As viewed from the right atrial side (see Fig. 1.2 in Chapter 1 ), the normal atrial septum may have defects in almost any location ( Box 29.1 ). Although the morphology of these defects has been known since the early descriptions by Robitansky in 1875, the advent of open heart surgery emphasized their surgically important aspects.

Typically in ASD and related conditions, the right atrium is greatly enlarged (at least grade 3 or 4 on a scale of 1 to 6) and thick walled. The left atrium is not enlarged. This discrepancy occurs in the absence of any flow or pressure restriction between the two, speculatively because the right atrial wall is more distensible than the left.

Right ventricular (RV) diastolic size is increased, often greatly, because of volume overload imposed by the left-to-right shunt. Whereas normal RV diastolic dimensions are between 0.6 and 1.4 cm · m ² , in patients with large left-to-right shunts at atrial level, they average 2.66 cm · m ² and may be as large as 4 cm · m ² . Consequently, the cardiac apex is often formed by the right ventricle.

Morphologically, the left ventricle is normal or slightly decreased in size. However, important left ventricular (LV) dynamic abnormalities are present in most patients (see “ Mitral Prolapse ”).

Pulmonary arteries are considerably dilated and elongated when pulmonary blood flow is increased. This dilation involves even the smallest branches, which tend to compress the smaller airways, with resultant retention of secretions and bronchiolitis.

Hypertensive pulmonary vascular disease develops infrequently in patients with ASD, and then usually not until the third or fourth decade of life (see “ Pulmonary Vascular Disease ” under Morphology in Section I of Chapter 33 ). This contrasts sharply with ventricular septal defects (VSDs), complete AV septal defects, and patent ductus arteriosus, in which pulmonary vascular disease may be present early in life. In ASD, pulmonary vascular disease is caused mainly by secondary thrombosis in the dilated pulmonary artery branches, with changes in the intima and media of vessels usually playing a minor role. Haworth has suggested, however, that an increase in pulmonary arterial smooth muscle may be the only finding.

ASDs and related conditions may coexist with almost all varieties of congenital heart disease, but such cases are not considered here unless the left-to-right shunt at atrial level is the dominant hemodynamic lesion. A wide spectrum of cardiac anomalies coexist with ASD as the dominant lesion ( Table 29.1 ).

Valvar heart disease may coexist with hemodynamically important ASDs. Six cases with moderate or severe rheumatic mitral stenosis and a hemodynamically significant ASD (Lutembacher syndrome) were observed among 443 patients with an ASD at Green Lane Hospital (GLH) (1957-1983). Eleven cases of moderate or severe mitral regurgitation were observed; in three, regurgitation was rheumatic in origin. Both mitral stenosis and regurgitation increase left-to-right shunting.

Tricuspid regurgitation of variable severity frequently complicates ASDs in older patients with heart failure, the mechanism generally being RV and tricuspid anular dilation.

Rarely, ASD may occur in patients with Marfan, Turner, Noonan, or Holt-Oram syndromes.

Left-to-right shunting across a nonrestrictive (>2 cm in an adult) ASD under ordinary circumstances is a function of the relative compliance (reflected in the diastolic pressures) of right ventricles and left ventricles. RV compliance in particular is unpredictable and is one factor causing variability in Q ˙ p/ Q ˙ s . A compliant distensible right ventricle (in association with a normal pulmonary vascular bed) will permit a large shunt; a less compliant one (such as may result from pulmonary hypertension or from morphologic RV changes occurring later in life ^, ) permits a more modest shunt. LV compliance tends to decrease with age, which tends to increase Q ˙ p/ Q ˙ s as patients become older. Shunting is increased by systemic hypertension when this results in decreased LV compliance.

Mitral regurgitation or stenosis increases Q ˙ p/ Q ˙ s . When the ASD is small and flow is restrictive, left-to-right shunting is limited. Even then, mitral stenosis may elevate left atrial pressure sufficiently that a large left-to-right shunt through all phases of the cardiac cycle results, leading to a soft continuous murmur.

Symptoms may be absent for several decades, but when they occur, they consist of effort breathlessness and a tendency toward recurrent respiratory tract infections. Palpitation from paroxysmal atrial tachycardia or atrial fibrillation may occur later in life. Older adults may present with chronic heart failure with fluid retention, hepatomegaly, and severe cardiac cachexia. Occasionally an infant with ASD and a large left-to-right shunt, often in association with PAPVC, may have heart failure with tachypnea, but this is uncommon. In such infants, other associated malformations may contribute to the heart failure.

