Br J Dis Chest aid of hypothermia: experimental accomplishments and the 1984 buy 200 mg avana impotence diabetes;78:113–34 purchase avana 50 mg erectile dysfunction at 17. New York: Raven vision closure of ventricular septal defects in eight patients by Press buy avana 200mg mastercard erectile dysfunction at 65, 1991: 677–87. Cardiac ture in lung tissue obtained at biopsy correlated with pulmo- Surgery of the Neonate and Infant. Hypoxic ischemic encephalopathy: basic aspects and Surgery of the Neonate and Infant. Marital stability and phur containing amino acids on the infant mouse central ner- congenital heart disease. The a wide range of techniques which are rarely written about in yellowish light from tungsten sources contains very much text books or journals. There is no question that certain indi- more infrared heat than halogen sources which have an obvi- viduals can master the necessary skills more easily than oth- ous blue hue. Modern overhead lights can be temperature ers, but fundamentally they are skills that can be taught and controlled with a warmer yellowish setting or cooler bluish learned. However, the limited spotlight of a halogen headlight will be taught through the apprenticeship system of surgical reduces tissue heating relative to dependence on large over- mentoring. The limited area that is illuminated by a head- such second nature to the senior surgeon that they tend to light also improves visualization for the surgeon by reducing be overlooked in the teaching process. Constant analysis and glare from areas other than the direct feld of view of the questioning by the trainee – “Why do you do it that way? One only needs to witness how obsessional the radi- – is likely to lead to a productive learning experience in the ologist is about switching off all other light sources when operating room. Many surgeons an essential part of brain, heart and spinal cord protection prefer expanded feld 3. It is impor- team are wearing loupes, they are able to keep their heads at tant to remember that the surgical team should be aiming to a distance from the feld and yet have improved vision relative keep the myocardial temperature at less than 10°C during to the naked eye. No matter how good one’s vision is without the cross-clamp period and during circulatory arrest or low loupes, it will be better with magnifcation. As time marches on fow the brain temperature should be maintained at less than and presbyopia develops, loupes become even more essential. Surface cooling before bypass is almost certainly use- In addition to improving vision, loupes are an important ful. Therefore, the room temperature should be maintained aid to optimal use of the surgical headlight. The feld of at less than 17–18°C until all clamps have been released and vision through the loupes must be carefully and accurately the patient is being rewarmed at full fow. Since almost all congenital cardiac surgery is in a sense ‘minimally invasive’ in that the cardiac incisions must be limited, it is often diffcult for all members of the team to be able to follow the progress of the procedure. These instruments are designed to Furthermore, the picture from the headlight camera can be be controlled by the fngers rather than by the arms. Unlike adults, children rarely complain of back, era, as well as an overhead camera mounted in the overhead neck or interscapular pain following a sternotomy. This composite sion does not require stretching, cutting or tearing of any image can be connected via the Internet to viewing stations muscles, unlike so many other incisions. The blood supply elsewhere in the hospital such as the senior surgeon’s offce of the bone is excellent in children so that healing is usually or remotely allowing a junior surgeon to call for input from rapid and complete. For example, the Norwood procedure with should be performed using small instruments. While it is a Blalock shunt involves work on the great vessels and right true that many of the instruments used for congenital car- subclavian artery so that the incision should extend up to the diac surgery need to be delicate, they should not necessarily sternal notch. They need to be long enough to allow three pairs sion can be limited and does not need to extend to the bot- of hands (the surgeon and two assistants) to simultaneously tom of the xiphoid process. On the other hand, the depth procedures, however, the top end of the skin incision can be of the surgical feld in neonates and infants is very much limited to end some distance below the sternal notch. This is an important cosmetic consideration since the major dis- is an important advantage for the surgeon in that it allows advantage of the standard incision is the fact that it can be the hand to be stabilized on the chest wall. By limiting the diac surgeons can use time in the dentist’s chair proftably upper end of the incision it is possible to conceal the incision by analyzing the methods by which dentists and hygienists with most clothing. As with It is critically important that the bone incision be exactly dental instruments, most of the movement of instruments in the midline. The width of the sternum varies tremendously used by the congenital cardiac surgeon should be controlled between children and it may be very narrow. If the incision by the fne muscles of the hand and not by the forearm and is made off midline there