Atrial Septal Defect

Front matter

Edited by P. Syamasundar Rao Edited by P. Syamasundar Rao Atrial Septal Defects (ASDs) are relatively common both in children and adults. Recent reports of increase in the prevalence of ASD may be related use of color Doppler echocardiography. The etiology of the ASD is largely unknown. While the majority of the book addresses closure of ASDs, one chapter in particular focuses on creating atrial defects in the fetus with hypoplastic left heart syndrome. This book, I hope, will give the needed knowledge to the physician caring for infants, children, adults and elderly with ASD which may help them provide best possible care for their patients. Photo by Dr_Microbe / iStock ISBN 978-953-51-0531-2

ATRIAL SEPTAL DEFECT Edited by P. Syamasundar Rao

ATRIAL SEPTAL DEFECT Edited by P. Syamasundar Rao http://dx.doi.org/10.5772/1588 Edited by P. Syamasundar Rao Contributors Mark D Reller, Teiji Akagi, Hiromasa Yamashita, P. Syamasundar Rao, Srilatha Alapati, Gurur Biliciler-Denktas, Mohammed Numan, Ismael Gonzalez, Duraisamy Balaguru, Nicoleta Daraban, Richard Smalling, Manuel Reyes © The Editor(s) and the Author(s) 2012 The moral rights of the and the author(s) have been asserted. All rights to the book as a whole are reserved by INTECH. The book as a whole (compilation) cannot be reproduced, distributed or used for commercial or non-commercial purposes without INTECH’s written permission. Enquiries concerning the use of the book should be directed to INTECH rights and permissions department (permissions@intechopen.com).

Section 1 General Review of Atrial Septal Defects Section 1 General Review of Atrial Septal Defects

Atrial Septal Defect – A Review P. Syamasundar Rao University of Texas at Houston Medical School, Houston, Texas, USA 1. Introduction Defects in the atrial septum cause left to right shunt because the left atrial pressure is higher than that in the right atrium. This causes vo lume overloading of the right ventricle. While this is generally well tolerated in infanc y and childhood, development of exercise intolerance and arrhythmias in later chil dhood and adolescence, and the risk for development of pulmonary vascular obstructive disease in adulthood make these defects important. There are four major types of atrial septal defects (ASDs) and these include ostium secundum, ostium primum, sinus venosus and coronary sinus defects. The clinical features are essentially similar and I will pres ent detailed discussion of ostium secundum and primum ASDs followed by brief presentation of the other two defects. Persistent patency of the foramen ovale in near ly one third of normal population makes the patent foramen ovale (PFO) a normal variant, although these become important in the presence of other structural abnormalities of the heart and when they become the seat of right to left shunt causing paradoxical embolism result ing in stroke/transient ischemic attacks or other problems, such as migraine, Caisson’s disease and platypnea-orthodexia syndrome. The issues related these types of PFOs will be briefed at the conclusion of this chapter. 2. Secundum atrial septal defect Atrial septal defects constitute 8% to 13% of all congenital heart defects (CHDs). Pathologically, there is deficiency of the septal tissue in the region of fossa ovalis. These may be small to large. Most of the time, these are single defects, although, occasionally multiple defects and fenestrated defects can also be seen . Because of left-to-right shunting across the defects, the right atrium and right ventricl e are dilated and somewhat hypertrophied. Similarly, main and branch pulmonary arteries are also dilate d. Pulmonary vascular obstructive changes are not usually seen until adulthood.

Mitral valve abnormalities, including mitral va lve prolapse and mitral insufficiency may be seen in some patients. It is not clear whet her these abnormalities are to due to right ventricular volume overloading or intrinsic abnormality of the mitral valve. Pulmonary valvar pressure gradients are seen frequently and are thought to be related to increased flow and/or differences in expression of kinetic and potential energies in the right ventricle and pulmonary artery (Rao et al 1973); however, true pulmonary stenosis is present in only 5% of ASD patients. Persistent left superior vena cava may be present in 10% patients.

