital heart disease. Aortic atresia: morphologic characteristics affecting survival and operative palliation. Updated national birth prevalence estimates for selected birth defects in the united states, 2004–2006. Familial risks of congenital heart defect assessed in a population-based epidemiologic study. Cardiac malformations in relatives of infants with hypoplastic left-heart syndrome. Echocardiographic evaluation of asymptomatic parental and sibling cardiovascular anomalies associated with congenital left ventricular outflow tract lesions. Acquired neuropathologic lesions associated with the hypoplastic left heart syndrome. Electroencephalographic abnormalities in infants with hypoplastic left heart syndrome. Plasma amino acids in interrupted aortic arch and the hypoplastic left heart syndrome. Coarctation of the aorta in turner syndrome: a pathologic study of fetuses with nuchal cystic hygromas, hydrops fetalis and female genitalia. Genetic disorders and major extracardiac anomalies associated with the hypoplastic left heart syndrome. Linkage analysis of left ventricular outflow tract malformations (aortic valve stenosis, coarctation of the aorta, and hypoplastic left heart syndrome). Hypoplastic left heart syndrome links to chromosomes 10q and 6q and is genetically related to bicuspid aortic valve. Effect of copy number variants on outcomes for infants with single ventricle heart defects. Submicroscopic chromosomal copy number variations identified in children with hypoplastic left heart syndrome. Excess birth prevalence of hypoplastic left heart syndrome in eastern wisconsin for birth cohorts 1997–1999. Seasonality of hypoplastic left heart syndrome in the united states: a 10- year time-series analysis. Hypoplastic left heart syndrome: progression of left ventricular dilation and dysfunction to left ventricular hypoplasia in utero. Left ventricular dysfunction in the fetus: relation to aortic valve anomalies and endocardial fibroelastosis. Left heart obstructive lesions and left ventricular growth in the midtrimester fetus. Premature closure of the foramen ovale associated with aortic stenosis, left ventricular dilation with thrombus, and early mortality. Hypoplasia of the eustachian valve and abnormal orientation of the limbus of the foramen ovale in hypoplastic left heart syndrome. Subcostal two-dimensional echocardiographic identification of anomalous attachment of septum primum in patients with left atrioventricular valve underdevelopment. Balloon dilation of severe aortic stenosis in the fetus: potential for prevention of hypoplastic left heart syndrome: candidate selection, technique, and results of successful intervention. Diagnosis and management of fetal cardiac anomalies: 10 years of experience at a single institution. Trends and outcomes after prenatal diagnosis of congenital cardiac malformations by fetal echocardiography in a well defined birth population, atlanta, georgia, 1990–1994. Reversed shunting across the ductus arteriosus or atrial septum in utero heralds severe congenital heart disease. Fetal aortic valve stenosis and the evolution of hypoplastic left heart syndrome: patient selection for fetal intervention. The hypoplastic left heart syndrome with intact atrial septum: atrial morphology, pulmonary vascular histopathology and outcome. Hypoplasia of the small pulmonary arteries in hypoplastic left heart syndrome with restrictive atrial septal defect. Intrauterine pulmonary venous flow and restrictive foramen ovale in fetal hypoplastic left heart syndrome. Pattern of pulmonary venous blood flow in the hypoplastic left heart syndrome in the fetus. World experience of percutaneous ultrasound-guided balloon valvuloplasty in human fetuses with severe aortic valve obstruction. Predictors of technical success and postnatal biventricular outcome after in utero aortic valvuloplasty for aortic stenosis with evolving hypoplastic left heart syndrome. Changing the natural history of borderline and hypoplastic left hearts in the fetus. Hypoplastic left heart syndrome with intact or highly restrictive atrial septum: outcome after neonatal transcatheter atrial septostomy. Creation of an atrial septal defect in utero for fetuses with hypoplastic left heart syndrome and intact or highly restrictive atrial septum. Results of in utero atrial septoplasty in fetuses with hypoplastic left heart syndrome. Prenatal prediction of lethal pulmonary hypoplasia: the hyperoxygenation test for pulmonary artery reactivity. Vasoreactive response to maternal hyperoxygenation in the fetus with hypoplastic left heart syndrome. Hypoplastic left heart syndrome with atrial level restriction in the era of prenatal diagnosis. Chronic intermittent materno-fetal hyperoxygenation in late gestation may improve on hypoplastic cardiovascular structures associated with cardiac malformations in human fetuses. Pathologic anatomy and interrelationship