Cardiology

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Chapter 6 Cardiology

Long Case

Cardiac disease

This chapter deals with problems that are likely to be discussion areas in the long-case section. Cardiac long-case patients may have complex cyanotic heart disease, or heart disease and other medical problems either causally related, as in Noonan syndrome or congenital rubella, or as a complication of their heart disease or its treatment (e.g. hemiparesis with cyanotic heart disease).

There have been many advances on several fronts in cardiology recently:

• Subacute bacterial endocarditis prophylaxis guidelines have been modified to reduce the number of cardiac conditions for which antibiotics are recommended with dental procedures (see below).

• Advances have been made in understanding the genetics and clinical aspects of the long QT syndrome, with risk stratification for experiencing a sudden life-threatening cardiac event (see below).

• Medical therapy for Marfan syndrome with angiotensin II receptor blockers (ARBs) has been shown to decrease the risk of aortic root dilatation, after a specific metabolic defect of the aortic wall was discovered that improved with ARBs (see below).

• Echocardiography has benefited from recent advances in computer technology, signal processing and high-frequency transducer design, to encompass new modalities: three-dimensional echocardiography (3DE), tissue Doppler imaging (TDI) and speckle tracking echocardiography (STE) are used to evaluate parameters including ventricular volume, myocardial velocity, left-ventricular twist/torsion (during systole) (STE), regional strain and strain rate (TDI and STE) and mechanical dyssynchrony (TDI, SDE, 3DE).

• Modification of cardiac risk factors is now actively occurring on children. In 2008, both the American Academy of Pediatrics and the American Heart Association reviewed obesity and the metabolic syndrome with insulin resistance, hypertension and early coronary artery disease, and now diet and drug therapy (including statins) are being recommended for children as young as 10 years.

History

Presenting complaint

Reason for current admission.

Diagnosis

When made (birth, days, weeks or months); where; symptoms at diagnosis (e.g. cyanosis, tachypnoea, poor feeding, failure to thrive, recurrent infection); how (initial investigations: chest X-ray, electrocardiography, echocardiography, angiography).

Initial treatment

1. Surgical (e.g. palliative, such as balloon septostomy or shunting procedures, or corrective, such as patent ductus ligation).

2. Pharmacological (e.g. digoxin and diuretics) and side effects thereof.

Past history

1. Aetiology (e.g. rheumatic fever, pregnancy complicated by maternal rubella, smoking, alcoholism, or drugs such as lithium, warfarin or phenytoin).

2. Indications for, and number of, previous hospital admissions.

3. Pattern and timing of change in condition (e.g. when cyanosis or heart failure developed, when and how it was controlled).

4. Episodes of infective endocarditis.

5. Other complications of disease (e.g. cerebral thrombosis or cerebral abscess with cyanotic heart disease).

Treatment

1. Past surgery, complications thereof, plans for further operative procedures.

2. Past interventional catheter procedures.

3. Past ablation therapy, pacemaker or defibrillator placement.

4. Medications, past and present, the side effects of these, monitoring levels (e.g. digoxin), treatment plans for future.

5. Exercise restrictions (may be inappropriately applied by parents).

6. Recommendations for antibiotic prophylaxis for dental procedures; maintenance of dental hygiene.

7. Compliance with treatment.

8. Any need for identification bracelet.

9. Instructions for air travel and high altitude.

10. Any recent investigations monitoring treatment (e.g. Holter monitoring; oxygen saturation).

11. Any recent changes in treatment regimen, and indications for these.

Current state of health

Note any of the following:

• Symptoms of cardiac failure, such as fatigue and shortness of breath (in comparison with peers), cough, sweating, poor feeding, recurrent chest infections.

• Cyanosis, squatting with ‘Fallot turns’.

• Episodes suggestive of arrhythmias, such as syncope, alteration of consciousness, dizziness, shortness of breath, palpitations in older children (what was the rate; i.e. faster than when usually playing or excited), or a ‘funny feeling’ in the chest, sweating, nausea, vomiting, or the parents being unable to count the rapid pulse rate, suggesting a tachyarrhythmia.

• Chest pain (e.g. myocardial ischaemia versus musculoskeletal, pleural or pericardial causes) or headache (e.g. polycythaemia in cyanotic heart disease, severe hypertension, cerebral abscess).