is a real risk that the sternal wires shoulder girdle muscles. Microvascular instruments, such as will cut through the delicate cartilaginous bone resulting in the Castro–Viejo needle holder are specifcally designed to an unstable sternum and poor healing. An unstable sternum be controlled by the fngers rather than by the arms and are will increase the risk of mediastinal infection. Relative to most other surgical incisions, it has There are a number of options to improve the cosmetic less postoperative pain, particularly in young children who appearance of the standard sternotomy incision. Opening the been possible to prove that minimally invasive incisions sternum requires hinging of the ribs at the costovertebral reduce pain or speed convalescence. It should be is suffciently fexible in children that there seems to be little exceedingly rare that axillary artery cannulation is required, or no advantage in ‘T-ing’ off the incision to one or other side. Carotid artery cannulation is not recommended other can be kept entirely below the level of the nipples. While this than in extreme situations because there is a risk that cerebral limited incision allows for safe closure of septal defects, we blood fow will be compromised. ReopeRaTiVe sTeRnoTomy The previous skin scar is usually excised and the sternal Reopening a sternal incision can be done safely as long as wires are cut and removed. Planning begins with and the linea alba is opened to allow a plane to be developed the preoperative studies which should document the distance behind the lower end of the sternum. The used to elevate the lower end of the sternum off the heart and sternal wires are quite helpful as markers on a direct antero- to provide a counter pressure to the oscillating sternal saw. If a conduit is known to be close to the left side of the status of the femoral and iliac vessels. This knowledge the sternum it may be advisable to free up only the right half may be available from the preoperative catheterization, from of the sternum until the retractor is placed. However, ulti- femoral ultrasound studies or simply from careful palpation mately dissection should extend to the pleural cavities bilat- of the femoral pulses and observation for evidence of previ- erally. At least one groin should be prepped completion of the procedure, but more importantly it allows into the surgical feld. Injury to the right heart can gener- the heart to be moved around more freely, thereby improving ally be dealt with easily by cannulating the femoral artery exposure without having to retract the chambers of the heart and placing a pump sucker in the injured structure. Even emergency cannulation of the femoral ves- nal retractor is in place, dissection is begun using the elec- sels after an aortic injury has occurred will not be helpful trocautery. Dissection should be begun in the space between because blood pumped into the arterial system from any the diaphragm and the inferior surface of the heart which is cannulation site will simply exit via the site of aortic injury.
They also these women 50 mg avana mastercard erectile dysfunction talk your doctor, the frequency of outbreaks will deter- should be aware that susceptible men are at lower risk mine the future therapeutic strategy effective avana 200mg diabetic with erectile dysfunction icd 9 code. In In the patient diagnosed with genital herpes buy avana 200mg with mastercard erectile dysfunction medication south africa, one study comparing the use of valacyclovir 500 mg the strategy of how to deal with recurrent episodes once a day to placebo in which condoms were used should be in place before the next episode occurs. In addi- effective than either valacyclovir or acyclovir tion, this is one population of patients in which the dosing regimens in persons who have very fre- possibility of the development of resistance by her- quent recurrences (i. Signifcance was achieved when the data on Fortunately, this is an uncommon event, estimated susceptible females were combined with that of sus- to be 1 in 3,200 deliveries in the United States10 ceptible males. These immuno- pling would be avoided in the event that they were compromised women can have severe episodes of asymptomatically shedding the virus at the time of genital herpes that often are prolonged and painful. If there are frequent sive antiviral therapy for the last 4 weeks of gesta- recurrences, these women should be candidates for tion. The treatment of genital herpes is shown to lower the numbers of newborn infections an important frst step but must be accompanied due to herpes. If they 5–10 days are, they should be instructed to recognize these reactivations and alert the physicians if they occur Vulvovaginal Infections 86 just prior to or at the onset of labor. A primary mater- Herpes, an incurable virus, threatens to undo nal infection with either virus in the third trimester the sexual revolution. Herpes simplex virus type 2 in the not yet been established, and the question of cost- United States, 1976 to 1994. N Engl J Med effectiveness in view of the infrequency of genital 1997;337:1105–1111. To decrease this risk, genital herpes simplex virus type 2 infection barring sexual abstinence, the male can either use in asymptomatic seropositive persons. Recurrence infection in a pregnant woman carries a higher rates in genital herpes after symptomatic risk of