Atypical presentations occur. Rarely, an unequivocal history of cyanosis may bring a patient with an uncomplicated ASD to medical attention. ^{, ,} For example, a large fossa ovalis ASD extending to the IVC may cause streaming of blood from the IVC into the left atrium, with resultant cyanosis. This coincides with occasional bidirectional shunting in patients with otherwise uncomplicated ASDs, usually older patients. For the same anatomic reasons (see “ Morphology ,” earlier), patients may present with paradoxical emboli or cerebral infarctions. This presentation occurred in 9 (2%) of a Mayo Clinic series of 546 patients. Infrequently the presentation may be modified by presence of severe pulmonary hypertension, in which case cyanosis, effort intolerance, and hemoptysis may be present.

Clinical signs diagnostic of a large shunt at the atrial level ( Q ˙ p/ Q ˙ s >1.8 to 2.0) are:

• •

  Overactive left parasternal systolic lift

• •

  Fixed splitting of the second heart sound throughout the respiratory cycle (absent when large Q ˙ p/ Q ˙ s is from PAPVC with an intact atrial septum)

• •

  A soft pulmonary midsystolic flow murmur (in second and third left intercostal spaces)

• •

  A mid-diastolic tricuspid flow murmur (in fourth and fifth left intercostal spaces) present in borderline situations only on inspiration

This last sign is occasionally absent, however, particularly in older patients and in those with a larger shunt.

In addition, an extremely large shunt produces a more marked left-sided precordial RV lift, occasionally some prominence of the left anterior chest wall, and leftward displacement of the cardiac apex. Many such patients are short and thin. When heart failure is present, jugular venous pressure is elevated, the liver is enlarged, and there is gross cardiomegaly.

Tricuspid regurgitation produces systolic liver pulsation and a greater tendency to ascites and peripheral edema. Important pulmonary hypertension is evident clinically by accentuation of the second heart sound and a more marked RV and pulmonary artery lift. A pulmonary regurgitation murmur may be heard, as well as a murmur of tricuspid regurgitation.

Chest radiography reflects the large Q ˙ p/ Q ˙ s . The right atrium and right ventricle are large. The pulmonary trunk shadow in the upper left portion of the cardiac silhouette is enlarged, and right and left pulmonary arteries are enlarged to the periphery of the lung field. In general, pulmonary vascular markings are increased, or plethoric. The shadow of the transverse aortic arch is abnormally small. Patients with heart failure may have interstitial pulmonary edema and areas of pulmonary consolidation and atelectasis. These signs are probably secondary to compression of smaller airways by enormously enlarged small pulmonary vessels.

The chest radiograph may suggest the specific anatomic diagnosis. Occasionally the right superior pulmonary vein can be identified lying more superiorly than normal leading to suspicion of sinus venosus syndrome. A crescentic shadow more or less parallel to the right-sided heart border suggests the diagnosis of anomalous pulmonary venous connection of right pulmonary veins to IVC (scimitar syndrome).

Electrocardiogram (ECG) almost always shows the pattern of incomplete right bundle branch block and a clockwise frontal loop. Left axis deviation and a counterclockwise loop strongly suggest an AV septal defect, although this pattern occurs in about 10% of patients with fossa ovalis ASDs.

Clinical diagnosis of ASD, particularly of the foramen ovale type, can be confirmed by visualizing the defect directly using two-dimensional echocardiography. ^{, ,} Echocardiography also gives indirect evidence of ASD in demonstrating RV volume overload, which includes increased RV diastolic size and abnormal (flat or paradoxical) septal motion. ^, Assessing pulmonary veins with transesophageal echocardiography (TEE) is feasible. However, the clear identification of anatomic variations might be challenging. More often these sinus venosus defects can be detected by transthoracic echocardiography (TTE) or computed tomography (CT). TEE also can localize fossa ovalis defects to the high, low, or posterior septum. AV septal defects can be separated from secundum defects, and localization of subcaval defects and anomalous pulmonary venous connection is usually possible. Addition of Doppler color flow interrogation allows a reasonable estimate of Q ˙ p/ Q ˙ s .

Limitations of echocardiography in delineating anomalous pulmonary venous connection can be largely overcome with magnetic resonance imaging (MRI). Anatomic detailing of pulmonary venous connection and calculation of Q ˙ p/ Q ˙ s are generally reproducible.

When diagnosis of a typical and apparently uncomplicated ASD has been made by noninvasive methods in children, adolescents, and young adults, cardiac catheterization is not required. The surgeon then becomes responsible for confirming the type of ASD at operation and presence or absence of any anomalous pulmonary venous connections. Cardiac catheterization and appropriate cineangiography are indicated in infants (because of possible associated anomalies), in many adults (for assessing possible pulmonary hypertension and status of mitral valve), and in any patient in whom noninvasive tests suggest PAPVC. Coronary angiography is performed in patients older than 35 to 40 years.

Assessment of operability in patients with pulmonary hypertension is particularly challenging. Even in Eisenmenger syndrome with shunt reversal at atrial level, pulmonary artery pressure (P pa ) is rarely more than two thirds that of systemic pressure.

