An formation of the foramen secundum. Resorption in

An atrial septaldefect (ASD) is a hole in the wall between the two upper chambers of your heart(atria) (Ferri, 2017).The condition is present from birth (congenital) and Small atrial septaldefects may close on their own during infancy or early childhood (Rochester andMinn 2017)The heart has two sides, separatedby an inner wall called the septum and hole in the septum between the heart’stwo upper chambers (or “atria”) is called an atrial septal defect (Ferri, 2017).This congenital (present at birth) heart defect occurs when normal heartdevelopment is disrupted during the first eight weeks of pregnancy (Ferri,2017). An atrial septal defect allowsblood to pass from the left side of the heart to the right side. Thus,oxygen-rich (red) blood mixes with oxygen-poor (blue) blood, and someoxygen-rich blood is pumped to the lungs instead of the body (Kutty , Hazeem ,Brown 2012).

There are four major types ofatrial septal defects: Ostium secundum ASD: This type of ASD results from incomplete adhesion between the flap valve associated with the foramen ovale and the septum secundum after birth (Kutty , Hazeem , Brown 2012). The patent foramen ovale usually results from abnormal resorption of the septum primum during the formation of the foramen secundum. Resorption in abnormal locations causes a fenestrated or netlike septum primum and excessive resorption of the septum primum results in a short septum primum that does not close the foramen ovale (Kutty , Hazeem , Brown 2012). An abnormally large foramen ovale can occur as a result of defective development of the septum secundum     (Kutty , Hazeem , Brown 2012).

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The normal septum primum does not close this type of abnormal foramen ovale at birth and combination of excessive resorption of the septum primum and a large foramen ovale produces a large ostium secundum ASD (Kutty , Hazeem , Brown 2012).   Ostium primum ASD: These defects are caused by incomplete fusion of septum primum with the endocardial cushion. The defect lies immediately adjacent to the atrioventricular (AV) valves, either of which may be deformed and incompetent (Putra, Djer , Idris et al,  2015).

In most cases, only the anterior or septal leaflet of the mitral valve is displaced, and it is commonly cleft. The tricuspid valve is usually not involved (Kutty , Hazeem , Brown 2012).  Sinus venosus ASD: Abnormal fusion between the embryologic sinus venosus and the atrium causes these defects (Ostermayer , Srivastava, Doucette 2015). In most cases, the defect lies superior in the atrial septum near the entry of superior vena cava and often there is associated anomalous drainage of the right superior pulmonary vein ( Ostermayer , Srivastava, Doucette 2015). The relatively uncommon inferior type is associated with partial anomalous drainage of the right inferior pulmonary vein. Anomalous drainage can be into the right atrium, the superior vena cava, or the inferior vena cava. ( Ostermayer , Srivastava, Doucette 2015).

  Coronary sinus ASD: The coronary sinus defect is characterized by unroofed coronary sinus and persistent left superior vena cava that drains into the left atrium. A dilated coronary sinus often suggests this defect (Kutty , Hazeem , Brown 2012). This can result is desaturation due to right-to-left shunt into the left atrium and the diagnosis can be made by injecting contrast agent into left upper extremity; coronary sinus opacification precedes right atrial opacification (Kutty , Hazeem , Brown 2012).      EpidemiologyThe three major types of atrialseptal defect (ASD) account for 10% of all congenital heart disease and as muchas 20-40% of congenital heart disease presenting in adulthood. The most commontypes of ASD include the following (Krumsdorf , Ostermayer , Billinger, 2004).

?  Ostium secundum: The most common type of ASD accounting for 75% of all ASD cases,representing approximately 7% of all congenital cardiac defects and 30-40% ofall congenital heart disease in patients older than 40 years (Krumsdorf ,Ostermayer , Billinger, 2004). ?  Ostium primum: The second most common type of ASD accounts for 15-20% of allASDs. Primum ASD is a form of atrioventricular septal defect and is commonlyassociated with mitral valve abnormalities (Krumsdorf , Ostermayer , Billinger,2004).

?  Sinus venosus: The least common of the three, sinus venosus (SV) ASD is seen in5-10% of all ASDs. The defect is located along the superior aspect of theatrial septum. Anomalous connection of the right-sided pulmonary veins iscommon and should be expected (Krumsdorf , Ostermayer , Billinger, 2004). Sex- and age-related demographicsASD occurs with a female-to-male ratioof approximately 2:1.Patients with ASD can be asymptomatic through infancy andchildhood, though the timing of clinical presentation depends on the degree ofleft-to-right shunt (Krumsdorf , Ostermayer , Billinger, 2004). Symptoms becomemore common with advancing age 40, 90% of untreated patients have symptoms ofexertional dyspnea, fatigue, palpitation, sustained arrhythmia, or evenevidence of heart failure (Krumsdorf , Ostermayer , Billinger, 2004).

