Fetal Cardiology Simplified

A Practical Manual

Sharland, Gurleen

• Publisher: tfm Publishing Ltd
• Year: 2013
• Print ISBN: 9781903378557
• eBook ISBN: 9781908986931
• Topic: Medicine
• Subtopic: Medical Theory, Practice & Reference

Fetal cardiology has developed dramatically into a subspecialty in the past 25 years. The majority of people examining the fetal heart are not 'experts' in fetal cardiology and therefore find interpreting images, particularly in case of abnormality, rather difficult. This book is designed as a practical guide, to be kept near the ultrasound machine, for all those performing fetal heart scans, but without the expertise of a fetal cardiologist. The aim is to allow the user to recognize the common forms of fetal cardiac abnormality and to appreciate the associated lesions and outcome. The book has a large number of illustrations to enable the reader to visualize the different types of problem and the various forms in which they may manifest. There are relatively few books published in the field of fetal cardiology. This book is aimed at all sonographers, obstetricians and radiologists performing obstetric ultrasound scans and at paediatric cardiologists, both at consultant and trainee level. Thus, this book should fulfill this unmet need in the market, although it is not designed as a comprehensive reference textbook in fetal cardiology.

Chapter 1

Screening for congenital heart disease

Summary

	Introduction
	Prenatal detection of congenital heart disease

•	Screening for fetal congenital heart disease
•	Factors influencing screening of low-risk populations
•	Spectrum of abnormality detected prenatally

	Referral reasons for fetal echocardiography
	Gestational age at diagnosis

Introduction

Cardiac abnormalities are the commonest form of congenital malformation, with moderate and severe forms affecting about 0.3-0.6% of live births. One of the main reasons for making an antenatal diagnosis is to detect major forms of cardiac abnormality early. Diagnosis of anomalies associated with significant morbidity and mortality in early pregnancy allows parents to consider all available options. Prenatal diagnosis also gives time to prepare families for the likely course of events after delivery and to optimise care for the baby at birth. Where appropriate, delivery can be planned at or near a centre with paediatric cardiology and paediatric cardiac surgical facilities. While treatment for the vast majority of cases will take place after birth, prenatal treatment may be considered in a few select cases. Additionally, the value of confirming normality and providing reassurance to anxious parents, particularly if they have already had an affected child, should not be underestimated.

Antenatal diagnosis of congenital heart disease has become well established over the last 30 years and a high degree of diagnostic accuracy is available and expected in tertiary centres dealing with the diagnosis and management of fetal cardiac abnormalities. Virtually all major forms of congenital heart disease, as well as some of the minor forms, can be detected during fetal life, in experienced centres. There are, however, some lesions that cannot be predicted before birth, even in experienced hands, and this should be acknowledged. These include a secundum type of atrial septal defect and a persistent arterial duct, as all fetuses should have a patent foramen ovale and an arterial duct as part of the fetal circulation. In addition, some types of ventricular septal defect may be difficult to detect, either because of their size or position. The milder forms of obstructive lesions of the aorta and pulmonary artery can develop later in life with no signs of obstruction during fetal life.

Prenatal detection of congenital heart disease

Screening for fetal congenital heart disease

A two-tier system has developed for the examination of the fetal heart. Pregnancies at increased risk for fetal congenital heart disease are generally referred to tertiary centres for detailed fetal echocardiography, though the expected rate of cardiac abnormality is relatively low in these groups. Table 1.1 shows the indications for fetal echocardiography and the common groups considered to be at increased risk. The majority of cases of congenital heart disease, however, will occur in low-risk groups and these will only be detected prenatally if examination of the fetal heart is incorporated as part of routine obstetric ultrasound screening. Whilst four-chamber view examination is an effective method of detecting some of the severe forms of cardiac malformation before birth, some major lesions, such as transposition of the great vessels and tetralogy of Fallot, are often associated with a normal four-chamber view. Therefore, including examination of the arterial outflow tracts would greatly improve the prenatal detection rates of major life-threatening forms of congenital heart disease. Current national guidelines recommend examination of the outflow tracts in addition to the four-chamber view at the time of the fetal anomaly scan (Table 1.2).

Factors influencing antenatal screening for heart defects

Antenatal screening for major forms of heart abnormality is possible though there are many issues relating to its success. Detection of cardiac abnormalities is mainly dependent on the skill of sonographers performing routine obstetric ultrasound scans. A formal programme for education and training regarding the fetal heart is necessary to ensure that sonographers are taught the skills of fetal heart examination. As well as learning to obtain the correct views of the heart, sonographers must learn to interpret the views correctly. It is also very important that they maintain these skills. In order to detect anomalies, obstetric ultrasound units need to have appropriate and adequate ultrasound equipment. The time allowed for the obstetric anomaly scan will also influence how long can be spent examining the fetal heart and, thus, the detection rates of abnormalities. A very important aspect of antenatal screening is audit of activity, including monitoring and feedback of both false positive and false negative cases, as well as the true positives.

Spectrum of abnormality detected in the fetus

The cardiac diagnoses in most large fetal cardiac series are generally skewed towards the severe end of the spectrum of cardiac abnormality, with the majority of abnormalities being associated with an abnormal four-chamber view. This bias is a reflection of four-chamber view screening which has been used in routine obstetric anomaly scanning for over 25 years. As a result there has been a predisposition towards lesions that will result in single-ventricle palliation rather than a corrective procedure. However, with the increasing inclusion of great artery examination at the time of the fetal anomaly scan there has been some improvement in the proportion of great artery abnormalities being detected by screening, though further improvement could still be made. Figure 1.1 shows the prevalence of 12 cardiac defects in the large fetal series seen between 1980 and 2010 at Evelina Children’s Hospital compared to expected prevalence of the same lesions in postnatal series. Also shown is the prevalence of the same cardiac defects in the last 10 years of the fetal series. It can b...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Contents
• Foreword
• Acknowledgements
• Dedication
• Abbreviations
• Chapter 1: Screening for congenital heart disease
• Chapter 2: The normal fetal heart
• Chapter 3: Abnormalities of cardiac size, position and situs
• Chapter 4: Abnormalities of the four-chamber view (I) Abnormalities of veno-atrial and atrioventricular connection
• Chapter 5: Abnormalities of the four-chamber view (II) Abnormalities of atrioventricular valves and the ventricular septum with normal connections
• Chapter 6: Abnormalities of the four-chamber view (III) Obstructive lesions at the ventriculo-arterial junction that may be associated with an abnormal four-chamber view
• Chapter 7: Great Artery Abnormalities (I) Abnormalities of ventriculo-arterial connection
• Chapter 8: Great Artery Abnormalities (II) Abnormalities of ventriculo-arterial connection
• Chapter 9: Aortic arch abnormalities
• Chapter 10: Cardiomyopathies
• Chapter 11: Cardiac tumours
• Chapter 12: Other cardiac anomalies
• Chapter 13: Rhythm disturbances in the fetus
• Chapter 14: Counselling and outcome following prenatal diagnosis of congenital heart disease
• Chapter 15: What could cardiac findings mean?
• Further reading
• Index