Free Research Paper About Congenital Heart Defects

Congenital heart defects are problems intrinsic to the heart that present at birth. They develop during fetal growth in utero mainly due to genetic malformations, environmental factors, and multifactorial reasons. The environment within which the fetus develops (the uterus) is a very crucial contribution to normal fetal growth and development. It is common to find disruptions within this microenvironment; the consequent effect being the disruption of normal growth and organ developments. The timing is, however, important as well. During the first trimester, organs are being crafted from primitive cells and tissues. Internal and external factors, therefore, take the opportunity to cause disruption. The most common congenital anomalies are heart defects. They present in many forms. This paper will look at various aspects related to congenital heart defects; the relation of zidovudine to congenital heart defects, types of congenital heart anomalies, causes of congenital heart defects and the diagnostic tools and interpretations. The treatment choice for common conditions will also be discussed; pulmonary hypertension for instance.
It is important to note that congenital heart defects may be sometimes detected many years after birth. Some may need treatment but some survive the defects though blood flow is highly compromised. Still, patients with hypertension have a likelihood of a heart defect especially if the condition develops at a younger age. There are two main variables monitored in hypertension; cardiac output and peripheral resistance. Cardiac output refers to the amount of blood ejected by the heart per unit time while peripheral resistance is the resistance to blood flow exerted by arterials in the systemic circulation.

Zidovudine exposure in utero and heart anomalies

Zidovudine is an antiretroviral drug that is part of HIV/AIDS regimen. It is a nucleoside reverse transcriptase inhibitor; blocks the action of the enzyme used by HIV virus in forming its DNA template. Studies have linked the use of Zidovudine during pregnancy or exposure by any other means to the development of congenital heart defects. The article below discusses a research conducted by physicians in 9 clinical centers.
Authors: Sibiude J, Le Chenadec J, Bonnet D, Tubiana R, Faye A, Dollfus C, Mandelbrot L, Delmas S, Lelong N, Khoshnood B, Warszawski J, Blanche S.

Publication date: 1st April, 2015

The study was done using a prospective approach. HIV-infected women on zidovudine in 10 clinical centers were examined, and their children followed up thereafter. The follow-up was extended to a period of two years. Control of the study was women on ARV regimen excluding nucleoside reverse transcriptase inhibitors. From the study, the researchers concluded the following findings; among those exposed to zidovudine in the first trimester, 1.5% developed congenital heart defects detectable before birth by use of echocardiography studies. Those exposed to other ARV regimens aside from zidovudine (control) gave 0.6% correlation. Ventricular septal defects registered the highest correlation with 1.1% correlation to zidovudine exposure and 0.7% to other regimens.
The researchers concluded a strong correlation between zidovudine exposure in utero and development of congenital heart defects. Though the article does not mention the role of zidovudine in congenital heart defects, this paper suggests mitochondrial dysfunction as the main involvement. However, further studies on the same are necessary. Just as thalidomide was recalled from the market due to its association with limb anomalies; zidovudine may too be recalled if reports necessitate so.

Common types of congenital heart defects

The normal mammalian heart has four chambers separated by a septum. Congenital defects may involve the heart chambers, the valves, or blood vessels within the heart’s locality. The diagram below illustrates the normal heart topography;
Tetralogy of fallot: If the septum, the muscular wall separating the ventricles fails to develop fully, a hole persists. Consequently, oxygenated blood in the left ventricle mixes with deoxygenated blood in the right ventricle. In the normal state, oxygenated blood from the lungs flows through the pulmonary vein into the left atrium from where the left ventricle pumps it through the aorta to the systemic circulation. In a way to compensate the low level of oxygen delivered to tissues and prevent hypoxia, the heart pumps blood with extra force; the result is the development of high blood pressure. Holes that neither are nor too wide heal on their own but larger ones may be fatal.
Atrial septal defect: just as tetralogy of fallot presents, the same case applies to atrial septal defects. A hole develops in the septum separating the right and left atria due to incomplete development in utero. As well, oxygenated blood in the left atrium mixes with deoxygenated blood in the right atrium.
Patent ductus arteriosus: In utero, the developing fetus has a blood vessel connecting the pulmonary artery and aorta. It is wise to recall that the developing fetus receives oxygen from the mother’s circulation through the placenta; the lung is still primitive. This vessel should close immediately after birth since the lungs have assumed gaseous exchange function. If it remains patent, it compromises the normal blood circulation.
Pulmonary valve stenosis: In this condition, there is narrowing of the right pulmonary valve. Pressure builds in the right ventricle that is compelled to pump blood at a faster rate to the pulmonary trunk. Right heart failure is likely to result if the same condition persists for long. The image below illustrates pulmonary valve stenosis ("Slide Show: Common Types of Congenital Heart Defects - Mayo Clinic");

Stenosis of other valves occurs; however, congenital stenosis mainly involves the pulmonary valve.