  Causes of Atrial Septal DefectsThe heart forms during the first eight weeks ofpregnancy and the heart begins as a hollow tube, as the heart develops, itpartitions, creating a wall (or “septum”) dividing the two sides of the heart(Ruiz-Perez , Ide , Strom, 2000). Atrial septal defects occur when thispartitioning process does not complete, thus leaving a hole in the atrialseptum (Ruiz-Perez , Ide , Strom, 2000).Heredity may play a role in some congenital heartdefects like ASD. Gene defects, chromosome abnormalities and environmentalexposure can cause heart problems to occur more often in certain families ( Li ,Newbury-Ecob , Terrett, 1997) . Most atrial septal defects occur by chance (orsporadically) with no clear cause. Scientists continue to search for the causesof congenital heart defects like ASD ( Li , Newbury-Ecob , Terrett, 1997).

 Howeverthere are some conditions that you can have or that can occur during pregnancymay increase your risk of having a baby with a heart defect, including: (Benson, Silberbach , Kavanaugh-McHugh 1999). Rubella infection. Becoming infected with rubella (German measles) during the first few months of your pregnancy can increase the risk of fetal heart defects.

Drug, tobacco or alcohol use, or exposure to certain substances. Use of certain medications, tobacco, alcohol or drugs, such as cocaine, during pregnancy can harm the developing fetus. Diabetes or lupus. If you have diabetes or lupus, you may be more likely to have a baby with a heart defect.

Obesity. Being extremely overweight (obese) may play a role in increasing the risk of having a baby with a birth defect. Phenylketonuria (PKU). If you have PKU and aren’t following your PKU meal plan, you may be more likely to have a baby with a heart defect.

   PathophysiologyThe magnitude of the left-to-rightshunt across the atrial septal defect (ASD) depends on the defect size, therelative compliance of the ventricles, and the relative resistance in both thepulmonary and systemic circulation and with small ASD, left atrial pressure mayexceed right atrial pressure by several millimeters of mercury, whereas withlarge ASD, mean atrial pressures are nearly identical (Warnes, Williams ,Bashore, 2008). Shunting across the interatrial septum is usually left-to-rightand occurs predominantly in late ventricular systole and early diastole withsome augmentation which may occur during atrial contraction, a transient andsmall right-to-left shunt can occur, especially during respiratory periods ofdecreasing intrathoracic pressure, even in the absence of pulmonary arterialhypertension (Warnes, Williams , Bashore, 2008).The chronic left-to-right shuntresults in increased pulmonary blood flow and diastolic overload of the rightventricle. Resistance in the pulmonary vascular bed is commonly normal in childrenwith ASD, and the volume load is usually well tolerated even though pulmonaryblood flow may be more than 2 times systemic blood flow (Wang , Niu , Wang ,2016). Altered ventricular compliance with age can result in an increasedleft-to-right shunt contributing to symptoms.

The chronic significantleft-to-right shunt can alter the pulmonary vascular resistance leading topulmonary arterial hypertension, even reversal of shunt and Eisenmengersyndrome and because of an increase in plasma volume during pregnancy, shuntvolume can increase, leading to symptoms (Wang , Niu , Wang , 2016). Symptoms of Atrial Septal DefectsMany babies born with ASDs have no signs orsymptoms. However, as they grow, these children may be small for their age (Benson, Silberbach , Kavanaugh-McHugh, 1999). If the ASD is large and permits alot of extra blood flow to the right side of the heart, the right atrium, rightventricle and lungs will become overworked, and it may cause symptoms (Benson,Silberbach , Kavanaugh-McHugh, 1999). While each child may experience symptomsof ASD differently, common signs include:  Tiring easily when playing Fatigue Sweating Rapid breathing Shortness of breath Poor growth Frequent respiratory infectionsDiagnosisIt can be diagnose when the doctor first suspect anatrial septal defect or other heart defect during a regular checkup if he orshe hears a heart murmur while listening to your heart using a stethoscope Oran atrial septal defect may be found when an ultrasound exam of the heart(echocardiogram) is done for another reason ( Tsai , Hsiung , Wei, 2017).If a doctor suspects you have a heart defect, hemay request one or more of the following tests: Echocardiogram,Chest X-ray, Cardiac catheterization, Magnetic resonance imaging (MRI)Computerized tomography (CT) scan ( Tsai ,Hsiung , Wei, 2017).


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