Atrial Septal Defect – A Review P. Syamasundar Rao University of Texas at Houston Medical School, Houston, Texas, USA 1. Introduction Defects in the atrial septum cause left to right shunt because the left atrial pressure is higher than that in the right atrium. This causes vo lume overloading of the right ventricle. While this is generally well tolerated in infanc y and childhood, development of exercise intolerance and arrhythmias in later chil dhood and adolescence, and the risk for development of pulmonary vascular obstructive disease in adulthood make these defects important. There are four major types of atrial septal defects (ASDs) and these include ostium secundum, ostium primum, sinus venosus and coronary sinus defects. The clinical features are essentially similar and I will pres ent detailed discussion of ostium secundum and primum ASDs followed by brief presentation of the other two defects. Persistent patency of the foramen ovale in near ly one third of normal population makes the patent foramen ovale (PFO) a normal variant, although these become important in the presence of other structural abnormalities of the heart and when they become the seat of right to left shunt causing paradoxical embolism result ing in stroke/transient ischemic attacks or other problems, such as migraine, Caisson’s disease and platypnea-orthodexia syndrome. The issues related these types of PFOs will be briefed at the conclusion of this chapter. 2. Secundum atrial septal defect Atrial septal defects constitute 8% to 13% of all congenital heart defects (CHDs). Pathologically, there is deficiency of the septal tissue in the region of fossa ovalis. These may be small to large. Most of the time, these are single defects, although, occasionally multiple defects and fenestrated defects can also be seen . Because of left-to-right shunting across the defects, the right atrium and right ventricl e are dilated and somewhat hypertrophied. Similarly, main and branch pulmonary arteries are also dilate d. Pulmonary vascular obstructive changes are not usually seen until adulthood.

Mitral valve abnormalities, including mitral va lve prolapse and mitral insufficiency may be seen in some patients. It is not clear whet her these abnormalities are to due to right ventricular volume overloading or intrinsic abnormality of the mitral valve. Pulmonary valvar pressure gradients are seen frequently and are thought to be related to increased flow and/or differences in expression of kinetic and potential energies in the right ventricle and pulmonary artery (Rao et al 1973); however, true pulmonary stenosis is present in only 5% of ASD patients. Persistent left superior vena cava may be present in 10% patients.

Atrial Septal Defect 4 2.1 Clinical features The clinical features are essentially simila r in all types of ASDs mentioned in the Introduction section. 2.1.1 Symptoms Isolated ASD patients are usually asymptomatic and are most often detected at the time of preschool physical examination. Sometimes these defects are detected when echocardiographic studies are performed for some unrelated reason. A few patients do present with symptoms of heart failure in infancy, although this is uncommon. 2.1.2 Physical examination The right ventricular and right ventricular outflow tract impulses are increased and hyperdynamic. No thrills are usually felt. The second heart sound is widely split and fixed (splitting does not vary with respiration) and is the most characteristic sign of ASD. Ejection systolic clicks are rare with ASDs. The ejection systolic murmur of ASD is soft and is of grade I-II/VI intensity and rarely, if ever, lo uder. The murmur is secondary to increased blood flow across the pulmonary valve and is heard best at the left upper sternal border. A grade I-II/VI mid-diastolic flow rumble is heard (with the bell of the stethoscope) best at the left lower sternal border. This is due to large volume flow across the tricuspid valve. There is no audible murmur because of flow across the ASD. 2.2 Noninvasive evaluation 2.2.1 Chest x-ray Chest film usually reveals mild to modera te cardiomegaly, prominent main pulmonary artery segment and increased pulmonary vascular markings.

Fig. 1. Chest x-ray in posterior-anterior view demonstrating mild cardiomegaly, increased pulmonary vascular markings and a slightly prominent main pulmonary artery segment as seen in patients with atrial septal defect.

Atrial Septal Defect – A Review 5 2.2.2 Electrocardiogram The ECG shows mild right ventri cular hypertrophy; the so-called diastolic volume overload pattern with rsR' pattern in the right chest leads.