• Recent change in condition. Note the temporal relationship between associated symptoms with any tachycardia or palpitation: they should coincide—functional chest pain can be followed by a reflex sinus tachycardia.

Other associated problems

These may either be related to the main diagnosis (e.g. Down syndrome, Marfan syndrome) or be more general problems (e.g. poor growth, developmental delay, especially involving gross motor abilities, exercise limitations and psychological effects).

Social history

1. Disease impact on child; for example, growth, development, schooling (academic performance, sports restrictions, teachers’ attitudes, peers’ attitudes, teasing, amount of school missed and whether schooling is appropriate).

2. Disease impact on parents; for example, financial situation, financial burden of disease so far, government allowances being received, marriage stability, restrictions on social life, plans for further children, genetic counselling, or at least an awareness of the risks of recurrence, and availability of fetal echocardiography.

3. Disease impact on siblings; for example, sibling rivalry, effect of family financial burden.

4. Social supports; for example, social worker, contact with other families of children with similar problems, break from managing child.

5. Coping: contingency plans (e.g. plan if child develops severe febrile illness); parents’ degree of understanding regarding cause, prognosis, exercise restriction, and antibiotic prophylaxis for operations and dental procedures.

6. Access to local doctor, paediatrician, cardiac outpatients clinic (where, how often), other clinics attended.

Family history

Any early cardiovascular death (e.g. hypertrophic cardiomyopathy [HCM]), unexplained death (e.g. long QT syndrome [LQTS]) or arrhythmias (e.g. Wolff–Parkinson–White [WPW] syndrome); any known cardiovascular diagnoses (e.g. cardiomyopathies); any known syndromes (e.g. Marfan).

Immunisations

Any unnecessary delays, local doctor attitudes, parents’ understanding of importance.

Examination

The physical examination of the cardiac long case includes a full cardiological appraisal (see the short-case section of this chapter), plus assessment of associated problems, either aetiologically associated (e.g. findings of syndromal diagnoses such as Down syndrome) or complicating the course of the disease (e.g. hemiplegia).

Management issues

The following covers most areas of management that may be relevant in the long-case context, but use of this section should be tailored to the case you are discussing.

1. General development, growth and nutrition

Most children with congenital heart disease develop normally, but children seen in the examination context often have cyanotic heart disease, congestive heart failure or underlying syndromal diagnoses, all of which may be associated with some degree of developmental delay. Children with cyanotic heart disease or chronic congestive cardiac failure may have delay in their motor milestones. Other children can have prolonged periods of hospitalisation or overprotective family or schooling environments, which can adversely affect social development. Parents should be counselled regarding development. In an otherwise normal child, the degree of delay associated with heart disease is not severe, and provision of a stimulating environment and encouragement of normal schooling should be discussed.

Chronic left-to-right shunts sufficient to cause cardiomegaly often cause growth retardation. This may be an indication for surgical correction even in the absence of other indications such as pulmonary hypertension. Marked hypoxia may be associated with growth retardation, but the hypoxia has to be severe to do so. Most patients who have Eisenmenger syndrome with cyanotic heart disease and pulmonary hypertension do not have increased energy requirements or inadequate caloric intake, and do not have growth retardation. It takes profound hypoxia to cause growth retardation.

Nutrition is an important issue in general development. Issues to discuss regarding feeding include role of solids, undesirability of fluid restriction, requirements for additional caloric intake, dangers of iron deficiency in cyanosed patients and, perhaps most importantly, support for the mother regarding the above. There is some evidence that more intensive nutritional treatment and early corrective surgery may optimise outcomes in some children with correctable lesions that have previously been associated with poor growth.

2. Prophylaxis against subacute bacterial endocarditis (SBE) risk

Dental procedures and dental care

Antibiotic prophylaxis with dental procedures is recommended only for cardiac conditions with the highest risk of endocarditis: prosthetic material (valve [especially—the highest risk], other device [first six months after placement], patch, material); cyanotic congenital heart disease (unrepaired; includes palliative shunts and conduits); previous endocarditis; and cardiac transplantation recipient with cardiac valvular disease. Tetralogy of Fallot has the highest risk of developing SBE of known cardiac conditions, and almost 10% of patients with CHD and endocarditis will have aortic insufficiency. Tooth brushing has been shown to yield positive blood cultures in 23%, compared to 33% for tooth extraction with SBE prophylaxis, and 60% for tooth extraction without SBE prophylaxis; hence tooth brushing represents the greatest risk of SBE, given the frequency of tooth brushing. A high level of dental hygiene should be maintained, and problems such as carious teeth and periodontal disease should be dealt with promptly, with appropriate antibiotic cover.