Ebstein’s anomaly: This is a congenital heart defect where a hole persists in a malformed heart valve. Before the blood in the lower chambers is pumped to either the lungs or systemic circulation, a small fraction spills to the upper chambers.

Causes of congenital heart defects

The main causes of congenital heart defects remain unknown (idiopathic) and creates room for further scientific research. Among the speculated causes include the following. Genetic syndrome; in this case, a group of genes in the developing fetus are involved. They undergo mutation alteration coding sequence of specific amino acids to be incorporated into the synthesis of particular proteins. Causes of mutations may be drug exposure (zidovudine for instance looked earlier), inheritance, or other external factors. In rare cases, a single gene may be involved, in which case the chance of another family having the same condition is more than fifty percent; a high value.
Environmental exposure during pregnancy is another cause cited in congenital heart defects. It was earlier pointed out that the uterus, the fetus’ environment, should be kept free from external contaminants. Use of drugs of abuse during pregnancy increases the risks of developing congenital heart defects. The article "Smoking during Pregnancy May Raise Risk for Heart Defects in Babies" in Science Daily links smoking during pregnancy with congenital heart defects.

Diagnosis and treatment

Two main tools are used in diagnosis; echocardiography and x-ray imaging. The former is also used before birth, in utero, revealing the characteristic heart sounds and murmurs. Any alterations in such sounds can easily be monitored before conclusions are made(Paladini and Volpe, 2009). In pulmonary valve stenosis, for instance, cardiac murmurs become exaggerated. X-ray imaging, on the other hand, is commonly used in adults. Thickening of the left or right heart chambers becomes a significant pointer in diagnosing congenital heart defects. History taking of the symptoms also plays a role in diagnosis.
In most cases, congenital heart anomalies can be corrected through surgical operations ("Care and Treatment for Congenital Heart Defects"). Patent ductus arteriosus management, for instance, involves closure surgically. In other cases, conditions that result should be managed first before the underlying anomaly is approached. Consider pulmonary hypertension. Antihypertensive medications are chosen depending on efficacy, price, and age of the individual. The classes of medications used include but not limited to diuretics, calcium channel blockers, beta-receptor blockers, angiotensin receptor blockers, and angiotensin inhibitors. Other congenital cardiac anomalies do not need medical attention and may persist throughout without causing health hazards.

Conclusion

Congenital heart defects are heart anomalies that develop in utero. The areas involved include; heart chambers, septum, valves, and blood vessels within the heart. There are many types of CHDs including; pulmonary valve stenosis, teratology of fallot, atrial septum defect, and patent ductus arteriosus. Causes include genetic alteration, and environmental factors to which the mother might be exposed to during pregnancy. As a guide to its management, treatment of other secondary conditions such as pulmonary hypertension should first be instituted before the underlying anomaly is corrected.

Works Cited

"Care and Treatment for Congenital Heart Defects." Www.heart.org. N.p., n.d. Web. 6 Apr. 2015.
"In Utero Exposure to Zidovudine and Heart Anomalies in the ANRS-EPF French Perinatal Cohort and the Nested PRIMEVA Randomized Trial. - PubMed - NCBI." National Center for Biotechnology Information. N.p., n.d. Web. 6 Apr. 2015.
Paladini, Dario, and Paolo Volpe. Ultrasound of Congenital Fetal Anomalies: Differential Diagnosis and Prognostic Indicators. London: Informa Healthcare, 2007. Print.
"Slide Show: Common Types of Congenital Heart Defects - Mayo Clinic." Mayo Clinic. N.p., n.d. Web. 6 Apr. 2015.
"Smoking During Pregnancy May Raise Risk for Heart Defects in Babies." Science Daily. N.p., n.d. Web. 6 Apr. 2015.