Tetralogy of Fallot: Literature Review
Tetralogy of Fallot is a congenital heart defect associated with systemic cyanosis, accounting for approximately 5 to 6% of all cases of congenital heart disease and is characterized by; ventricular septal defect, aortic override, pulmonary stenosis and right ventricular hypertrophy. It is the most common cause of blue baby syndrome with children diagnosed developing Tet spells. Sudden increases in cyanosis followed by syncope characterize Tet spells and may result in hypoxic brain injury and death. Environmental and genetic disorders are other causes of TOF; always associated with chromosome 22 deletions and DiGeorge syndrome and occurs slightly more often in males than in females. If left untreated, Tetralogy of Fallot rapidly results in progressive right ventricular hypertrophy due to the increased resistance on the right ventricle. This progresses to dilated cardiomyopathy which begins in the right heart chambers often leading to left heart failure. Actuarial survival for untreated Tetralogy of Fallot is approximately 75%, 60%, 30% and 5% after the first year of life, four years, ten years, and forty years respectively.
Review of the Literature
According to Digilio, et al. (2001), Transposition of the Great Arteries (TGA) has a prevalence rate of 0.2 per 1000 live births in the United States accounting for approximately 5 to 7% of all Congenital Heart Defects (CHDs). TGA is the most frequent cyanotic CHD diagnosed in the neonatal period and genetic contribution to the pathogenesis of TGA is not considered to be strong. This is due to few familial cases identified and that genetic syndromes are uncommonly associated with TGA. The study concludes that the mean precurrence risk for CHD among siblings of patients affected with TGA is 1.4%, and TGA is not always a sporadic occurrence in these families. Familial precurrence of concordant cardiac defects within affected family members’ supports monogenic or oligogenic inheritance of TGA in selected pedigrees. In addition, TGA and congenitally corrected TGA can segregate in the same family due to a probable monogenic transmission supporting a pathogenetic link between some cases of complete TGA and looping abnormalities.
In their publication, Nembhard, Salemi, Wang, Loscalzo, & Hauser (2010) argue that birth defects are the leading cause of infant morbidity and mortality in the United States and CHD is the most common of all birth defects. Despite having an annual prevalence of six to twelve affected infants per 1,000 live births, a meager 5% of CHDs are attributed to chromosomal abnormalities and single gene defects. They argue that though etiologies of most cases of CHDs are unclear, there are other modifiable factors that may result in increased risk of congenital heart defects. There are maternal illnesses such as phenylketonuria, diabetes, rubella, maternal febrile illnesses, and influenza that may increase the risks of CHD-affected pregnancy. In addition, the results of studies investigating the effect of environmental exposures on CHD risk are inconclusive, but, organic solvents have been identified as directly associated with increased risk of CHD among children. In contrast, the association between socio-demographic factors, such as maternal and paternal age, socioeconomic status, and pre-natal maternal stress are inconsistent.
The role of other socio-demographic factors such as maternal race and ethnicity, are also unclear. The publication outlines that most studies report excess risk of specific types of CHDs for Whites compared to Blacks and that very few studies have reported risk of specific types of CHD for Hispanics. Moreover, the report provides information on the prevalence of isolated, multiple heart and CHD with non-cardiac defects by maternal race and ethnicity. Hence, their publication’s intent is to determine the prevalence of CHD at live birth and determine the prevalence of isolated CHD, multiple heart and CHD plus non-cardiac defects for non-Hispanic-White, non-Hispanic-Black and Hispanic infants.
As portrayed by Jing-bin, Ying-long, Pei-wu, Xiao-dong, Ming, & Xiang-ming (2010), CHD is the most common type of birth defect. Despite the many advances in understanding cardiac development and many genes related to cardiac development, the fundamental etiology for the majority of cases of congenital heart disease remains unknown. CHD is a multifactorial complex disease, with both environmental and genetic factors playing roles in its spread among children. There have been several causative genes and genetic syndromes isolated as having direct impacts on congenital heart defects. The molecular mechanisms of CHD may include mutations in components of the cardiac gene network, altered haemodynamics, and regulatory pathway of cardiac genes, micro-RNA dysfunction, epigenetics, and adult congenital heart diseases, among others. The molecular basis of CHD is a rapidly evolving field and continuing advances in the understanding of the molecular mechanisms of CHD is likely to result in improved genetic counseling and care of affected individuals and their families.