Endocarditis has a bimodal peak in age, the largest groups being patients under 12 months, and over 16 years. In a study reviewing a national database, between 2000 and 2003, most children diagnosed with endocarditis (900 out of 1558) had no pre-existing heart disease, but had various medical conditions that predisposed them to increased risk of SBE. Four risk groups have emerged: (a) patients with multiple interventions, including chronic line placements; (b) immune compromised patients (e.g. primary immune deficiencies [such as 22q11.2 deletion syndrome], sickle cell anaemia, secondary immune deficiencies [immunomodulator therapies]); (c) unrepaired cyanotic heart disease and those with prosthetic materials; and (d) older patients with CHD.

Prophylaxis is usually given as amoxycillin, 1 hour before the procedure, orally, or when anaesthesia is needed, parenterally. The usual oral dose is 3 g for a child over 10 years, and 1.5 g if under 10 years of age. If the patient is allergic to penicillin, then a cephalosporin can be used. For patients with prosthetic heart valves, who have the highest risk of acquiring endocarditis from any procedure; some units add an aminoglycoside to the usual cover for other valve disease. All children with congenital heart disease who require prophylaxis should be given a letter or card to show any dentist or doctor, explaining the need for antibiotic prophylaxis for any dental or similar procedure (e.g. tonsillectomy), including the recommended doses.

Genitourinary and gastroenterological surgery

As enterococci are the usual problem, the recommended treatment should adequately cover these organisms; thus parenteral gentamicin and ampicillin is an appropriate choice.

Non-cardiac surgery

Generally, it is sensible to consult with the child’s cardiologist before any surgical procedure, as the concerns are not only those of bacteraemia, but of acid-base and electrolyte balance and oxygenation. The patient groups of most concern are those with severe congestive cardiac failure, pulmonary hypertension, severe cyanosis or severe outflow tract obstruction. Other children who need careful monitoring are those with conduction disturbances and those with significant arrhythmias. Polycythaemic cyanotic patients must have adequate hydration and intravascular volume maintained, to avoid risks of thrombosis, hypoxia and acidosis.

During any procedure, monitoring of blood pressure, oxygenation (with provision of supplemental oxygen if necessary, although avoid unnecessary oxygen in patients with failure due to left-to-right shunts), arterial pH and electrolyte balance are of paramount importance. Preoperatively, checking of electrolyte levels is mandatory. Digoxin need be stopped only for bypass operations. Diathermy is contraindicated in patients with pacemakers.

3. Infection

Common infections

Viral upper respiratory tract infections can cause significant problems in children with cardiac failure or cyanosis (e.g. respiratory syncytial virus) because of the effect of hypoxia on pulmonary vascular resistance (especially in Down syndrome).

Gastroenteritis can lead to dehydration and result in thromboses in polycythaemic patients; care must be taken to avoid dehydration. Gastroenteritis can also lead to hypokalaemia in patients taking diuretics, or cause toxicity in patients taking digoxin.

Any febrile illness may precipitate cardiac decompensation via the increase in the body metabolic needs. Appropriate cultures should always be taken; if subacute bacterial endocarditis is suspected antibiotics are contraindicated until multiple blood cultures have been taken, unless the child is very sick.

Cerebral abscess

Children over 2 years of age with cyanotic congenital heart disease have an increased incidence of brain abscess, the severity of which relates to the degree of hypoxia. They may present with fever, headache, seizures or focal neurological signs.

Immunisation

There is no contraindication to immunisation, with the exception of associated immune defects (e.g. asplenia, DiGeorge syndrome). Children with heart disease are particularly at risk if not immunised.

4. Social issues

Impact of disease

The young child may be pampered and overprotected. During adolescence, issues such as anxiety regarding contraception, sexual performance and peer approval become important.

Parents tend to overprotect and pamper the child and give the other siblings less attention. Parents should be given adequate education regarding the nature of the defect; they should appreciate the need for antibiotic prophylaxis for dental and other surgical procedures and understand the rationale for treatment—for example, with digoxin—and be supplied with clear guidelines as to age-appropriate activities and any exercise restrictions (see later). Common problem areas can be anticipated and dealt with before they become a concern.