transmission to the newborn than a pri- frst-episode infection. Herpes simplex virus infection as a risk factor for human immunodefciency provide added protection. Animal trials of this drug have been States among asymptomatic women unaware of promising, for they have lowered the frequency of any herpes simplex virus infection (Herpevac virus shedding. Overlapping reactivations of herpes sim- Herpes simplex virus type 2 detection by plex virus type 2 in the genital and perianal culture and polymerase chain reaction and mucosa. An appraisal of screen- tion increases the risk of subsequent epi- ing for maternal type-specifc herpes simplex sodes of bacterial vaginosis. Neonatal herpes sim- Neutrophil gelatinase-associated lipocalin plex infection in the British Isles. Paediatr concentration in vaginal fuid: Relation to bac- Perinat Epidemiol 1996;10:432–442. Once daily ery on transmission of herpes simplex virus valacyclovir to reduce the risk of trans- from mother to infant. J Am Med Assoc herpes simplex virus shedding and cesarean deliv- 1999;282:331–340. A case for wider adaptive immunity against herpes simplex herpes simplex virus serologic testing. Glycoprotein d-adjuvant vaccine the genital mucosa: Insights into the mucosal to prevent genital herpes. Male circumcision and herpes simplex virus Antiviral activity of trappin-2 and elafn type 2 infections in female partners: A ran- in vitro and in vivo against genital herpes. They have been will cause these women to overwhelm private physi- labeled “low risk” because they are not associated cian offces with phone calls seeking assurances that with cancers of the cervix, vagina, vulva, or rectum. Anyone testing asymptomatic women Annual Pap smear screening is no longer con- will fnd many more patients with a positive low-risk sidered the standard of care in the United States. If the Pap smear is absence of any clinical abnormalities will require an normal, then repeated Pap smears can be done at explanation and a follow-up plan. Equally damaging, these lesions con- England, for example, the frst Pap smear is not rec- frm that her partner was indiscreet in a relationship ommended until the age of 25. The unexpected tioners must be prepared to modify these guidelines appearance of genital warts in the trusting female if uncommon individual patient circumstances sug- of a married couple is frequently the frst step on gest alterations. Very reaction of most women to this new physical reality early sexual exposure could lead to invasive cervical is to seek immediate treatment to rid themselves of Vulvovaginal Infections 90 these lesions. They also want to be assured that con- study of poor urban women in Sao Paulo, Brazil, dyloma removal will end their concerns about trans- had similar fndings. They feel violated and unclean, and they want the physician, the clinical reality is a large popula- immediate treatment to eliminate these growths. Their immune response is specifc men remain symptom-free and clear these viruses for the strain encountered so that elimination of one with no awareness they had ever been infected. If negative, the patient will be scheduled lesion, or frank squamous or glandular carcinoma. This report dic- cases by the too-often incorrect unfltered data tates immediate colposcopy and biopsy no matter available on a variety of Internet sites. One careful copy and biopsy are indicated, even in patients with study of sexually active female college undergradu- a normal Pap smear. There is some of sensitivity and specifcity associated with cyto- logic to this guideline. Because of this, they are at greater risk of Two separate studies highlight this concern, one in developing abnormal cervical cytology. The with a visually normal cervix after application of ace- focus remains on cytology, as it has been since the tic acid. Individual risk factors have not been identi- Another future focus will be dependent upon medi- fed. To date, no specifc immunologic differences cal treatments to enhance viral clearance. A recent had a greater incidence of abnormal Pap smears than investigation of women with normal cervical cytol- did their white classmates. Further three doses of the vaccine are recommended, recent studies are needed to delineate the mechanisms studies have suggested that two or even one dose of whereby the composition of the vaginal microbiota the vaccine may have a similar effcacy. Usually, the road to discovery and are eventually eliminated by the immune system. The ability of the The wild virus pathogen is identifed, isolated, and host immune system to eventually, over a variable grown on cell culture in the laboratory. Ongoing the clinical focus from the diagnosis and treatment postlicensure surveillance indicated as of March of established disease to the prevention, in women, 2014 that about 67 million vaccine doses had been of condyloma acuminata, precancers, and cancers of administered in the United States with only 25,176 the cervix, vulva, vagina, rectum, and oral cavity, adverse events reported to the Vaccine Adverse and, in men, of condyloma acuminata, plus penile, Event Reporting System, 92% of which were “not rectal, and oral cancers. Of great clinical interest, the 11, 16, and 18, the bivalent vaccine Cervarix against U. Centers for Disease Control and Prevention has 16 and 18, and the most recent addition to the mar- reported that adverse event reports peaked within ket, Gardasil 9, against 6, 11, 16, 18, 31, 33, 45, 52, 2 years of the frst use of the vaccine and decreased and 58. The bivalent vaccine contains what appears to abundantly clear that physicians have a highly effec- be a more effective adjuvant that offers cross-protec- tive and safe vaccine available to them. The benefcial clinical results larly called “Obamacare,” a tag frst coined by its were striking.