of hypoplasia of the aortic tract complexes. Home surveillance program prevents interstage mortality after the norwood procedure. Improved survival of patients undergoing palliation of hypoplastic left heart syndrome: lessons learned from 115 consecutive patients. Survival after reconstructive surgery for hypoplastic left heart syndrome: a 15-year experience from a single institution. Hypoplastic left heart syndrome: lack of correlation between preoperative demographic and laboratory findings and survival following palliative surgery. Surgical outcome for patients with the mitral stenosis-aortic atresia variant of hypoplastic left heart syndrome. Impact of mitral stenosis and aortic atresia on survival in hypoplastic left heart syndrome.
The main advantage of sequencing in this way is the ability to automate almost all parts of the process generic erectafil 20 mg with amex erectile dysfunction drug types. Sequencing reactions can be set up robotically in the wells of microtitre dishes and subjected to thermocycle sequencing cheap 20 mg erectafil with amex erectile dysfunction treatment medscape. The different terminators have different emission properties depending on the nature of the R groups discount erectafil 20mg on line erectile dysfunction ultrasound. This level of accuracy may sound impressive, but if one base in every 100 is incorrectly assigned, then virtually all genes whose sequence is obtained in this way will contain errors. The series of peaks obtained has been separated into the individual ﬂuorescent components and the sequence assembled based on the data obtained. The problem then is how to reconstruct the original genome sequence based on the small fragments that are cloned into individual vectors. The second clone is then sequenced and the information used to identify a third clone, whose insert overlaps with the second clone, and so on. A single clone has be isolated and sequenced before the next overlapping clone can be sought. Additionally, repetitive sequences within the genome can give rise to incorrect contig assignment. The fragments of the genome, which have been randomly generated, are cloned into a vector and each insert is sequenced. The sequence is then examined for overlaps (sequences that occur in more than one clone) and the genome is reconstructed by assembling the overlapping sequences together (Figure 9. This approach was ﬁrst used to sequence the genome of the bacterium Haemophilus inﬂuenzae. Theentire genome of the organism was randomly fragmented using sonication and then small fragments (in the range of 1. Each of these was then sequenced to generate approximately 12 million base pairs of sequence information (Fleischmann et al. The sequence obtained from each clone was then assembled into contigs based on the overlaps between the individual clones. Any sequence gaps were ﬁlled in subsequently by identifying additional clones (from a different library) that contained sequences close to the gap-point. The main advantage of the shotgun approach is that no prior knowledge of the sequence of the genome is required. The approach is, however, limited by the ability to identify overlapping sequences. Every sequence obtained must be compared with every other sequence in order to identify the overlaps. This can be a time-consuming process and requires large amounts of computational 9. Assembling genomic data using the hierarchical and whole genome shot- gun approaches. Adapted from Waterston, Lander and Sulston (2002), with permission power (Myers et al. The shotgun approach to contig assembly has proved immensely successful in sequencing comparatively small genomes. For larger genomes, however, it is not the sequencing itself that is the rate limiting step, but the assembly of contigs. The project was planned to last for 15 years, but technological advances have accelerated the expected completion date to 2003. In generating the draft sequence, the order of bases in each chromosome was determined at least four or ﬁve times to ensure data accuracy and to help with contig assembly. Draft sequence data is mostly in the form of ∼10 000 bp contigs whose approximate chromosomal locations are known. The human genome sequence does not represent an exact match for any single person. As a publicly funded group, the data obtained from their sequencing efforts is made freely available. The Bermuda Principle (determined during a 1997 conference in Bermuda) states that sequence assemblies of 2 kbp or larger should be automatically released to public databases within 24 hours of their generation. Celera Genomics undertook a whole genome shotgun approach to sequencing the human genome. To generate a high-quality ﬁnal sequence of the human genome, additional sequencing is needed to close gaps, reduce ambiguities and allow for only a single error every 10 000 bases, giving an accuracy of 99. To