The most reliable criterion of inoperability is the absolute level of pulmonary vascular resistance normalized to body surface area (pulmonary vascular resistance index [PVRi]) and calculated when possible using measured, rather than assumed, oxygen uptake. Q ˙ p/ Q ˙ s or resistance ratios are much less discriminating. A PVRi >8 WU · m² precludes complete operative closure. In this event, PVRi must also be calculated while using a pulmonary vasodilator. (For testing of acute pulmonary vascular reactivity, use inhaled nitric oxide (NO), oxygen (O ₂ ), aerosolized iloprost, or combinations of these substances. )

If arterial desaturation (<97%) exists when measured by the usual finger sensor, cardiac catheterization is indicated in both adults and children. Interventions such as 100% O ₂ , exercise, and NO are appropriate to gauge pulmonary vascular reactivity, response of pulmonary vascular resistance, and reversion to a strictly left-to-right shunt condition. If arterial oxygen saturation (Sa o ₂ ) increases to normal levels and pulmonary vascular resistance falls, operation can be done even in the presence of intermittent arterial desaturation (right-to-left shunt).

A vasodilator must produce a fall in PVRi to below 7 WU · m ² before the patient can be considered operable, ^, because only then can pulmonary vascular disease be expected to regress. Otherwise, disease is likely to progress despite closure of the ASD. Progressive pulmonary vascular disease is less well tolerated when the atrial septum is intact, because the right side of the heart is then unable to decompress through a right-to-left shunt at atrial level; thus, ASD closure under such circumstances usually decreases life expectancy.

Cardiac catheterization and angiography are also useful in defining anatomic details of related conditions that can cause shunting at the atrial level. Increased Sa o ₂ in the low SVC provides presumptive evidence of sinus venosus syndrome, and this becomes virtually certain if the catheter can be passed through a subcaval ASD into the left atrium. An indicator dilution curve obtained after injecting dye into the SVC may show some right-to-left shunting, which is generally completely absent in patients with a fossa ovalis ASD (who may have right-to-left shunting from the IVC). In addition, curves obtained after injection into the right pulmonary artery generally show a much larger left-to-right shunt, a result of the anomalously draining right pulmonary veins, than curves obtained after injection into the left pulmonary artery.

Identification of the specific anatomic details of sinus venosus syndrome is best accomplished by angiography after right pulmonary artery injection, because the typical location and drainage of the right superior pulmonary vein can then be seen. Pulmonary artery injection may confirm anomalous connection of the right pulmonary veins to the right atrium or IVC, of left veins to brachiocephalic or other veins, or of bilateral anomalous pulmonary venous connections. When anomalous connection of the right pulmonary veins to the IVC is demonstrated, aortography should also be done to identify any anomalous systemic arteries from the abdominal or thoracic aorta to the right lower lobe. If the right lung is small, if the right lower lobe is contracted or seems otherwise abnormal on chest radiography, or if the patient gives a history of hemoptysis or recurrent pulmonary infections, bronchoscopy or bronchography is also indicated.

Calculations of Q ˙ p/ Q ˙ s are of particular importance in patients with isolated PAPVC of only part of one lung. An operation is not indicated when the ratio is less than 1.8 (see “ Indications for Operation ” later in this chapter). This approach is especially relevant with isolated connection of some of the right upper lobe veins to the high SVC, because diversion or transfer to the left atrium is quite difficult (and probably needless). Even when only the right superior pulmonary vein is involved and the atrial septum is intact, the shunt may be greater than this, presumably because right atrial and caval pressures are distinctly lower than left atrial pressures, producing a larger-than-usual pulmonary venous gradient.

In 1970, Campbell published the most detailed study available on survival of patients with ASD treated nonsurgically. Transformation of these findings into conventional survival format and comparison with life expectancy of the general population provide good insight into the life expectancy of patients with ASD ( Fig. 29.7 ). Campbell’s data support the idea that only 0.1% of individuals born with a large ASD and no other important cardiac anomaly die in infancy, and that few who are unrepaired die in the first or second decade. About 5% to 15% die in the third decade, usually with pulmonary hypertension and Eisenmenger syndrome. Premature late death with heart failure occurs in an increasing proportion after the fifth decade. Even so, probably no more than 25% of persons born with a large ASD die from the defect, because lethal manifestations of the disease tend to occur so late in life that other unrelated conditions cause death first.

Plot of Campbell’s survival computations of life expectancy for surgically untreated patients with ASDs who reach age 1 year, based on three sets of collected data. Spread among the data sets indicates confidence limits of modest width around point estimates (confidence limits cannot be calculated from data). Life expectancy of the general population at age 1 year is also from Campbell and is close to that computed from US life tables. Data suggest that 99.9% of patients born with ASD reach the first year of life unless unrelated conditions cause their death.

(From Campbell M. Natural history of atrial septal defect. Br Heart J . 1970;32:820.)