Recent genetic lineage studies using the Cre-lox technology to mark progenitor cells and their descendants indicate that the primitive heart tube provides only a scaffold that enables a population of cells to be added to the heart during the second phase of differentiation of the cardiac progenitors order avana 100mg impotence xanax. While the primitive heart tube is being formed from the myocardializing splanchnic mesoderm generic avana 100mg with amex erectile dysfunction code red 7, most of the secondary cardiogenic mesoderm is located medially and dorsally (87 order online avana lipitor erectile dysfunction treatment,88,89,90,91,92,93,94,95,96,97,98,99). These cells remain in a highly proliferating and undifferentiated progenitor state until incorporation into the heart, possibly due to their closer proximity to inhibitory Wnt signals emanating from the ectoderm (Fig. Along the course of development, the secondary heart field progenitor cells contiguous with the primitive cardiac tube differentiate into cardiomyocytes, by which the heart tube elongates. Because of this delayed differentiation, these precursors are commonly referred to as the secondary heart field. It should be realized, however, that this terminology only is based on the temporal aspect of two waves of the differentiation of cardiomyocyte progenitors formed from the common mesodermal source (40). A: Shows a slightly modified reproduction of the results of classic labeling experiments by Maria de la Cruz in early chicken embryos, which have shown already in the 1970s that considerable parts of the venous and arterial poles (hatched green areas) of the primitive heart tube are formed by addition of the cells from outside the heart. Note that distance between colored dots does not change significantly (dashed arrows). B–D: Show the three independently performed studies, all published in 2001, which have confirmed the findings of the classic labeling experiments and led to rediscovery of the secondary heart field of cardiac progenitors. Labeling technique using a fluorescent marker demonstrated the addition of the cells adjacent to the Fgf8-expressing pharyngeal mesenchyme to the cardiac outflow tract (asterisk). Note that there is considerable length of the outflow tract lacking fluorescent labeling (star). Such an addition of cells from outside the heart resulted in the formation of the outflow tract (arrow) even after complete ablation of the primary heart fields (asterisks). Prior to outflow tract formation, the lacZ staining was observed in a discrete population of Fgf10-expressing pharyngeal mesodermal cells (arrowheads). Experimental study of the development of the truncus and the conus in the chick embryo. The arterial pole of the mouse heart forms from Fgf10-expressing cells in pharyngeal mesoderm. A: Depicts schematically the progression from cardiac crescent through the primitive heart tube toward the four-chambered heart. The secondary heart field is located dorsally from the forming heart derived from the primary field. The cells making up the secondary heart field encompass the dorsal pericardial wall, and are added at the venous and arterial poles of the definitive heart. B: Summarizes current knowledge about genetic regulation of proliferation, migration, and differentiation of cardiomyocytes derived from the second heart field. These signals both regulate and are regulated by transcription factors in the pharyngeal mesoderm and adjacent cells, including pharyngeal epithelia and neural crest–derived cells, as well as autocrine signals from pharyngeal mesoderm itself (88,89). Transcription factors such as Islet1 and Tbx1 play central roles in integrating the output of different signaling pathways during secondary heart field development (87,94). Islet1, named after its involvement in pancreatic development, is essential for proliferation and differentiation of secondary heart field cells (ref), but Islet1 expression is extinguished as soon as progenitor cells have differentiated into cardiomyocytes (Fig. As such, the pathways regulating the determination and differentiation of secondary heart field cells may provide the foundation for efforts to induce the cardiac lineage from progenitor cells. Furthermore, delineation of the factors that regulate the development of the secondary heart field has revealed differences as compared to the factors governing differentiation of the primary heart field. Chamber Formation and Ventricular Septation A fundamental question in cardiac development relates to the establishment of the correct disposition of the chambers and the conduction system (95,96). Whereas the primitive peristaltically contracting heart tube does not need valves, they are essential for the proper functioning of the synchronously contracting four-chambered heart to prevent backflow from a downstream compartment during relaxation and to an upstream compartment during contraction. In the early developing heart, it is