Siblings receiving less parental attention than expected in a normal family is a commonly encountered problem.

Schooling

The teachers and school nurse need sufficient education regarding the disease to help them understand the most likely type of future employment (e.g. sedentary) for that patient, the symptoms that warrant referral for a medical opinion, and in the case of athletics, whether restrictions apply (see below).

Exercise

Parents and school teachers often ask about exercise. It is a difficult area, and parents’ questions must be answered on an individual patient basis. Many units let children set their own levels rather than try to enforce restrictions, but may suggest avoidance of strenuous or competitive sport (and anaerobic exercise) if there is severe pulmonary hypertension, or more than mild aortic stenosis, subaortic stenosis or hypertrophic cardiomyopathy (HCM).

Adolescence

The problems of non-compliance, peer group acceptance, non-participation in sporting activities, decisions regarding future career possibilities, delayed puberty and anxiety related to sexual performance are commonly encountered. Other issues include contraception, pregnancy, genetic counselling (see later), eligibility for life insurance and obtaining a driving licence (if suffering recurrent syncope).

Some teenagers have never had their heart disease explained to them, as it has been discussed only between doctors and parents in the past; this area should be considered.

Pregnancy

Pregnancy is contraindicated in the setting of Eisenmenger syndrome (pulmonary hypertension with right-to-left shunting), or severe pulmonary hypertension (from any cause), because of a high risk of maternal and fetal morbidity and mortality. Relative contraindications to pregnancy include severe congestive cardiac failure and severe cyanosis, with oxygen saturation below 80%. Several other problems (e.g. severe aortic valve disease, cardiomyopathy, hypertension) also carry an increased risk to both mother and fetus. Teratogenic drugs (e.g. warfarin) should be ceased for the pregnancy, fetal echocardiography can be performed to detect congenital heart disease and, at birth, prophylaxis against endocarditis is given. Breast milk from mothers who are taking warfarin, propranolol or quinidine can produce toxic effects in the baby; digoxin, however, is safe in this respect.

Genetic counselling

Most parents will ask about the risk of recurrence. The answer depends on whether the heart disease is the only problem, or whether it is part of a syndromal diagnosis, such as Marfan or Noonan syndrome. Most cardiac defects have a multifactorial inheritance, with a recurrence risk of between 1% and 4% if one sibling has the condition, and between 2% and 4% if one parent has the condition; the percentage may be higher in some conditions, such as truncus arteriosus. A notable exception is HCM, which has an autosomal dominant mode of inheritance. Those with syndromal diagnoses will have the recurrence risk of that syndrome. The parents should be advised about fetal echocardiography (available from around 18 weeks’ gestation).

Travel

All these children should carry a letter explaining the nature of their heart lesion, their usual medications, and the name of their doctor or usual treatment centre, and have access to a hospital if they have a disease prone to sudden deterioration (e.g. Fallot spells). An identification bracelet should also be worn. Those with pacemakers in particular should carry written details regarding their unit and its program. Patients with severe congestive cardiac failure, severe cyanosis or pulmonary hypertension must avoid high altitudes (e.g. above 1500 m) and require supplemental oxygen to be available during commercial air travel. Hot climates can be a problem in children with polycythaemia, and adequate hydration must be maintained. The child’s exercise tolerance must be considered when planning the trip itinerary.

5. Specific problems

Drugs

The more common medications prescribed for congenital heart disease include digoxin, diuretics and antiarrhythmics. Most candidates will be fairly familiar with these agents. The candidate should also be familiar with vasodilators. Angiotensin-converting enzyme (ACE) inhibitors (e.g. captopril) are often used in the treatment of cardiac failure, as they reduce afterload (mainly) and preload. Important side effects of captopril include hypotension, renal impairment and hyperkalaemia.

The issues to consider include whether the dose is appropriate, noting any adverse side effects, and whether regular monitoring of levels, and of electrolytes, has been performed. In children with prosthetic valves receiving warfarin therapy, the prothrombin ratio should be checked regularly. Drug interactions can pose problems; these should be considered when changing drugs or adding any new drug to the treatment regimen.