Fig. 2. An electrocardiogram demonstrating rsR’ pattern in right chest leads, the so called diastolic overloading pattern, indicative mild right ventricular hypertrophy, seen in patients with atrial septal defects. 2.2.3 Echocardiogram Echocardiographic studies reveal enlarged right ventricle with paradoxical septal motion, particularly well-demonstrable on M-mode echo cardiograms in patients with moderate to large ASDs. Dilatation of the right ventricle may not be present in small defects. By two-dimensional echocardiogram, the defect can be clearly visualized (Figure 3 left panel). Fig. 3. Two dimensional subcostal echocardiographic views of the atrial septum demonstrating secundum atrial septal defect (ASD) in the mid septum (left panel) and color Doppler with left to right shunt (right panel). LA, left atrium; RA, right atrium.

Atrial Septal Defect 4 2.1 Clinical features The clinical features are essentially simila r in all types of ASDs mentioned in the Introduction section. 2.1.1 Symptoms Isolated ASD patients are usually asymptomatic and are most often detected at the time of preschool physical examination. Sometimes these defects are detected when echocardiographic studies are performed for some unrelated reason. A few patients do present with symptoms of heart failure in infancy, although this is uncommon. 2.1.2 Physical examination The right ventricular and right ventricular outflow tract impulses are increased and hyperdynamic. No thrills are usually felt. The second heart sound is widely split and fixed (splitting does not vary with respiration) and is the most characteristic sign of ASD. Ejection systolic clicks are rare with ASDs. The ejection systolic murmur of ASD is soft and is of grade I-II/VI intensity and rarely, if ever, lo uder. The murmur is secondary to increased blood flow across the pulmonary valve and is heard best at the left upper sternal border. A grade I-II/VI mid-diastolic flow rumble is heard (with the bell of the stethoscope) best at the left lower sternal border. This is due to large volume flow across the tricuspid valve. There is no audible murmur because of flow across the ASD. 2.2 Noninvasive evaluation 2.2.1 Chest x-ray Chest film usually reveals mild to modera te cardiomegaly, prominent main pulmonary artery segment and increased pulmonary vascular markings.

Fig. 1. Chest x-ray in posterior-anterior view demonstrating mild cardiomegaly, increased pulmonary vascular markings and a slightly prominent main pulmonary artery segment as seen in patients with atrial septal defect.

Atrial Septal Defect – A Review 5 2.2.2 Electrocardiogram The ECG shows mild right ventri cular hypertrophy; the so-called diastolic volume overload pattern with rsR' pattern in the right chest leads.

Fig. 2. An electrocardiogram demonstrating rsR’ pattern in right chest leads, the so called diastolic overloading pattern, indicative mild right ventricular hypertrophy, seen in patients with atrial septal defects. 2.2.3 Echocardiogram Echocardiographic studies reveal enlarged right ventricle with paradoxical septal motion, particularly well-demonstrable on M-mode echo cardiograms in patients with moderate to large ASDs. Dilatation of the right ventricle may not be present in small defects. By two-dimensional echocardiogram, the defect can be clearly visualized (Figure 3 left panel). Fig. 3. Two dimensional subcostal echocardiographic views of the atrial septum demonstrating secundum atrial septal defect (ASD) in the mid septum (left panel) and color Doppler with left to right shunt (right panel). LA, left atrium; RA, right atrium.

Atrial Septal Defect 6 The type of ASD, ostium secundum (Figure 3) versus ostium primum (Figure 4) can also be delineated by the echocardiographic study.

Fig. 4. Four chambered view of the heart demonstrates ostium primum atrial septal defect (ASD), arrow. Note absence of any atrial septal tissue superior to the crest of the ventricular septum. The right atrium (RA) and right ventricle (RV) are enlarged. LA, left atrium; LV. left ventricle.