not possible to histologically identify the components of the conduction system as one can in the postnatal heart. Despite the absence of a specialized conduction system and valves, the electrical configuration of the embryonic heart consisting of alternating slowly and rapidly contracting segments, as described below, allows the early chamber-forming heart to produce coordinated atrial and ventricular contractions effectively propelling blood forward (97). Because slow conduction is also a prerequisite for nodal function, it may not be coincidental that nodes in these areas have developed, as discussed in Chapter 18. Development of the Basic Building Plan of the Mammalian Heart The elongation of the primitive heart tube is followed by the process of looping, during which the ventral part of the tube deviates to the right while bulging more and more ventrally as the ventricular chambers start to develop. At the same time the atrial chambers develop dorsally to the right and left of the forming outflow tract, which leads to the definitive appearance of the human heart at the end of the 8th week of development, when the fetal period begins (Fig. Subsequent to looping of the primitive heart tube, it becomes possible to distinguish its outer and inner curvatures (Fig. At localized areas of the outer curvature, the primary cardiomyocytes start to proliferate and initiate a genetic program governing their differentiation toward the working myocardium phenotype, which is characterized by the expression of fast-conducting gap-junctional proteins and atrial natriuretic factor P. Morphologically this differentiation can be recognized by the rapid expansion of the atrial chambers dorsally and the trabeculated ventricular chambers ventrally, a process that has been called ballooning (98,99). In the human-developing heart, this process was nicely illustrated by Streeter already in the 1940s (100). He demonstrated that the remnants of the smooth-walled primary heart tube persist as a continuous space in between the expanding trabeculated cardiac chambers. This space provides from the very beginning direct communications not only between the developing atria and the respective ventricles, but also between two developing ventricles and the outflow tract (Fig. After initiation of chamber formation, a new myocardial structure, the systemic venous sinus, is formed at the inflow region of the heart (102,103). Similar to the myocardium of the primary heart tube, the myocardium of the venous sinus initially escapes further differentiation, does not express fast- conducting connexins, and is characterized by high intrinsic automaticity, ensuring dominant pacemaker activity at the inflow of the heart (102,103,104,105,106). The panels show ventral views of the hearts after removal of the ventral body wall. A: Depicts the prototypic linear heart tube as seen in ventral and right lateral views. The primary myocardium is indicated in gray, the secondary myocardium of the atrial chambers ballooning at the dorsal aspect of the heart tube (arrows) is indicated in blue, and the myocardium of the ventricular chambers growing ventrally along the outer curvature of the heart tube (arrows) is indicated in red. The chamber myocardium is first seen locally at the stage of looping and does not involve the entire circumference of the tube. D: Shows the separation of the blood flow streams within the chamber-forming heart, even without completed septation. This enigma was solved by careful analysis of the expression pattern of a neural tissue antigen Gln2 in the developing human heart. A, A*: Show that at 30 to 34 days of development, a single ring of Gln2-staining tissue (brown staining on the sections) can be identified. Immunohistochemical analysis of the distribution of the neural tissue antigen Gln2 in the embryonic human heart. Green arrows indicate positive regulation and red lines suppression for differentiation toward the working phenotype or retention of the more primitive phenotype. Discovery of the secondary heart field led to a reinterpretation of the findings in mice lacking critical regulatory proteins and in transgenic mice harboring enhancers of genes expressed in the heart (117) (Fig. This observation further supported the concept that separable regulatory pathways control the development of the ventricles. Right ventricular hypoplasia in mice lacking transcription factor Mef2c, now a known target of Isl1, Gata4, Foxh1, and Tbx20 in the secondary heart field, may, similar to the Hand2 disruption, represent a defect of secondary heart field development (121,122).