The natural history of patients with sinus venosus syndrome and most other types of PAPVC and ASD ^, is similar to that of patients with large fossa ovalis ASD. Patients with sinus venosus syndrome in the fourth to sixth decades present with heart failure or severe pulmonary hypertension from pulmonary vascular disease. Untreated patients with a scimitar syndrome have a high overall survival, which is significantly lower when the defect is associated with an associated congenital heart defect or pulmonary hypertension. Many patients are incidentally diagnosed and remain asymptomatic or mildly symptomatic for many years. ^, Presumably, patients without important anomalies of the right lung and with a large left-to-right shunt have a life history similar to patients with a large fossa ovalis ASD. Those with right lung hypoplasia, however, often have a life history dominated by their pulmonary pathology, including hemoptysis and recurrent pulmonary infections. When there is isolated PAPVC of part of one lung and is less than Qp:Qs of 1.8, life expectancy may be normal. Rarely, paradoxical emboli occur in patients with sinus venosus syndrome (from SVC) as well as in those with fossa ovalis ASDs (from IVC).

In a surgical series from the University of Alabama at Birmingham (UAB), 14% of patients catheterized had pulmonary hypertension with mean P pa greater than 25 mmHg. In a GLH surgical series, systolic P pa was greater than 50 mmHg in 13% of catheterized patients and 11% of the total series. Prevalence of elevated PVRi (≥4 WU · m ² ) was 4.5%, and rare (1%) in patients younger than 20 years of age. In a few high-altitude locations, however, prevalence of pulmonary hypertension is greater. Cherian and colleagues reported that in their region of India, pulmonary hypertension was present in 13% of patients younger than age 10. Pulmonary hypertension is particularly prevalent in patients with scimitar syndrome, partly due to increased pulmonary blood flow but also to stenosis of the anomalous vein, presence of systemic arterial collaterals to the right lung, or reduction of the pulmonary vascular bed on the right side.

Probably only about 1% of patients born with a large ASD have symptoms during the first year. Most are asymptomatic through the first and second decades, although many are short and thin. Effort intolerance and easy fatigability may develop in the second or third decade or as late as the fifth or sixth decade. These symptoms progress gradually to fluid retention, hepatomegaly, and elevated jugular venous pressure, leading to gradually increasing disability. These phenomena are well exemplified in the surgical experience, in which preoperative New York Heart Association (NYHA) functional class and age at operation are moderately well correlated ( r =.61, P <.05) ( Table 29.2 ). When heart failure becomes advanced, both mitral and tricuspid regurgitation are likely to have developed.

Spontaneous closure of an isolated ASD occasionally occurs. Studies revealed a dependence on defect size and age. Defects smaller than 6 mm in diameter are very likely to close spontaneously (up to 90%), while defects larger than 8 mm have a high probability for the need of surgical closure. Spontaneous closure of a hemodynamically significant isolated ASD occasionally occurs in the first year. Cockerham and colleagues found closure in 22% of 87 patients up to the age of 4 years and Ghisla and colleagues in 14%. Smaller left-to-right shunts were present in patients whose defects spontaneously closed than in those whose did not.

As already noted, decreasing LV compliance increases Q ˙ p/ Q ˙ s in patients with ASD, and this may develop during the fifth and sixth decades. Systemic arterial hypertension accelerates this process and may unmask an ASD that was not an important shunt before onset of decreased LV compliance. It is also likely that most ASDs increase in size as time passes; this has been clearly demonstrated in the case of patent foramen ovale. The direct relationship between Q ˙ p/ Q ˙ s and the tendency toward mitral valve prolapse also support the concept that the shunt increases with age. These increases in Q ˙ p/ Q ˙ s with time do not occur when the shunt is due to anomalous pulmonary venous connection without ASD. Q ˙ p/ Q ˙ s decreases when pulmonary hypertension develops, a result of decreased RV compliance that accompanies RV hypertrophy (see “ Determinants of Interatrial Shunting ” under Clinical Features and Diagnostic Criteria).

RV volume overload and consequent increased RV diastolic dimensions are characteristic of patients with a hemodynamically significant ASD or PAPVC. The ventricular septum is displaced posteriorly and leftward under such circumstances, but systolic anterior motion of the septum occurs. ^, These features are well tolerated by the right ventricle for many years, much longer than for the volume-overloaded left ventricle and probably longer than for volume overload produced by acute tricuspid or pulmonary valve regurgitation. RV failure eventually occurs, however, with decreased RV ejection fraction and hypokinesia. Doty and colleagues demonstrated loss of coronary reserve in patients with ASD and volume-induced RV hypertrophy, which contributes further to development of RV failure. Associated signs and symptoms of elevated systemic venous pressure then develop (peripheral edema, elevated jugular venous pressure, hepatomegaly, and finally ascites), often with tricuspid regurgitation.