Gelson, Gatzoulis, Lupton, Steer, & Johnson (2008) highlight that Tetralogy of Fallot is the most common congenital heart defect associated with systemic cyanosis, and accounts for 5 to 6% of all cases of congenital heart disease. It is characterized by ventricular septal defect, aortic override, pulmonary stenosis and right ventricular hypertrophy. With advances in reparative surgery, women are now surviving into their childbearing years with survival rates of 94% to age 20 years and 85% up to the age of 36 years.
Although a good quality of life is usually achieved following repair, late complications such as pulmonary regurgitation, pulmonary stenosis, right ventricular dysfunction, tricuspid regurgitation, atrial and ventricular arrhythmias and sudden cardiac death still occur among women in few circumstances. During normal pregnancy and delivery, systemic vascular resistance falls, blood volume increases, cardiac output increases secondary to increased heart rate and stroke volume, and a physiological left ventricular hypertrophy occurs.
Pregnancy in unrepaired TOF carries a major risk of maternal complications, including heart failure, arrhythmia and endocarditis, which can give rise to fetal problems including miscarriage and pre-term labor. In repaired Tetralogy of Fallot, pregnancy is usually well tolerated in the absence of pregnancy complications such as pre-eclampsia. However, in women with residual shunts, right ventricular outflow obstruction and right ventricular dysfunction, the increased volume overload of pregnancy can lead to heart failure and arrhythmias.
The authors deduce that Tetralogy of Fallot though is the most common form of congenital cyanotic heart disease, advances in cardiac surgery and medication, can increase the number of women with repaired TOF are help them reach their childbearing years and embarking on pregnancy.
According to Marshall (2007), CHD is a congenital defect in the heart, valves or great vessels occurring in about 1% of all pregnancies and 1 in 170 live births. Children with cardiac diseases are at risk for alterations in health such as growth and development, nutrition, psychosocial implications, schooling as well as being at an increased risk for infection, acquiring other diseases, and even cardiopulmonary arrest. Sometimes these children have significantly altered lifestyles and undergo constant medical treatment. For this reason, during care of children diagnosed with CHD, nurses must have a good understanding of common cardiac diseases in children and be able to provide essential nursing care measures.
The nurse providing nursing care to the child must have undergone procedural treatments with closure devices or surgery. The nursing plan of care for the child with a cardiac condition consists of assessment, outcomes, intervention, and evaluation. Post-cardiac surgical patients generally require admission to a pediatric intensive care unit for recovery requiring specific care by highly trained nurses.
In addition, the writer highlights that teaching children and families about their cardiac conditions is essential to help ensure good growth and developments as well as helping the child achieve their highest level of health. Essential information includes cardiopulmonary resuscitation, vital signs, medications, the disease entity, and resources. Extending proper and high quality care to individuals affected by congenital heart defects whether caused by genetic factors or other complications can increase their longevity and cultivates a positive perception of the world among them.
References
Digilio, M.C., Casey, B., Toscano, A., Calabro, R., Pacileo, G., Marasini, M., et al. (2001). Complete Transposition of the Great Arteries: Patterns of Congenital Heart Disease in Familial Precurrence. Journal of the American Heart Association, 2809-2814.
Gelson, E., Gatzoulis, M., Lupton, M., Steer, P., & Johnson, M. (2008). Tetralogy of Fallot: Maternal and Neonatal Outcomes. British Journal of Obstetrics and Gynaecology, 398-402.
Jing-bin, H., Ying-long, L., Pei-wu, S., Xiao-dong, L., Ming, D., & Xiang-ming, F. (2010). Molecular Mechanisms of Congenital Heart Disease. Cardiovascular Pathology, 183-193.
Marshall, J. (2007). Caring for the Child with a Cardiovascular Condition. Maternal-Child Nursing Care, 853-884.
Nembhard, W.N., Salemi, J.L., Wang, T., Loscalzo, M.L., & Hauser, K.W. (2010). Is the Prevalence of Specific Types of Congenital Heart Defects Different for Non-Hispanic White, Non-Hispanic Black and Hispanic Infants? Maternal Child Health Journal, 184-193.