Apical and precordial views may show "sep tal drop-outs” without an ASD because of thinness of the septum in the region of fossa ovalis. Therefore, subc ostal views should be scrutinized for evidence of ASD. In addition, demonstration of flow across the defect with pulsed Doppler and color Doppler (Figure 3, right panel) echocardiography is necessary to avoid false positive studies. In adolescents an d adults transesophageal echo (TEE) is needed to make definitive diagnosis of ASD. (Figures 5 and 6) Fig. 5. Selected two-dimensional and color flow frame from a transesophageal echocardiographic (TEE) study (in adult patient) of the atrial septum shows an atrial septal defect (arrow) with left to right shunt (blue flow). Measurements of septal margins (1 Dist and 3 Dist) and of the defect (2 Dist) are shown in the insert. LA, left atrium; RA, right atrium. Atrial Septal Defect – A Review 7 Fig. 6. Selected two-dimensional and color flow frame from a transesophageal echocardiographic (TEE) study (in another adult patient) of the atrial septum shows multi-fenestrated atrial septal defect (arrows) with left to right shunt (blue flow). LA, left atrium; RA, right atrium. 2.2.4 Other imaging studies Other imaging studies such as three-dimensional echo, MRI and CT can and do demonstrate the defect, but are not necessary for routine cases. 2.3 Catheterization and angiography Clinical and echocardiographic features are sufficiently characteristic so that cardiac catheterization is not necessary for the diagno sis. However, cardiac catheterization is an integral part of transcatheter occlusion of the ASD.

When catheterization is performed, one will ob serve step-up in oxygen saturation at the right atrial level. The right ventricular or pu lmonary arterial saturations may be better to estimate the degree of shunting because of im proved mixing in these distal sites. The pulmonary venous, left atrial, left ventricula r and aortic saturations are within normal range. In large defects, the pressures in both atria are equal while in small defects, an interatrial pressure difference is noted. The right ventricular and pulmonary arterial pressures are usually normal during childhood. Calculated pulmonary-to-systemi c flow ratio (Qp:Qs) is used to quantify the degree of shunting an d a Qp:Qs in excess of 1.5:1 is considered an indication for closure of ASD.

Selective cineangiography in the right upper pu lmonary vein at its junction with the left atrium in a left axial oblique view will reve al location and the size of the ASD. When anomalous pulmonary venous connection is suspected, selective left or right pulmonary arterial angiography should be performed and the levophase of angiogram should be scrutinized for anomalous pulmonary venous connections.

To avoid missing a diagnosis of partial anom alous pulmonary venous return, we usually perform a number of routine maneuvers and these include (i) measurement of oxygen

Atrial Septal Defect 6 The type of ASD, ostium secundum (Figure 3) versus ostium primum (Figure 4) can also be delineated by the echocardiographic study.

Fig. 4. Four chambered view of the heart demonstrates ostium primum atrial septal defect (ASD), arrow. Note absence of any atrial septal tissue superior to the crest of the ventricular septum. The right atrium (RA) and right ventricle (RV) are enlarged. LA, left atrium; LV. left ventricle.

Apical and precordial views may show "sep tal drop-outs” without an ASD because of thinness of the septum in the region of fossa ovalis. Therefore, subc ostal views should be scrutinized for evidence of ASD. In addition, demonstration of flow across the defect with pulsed Doppler and color Doppler (Figure 3, right panel) echocardiography is necessary to avoid false positive studies. In adolescents an d adults transesophageal echo (TEE) is needed to make definitive diagnosis of ASD. (Figures 5 and 6) Fig. 5. Selected two-dimensional and color flow frame from a transesophageal echocardiographic (TEE) study (in adult patient) of the atrial septum shows an atrial septal defect (arrow) with left to right shunt (blue flow). Measurements of septal margins (1 Dist and 3 Dist) and of the defect (2 Dist) are shown in the insert. LA, left atrium; RA, right atrium. Atrial Septal Defect – A Review 7 Fig. 6. Selected two-dimensional and color flow frame from a transesophageal echocardiographic (TEE) study (in another adult patient) of the atrial septum shows multi-fenestrated atrial septal defect (arrows) with left to right shunt (blue flow). LA, left atrium; RA, right atrium. 2.2.4 Other imaging studies Other imaging studies such as three-dimensional echo, MRI and CT can and do demonstrate the defect, but are not necessary for routine cases. 2.3 Catheterization and angiography Clinical and echocardiographic features are sufficiently characteristic so that cardiac catheterization is not necessary for the diagno sis. However, cardiac catheterization is an integral part of transcatheter occlusion of the ASD.