However best 50mg avana impotence hypothyroidism, on occasion assessment must be made as to whether the valve is adequate there may be obstruction within the infundibular chamber to allow a two-ventricle repair avana 50 mg discount erectile dysfunction and diabetic neuropathy. Calculation of the z value for because of anterior malalignment of the conal septum purchase avana 100mg on-line erectile dysfunction homeopathic drugs. In general, the aorta under these circum- consider the Holmes heart as part of a spectrum which merges stances arises from a subaortic conus. In may be suffcient imbalance that the patient is best managed contrast, the unoperated patient who has a single ventricle has as though having a single ventricle. These patients to each unless there is anatomical obstruction to pulmonary frequently have a coarctation and/or hypoplasia of the aortic outfow or obstruction to systemic outfow. Heterotaxy “balanCed” single VentriCle There are a number of synonyms for heterotaxy17 including Occasionally, an individual will have just the right amount asplenia/polysplenia syndrome and atrial isomerism. The of natural obstruction to pulmonary blood fow to achieve a fundamental lesion in these patients is that there is poor dif- reasonably equal distribution of blood to the lungs and to the ferentiation into right and left side. This will result in an arterial oxygen right sidedness (asplenia syndrome) which may be associated saturation of approximately 80% and is consistent with sur- with bilateral right lungs (i. The single ventricle under these circumstances is is covered in detail in Chapter 24, Heterotaxy. Most Mitral Atresia Including Hypoplastic Left Heart Syndrome amphibians such as frogs have exactly this type of circula- Absence of the mitral valve as with marked absence of the tri- tion (see Chapter 34, Vascular Rings, Slings, and Tracheal cuspid valve excludes the possibility of a biventricular repair. They often live for 10–20 years and have been recorded to live as long as 40 years. If the mitral valve is the only under- Much more common than the long-term balanced single developed structure in the left heart an assessment must be ventricle is the single ventricle with a progressive increase Three-Stage Management of Single Ventricle 483 in obstruction to pulmonary outfow so that the patient a modest degree of cyanosis. In time, the demonstrate the systolic murmur which results from either patient will suffer the usual consequences of severe cyanosis pulmonary or systemic outfow obstruction. If there is neither including polycythemia, stroke, brain abscess, hemoptysis, there may be little to be heard since it is unlikely that there and ultimately death. At the other end of the spectrum the will be a murmur generated within the single ventricle itself. So long as there is no associated Although the patient’s symptoms may abate for some time obstruction to systemic outfow the arterial oxygen saturation as pulmonary resistance itself comes to balance systemic provides a helpful estimate of pulmonary blood fow. The ultimate result is similar to 80% indicates that there is reasonable protection of the pul- the patient who has a severe fxed degree of obstruction to monary vascular bed from excessive fow and pressure. Assessment of oxygen saturation is also complicated if As described in the anatomy section above, there are many there is either very low or very high cardiac output or if there potential sites for obstruction to develop between the single is streaming, for example transposition physiology where the functional ventricle and the ascending aorta. In most cases oxygen saturation in the aorta is less than the oxygen satu- the obstruction is progressive in nature. Streaming also complicates tion to pulmonary outfow the consequence of increasing assessment of pulmonary blood fow in the neonate with systemic outfow obstruction is increasing pulmonary blood hypoplastic left heart syndrome who has antegrade blood fow fow. The single ventricle becomes progressively volume in the ascending aorta, that is, there is not complete mixing of loaded and ultimately will fail unless pulmonary vascular the systemic and pulmonary venous return. On the other hand, if there is concomi- the neonate and young infant, in spite of these caveats, there tant obstruction to pulmonary outfow, either natural or in is generally no need to undertake cardiac catheterization for the form of a surgically placed pulmonary artery band, the assessment of pulmonary blood fow and pressure. The serious consequence of a pressure load for the single ven- patient with no obstruction to pulmonary outfow will have tricle is progressive ventricular hypertrophy with accompa- congested lung felds and an enlarged heart. Once again it is important to remem- ber that occasionally there can be streaming of blood fow with a single VentriCle within a single ventricle creating transposition-type physiol- The clinical presentation of the patient with a single ventricle ogy, that is, systemic venous return is preferentially directed is dependent on the balance of blood fow between the sys- through the single ventricle into the aorta while pulmonary temic and pulmonary circulation. For example, the neonate venous return tends to be preferentially directed to the pul- who has a severe degree of fxed pulmonary outfow obstruc- monary circulation. However, this situation is highly unusual tion will present with profound cyanosis at the time of ductal in the patient who has a true form of single ventricle. Two-dimensional echo- tion to pulmonary outfow may initially appear to be free of cardiography with color Doppler mapping is usually diagnos- symptoms but as pulmonary resistance falls in the frst days tic. It is important at the outset that the echocardiographer and weeks of life there will be progressive onset of symp- determine whether the ductus is patent. Even though the patient has tus will complicate assessment of the degree of obstruction symptoms and signs of congestive heart failure, nevertheless to pulmonary outfow. However, if the ductus is confrmed mixing of pulmonary and systemic venous return usually at to be closed it is generally