SERIES: PULMONARY VASCULAR DISEASECongenital heart disease in relation to pulmonary hypertension in paediatric practice
Section snippets
INTRODUCTION
We have come a long way since Paul Wood described in 1958 the effects of high blood flow and high pressure on the pulmonary vascular bed.1 Since then cardiac catheterisation has become a widely used tool in the assessment of pulmonary vascular resistance (PVR) to determine suitability for cardiac surgery. The description of the histo-pathological changes in Eisenmenger syndrome2 have changed substantially from the time of Heath & Edwards,3 now being recognised as variable and not correlating
DEFINITION AND DIAGNOSIS
A recent re-classification, by the World Health Organisation, of the causes of PHT has demonstrated the similarity between secondary PHT and idiopathic or primary PHT.7
The definition (mean pulmonary artery (PA) pressure >25 mmHg at rest or 30 mmHg with exercise)8 is not so useful in clinical practice as it tends to apply to adults rather than children. Also, we use echocardiography rather than cardiac catheterisation to undertake the initial screening and diagnosis so we need to use different
Left to right shunt
The main factors for developing PHT are the size of the shunt and the pressure of blood in the pulmonary artery.14 It seems likely that the degree of shunt causes more stretch in the pulmonary artery and hence increased injury to the endothelium and pulmonary arterial smooth muscle cells. However, it is clear that the type of cardiac defect and the oxygen saturation of the blood in the pulmonary artery are also important. For example, rarely does an atrial septal defect (ASD) cause pulmonary
PATHOLOGICAL CHANGES AND GENETICS
Despite differences in causation, there are many similarities in the histo-pathological changes in the pulmonary vasculature independent of the presence of idiopathic PHT or PHT secondary to congenital heart disease. The first change observed is an extension of muscle into peripheral, normally non-muscular arteries.21 Electron microscopic examination confirms that this is due to differentiation of precursor cells into mature smooth muscle cells.22 Medial hypertrophy then occurs in normally
CONTROL OF PULMONARY VASCULAR RESISTANCE
To understand the management of PHT, it is important to have a basic knowledge of the factors involved in PVR control. Although there is some understanding of how relaxation of pulmonary vascular smooth muscle is mediated at the cellular level (Fig. 1), the exact mechanisms by which oxygen, carbon dioxide and pH actually control PVR are poorly understood.
There are a number of different pathways by which control of the PVR is effected (Fig. 2). The NO pathway appears to be less effective in the
PREVENTION AND TREATMENT OF PHT
The most important advance in the prevention of morbidity and mortality for children with congenital heart disease and high pulmonary artery pressure and flow, is to operate early in order to prevent the development of pulmonary vascular disease.17 Historically, the measured PVR had to be less than 7 U.m2 but this is changing with improved intensive care facilities and the use of NO and other pulmonary vasodilators postoperatively. Certainly, the incidence of PHT postoperatively is much less
MANAGEMENT OF CHRONIC PULMONARY HYPERTENSION
The British Cardiac Society has recently published guidelines for the management of longstanding pulmonary hypertension in adults and children.8 This document emphasises the need for such patients to be managed in specialist units with experience in investigation and provision of complex forms of treatment. Choice of therapy is based on the findings of vasodilator testing at cardiac catheterisation and includes oral vasodilator therapy with calcium antagonists (such as nifedipine or diltiazem),
PRACTICE POINTS
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Primary pulmonary hypertension (PHT) is rare and often genetic in origin.
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Secondary PHT is common and most often due to left to right shunt or chronic lung disease. Large ventricular (VSD) or atrioventricular septal defect (AVSD) should be corrected before 4 months of age to prevent pulmonary vascular disease.
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Investigation is multifaceted and should be undertaken by a team with cardiac and respiratory facilities.
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Echocardiography provides the mainstay of diagnostic tools for PHT.
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Cardiac
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2015, Paediatrics and Child Health (United Kingdom)Patent ductus arteriosus in an adult cat with pulmonary hypertension and rightsided congestive heart failure: Hemodynamic evaluation and clinical outcome following ductal closure
2014, Journal of Veterinary CardiologyCitation Excerpt :In the classification scheme of Heath and Edwards histological lesions exceeding grade III, which includes presence of plexiform lesions or necrotizing arteritis, were considered inoperable as this stage was considered irreversible and likely progressive even if the shunt was still left-to-right.22,23 However, more recently the use of lung biopsies as the sole method of assessing reversibility of lung lesions and operability in humans with PDA has been questioned because a direct correlation between histologic findings and hemodynamics is not always evident.24,25 Testing vascular reactivity using oxygen or nitric oxide has been extensively studied in humans as a way to assess reversibility of the vessel lesions.
A study to determine the prevalence of pulmonary arterial hypertension in children with Down Syndrome and congenital heart disease
2013, Medical Journal Armed Forces IndiaCitation Excerpt :It is well recognized that one of the complication of CHD in patients with DS is the development of pulmonary arterial hypertension (PAH).3 PAH is the development of raised pulmonary arterial (PA) pressure, and is defined as a mean PA pressure of >25 mmHg at rest with no evidence of left atrial hypertension (with a pulmonary capillary wedge pressure <15 mmHg).4 In addition, it has been suggested that the children with Down syndrome with large left-to-right shunt lesions tend to develop PAH much earlier than normal children with similar defects.5,6
Clinical Characterization of Pediatric Pulmonary Hypertension: Complex Presentation and Diagnosis
2009, Journal of PediatricsCitation Excerpt :In uncorrected pre-tricuspid shunt defects, development of irreversible PAH occurs in only 10% to 20% of adult patients, mainly in their third or fourth decade.11 In children with isolated pre-tricuspid shunt defects, development of irreversible PH is extremely unusual.12,13 The same holds for patients with small restrictive hemodynamically insignificant post-tricuspid shunt defects.
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