These RV phenomena have been documented by several studies. Liberthson and colleagues found increased RV volume but normal (64%) ejection fraction in 9 asymptomatic patients with a mean age of 25 years. However, 11 symptomatic patients with a mean age of 52 years had diffuse RV hypokinesia and ejection fraction averaging 36%, in addition to increased RV volume. In a possibly related finding, adult patients with ASD but without pulmonary hypertension occasionally have marked pulmonary valve regurgitation, which disappears after ASD repair.

Most adult patients with hemodynamically significant ASD or PAPVC have normal LV systolic dimensions but subnormal diastolic dimensions. ^{, ,} Some loss of LV functional reserve is present in most adult patients and in some children with ASD. In contrast to normal persons, such individuals do not increase LV ejection fraction during maximal exercise ( Fig. 29.8 ), although resting ejection fraction is usually within normal limits. ^, These preoperative LV abnormalities likely result from effects of the volume-overloaded right ventricle. Even in the absence of symptoms of systemic venous hypertension from RV failure, LV structure and function are influenced by increased RV volume rather than changes in LV compliance. ^{, ,}

Left, Normal response of increased left ventricular ejection fraction with maximal exercise. Right, In contrast, adult patients with atrial septal defects generally do not increase ejection fraction with maximal exercise. NS, Not significant.

(From Bonow RO, Borer JS, Rosing DR, Bacharach SL, Green MV, Kent KM. Left ventricular functional reserve in adult patients with atrial septal defect: pre- and postoperative studies. Circulation . 1981;63:1315.)

As discussed earlier, important mitral regurgitation is present in 2% to 10% of adults with large ASDs, and both mitral and tricuspid regurgitation may become prominent in older patients who develop heart failure. When viewed at operation, the tricuspid valve does not appear to be intrinsically abnormal. Presumably, regurgitation develops because of anular dilation and lack of proper shortening of the tricuspid anulus during systole, secondary to RV enlargement resulting from long-standing volume overload. ^,

After the third decade, supraventricular arrhythmias complicate the natural history of patients with large ASDs and related conditions in increasing numbers over time. Most often this begins with paroxysmal atrial fibrillation, which gradually becomes permanent. Atrial fibrillation was present in 15 (20%; CL 15%–26%) of 75 patients over age 40 operated on by Magilligan and colleagues. Of 19 patients preoperatively in NYHA class III or IV, 47% (CL 34%–64%) had this arrhythmia, compared with 11% (CL 6%–17%) of 56 patients in class I or II. St. John Sutton and colleagues found that 56% of their patients over age 60 had atrial fibrillation at operation.

In addition, more subtle abnormalities of conduction system function develop. Benedini and colleagues found concealed sinus node dysfunction in 17 (65%; CL 53%–76%) of 26 adult patients with fossa ovalis ASD, which became evident only with electrophysiologic testing. Such abnormalities are less common in children with ASDs.

Adult patients with hemodynamically important ASDs are likely to have systemic arterial hypertension. In a Mayo Clinic study, 25 (38%) of 66 patients had systemic arterial blood pressure above 150/90, a higher proportion ( P <.01) than an age-matched general population. As noted, this relationship may result partly from the effect of hypertension on shunt size.

Anesthesia management, patient positioning and preparation, median sternotomy, and preparations for CPB are discussed in detail in Section III of Chapter 2 and in Chapter 4 . An alternative to a midline skin incision may be used for aesthetic reasons. In this approach, a right-fifth intercostal subaxillary skin incision is made. ASD repair can also be performed using a small inferior ministernotomy approach or a small anterior right submammary minithoracotomy ( Figs. 29.9 and 29.10) . Each requires modification of the configuration for caval cannulation (see Section III in Chapter 2 ).

3D reconstruction of a chest and heart in a patient with normal cardiac anatomy, showing the three approaches used in minimally invasive cardiac surgery. (A) Lower ministernotomy (orange dotted line). (B) Right anterior minithoracotomy, performed in the fourth intercostal space at the anterior axillary line (blue dotted line). (C) Right lateral minithoracotomy, performed at the middle axillary line in the fourth intercostal space (light green dotted line) or in the fifth intercostal space (dark green dotted line).

Postoperative pictures of surgical approaches used in minimally invasive cardiac surgery. (A) Lower ministernotomy; (B) Right anterior minithoracotomy; (C) Right lateral minithoracotomy (axillary).

In children and young adults with uncomplicated ASD, routine placement of a catheter to monitor left atrial pressure is usually unnecessary, but such monitoring should be done routinely in older patients whose left atrial pressure may be significantly higher than the right atrial pressure after repair.