Contraception

Patients need to be aware of the theoretical risk of thrombosis potentiated by oestrogens, and therefore a low-oestrogen formulation of contraceptive pill is preferred; alternatives include depo provera, implanon or low-dose minipill, plus one other method (e.g. barrier methods). The combined oral contraceptive pill is not contraindicated, but should be used with caution in girls with prosthetic heart valves, cyanotic heart disease or pulmonary hypertension. Intrauterine devices are potentially a source of bacteraemia, causing endocarditis. The risks of pregnancy for each patient must be assessed and suitable counselling given.

Specific syndromes: cardiac involvement

Marfan syndrome

This is an autosomal dominant condition caused by defective fibrillin, a protein important to the integrity of connective tissue (see Figure 6.1). The relevant gene (FBN1) has been mapped to chromosome 15q21.1. The cardiac features are the most important and life-threatening aspects of Marfan syndrome, manifesting in childhood in 25% of those affected. The cardiac involvement is progressive in around one third of these children. Features include the major diagnostic criterion of dilatation of the ascending aorta with or without aortic regurgitation, and involving at least the sinuses of Valsalva or dissection of the ascending aorta. Minor diagnostic criteria for Marfan syndrome include mitral valve prolapse with or without mitral valve regurgitation, dilatation of the main pulmonary artery in the absence of another anatomic cause (before age 40), calcification of the mitral annulus (before age 40), and dilatation or dissection of the descending thoracic or abdominal aorta (before age 50).

image

Figure 6.1 Marfan syndrome—joint hypermobility.

Jones, Kenneth. 2005. Smith’s Recognizable Patterns of Human Malformation, 6th edition, p. 550.

Parental education regarding the importance of avoiding strenuous exercise and competitive or contact sports is important, and should begin before preschool, placing less emphasis on the importance of sporting activities. Non-strenuous activities should be encouraged (e.g. walking, fishing, golf). The symptoms of aortic dissection must be discussed, including chest pain and syncope.

In teenage years, important issues include consideration of beta blockers to slow the progress of aortic dilatation, and counselling to teenage girls about the risks of pregnancy, as rupture of the aorta can occur during pregnancy or at delivery. Angiotensin II receptor blockers (ARBs) have been used as an alternative to beta blockers, after an animal model found a metabolic defect of the aortic wall that improved with the use of ARBs; in 18 patients treated with ARBs for 12–47 months, there was a decrease in the rate of aortic root diameter change compared to when they were receiving beta-blocker therapy.

The clinical diagnosis of Marfan syndrome is based on major and minor criteria; there are four findings with major significance (all in bold and made to start with D):

Dilatation or dissection of aorta at level of sinuses of Valsalva

Displacement of lens (ectopia lentis)—directed upward; also early cataract formation

Dural ectasia (lumbosacral)

Dolichostenomelia: disproportionately long extremities; decreased upper to lower segment ratio (US:LS < 0.85 for older children/adults) or arm span to height ratio > 1.05; other diagnostic skeletal features—

Deformed spine (scoliosis > 20°, or spondylolisthesis)
Deformed sternum (pectus excavatum or pectus carinatum, requiring surgery)
Deep acetabulum with accelerated erosion (protrusio acetabulum)
Decreased elbow extension (< 170°) (in contradistinction to hypermobility of other joints)
Digit-related eponymous signs—(a) the thumb (Steinberg) sign, this being an extension of the whole distal phalanx of the thumb beyond the ulnar border of the hand when apposed across the palm (see Figure 6.2), and (b) the wrist (Walker–Murdoch) sign, this being overlapping of the distal phalanx of the thumb with the distal phalanx of the little finger when encircling the opposite wrist (see Figure 6.3)
Downward (medial) rotation of medial malleolus causing pes planus—four of these skeletal features are considered one major criterion

Distinctive facial features (dolichocephaly, down-slanting palpebral fissures, deeply set eyes (enophthalmos), decreased malar prominence (malar hypoplasia), diminished jaw (retrognathia)

image

Figure 6.2 Steinberg thumb sign.

Jones, Kenneth. 2005. Smith’s Recognizable Patterns of Human Malformation, 6th edition, Figure 2B.

image

Figure 6.3 Walker–Murdoch wrist sign.

Jones, Kenneth. 2005. Smith’s Recognizable Patterns of Human Malformation, 6th edition, Figure 2C.