date, ﬁnished sequences have been generated for the three smallest human chromosomes −20, 21 and 22. For example, the 56 Mbp sequence of human chromosome 22 was declared essentially complete in 1999, yet only 33. Also, the 180 Mbp genome of the fruit ﬂy Drosophila was announced as completed, although just 120 Mbp were sequenced (Adams et al. These regions include telomeres and centromeres (the ends and middle of chromosomes), as well as many chromosomal areas rich in other sequence repeats. Although the goal of the human genome project is to have a complete sequence for each chromosome, obtaining a full sequence still presents a great challenge. The search for a gene can therefore be thought of as a scan for an initiation and termination codon that are separated by, say, at least 100 codons. Unfortunately, these latter sequences can be quite variable, and precise gene identiﬁcation remains problematical. An alternative approach to gene identiﬁcation is to use previously identiﬁed genes as a guide. Many of these sequences are, of course, repetitious (Banﬁ, Guf- fanti and Borsani, 1998), with highly expressed genes being represented many times. In less experimentally amenable organisms, especially in humans, comparatively few genes were known before large-scale sequencing projects were undertaken. There are, however, several methods there are currently used to assign the function of a gene based only on its sequence. Just as computational methods play an important role in deﬁning those portions of the genome that may encode genes, the availability of large databases of known gene sequences can also be used to assign function to unknown ones. Many genes that encode proteins with the same function in different organism will be similar. For example, almost all organisms have the ability to convert the sugar galactose into glucose-6-phosphate so that it can be fed into the gly- colytic cycle. The ﬁrst step of this pathway is the conversion of galactose into galactose-1-phosphate – a reaction that is catalysed by the enzyme galactokinase. All organisms possess their own galactokinase enzyme, and the galactokinases from different organisms each have their own unique sequence. However, most likely as a result of having to perform the same chemical reaction, galactokinase enzymes are related to each other. That is, the amino acid sequence of the galactokinase from one organism shares similarity to the galactokinase from another organism (Figure 9.
In chronic ulcera- is loss of the normal colonic haustra in the affected portions tive colitis there is visible fatty infltration in the submu- of the colon cheap erectafil 20 mg mastercard young erectile dysfunction treatment. Oedema of the perirectal tissues causes widen- cosa buy erectafil on line amex impotence caused by diabetes, resulting in a ‘target sign’ appearance (Fig cheap 20mg erectafil overnight delivery smoking and erectile dysfunction statistics. When the whole colon is involved, the terminal ileum Narrowing and shortening of the colon, giving the appear- may become dilated. The diagnosis is made on clinical grounds these islands of infamed mucosa makes it diffcult to assess and on examination of the plain abdominal flm or stand- the true depth of the ulceration. In this case of ulcerative colitis, the ulceration causes the normally smooth outline of the colon (a) (b) to be irregular. With longstanding disease, the haustra are lost and the colon becomes narrowed and shortened, coming to resemble a rigid tube. The transverse and descending colon are thick-walled and infamed with enhancement of the mucosa and marked dilatation of the lumen. The colon may be the only part of the alimentary tract to be involved, but usually the disease affects the small bowel if the colon is involved. At an early stage in the disease, the fndings at barium enema are loss of haustration, narrowing of the lumen of the bowel and shallow ulceration. This criss-crossing ulcer- ation combined with mucosal oedema may give rise to a ‘cobblestone’ appearance of the mucosa (Fig. The ulcers may be very deep, penetrating into the muscle layer, when they are described as ‘rose-thorn ulcers’ or deep fssures. The deep ulceration in Crohn’s disease may lead to the formation of intra- and extramural abscesses. The disease is not always circumferential; one of the features that distinguish it from ulcerative colitis is that it may involve only one portion of the circumference of the bowel. Another important diagnostic feature is the presence of the so-called ‘skip lesion’ (Fig. Skip lesions are virtually ‘cobblestone’ appearance due to criss-crossing fne ulceration. However, the entire colon may be involved or the disease may be limited to just one Diverticular disease segment. The rectum is often spared – another important Diverticula are sac-like out-pouchings of mucosa through differentiating feature from ulcerative