After the incision is made and pericardial stay sutures are placed (which can be tunneled outside of the chest cavity with cannulae to augment the direct vision through the incision, Fig. 29.11 ), the intrapericardial anatomy is assessed. The characteristically large right atrium and right ventricle are noted, as well as the normal-sized left atrium and left ventricle. The external position and connections of the right superior and inferior pulmonary veins are noted. Optimally, TEE is available to establish the position of the ASD, relationship of the pulmonary veins, and function of the mitral and tricuspid valves.

(A) Stay stitches on the pericardium that are passed through the chest wall (upper corner) to evert the pericardium (B) for achieving a better view of the surgical field (especially during minimally invasive procedures).

The patient is heparinized and peripheral cannulation is typically employed through a femoral incision when a minimally invasive approach is implemented. The SVC can be cannulated either percutaneously in the internal jugular vein or directly with an angled or straight cannula. CPB is established, with the perfusate temperature at 34°C. The cardioplegic needle or aortic root catheter is placed in the ascending aorta, the aorta clamped, and cold cardioplegic solution injected. Alternatively induced ventricular fibrillation can be used. Rewarming of the patient with the perfusate is begun once the heart is cold and isolated. The caval tapes are “snugged,” and the right atrium is opened obliquely ( Fig. 29.12 ). A left atrial suction catheter is not inserted through the left atrial wall in fossa ovalis ASD, because it is unnecessary and imposes a remote risk of cerebral air embolism.

Internal anatomy of a fossa ovalis (secundum) atrial septal defect as seen through usual atrial incision. Sinus node is lateral at cavoatrial junction at superior aspect of crista terminalis. Anterior inferior rim of defect lies near atrioventricular (AV) node, which lies in the muscular portion and just inferior to membranous portion of AV septum. ASD, Atrial septal defect; IVC, inferior vena cava; SA, sinoatrial; SVC, superior vena cava.

A few fine stay sutures are placed on the edges of the atriotomy incision. Blood in the left atrium is suctioned only enough to clearly expose the edges of the ASD; evacuation of more blood than this from the left side of the heart needlessly exposes the patient to risk of air entrapment and subsequent air embolization. An exception to this policy is presence of mitral valve pathology.

The entire right atrial internal anatomy is examined, particularly identifying the limbus and defining any rim of the ASD. The relationship of the defect to the ostium of the coronary sinus, membranous portion of the AV septum, and commissural area between the septal and anterior tricuspid leaflets is studied because these features serve as guides to the location of the AV node and penetrating portion of the bundle of His (see Fig. 29.12 ).

Possible fenestrations in the valve (floor) of the fossa ovalis are sought; these are usually between the fossa ovalis and limbus anteriorly or near the IVC inferiorly. When present in thin tissue, fenestrations may be joined to the main defect by excising sufficient tissue to create an edge strong enough to hold sutures well, or the fenestrated tissue simply may be imbricated into the suture line.

Usually, the fossa ovalis ASD is closed directly (see “ Direct Suture Versus Patch Repair ” under Special Situations and Controversies later in this chapter). The suturing is usually begun at the inferior rim of the ASD. Care is taken to catch good, substantial anterior and posterior limbic tissue with the first and last bites of this stitch ( Fig. 29.13 ), which must be inferior to any remaining fenestrations. Great care is taken to avoid confusing the eustachian valve of the IVC with the remnant of the floor of the fossa ovalis. Such an error results in connecting the IVC to the left atrium, which can occur when the operation is done under circulatory arrest and there is no IVC cannula, or when direct caval cannulation is used. The suture line is then carried superiorly, catching tough limbic tissue anteriorly and posteriorly. To avoid damaging the AV node, the sutures must not be placed too far from the edge anteriorly.

Repair of fossa ovalis ASD. (A) Usual oblique right atriotomy is made and retracting sutures placed. (B-C) After exposure is arranged and all structures examined (orifices of pulmonary veins, valve of inferior vena cava [eustachian] coronary sinus), the first sutures are taken as a half purse-string stitch. If ASD extends to inferior vena cava (IVC), initial sutures are placed in floor of the IVC; eustachian valve of the IVC must be noted so that it is not erroneously included. (D) After first set of stitches is tied, ASD becomes slitlike. (E) Before last stitch is tied, anesthesiologist places positive pressure on lung to express air from left atrium. (F) Completed repair. CS, Coronary sinus; RSPV, right superior pulmonary vein.

Before the last few stitches are pulled up, a clamp or tissue forceps is placed in the aperture, and the anesthesiologist inflates the lung to expel any air from the left atrium. The suture line is snugged while lung inflation is maintained, and an additional bite is taken with the stitch, which is then tied. After the right atrium is sucked dry, once again the lungs are inflated to drive through left atrial blood and thus identify any defects in the suture line. If seen, defects are closed with interrupted sutures. Generally, the clamp has been in place about 10 minutes or less for this procedure. Strong suction is placed on the aortic needle vent, and the aortic clamp is removed or induced ventricular fibrillation is discontinued. The right atrium is then closed. The caval tapes are released.