The acronym MARFANS also can be used as an (alternative) aide-mémoire:

M. Mitral prolapse ± Mitral regurgitation

A. Ascending aorta dilatation (involving sinuses of Valsalva)/dissection/Arched palate (high arched, with tooth crowding)/Acetabuli (protrusio acetabuli)

R. Regurgitation of aorta/mitral/Retinal detachment/Reduced US:LS ratio

F. Fibrillin defective/Facial gestalt (dolichocephaly, down-slanting palpebral fissures, deeply set eyes (enophthalmos), decreased malar prominence (malar hypoplasia), diminished jaw (retrognathia)/Flat cheek bones/Flat cornea/Flexible joints (joint hypermobility)

A. Apical blebs (on CXR)/Air leaks (spontaneous pneumothorax)/Arachnodactyly

image Near-sightedness (myopia)/Neurological involvement related to dural ectasia—stretching of dural sac in the lumbosacral region/Nerve entrapment—CSF leak from dural sac (causing postural hypotension and headache)

S. Scoliosis/Sternal deformity/Skeletal dolichostenomelia/Sacral dural ectasia

Noonan syndrome (NS)

NS is an autosomal dominant condition, associated with four genes. In 50% of cases, the associated gene locus is at 12q24.1, with mutations in PTPN11, the gene encoding the non-receptor type protein, tyrosine phosphatase SHP-2. The other genes are KRAS, SOS and RAF1. Almost all patients with NS have some cardiac defect, particularly a dysplastic (and often stenotic) pulmonary valve, which is more common with a PTPN11 mutation, or hypertrophic cardiomyopathy (HCM), which affects around 20–30% of NS children, but is less common with a PTPN11 mutation. The ECG frequently shows left-axis deviation and a dominant S wave over the praecordial leads, even in NS patients with no known cardiac disease; the cause for this is not known. Phenotypic features of NS include dysmorphic facial features, short stature, webbed neck and skeletal anomalies (see the short case on dysmorphism).

NS patients with dysplastic pulmonary valves can have rapid progression of pulmonary valvular obstruction and may require review more frequently than for non-NS pulmonary valve lesions. Also, NS-associated valve obstruction is more likely to require surgical intervention. Balloon valvoplasty is usually unsuccessful in abolishing the obstruction, and simple valvotomy may be inadequate. Often complete excision of the valve, resection of the right-ventricular outflow muscle, and occasionally an outflow tract patch may be needed. Atrial septal defects (ASDs) (Figure 6.10) and pulmonary artery branch stenoses may coexist with valvular pulmonary stenosis (Figure 6.4). Other infrequent findings with NS include ventricular septal defects (VSDs) (Figure 6.12) and tetralogy of Fallot (Figure 6.17 and Figure 6.16).

image

Figure 6.10 Physiology of atrial septal defect (ASD).

Circled numbers represent oxygen saturation values. The numbers next to the arrows represent volumes of blood flow (in L/min/m2). This illustration shows a hypothetical patient with a pulmonary-to-systemic blood flow ratio (Qp:Qs) of 2:1. Desaturated blood enters the right atrium from the vena cavae at a volume of 3 L/min/m2 and mixes with an additional 3 L of fully saturated blood shunting left to right across the ASD; the result is an increase in oxygen saturation in the right atrium. Six litres of blood flows through the tricuspid valve and causes a mid-diastolic flow rumble. Oxygen saturation may be slightly higher in the right ventricle because of incomplete mixing at the atrial level. The full 6 L flows across the right-ventricular outflow tract and causes a systolic ejection flow murmur. Six litres returns to the left atrium, with 3 L shunting left to right across the defect and 3 L crossing the mitral valve to be ejected by the left ventricle into the ascending aorta (normal cardiac output). Behrman et al, 2007. Nelson Textbook of Paediatrics, 17th edition, Figure 419.1.

image

Figure 6.4 Physiology of valvular pulmonary stenosis.

Boxed numbers represent pressure in mmHg. Because of the absence of right-to-left or left-to-right shunting, blood flow through all cardiac chambers is normal at 3 L/min/m2. The pulmonary-to-systemic blood flow ratio (Qp:Qs) is 1:1. Right atrial pressure is increased slightly as a result of decreased right ventricular compliance. The right-ventricle is hypertrophied, and systolic and diastolic pressure is increased. The pressure gradient across the thickened pulmonary valve is 60 mmHg. The main pulmonary artery pressure is slightly low, and poststenotic dilatation is present. Left heart pressure is normal. Unless right-to-left shunting is occurring through a foramen ovale, the patient’s systemic oxygen saturation will be normal. Behrman et al, 2007. Nelson Textbook of Paediatrics, 17th edition, Figure 420.1.

image

Figure 6.12 Physiology of a large ventricular septal defect (VSD).