When catheterization is performed, one will ob serve step-up in oxygen saturation at the right atrial level. The right ventricular or pu lmonary arterial saturations may be better to estimate the degree of shunting because of im proved mixing in these distal sites. The pulmonary venous, left atrial, left ventricula r and aortic saturations are within normal range. In large defects, the pressures in both atria are equal while in small defects, an interatrial pressure difference is noted. The right ventricular and pulmonary arterial pressures are usually normal during childhood. Calculated pulmonary-to-systemi c flow ratio (Qp:Qs) is used to quantify the degree of shunting an d a Qp:Qs in excess of 1.5:1 is considered an indication for closure of ASD.

Selective cineangiography in the right upper pu lmonary vein at its junction with the left atrium in a left axial oblique view will reve al location and the size of the ASD. When anomalous pulmonary venous connection is suspected, selective left or right pulmonary arterial angiography should be performed and the levophase of angiogram should be scrutinized for anomalous pulmonary venous connections.

To avoid missing a diagnosis of partial anom alous pulmonary venous return, we usually perform a number of routine maneuvers and these include (i) measurement of oxygen

Atrial Septal Defect 8 saturations from both right and left innominate veins at the time of superior vena caval sampling, (ii) left innominate vein cineangiogram in posterior-anterior view with diluted contrast material, (iii) probe for all the four pulmonary veins from the left atrium and (iv) as mentioned before, obtain cineangiography fr om the right upper pulmonary vein at its junction with the left atrium in a left axial oblique (300 LAO and 300 cranial) view. 2.4 Management The management of ASD patients is largely de pendent of the age at presentation, presence of symptoms, particularly those of congestive heart failure and the size of the defect (and magnitude of the shunt). 2.4.1 Medical management As mentioned earlier, congestive heart failure is rare with ASDs, although occasionally, failure symptoms may be present in infancy. In these infants anti-congestive measures (diuretics and digoxin) should be instituted. If they do not improve, surgical and more recently trans-catheter intervention to close the defects are considered. Small ASDs, not requiring closure may be followed at infrequent intervals. SBE prophylaxis and activity restriction are not generally recommended for ASD patients. 2.4.2 Indications for closure Despite lack of symptoms at presentation, closure of moderate to large ASDs is recommended so as to 1) prevent development of pulmonary vascular obstructive disease later in life, 2) reduce chances for supr a-ventricular arrhythmias and 3) prevent development of symptoms during adolescence and adulthood.

Elective closure around age 4 to 5 years is recommended. Closure during infancy is not undertaken unless the infant is symptomatic. Right ventricular volume overloading by echocardiogram and a Qp:Qs >1.5 (if the child had cardiac catheterization) are indications for closure. 2.4.3 Surgical management Following the introduction of cardiopulmonar y bypass techniques for open heart surgery and the description of surgical closure of ASD by Gibbon, Lillehei and Kirklin in 1950s, it rapidly became a standard treatment for atrial defects. The conventional treatment of choice of moderate and large defects until recently is surgical correction. Under general anesthesia, a median sternotomy or a right submammary inci sion is made, the aorta and vena cavae are cannulated and the patient placed on cardiopulmonary bypass. Right atriatomy is made and the defect exposed and closed either by a pproximating the defect margins with suture material or by using a pericardial patch, depending upon the size of the defect. While surgical closure of ostium secundum ASDs is safe and effective with low (<1%) mortality, the morbidity associated with sternotomy/thoracotomy, cardiopulmonary bypass and potential for postoperative complications cannot be avoided. Other disadvantages of surgical therapy are the expense associated with surgical correction, residual surgical scar and psychological trauma to the patients an d/or the parents. Because of these reasons Atrial Septal Defect – A Review 9 several trans-catheter methods have been developed (Chopra and Rao, 2000; Rao, 2003) which will be reviewed in the next section.