After good cardiac action has developed, usual de-airing procedures are carried out (see “ De-airing the Heart ” in Section III of Chapter 2 ). Atrial wires are placed routinely or may be omitted in young patients. CPB is now discontinued, with care taken not to overdistend the left side of the heart in the process. Even when a left atrial catheter is not left for the postoperative period, left atrial pressure is measured at this time (or estimated by palpation of the pulmonary artery) and noted to be 5 to 15 mmHg higher than right atrial pressure. This increase is related to small size and decreased compliance of the left ventricle compared with that of the right ventricle (see “ Determinants of Interatrial Shunting ” under Clinical Features and Diagnostic Criteria in this chapter and “Relative Performance of Left and Right Ventricles” under Cardiac Output and Its Determinants in Section I of Chapter 4 ). The remainder of the operation is completed as usual.

If the anomaly is a pure posterior ASD, closure by direct suture is possible in a manner similar to that described in the previous text. If the posterior ASD is confluent with a fossa ovalis ASD, the defect may be too large for direct closure. Then a patch of pericardium (autologous or heterologous), knitted polyester velour, or polytetrafluoroethylene (PTFE) is used.

Because coronary sinus ASDs are close to the AV node ( Fig. 29.14 ), stitches must be placed near the edge of the defect superiorly in tissue that may not be strong. For these reasons, patch closure is generally advisable. Additionally, when a coronary sinus ASD is identified, presence of a completely or partially unroofed coronary sinus must be ruled out (see Section II ). These defects are often associated with a left SVC. Inappropriate simple closure of the defect may result in a right-to-left shunt.

Repair of coronary sinus ASD. (A) Anatomy of coronary sinus ASD showing its proximity to atrioventricular (AV) node. ASD is closed with a patch sutured to edges of defect to avoid AV node, but only after surgeon is assured there is no unroofing of coronary sinus. If sinus is unroofed, a different type of repair is done by opening the atrial septum for better access (see Technique of Operation in Section II ). (B) Normal coronary sinus without ASD, diagrammed in transverse section. (C) Coronary sinus ASD associated with unroofed coronary sinus allowing left-to-right (and obligatory right-to-left) shunt. A large coronary sinus defect suggests an unroofed coronary sinus, whereas a small defect indicates an ASD. LA, Left atrium; SVC, superior vena cava.

Preparation and positioning of the patient are as usual. In this case, a right minithoracotomy is an alternative approach. The pericardium is cleared of pleural reflections bilaterally, and a large pericardial piece is removed and set aside between moist towels or in 0.6% glutaraldehyde. Alternatively, a PTFE patch is used. Stay sutures are placed and the anatomy examined. The right superior pulmonary vein is easily seen attached to the low SVC or SVC–right atrial junction. At this point, the pulmonary vein (or veins) should be differentiated from the azygos vein, which is slightly more cephalad and directed more medially. Size of the SVC is noted, as is the possible presence of a left SVC, in which case the right-sided SVC is likely to be small. The right atrium and right ventricle are usually considerably enlarged.

If approached through a sternotomy, purse-string sutures are inserted, including those for direct caval cannulation. SVC cannulation purse-string sutures are placed on the anterior aspect of the SVC well above the entry point of the anomalous connection of the right superior pulmonary vein.

If approached through a right minithoracotomy, peripheral cannulation is generally employed through a femoral incision. The SVC can be cannulated either percutaneously in the internal jugular vein or directly with an angled or straight cannula. This allows cannulation of the upper part of the SVC in case of a PAPVC is present.

CPB is then established, the aorta clamped, and cold cardioplegia infused (see “ Cold Cardioplegia, Controlled Aortic Root Reperfusion, and [When Needed] Warm Cardioplegic Induction ” in Chapter 3 ). The caval tapes are secured. In infants, repair may be done with a single venous cannula and hypothermic circulatory arrest. When the aorta is clamped, the perfusate temperature is stabilized at 34°C.

When configuration of the superior pulmonary vein is usual and the SVC–right atrial junction is wide, the right atrium is opened through the usual oblique incision beginning at the base of the right atrial appendage and extending down toward the IVC cannula ( Fig. 29.15 ). This does not damage the sinoatrial node or its artery. Stay sutures are placed. A pump sump-sucker is placed across the foramen ovale into the left atrium (or through a stab wound), or no left atrial vent may be used. The repair directs pulmonary venous drainage through the ASD into the left atrium while closing the interatrial communication (see Fig. 29.15 ). A pericardial baffle forms approximately the anterior half of this internal conduit. Width of the pericardial patch should be about 1.5 times the diameter of the ASD, and length about 1.25 times the estimated length of the distances from the superior edge of the anomalous vein to the inferior edge of the ASD. This ensures an adequate pulmonary venous pathway and does not obstruct the SVC. In some cases, the ASD can be enlarged down to the fossa ovalis to ensure unobstructed drainage.

