SERIES: PULMONARY VASCULAR DISEASE
Congenital heart disease in relation to pulmonary hypertension in paediatric practice

https://doi.org/10.1016/j.prrv.2005.06.010Get rights and content

Summary

Pulmonary hypertension (PHT) is a well recognised feature of untreated congenital heart disease. This article will review the causes, known mechanisms, appropriate investigations and current therapies for PHT. The reader will understand the difference between PHT due to high pulmonary blood flow and PHT that is due to high pulmonary vascular resistance. The former is best treated by surgical or catheter intervention, whereas for the latter (Eisenmenger syndrome) only palliation is possible with medication or transplantation.

Echocardiography and electrocardiography (ECG) should be performed in any child where there is a possibility of pulmonary hypertension, especially with long standing chronic lung disease and minor left to right shunt. Often these children may have dual pathology and their investigation and management may be a complex interaction between cardiac and respiratory therapists.

New treatments and new techniques of assessment are now available and this may lead to improved recognition of PHT and prevention of long term disability as a result.

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

  • Primary pulmonary hypertension (PHT) is rare and often genetic in origin.

  • 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.

  • Investigation is multifaceted and should be undertaken by a team with cardiac and respiratory facilities.

  • Echocardiography provides the mainstay of diagnostic tools for PHT.

  • Cardiac

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