At the present time, surgical repair is largely reserved for defects with poor septal rims in which the interventional cardiologist deems th at defect is difficult to close with transcatheter methodology or was unsuccessful in clos ing the defect. Also, if intra-cardiac repair of other defects is contemplated, surgical closure of ASD could be performed at the same time. 2.4.4 Trans-catheter closure As alluded to above, a large number of device s have been developed over the last three and one-half decades. Some of the devices have been discontinued and others modified and redesigned (Rao, 1998; Rao, 2000; Rao, 2003b). C linical trials have been undertaken with a large number of devices as reviewed elsewhere (Rao, 2000; Rao, 2003b) and feasibility, safety and effectiveness of these devices in occluding the ASD have been demonstrated. Clinical trials have been undertaken in a large number of patients with Bard clamshell septal occluder and buttoned device and feasibility an d effectiveness of these devices in occluding the ASD have been demonstrated. Fractures of one or more arms of the clamshell device with occasional embolization, has prompted the investigators and th e US Food and Drug Administration (FDA) to withdraw the device from clinical trials. The buttoned device has undergone clinical trials and, immediate and short-term follow-up results are encouraging (Rao et al 1992, Rao et al 1994, Rao et al 2000, Rao and Sideris 2001). However, pre-marketapproval (PMA) application was not made and consequently it is not approved by the FDA and is not available for general clinical use.

Subsequently, a large number of other devices (Das Angel-Wing, ASDOS, Amplatzer, CardioSeal, HELEX and others) have been introduced and clinical trials began (Chopra and Rao 2000). At the present time however, Amplatzer Septal Occluder and HELEX are th e only two devices that are approved for general clinical use by the FDA. The experience with Amplatzer for most defects has been encouraging. HELEX device is only useful in small to medium-sized defects. A number of other devices are in clinical trials either in the US or in other co untries with local, national or regional IRB supervision. These devices, to the best of my knowledge, are CardioSeal/StarFlex devices, transcatheter pa tch, pfm ASD-R device, bio-absorbable NMT devices (Bio-STAR and Bio-TREK), Occlutech Flex device, Cardia devices (INTRASEPT, ATRIASEPT I/II-ASD and ULTRASEPT), Solysafe Septal Occluder, Heart R Septal Occluder (manufactured in China) and others. The Ampl atzer Septal Occluder is rapidly becoming the device of choice because of ease with which the device can be implanted, retrieved and repositioned plus the comfort that the device is FDA approved. 2.4.4.1 Amplatzer septal occluder Amplatzer septal occluder is a double disk de vice constructed with 0.004" to 0.007" Nitinol (nickle-titanium compound) wire with shape memory. A 4 mm wide waist connects the left and right atrial disks and stents th e ASD. The left atrial disk is slightly larger than the right. Dacron polyester patches are sewn into each disk. Multiple sizes are available from the manufacturer (AGA); the device size is expre ssed as the size of waist of the device. The device can be withdrawn into a delivery sheath and can be implanted across the defect and if necessary pulled back into the sheath and repositioned.

Atrial Septal Defect 8 saturations from both right and left innominate veins at the time of superior vena caval sampling, (ii) left innominate vein cineangiogram in posterior-anterior view with diluted contrast material, (iii) probe for all the four pulmonary veins from the left atrium and (iv) as mentioned before, obtain cineangiography fr om the right upper pulmonary vein at its junction with the left atrium in a left axial oblique (300 LAO and 300 cranial) view. 2.4 Management The management of ASD patients is largely de pendent of the age at presentation, presence of symptoms, particularly those of congestive heart failure and the size of the defect (and magnitude of the shunt). 2.4.1 Medical management As mentioned earlier, congestive heart failure is rare with ASDs, although occasionally, failure symptoms may be present in infancy. In these infants anti-congestive measures (diuretics and digoxin) should be instituted. If they do not improve, surgical and more recently trans-catheter intervention to close the defects are considered. Small ASDs, not requiring closure may be followed at infrequent intervals. SBE prophylaxis and activity restriction are not generally recommended for ASD patients. 2.4.2 Indications for closure Despite lack of symptoms at presentation, closure of moderate to large ASDs is recommended so as to 1) prevent development of pulmonary vascular obstructive disease later in life, 2) reduce chances for supr a-ventricular arrhythmias and 3) prevent development of symptoms during adolescence and adulthood.