Circled numbers represent oxygen saturation values. The numbers next to the arrows represent volumes of blood flow (in L/min/m2). This illustration shows a hypothetical patient with a pulmonary-to-systemic blood flow ratio (Qp:Qs) of 2:1. Desaturated blood enters the right atrium from the vena cava at a volume of 3 L/min/m2 and flows across the tricuspid valve. An additional 3 L of blood shunts left to right across the VSD, the result being an increase in oxygen saturation in the right ventricle. Six litres of blood is ejected into the lungs. Pulmonary arterial saturation may be further increased because of incomplete mixing at right-ventricular level. Six litres returns to the left atrium, crosses the mitral valve, and causes a middiastolic flow rumble. Three litres of this volume shunts left to right across the VSD, and 3 L is ejected into the ascending aorta (normal cardiac output). Behrman et al, 2007. Nelson Textbook of Paediatrics, 17th edition, Figure 419.5.

image

Figure 6.17 Blalock–Taussig shunt in the patient with tetralogy of Fallot.

Circled numbers represent oxygen saturation values. The intracardiac shunting pattern is as described for Figure 423.1. Blood shunting left to right across the shunt from the right subclavian artery to the right pulmonary artery increases total pulmonary blood flow and results in a higher oxygen saturation than would exist without the shunt (see Fig. 423.1). Behrman et al, 2007. Nelson Textbook of Paediatrics, 17th edition, Figure 423.5.

image

Figure 6.16 Physiology of the tetralogy of Fallot.

Circled numbers represent oxygen saturation values. The numbers next to the arrows represent volumes of blood flow (in L/min/m2). Atrial (mixed venous) oxygen saturation is decreased because of the systemic hypoxemia. A volume of 3 L/min/m2 of desaturated blood enters the right atrium and traverses the tricuspid valve. Two litres flows through the right-ventricular outflow tract into the lungs, whereas 1 L shunts right to left through the ventricular septal defect (VSD) into the ascending aorta. Thus, pulmonary blood flow is two thirds normal (Qp:Qs of 0.7:1). Blood returning to the left atrium is fully saturated. Only 2 L of blood flows across the mitral valve. Oxygen saturation in the left ventricle may be slightly decreased because of right-to-left shunting across the VSD. Two litres of saturated left-ventricular blood mixing with 1 L of desaturated right-ventricular blood is ejected into the ascending aorta. Aortic saturation is decreased, and cardiac output is normal. Behrman et al, 2007. Nelson Textbook of Paediatrics, 17th edition, Figure 423.1.

HCM in NS does not have a clearly defined natural history. HCM can become progressive in infancy, or may not develop or be recognised until late in childhood. Symptomatic HCM in NS can lead to sudden cardiac death, even in infancy. Treatment is as for non-syndromic HCM, including cardiac transplantation. See the section on familial HCM below.

The acronym NOONANS can be used as an aide-mémoire:

image Neurodevelopmental problems: 25% learning disability, 10–15% special education, <30% mild intellectual impairment, 72% articulation problems, non-verbal abilities better than verbal, specific learning problems/Neuromuscular examination—hypotonia (floppy strong): joint hyperextensibility/Neurosurgical—Arnold–Chiari type I

O. Obstructive heart lesions: RVOT (pulmonary valve); LVOT (HCM)/Other: ASD, VSD, tetralogy of Fallot, coarctation of aorta, branch pulmonary artery stenosis

O. Ocular anomalies in up to 95%: strabismus, refractive errors, amblyopia, nystagmus; hypertelorism, epicanthic folds, droopy eyelids, vivid blue or blue–green irises

image Neoplasia risk: juvenile myelomonocytic leukaemia (JMML); myeloproliferative disorders; Noonan-like/multiple giant-cell lesion syndrome (granulomas and joint and bone anomalies); hepatosplenomegaly (related to subclinical myelodysplasia)

A. Abnormal coagulation (33% have one or more defects)/Abnormal lymphatics: lymphoedema (hands/feet/scrotum/vulva), lymphangiectasia (lung, gut or testis)

image Neck webbing, with low-set posteriorly rotated ears/Nipples appear low-set/Nephrological anomalies: duplex collecting systems, renal hypoplasia

S. S

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