Atrial Septal Defect

Atrial septal defect (ASD) is a congenital cardiac disorder. It is caused by the spontaneous malformation of the interatrial septum resulting in one or more openings, commonly referred to as holes in the heart. ASD produces a left-to-right shunt—a diversion of the blood flow through an anomalous opening from the left side of the heart to the right side—from the systemic to the pulmonary circulation.¹ Factors such as the size of the defect and extent of the shunt and associated anomalies create a spectrum of disease from insignificant cardiac sequelae to right-sided volume overload, pulmonary arterial hypertension, and even atrial arrhythmias and stroke.^2,3 Many individuals may live their entire lives with small ASDs while remaining unaware that any abnormality exists.⁴

If an individual has no other concomitant congenital defect, symptoms may be absent, particularly in children. Symptoms may, however, begin any time after birth through childhood.⁵ The most common symptom of ASD is dyspnea on exertion, which for most does not occur until they are in their second or third decade of life.⁴ Signs or symptoms usually begin by age 30 years in adults; however, in some cases they may not occur until decades later.³

While ASD is not common, it is the most common congenital cardiac anomaly that is usually asymptomatic until adulthood.^5,6 The majority of cases (more than 70%) are diagnosed by the fifth decade.² This condition may be uncorrected in some seniors, and the presence of ASD in seniors may complicate medication management. Almost all patients who survive beyond 60 years of age with an ASD are symptomatic.²

ASD occurs with a female-to-male ratio of approximately 2 to 1. While most cases of ASD are isolated and sporadic, genetically ASD may be a familial trait, due to a chromosomal mutation, or an autosomal recessive disorder.^2,7 Rubella infection and the use of certain medications, alcohol, or drugs (e.g., cocaine) during pregnancy interfere with the developing fetus and can increase the risk of a heart defect.³ Incidence of ASD has increased due to improved detection with the growth of routine diagnostic echocardiography.²

Types of ASD

ASDs account for approximately 10% of all congenital heart disease and up to 20% to 40% of congenital heart disease presenting in adulthood.^2,7 The following are the three most common types of ASD that pharmacists may see documented in the medical record:

Ostium secundum (defect in the fossa ovalis in the middle of the atrial septum) is the most common type of ASD, accounting for 75% of all ASD cases.^2,7 This type represents approximately 7% of all congenital cardiac defects and 30% to 40% of all congenital heart disease in adults over the age of 40.²

Ostium primum (defect in the anteroinferior aspect of the septum) is the second most common type of ASD, accounting for 15% to 20% of all ASDs. A form of atrioventricular septal defect, this type of ASD is commonly associated with mitral valve abnormalities.^2,7

Sinus venosus (defect in the posterior aspect of the septum) is the least common of the three ASD types and accounts for 5% to 10% of all ASDs. In this defect, it is common to see an anomalous connection of the right-sided pulmonary veins.²

Hemodynamic Changes: Symptoms and Complications

As previously mentioned, ASDs produce a left-to-right shunt, allowing oxygen-rich blood from the left atrium to mix with oxygen-poor blood from the right atrium (see Resources).⁸ Other hemodynamic changes (Table 1) also occur, such as pulmonary blood flow up to two to four times normal.⁶ While most isolated ASDs are well tolerated, some neonates may be vulnerable to profound congestive heart failure.⁶ Most small defects are asymptomatic, and even moderately sized defects may produce no symptoms, or not produce symptoms until middle age.⁵ While symptoms usually do not appear until the third decade of life, the timing of clinical presentation depends on the degree of left-to-right shunt.^2,6

With advancing age, symptoms such as exercise intolerance, dyspnea, fatigue, and atrial arrhythmias (with or without palpitations) become more common; 90% of untreated patients experience these symptoms, or may show evidence of heart failure, by the age of 40 years.^2,5,7 Swelling of the legs, feet, or abdomen and bluish skin color may also be symptoms of ASD.³ Further, a low-pitched diastolic murmur may be detected at the left lower sternal border (secondary to increased blood flow across the tricuspid valve) in patients with a large left-to-right atrial shunt.^5,7