Elective closure around age 4 to 5 years is recommended. Closure during infancy is not undertaken unless the infant is symptomatic. Right ventricular volume overloading by echocardiogram and a Qp:Qs >1.5 (if the child had cardiac catheterization) are indications for closure. 2.4.3 Surgical management Following the introduction of cardiopulmonar y bypass techniques for open heart surgery and the description of surgical closure of ASD by Gibbon, Lillehei and Kirklin in 1950s, it rapidly became a standard treatment for atrial defects. The conventional treatment of choice of moderate and large defects until recently is surgical correction. Under general anesthesia, a median sternotomy or a right submammary inci sion is made, the aorta and vena cavae are cannulated and the patient placed on cardiopulmonary bypass. Right atriatomy is made and the defect exposed and closed either by a pproximating the defect margins with suture material or by using a pericardial patch, depending upon the size of the defect. While surgical closure of ostium secundum ASDs is safe and effective with low (<1%) mortality, the morbidity associated with sternotomy/thoracotomy, cardiopulmonary bypass and potential for postoperative complications cannot be avoided. Other disadvantages of surgical therapy are the expense associated with surgical correction, residual surgical scar and psychological trauma to the patients an d/or the parents. Because of these reasons Atrial Septal Defect – A Review 9 several trans-catheter methods have been developed (Chopra and Rao, 2000; Rao, 2003) which will be reviewed in the next section.

At the present time, surgical repair is largely reserved for defects with poor septal rims in which the interventional cardiologist deems th at defect is difficult to close with transcatheter methodology or was unsuccessful in clos ing the defect. Also, if intra-cardiac repair of other defects is contemplated, surgical closure of ASD could be performed at the same time. 2.4.4 Trans-catheter closure As alluded to above, a large number of device s have been developed over the last three and one-half decades. Some of the devices have been discontinued and others modified and redesigned (Rao, 1998; Rao, 2000; Rao, 2003b). C linical trials have been undertaken with a large number of devices as reviewed elsewhere (Rao, 2000; Rao, 2003b) and feasibility, safety and effectiveness of these devices in occluding the ASD have been demonstrated. Clinical trials have been undertaken in a large number of patients with Bard clamshell septal occluder and buttoned device and feasibility an d effectiveness of these devices in occluding the ASD have been demonstrated. Fractures of one or more arms of the clamshell device with occasional embolization, has prompted the investigators and th e US Food and Drug Administration (FDA) to withdraw the device from clinical trials. The buttoned device has undergone clinical trials and, immediate and short-term follow-up results are encouraging (Rao et al 1992, Rao et al 1994, Rao et al 2000, Rao and Sideris 2001). However, pre-marketapproval (PMA) application was not made and consequently it is not approved by the FDA and is not available for general clinical use.

Subsequently, a large number of other devices (Das Angel-Wing, ASDOS, Amplatzer, CardioSeal, HELEX and others) have been introduced and clinical trials began (Chopra and Rao 2000). At the present time however, Amplatzer Septal Occluder and HELEX are th e only two devices that are approved for general clinical use by the FDA. The experience with Amplatzer for most defects has been encouraging. HELEX device is only useful in small to medium-sized defects. A number of other devices are in clinical trials either in the US or in other co untries with local, national or regional IRB supervision. These devices, to the best of my knowledge, are CardioSeal/StarFlex devices, transcatheter pa tch, pfm ASD-R device, bio-absorbable NMT devices (Bio-STAR and Bio-TREK), Occlutech Flex device, Cardia devices (INTRASEPT, ATRIASEPT I/II-ASD and ULTRASEPT), Solysafe Septal Occluder, Heart R Septal Occluder (manufactured in China) and others. The Ampl atzer Septal Occluder is rapidly becoming the device of choice because of ease with which the device can be implanted, retrieved and repositioned plus the comfort that the device is FDA approved. 2.4.4.1 Amplatzer septal occluder Amplatzer septal occluder is a double disk de vice constructed with 0.004" to 0.007" Nitinol (nickle-titanium compound) wire with shape memory. A 4 mm wide waist connects the left and right atrial disks and stents th e ASD. The left atrial disk is slightly larger than the right. Dacron polyester patches are sewn into each disk. Multiple sizes are available from the manufacturer (AGA); the device size is expre ssed as the size of waist of the device. The device can be withdrawn into a delivery sheath and can be implanted across the defect and if necessary pulled back into the sheath and repositioned.