Repair of sinus venosus malformation, which typically consists of subcaval ASD associated with partial anomalous pulmonary venous connection of right superior pulmonary vein (RSPV) to low superior vena cava (SVC). (A) Usual atriotomy is away from sinus node. (B) Incision can be extended superiorly and medially to sinoatrial node. Subcaval ASD is superior to limbus. At times the SVC overrides the defect to drain in part directly into left atrium. ASD is far removed from tricuspid valve and atrioventricular node. First stitches for inserting pericardial patch are shown at right lateral edge of SVC orifice at its junction with laterally placed orifice of RSPV. Patch is sewn into place with continuous 4-0 or 5-0 polypropylene suture. Suture line continues medially in an anterior and posterior direction to form a tunnel or roof leading the anomalous RSPV through ASD. (C) Convex roof of tunnel has been completed, and blood from anomalously connected RSPV drains beneath this roof into left atrium. Pathway from SVC to right atrium is unobstructed. When SVC is cannulated directly, exposure is good through this incision, and augmentation of the atrial closure is not necessary. (D) Transverse section through repair seen from below.

After the ASD is repaired, the sump (if used) is removed, and the created defect closed. Rewarming is begun, and with suction on the needle vent in the ascending aorta, the aortic clamp is released. The right atriotomy is closed, and the operation is completed as usual (see “ Completing Cardiopulmonary Bypass ” in Section III of Chapter 2 ).

When the right superior pulmonary veins enter more cephalad in the SVC or when the SVC is small (as in the presence of bilateral SVCs), the single patch technique described earlier may require a long tunnel or create possible SVC obstruction, or both. In this case a second patch (“double patch technique”) is used to enlarge the cavoatrial junction. When the most superior pulmonary vein (PV) is far from the ASD, the Warden operation may be used ( Fig. 29.16 ). After extensive mobilization and division of the azygos vein, the SVC is divided cephalad to the anomalously connected right pulmonary veins. The central end is closed, and as a final step the distal end is anastomosed to the right atrial appendage either directly in smaller patients or with patch enlargement in older patients. Particular care is needed to completely excise all trabeculated muscle within the appendage and the associated pathway into the right atrial chamber. From within the right atrium, the inferior lip of the subcaval ASD is joined to the right atrial wall, anterior and lateral to the caval orifice. This closes the interatrial communication and diverts pulmonary venous drainage from the anomalously connected right pulmonary veins to the left atrium.

Warden operation for sinus venosus malformation with right upper and middle lobe pulmonary veins entering superior vena cava (SVC). (A) Right upper and middle pulmonary veins entering SVC. Right atrial appendage is amputated. (B) High SVC or innominate vein is cannulated. Dashed line indicates the transecting incision in SVC. (C) Cephalad end of transected SVC is anastomosed to amputated right atrial appendage. For mobilization, azygos vein is divided. (D) Small incision is made in right atrial wall. Lateral edge of SVC orifice is sutured to lower rim of subcaval ASD, or the pathway is completed with a pericardial or polytetrafluoroethylene patch. Cardiac end of transected SVC is closed. (E) Right pulmonary vein blood now flows (arrows) across the roofed ASD into left atrium. RA, Right atrium; RAA, right atrial appendage.

(From Warden HE, Gustafson RA, Tarnay TJ, Neal WA. An alternative method for repair of partial anomalous pulmonary venous connection to the superior vena cava. Ann Thorac Surg . 1984;38:601.)

The operation begins exactly as described for sinus venosus malformation, including opening the right atrium through the usual oblique incision. The interior of the right atrium is examined, anomalous connections of the right pulmonary veins and normal connections of the left pulmonary veins to the left atrium are confirmed, and any defects in the atrial septum are identified.

When the atrial septum is intact, repair can often be accomplished by making a longitudinal incision in it next to the atrial wall posteriorly and resuturing it to the lateral right atrial wall in front of the right pulmonary vein orifices. Alternatively, and particularly when geometry in the right atrium does not lend itself to this simple repair, the fossa ovalis and posterior limbic tissue may be excised and a pericardial, PTFE, or knitted polyester patch used for baffle reconstruction ( Fig. 29.17 ).

Repair of anomalous connection of right superior and inferior pulmonary veins to right atrium without atrial septal defect. (A) Right atrial incision is the usual oblique transverse one, and fossa ovalis and posterior limbus are excised. (B) Repair is made by replacing excised portion of atrial septum with a patch, sewn to right of (anterior to) the right pulmonary vein orifices. LA, Left atrium; RA, right atrium.

When an ASD is present, repair is similar. When the defect is large and of the fossa ovalis or confluent type, a patch similar to the one shown in Fig. 29.17 is used. Occasionally, and particularly when the associated ASD is posterior, repair by direct suture is possible.