colitis. Very deep ulcers are present; two examples of an ulcer tracking in the submucosa are arrowed. A long stricture is present in the transverse colon (between the curved arrows) and a shorter one in the sigmoid colon (between the small arrows). These two abnormal segments with normal intervening bowel are an example of ‘skip lesions’ – an important diagnostic feature of Crohn’s disease. The term diverticulitis is used when infection of the affected segment causes symptoms such as sepsis, diarrhoea or obstruction. The diverticula, when flled with barium, are seen as spherical out-pouchings with a narrow neck (see Fig. Numerous diverticula are seen as of the stricture, it is impossible to defnitely exclude a carcinoma. An appendicolith may be visible stranding of the surrounding fat due to oedema and infam- within the appendix as a hyperechoic area casting an acous- matory change (Fig. An appendix abscess can be diagnosed abscess or fstula into the bladder, small bowel or vagina. Occasionally, diverticula perforate directly into the peritoneal cavity causing peritonitis, and Acute infarction of the large bowel is very rare. Ischaemia free intraperitoneal air should be looked for on a plain is usually a more chronic process giving rise, initially, to abdominal flm if necessary. Usually, Chronic mesenteric ischaemia is often a delayed diagnosis this is clearly within an area of recognizable diverticular as patients may present with vague symptoms, and not the disease. It is, however, often impossible to differentiate classic history of post-prandial pain. It occurs due to nar- such a stricture from a carcinoma occurring coincidentally rowing of the arteries supplying the bowel, and usually at in a patient with diverticular disease. In cases of doubt the and helping determine whether revascularization can be diagnosis can be made with ultrasound, which shows a undertaken by an endovascular or surgical approach. In the distended, non-compressible appendix with a thickened later stages, a stricture may form (Fig. If stricture formation occurs, the stricture Sacculations may be seen arising from one side of the stric- will be smooth and have tapered ends. Gastrointestinal Tract 183 Pneumatosis coli In this unusual condition, gas-flled spaces are present in the wall of the bowel. They can be identifed on a plain flm of the abdomen, but the diagnosis is much easier with a barium enema where the cysts cause smooth, translucent flling defects projecting from the wall of the bowel (Fig. The appearance could be confused with intramural haemorrhage and oedema, or with colitis if the presence of air within the cysts is not appreciated. This happens most frequently in the sigmoid colon, particularly when it is redundant, and less often in the caecum. The twisted loop becomes greatly distended and the bowel proximal to the volvulus is obstructed by the twist and may, therefore, also be dilated. Intussusception An intussusception is the invagination of one segment of the bowel into another. Part of the colon showing numerous By far the commonest type is an ileocolic intussusception, translucencies in the colon wall owing to many gas-flled cysts. Other types are colocolic, when the colon invaginates into another part of the colon, and ileo-ileal when the ileum invaginates into a per rectum under fuoroscopic or ultrasound control, the more distal segment of ileum. In infants and a reduction is to be safely carried out, the child should have young children, in particular, the diagnosis is often con- no clinical signs of peritonitis. The longer the symptoms frmed by an enema with air or carbon dioxide as the have been present, the greater the risk of perforating gan- contrast agent, and an attempt at reduction of the intus- grenous bowel. When gas is insuffated presence of a neoplasm, typically in the submucosa, such 184 Chapter 6 Fig. A sausage-shaped mass less than 1 cm in size, and very few less than 2 cm, are is demonstrated, which has mesenteric fat within the cancers. The features that suggest malignancy are a diam- lumen of the intussuscipiens (Fig. Surgical treatment eter of more than 2 cm, a short thick stalk or an irregular is invariable. They are, there- Polyps fore, removed endoscopically when discovered, regardless The word ‘polyp’ means a small mass of tissue arising from of whether or not an individual polyp is believed to be the wall of the bowel projecting into the lumen. They may be single or multiple and on radiological grounds to exclude frank malignancy in a are found most frequently in the rectosigmoid region. Gastrointestinal Tract 187 familial polyposis they are numerous and one or more will, these two sites are usually quite different.