possible to make a reasonable both atrial and ventricular level will mean that there is at least assessment of pulmonary outfow obstruction by estimating 484 Comprehensive Surgical Management of Congenital Heart Disease, Second Edition the Doppler gradient between the single ventricle and the chamber. Once again in the neonate and young the ductus is patent there will be no gradient across either of infant, however, this information should be considered sim- these areas even when relatively severe obstruction is pres- ply adjunctive to the systemic arterial oxygen saturation. The area should be reassessed when the ductus is pulmonary artery pressure appears to be modestly elevated, closed. Even if the ductus is not closed or in the event that for example at half systemic level in the young infant. Studies have suggested that a cross-sectional area of classifcation of the patient’s cardiac anatomy. The anatomy less than 2 cm2/m2 is likely to be inadequate and either cause of the systemic veins and pulmonary veins must be carefully or lead to systemic outfow obstruction. In addition to assessing the degree of obstruction to pulmonary outfow, Only a small percentage of patients with a single ventricle the echocardiographer should determine the mechanism of have a reasonable natural balance of pulmonary and systemic obstruction as this may help to indicate whether obstruction blood fow. These patients are ductally depen- normally related great arteries is likely to have progressive dent and therefore require infusion of prostaglandin E1 until closure of the defect and therefore falling pulmonary blood a systemic to pulmonary arterial shunt can be performed. Patients who have no obstruction to pulmonary outfow may Careful determination should be made as to whether the have relatively few symptoms initially but gradually develop branch pulmonary arteries are in continuity and whether any congestive heart failure as their pulmonary resistance falls. Fortunately, it is uncommon for They will require treatment with the usual anticongestive the patient with a single ventricle to have multiple peripheral therapy and when their condition has been stabilized satis- pulmonary artery stenoses and even if these are present it is factorily they should proceed to application of a pulmonary not important to defne them at the time of the child’s presen- artery band assuming that there is no obstruction to systemic tation in the neonatal period or early infancy. In rare circumstances, where It is critically important that careful assessment be made at the there is mitral atresia and an obstructive atrial septum, it is time of presentation as to the presence or potential presence important to open the atrial septum before surgery, not only of obstruction to systemic outfow. A particularly helpful “red to allow adequate pulmonary blood fow for reasonable oxy- fag” that obstruction may be present or is likely to develop genation but also to lower the pulmonary resistance before is the presence of a juxtaductal coarctation of the aorta. However, this should only be done if When the ductus is widely patent it is unlikely that there will the oxygen saturation is so low that it is resulting in acidosis, be any gradient in the coarctation area. The ence of a prominent coarctation shelf should stimulate the decision to open the atrial septum should not be based on echocardiographer to return for a repeat study within a day or a Doppler gradient across the atrial septum. In addition, careful measure- opening of the septum can result in excessive pulmonary ments must be taken of the proximal aortic arch, distal aortic blood fow and metabolic acidosis. When the z It is generally not advisable to consider balloon dilation value is smaller than −2 the arch segment should be consid- of an obstructive pulmonary valve when there is a single ered hypoplastic and particularly careful study of the internal ventricle with obstruction to pulmonary outfow. As result in excessive pulmonary blood fow which can be just discussed in the anatomy section above, obstruction to sys- as problematic as inadequate pulmonary blood fow. Many patients achieved surprisingly good pal- A basic premise of the management of a single ventricle liation with both the classic Glenn shunt as well as the bidi- today is that the natural history of an untreated single ven- rectional Glenn shunt during the 1950s and 1960s. Although a small subset of During the 1960s homografts were introduced by Ross patients with single-ventricle physiology can have a balance and Barratt-Boyes both as valves and as valved conduits (see of systemic and pulmonary blood fow over the long term, Chapter 14, Choosing the Right Biomaterial). He and his cardiologist Choussat enu- needs to be paid very early in infancy or ideally in the neona- merated a list of 10 conditions which were felt to be impor- tal period to preventing excessive volume or pressure loading tant for patients undergoing the Fontan procedure. Following description of the to protect the pulmonary vascular bed as well as to prevent Ross procedure, that is use of the pulmonary valve as an distortion of the central pulmonary arteries. Surgical proce- autograft,28 Kreutzer in Argentina29 applied the concept of dures must also preserve sinus node function. Although it is possible to defer the subsequent Fontan the need for a nongrowing homograft conduit.