Patients with ASD are at an increased risk for complications (Table 1), which develop over many years and include pulmonary hypertension, heart failure, atrial fibrillation, and stroke.³ Complications rarely occur in infants and children; they also are rare in adults since most ASDs close on their own or are repaired in early childhood.⁸ While spontaneous closure of secundum ASD may occur in childhood, spontaneous closure is unlikely in adulthood.² Though some small ASDs that do not cause any problems may not require treatment, many large (persistent) ASDs eventually require corrective surgery and other treatment (see below) to prevent or help manage many of these complications.³

Atrial fibrillation or atrial flutter occurs in approximately 20% of adults who have an unrepaired ASD, with atrial fibrillation predominating in the majority of patients; incidence of these conditions increases with age.⁹ Irreversible pulmonary hypertension develops in less than 10% of those with isolated unrepaired ASD.⁶ Frequent respiratory infections may be seen in children.⁵

Diagnosis and Prognosis

A cardiac examination, chest x-ray, or ECG can suggest a diagnosis of ASD, with confirmation attained by echocardiography and Doppler studies.⁷ Signs of heart failure may be revealed by a physical exam in some adults.⁵ Additional tests or procedures that may be utilized include cardiac catheterization, coronary angiography (for patients over 35 years old), heart MRI, transesophageal echocardiography (TEE), and pulse oximetry.^3,5

A small-to-moderate atrial septal defect may be associated with a normal life span without symptoms, as compared to larger defects which may cause disability by middle age.⁵ Mortality in patients with ASD is low.¹⁰ Surgical mortality rates for uncomplicated secundum ASD are approximately 1% to 3% for both children and adults.² In general, postoperative survival is comparable to that of the general population.^7,10 In patients with a clinically insignificant shunt and in those who have severe pulmonary arterial hypertension or irreversible pulmonary vascular occlusive disease (with a reversed shunt with at-rest arterial oxygen saturations of less than 90%), closure of an ASD is not recommended due to a potentially worse prognosis and a high surgical mortality and morbidity risk.²

Treatment

If there are few or no symptoms, or if the defect is small, ASD may not require treatment.⁵ However, treatment involving surgical or catheter-based repair is often necessary for ASDs to prevent complications.^3,7 In general, it is advised that all ASD patients with evidence of right ventricular overload or with a clinically significant shunt have elective closure; the absence of symptoms is not a contraindication for repair.² In an attempt to prevent death and complications from ASD in the long term, it is best to proceed with ASD closure before age 25 years and when the systolic pressure in the main pulmonary artery is less than 40 mmHg.² However, excluding contraindications to surgery, surgical closure can be performed even in elderly patients with large (persistent) shunts, with low risk and good results in reducing ASD-associated symptoms.²

Pharmacologic agents are used to reduce some of the signs and symptoms that can accompany an ASD or to reduce the risk of postsurgical complications; they include: digoxin, beta-blockers (e.g., metoprolol, propranolol), anticoagulants (e.g., warfarin), and antiplatelet agents (e.g., aspirin).³ It has been recommended that before surgical repair, patients with large (persistent) shunts and heart failure should be treated with diuretics, digoxin, or ACE inhibitors.⁷

Infective Endocarditis: Antibiotic Prophylaxis

The American Heart Association (AHA) recommends antibiotic prophylactic regimens only for patients with underlying cardiac conditions associated with the highest risk of adverse outcome from infective endocarditis.^11,12 Except for the conditions listed, antibiotic prophylaxis is no longer recommended for any other form of congenital heart disease (CHD): (1) unrepaired cyanotic CHD, including palliative shunts and conduits; (2) completely repaired congenital heart defect with prosthetic material or device, whether placed by surgery or by catheter intervention, during the first 6 months after the procedure; and (3) repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibits endothelialization).^11,12