In 1979 buy erectafil without a prescription erectile dysfunction caused by medications, Sos first experimented with balloon angioplasty of native coarctation in postmortem specimens (90) and this was followed by some fundamental work by Dr buy generic erectafil 20mg on-line erectile dysfunction niacin. He performed balloon angioplasty on excised human coarctation segments as well as experimentally induced coarctation in lambs (91 discount 20 mg erectafil amex erectile dysfunction 47 years old,92). He showed that balloon angioplasty achieved its therapeutic result by creating micro- or macroscopic intimal and medial tears over a variable distance in the vessel. These intimal injuries appeared to have healed completely on late pathologic examination, leaving the ballooned segment with a normal looking intima. The studies also documented that a balloon diameter of less than twice the size of the coarctation segment was unlikely to achieve a successful dilation, while diameters greater than three times appeared to carry a higher risk of deep and extensive tears. In animal experiments, they implanted Palmaz P308, 188 and 108 stents in the abdominal aorta and documented that stents can be safely redilated P. While one should generally avoid endovascular stent therapy in small infants, in some very rare circumstances the implantation of a low-profile stent in very sick infants may be justifiable, even though one has to accept that these low-profile stents are not expandable to adult size and therefore will eventually require surgical removal. Coarctation with 30 mm Hg peak systolic gradient incidentally found during procedure. A 15-year-old child with a history of coarctation repair (end-to-end) during infancy. One of the major difficulties when comparing the various treatment modalities for native or recurrent coarctation of the aorta, such as surgery, balloon angioplasty, and endovascular stenting, is the fundamental lack of prospective, evidence- based data (98). As such, one has to rely on institutional series (98), the results of which are necessarily influenced by not only the skill of the individual interventional cardiologist and cardiac surgeon in the respective institution, but also by the common institutional policy and experience in treating these lesions. Similar to the comparison of surgical and interventional approaches to coarctation, the decision between balloon angioplasty and primary stenting is often dependent on the individual institutional policy, rather than being guided by evidence-based data. While both balloon angioplasty and endovascular stenting have an important role to play in the primary management of aortic coarctation, there are a number of valid reasons that make primary stenting the more suitable treatment modality, if the size of the patient permits this procedure: Firstly, the results of balloon angioplasty are limited due to elastic recoil of the coarcted segment and the rigidity of an endovascular stent obviously overcomes this problem. Secondly, the degree of trauma to the aortic vessel wall plays an important factor in the potential development of complications such as aneurysm formation. While balloon angioplasty often requires a degree of overexpansion of the coarctation and adjacent vessel wall to achieve a maintainable result, endovascular stenting allows having a successful result while dilating the vessel wall only to the desired diameter—overexpansion is not required. Finally, a subgroup of longer-segment coarctation or arch hypoplasia typically has a poorer outcome after balloon angioplasty alone. Even though primary endovascular stenting offers significant benefits, it is usually avoided in small children and infants, because of the potential for injury to the arterial vessels and access sites as well as the higher likelihood of developing in-stent stenosis when stents are only expanded to fairly small diameters. As with any other aspect of interventional therapy, the catheterization laboratory has to be equipped to allow the operator to deal with potential complications that are specific to the procedure performed (Fig. The goal of the procedure is to achieve reduction in the gradient to less than 10 mm Hg or a 90% or greater relief of the obstruction angiographically. In an observational study, Zabal and colleagues analyzed a cohort of 54 consecutive adult patients who underwent transcatheter treatment for coarctation with the primary endpoint being a composite index of failure, made up of heart-related death, a gradient on follow-up of more than 20 mm Hg, the need for reintervention or complications such as aneurysm formation (99). They identified that a residual gradient of more than 10 mm Hg was associated with a significantly higher failure index. Upon sheath removal injury to right iliac artery which was treated through implantation of a covered Atrium Cast stent. With the present techniques and equipment, dilation and/or stent implantation for native or recurrent coarctation appears to be successful in achieving immediate relief on the obstruction