Therefore, since ASD (secundum variety) is rarely associated with infective endocarditis,^3,13 bacterial endocarditis prophylaxis is required for the first 6 months following device closure or surgical closure with a patch of an ostium secundum–type ASD.¹⁴ Preoperatively, antibiotic prophylaxis is not required in an isolated ostium secundum ASD.¹⁴ If other heart defects in addition to the ASD are present, patients may require antibiotic prophylaxis before certain dental or surgical procedures. ³

Conclusion

ASD is characterized by a defect in the interatrial septum producing a left-to-right shunt and is one of the more commonly recognized congenital cardiac anomalies presenting in adulthood. Patients with ASD are at an increased risk for developing complications including pulmonary arterial hypertension, heart failure, atrial fibrillation, and stroke. An awareness and understanding of this condition, which may be uncorrected in some seniors, is helpful for pharmacists in their responsibility for medication monitoring and management. 

REFERENCES

1. Dorland’s Pocket Medical Dictionary. 28th ed. Philadelphia, PA: Elsevier Saunders; 2009.
2. Markham LW, Cribbs MG, Willis PW IV, et al. Atrial septal defect. Emedicine. Medscape.com. http://emedicine.medscape.com/ article/162914-overview. Updated April 14, 2011. Accessed January 16, 2012.
3. Atrial septal defect (ASD). Mayoclinic.com. www.mayoclinic.com/health/ atrial-septal-defect/DS00628. Updated December 14, 2011. Accessed January 1, 2012.
4. Bloch M. Atrial septal defect. Developmental Disabilities Health Alliance. www.ddha.com/viewArticle?ID= 170148. Published October 3, 2001. Accessed January 15, 2012.
5. Atrial septal defect. MedlinePlus. U.S. National Library of Medicine. National Institutes of Health. www.nlm.nih.gov/medlineplus/ ency/article/000157.htm. Updated May 04, 2010. Accessed January 16, 2012.
6. Schoen FJ. The heart. In: Cotran RS, Kumar V, Collins T. Robbins, eds. Robbins Pathologic Basis of Disease. 6th ed. Philadelphia, PA: WB Saunders Company; 1999:591-599.
7. Beers MH, Porter RS, Jones TV, et al. The Merck Manual of Diagnosis and Therapy. 18th ed. Whitehouse Station, NJ: Merck Research Laboratories; 2006:2407-2408, 2420-2421.
8. Types of holes in the heart. National Heart Lung and Blood Institute. U.S. Department of Health and Human Services. www.nhlbi.nih.gov/health/ health-topics/topics/holes/ types.html. Updated July 1, 2011. Accessed January 15, 2012.
9. Blomström-Lundqvist C, Scheinman MM, Aliot EM, et al. ACC/AHA/ESC Guidelines for the management of patients with supraventricular arrhythmias—executive summary. A report of the American College of Cardiology/American Heart Association task force on practice guidelines and the European Society of Cardiology committee for practice guidelines (writing committee to develop guidelines for the management of patients with supraventricular arrhythmias) developed in collaboration with NASPE-Heart Rhythm Society. J Am Coll Cardiol. 2003;42:1493-1531.
10. Murphy JG, Gersh, BJ, McGoon, MD, et al. Long-term outcome after surgical repair of isolated atrial septal defect. N Engl J Med. 1990;323:1645-1650.
11. Windle ML. Antibiotic prophylactic regimens for endocarditis. http://emedicine.medscape.com/ article/1672902-overview. Updated May 31, 2011. Accessed January 18, 2012.
12. Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. 2007;116(15):1736-1754.
13. Brusch JL. Infective Endocarditis. Emedicine. Medscape.com. http://emedicine.medscape.com/ article/216650-overview. Updated November 29, 2011. Accessed January 17, 2011.
14. Ostium secundum atrial septal defects. Emedicine. Medscape.com. http://emedicine.medscape.com/ article/890991-medication. Updated December 01, 2011. Accessed January 17, 2012.

To comment on this article, contact rdavidson@uspharmacist.com.