in more than 90% of cases. However, the cumulative composite procedural success decreased to 86% at intermediate follow-up (3 to 18 months) and 77% at long-term follow-up (>18 months). However, balloon angioplasty alone for native coarctation in smaller children and infants has lower long-term success rates and the results are frequently not well maintained, with up to 66% recoarctation rate. An additional concern when discussing transcatheter interventions for native coarctation is the potentially greater incidence of aortic aneurysm formation in the area of the coarctation dilation. However, the follow-up data is limited, and the long-term outcome is uncertain, at best. Another concern with these aneurysms, particularly following an otherwise successful dilation, is that if subsequent surgery is necessary, it could be more hazardous because of the disappearance of collaterals following a hemodynamically successful dilation. As more follow-up information is gathered regarding dilation of native coarctation, this technique appears more reasonable for discrete lesions in patients over 7 to 12 months of age (102). In the larger child, primary stent therapy for native coarctation is a suitable treatment alternative to balloon angioplasty, even though aneurysms can occur with these stent implants. It has been suggested that gradual conservative expansion of these stents be performed over two or three procedures, especially in tight lesions, to reduce the incidence of dissection or aneurysm formation. If balloon angioplasty alone is performed, a balloon of the same diameter as the narrowest aortic diameter adjacent to the coarctation is prepared. A “J” or curved-tip stiff guidewire is positioned retrograde through the coarctation, around the aortic arch, and into the aortic root or occasionally into the right innominate artery. The dilation balloon catheter is passed over the wire and across the area of coarctation. The inflation may be repeated several times until the waist in the balloon or the gradient disappears. In smaller children and infants, cutting balloon angioplasty frequently adds an additional treatment alternative in patients where endovascular stent placement should be avoided. In the slightly larger patient, when the results of the dilation are not satisfactory and where larger sheaths can be introduced into the arteries, intravascular stents can be used to support the dilated segment of aorta. When stents are used, it is imperative that only stents that eventually can be dilated to the full diameter of the adult descending aorta are used. Transcatheter management of coarctation in the adult has some important differences when compared to its management in the younger child. For example, limiting factors in younger children when considering endovascular stent therapy, are the potential for injury to the arterial vessels and access sites due to the need for larger-sized hemostatic sheaths as well as the higher likelihood of developing in-stent stenosis when stents are only expanded to fairly small diameters. The goal of the interventional procedure in adults is similar to children: To achieve reduction in the gradient to less than 10 mm Hg or a 90% or greater relief of the obstruction angiographically. It has been advocated that the risk of catastrophic aortic injury during or after balloon angioplasty and/or stent placement in the adult (106,107,108) is higher than what would be expected in the younger child, especially when treating primary coarctation. Many adult patients with systemic and exercise-induced hypertension, may present with “just” a 20 to 30 mm Hg upper-to-lower limb blood pressure gradient with an angiographic discrepancy between coarcted segment and the aorta at the diaphragm of not more than 30% to 50%. To achieve an adequate result with balloon angioplasty alone, one would ideally have to expand the area to at least twice the size of the coarctation segment (91,92). However, using this as a guide would lead to significant overdilation of not only the coarcted segment, but also the adjacent “healthy” aorta. Primary stent therapy is therefore the treatment of choice in adults with primary or recurrent coarctation, as it not only avoids the need for overexpansion, but also has a lower risk of recurrence when compared to balloon angioplasty. A 34-year-old pregnant woman hospitalized during her 24th week gestation with severe systemic hypertension. Fluoroscopy time was minimized and appropriate radiation protection measure were taken. This not only identifies areas with medial and intimal disruption as could relate from a previous attempt at balloon angioplasty, but it also allows to clearly define the extension of the abnormal vessel wall, thereby allowing to choose a stent that is of sufficient length to cover the full length of the abnormal vasculature.
By S. Fasim. Kennedy-Western University.