Pulmonary

Any lesion that results in either increased pulmonary blood flow or pulmonary venous obstruction can cause increased pulmonary interstitial fluid with decreased pulmonary compliance and increased work of breathing.¹⁴ Patients with cyanotic heart disease have increased minute ventilation and maintain normocarbia.¹⁵ These patients have a normal ventilatory response to hypercapnia but a blunted response to hypoxemia that normalizes after corrective surgery and the establishment of normoxia.^16–18 End-tidal CO₂ underestimates arterial Paco₂ in cyanotic patients with decreased, normal, or even increased pulmonary blood flow.¹⁹

Although enlarged hypertensive pulmonary arteries or an enlarged left atrium can impinge on bronchi in children, this is rare in adults. Late-stage Eisenmenger syndrome can result in hemoptysis, and patients with Eisenmenger physiology and erythrocytosis can develop thrombosis of upper lobe pulmonary arteries.²⁰ Prior thoracic surgery could have injured the phrenic nerve with resultant diaphragmatic paresis or paralysis.

Scoliosis can occur in up to 19% of CHD patients, most commonly in cyanotic patients. It can also develop in adolescence, years after surgical resolution of cyanosis.²¹ The relative contributions of cyanosis and congenital cardiovascular defects versus early lateral thoracotomy remain unclear: Scoliosis occurs more commonly with open surgical versus interventional techniques but is nevertheless increased over the general population in children with coarctation or patent ductus who had percutaneous rather than open interventions.²² Scoliosis is rarely severe enough to impact respiratory function.

In an attempt to increase pulmonary blood flow, large collateral vessels originating from the aorta may have developed. These are sometimes embolized in the catheterization laboratory before thoracic surgery to prevent excessive intraoperative blood loss.

Hematologic

Hematologic manifestations of chronic CHD are primarily a consequence of longstanding cyanosis and incorporate abnormalities of both hemostasis and red cell regulation. Longstanding hypoxemia causes increased erythropoietin production in the kidney and resultant increased red cell mass. Because solely red cell production is affected, these patients are correctly referred to as erythrocytotic rather than polycythemic. There is, however, a fairly poor relation among oxygen saturation, red cell mass, and 2,3-diphosphoglycerate.²³ The oxygen-hemoglobin dissociation curve is normal or minimally shifted to the right. Most patients have established an equilibrium state at which they have a stable hematocrit and are iron replete. Some patients, however, develop excessive hematocrits and are iron deficient, causing a hyperviscous state. Iron-deficient red cells are less deformable and have been said to cause increased viscosity for the same hematocrit.²⁴ However, recently there is some conflicting evidence.²⁵ Symptoms of hyperviscosity are uncommon and typically develop only at hematocrits exceeding 65% provided the patient is iron replete. Iron deficiency also shifts the oxygen-hemoglobin dissociation curve to the right, decreasing oxygen affinity in the lungs.²⁶ Symptoms of hyperviscosity are listed in Box 20-3. Iron deficiency can be the result of misguided attempts to reduce the hematocrit by means of repeated phlebotomies.²⁷ The red cells in these patients may be hypochromic and microcytic despite the high hematocrit. Assessment of iron status is best done by measures of serum ferritin and transferrin rather than inferences from red cell indices.²⁷ Treatment with oral iron needs to be undertaken with care because rapid increases in hematocrit can result.

Symptomatic hyperviscosity is the indication for treatment to temporarily relieve symptoms. It is not indicated to treat otherwise asymptomatic increased hematocrits (generally hemoglobin > 20 and hematocrit > 65). Treatment is by means of a partial isovolumic exchange transfusion, and it is assumed that the increased hematocrit is not related to dehydration. Partial isovolumic exchange transfusion usually results in regression of symptoms within 24 hours. It is rare to require exchange of more than 1 unit of blood. Before surgery, phlebotomized blood can be banked for autologous perioperative retransfusion if required. Elective preoperative isovolumic exchange transfusion has decreased the incidence of hemorrhagic complications of surgery.^28,29

Hyperviscosity and erythrocytosis can cause cerebral venous thrombosis in younger children, but it is not a problem in adults, regardless of the hematocrit.²⁰ Protracted preoperative fasts need to be avoided in erythrocytotic patients because they can be accompanied by rapid increases in the hematocrit.

Bleeding dyscrasias have been described in up to 20% of patients. A variety of clotting abnormalities have been described in association with cyanotic CHD, although none uniformly.³⁰ Bleeding dyscrasias are uncommon until the hematocrit exceeds 65%, although excessive surgical bleeding can occur at lower hematocrits. Generally, higher hematocrits are associated with a greater bleeding diathesis. Abnormalities of a variety of factors in both the intrinsic and extrinsic coagulation pathways have been described inconsistently. Both cyanotic and acyanotic patients have been reported with deficiencies of the largest von Willebrand factor multimers, which have normalized after reparative surgery.³¹ Fibrinolytic pathways are normal.³²

The decreased plasma volume in erythrocytic blood can result in spuriously increased measures of the prothrombin and partial thromboplastin times, and the fixed amount of anticoagulant will be excessive because it presumes a normal plasma volume in the blood sample. Erythrocytic blood has more red cells and less plasma in the same volume. If informed in advance of a patient’s hematocrit, the clinical laboratory can provide an appropriate sample tube. Normalizing to a hematocrit of 45%, the amount of citrate added to the tube can be calculated as follows:

Platelet counts are typically normal or occasionally low, but bleeding is not due to thrombocytopenia. Platelets are reported per milliliter of blood, not milliliter of plasma. When corrected for the decreased plasma fraction in erythrocytic blood, the total plasma platelet count is closer to normal. That said, abnormalities in platelet function and life span have on occasion been reported.^33,34 Patients with low-pressure conduits (Fontan pathway) or synthetic vascular anastomoses are often maintained on antiplatelet drugs.

Cyanotic erythrocytotic patients have excessive hemoglobin turnover, and adults have an increased incidence of calcium bilirubinate gallstones. Biliary colic can develop years after cyanosis has been resolved by cardiac surgery.²⁰

A variety of mechanical factors can also affect excessive surgical bleeding in cyanotic CHD patients. These factors include increased tissue capillary density, increased systemic venous pressure, aortopulmonary and transpleural collaterals that have developed to increase pulmonary blood flow, and prior thoracic surgery. Aprotinin and ε-aminocaproic acid improve postoperative hemostasis in patients with cyanotic CHD.³⁵ The results with tranexamic acid have been mixed.³⁶

Renal

Some degree of renal insufficiency is not uncommon in adults with CHD, and the severity is a predictor of mortality. Moderate or severe renal dysfunction (estimated glomerular filtration rate < 60 mL/min/m²) carry a fivefold increased risk for death at 6-year follow-up compared with patients with normal glomerular filtration rate and a threefold increase over those with mild increases in glomerular filtration rate.³⁷ Renal dysfunction is particularly prevalent in cyanotic patients and those with poor cardiac function. Adult patients with cyanotic CHD can develop abnormal renal histology with hypercellular glomeruli and basement membrane thickening, focal interstitial fibrosis, tubular atrophy, and hyalinized afferent and efferent arterioles.³⁸ Cyanotic CHD is often accompanied by increases in plasma uric acid levels that are due to inappropriately low fractional uric acid excretion.³⁹ Decreased urate reabsorption is thought to result from renal hypoperfusion with a high filtration fraction. Despite the increased uric acid levels, urate stones and urate nephropathy are rare.⁴⁰ Although arthralgias are common, true gouty arthritis is less frequent than would be expected from the degree of hyperuricemia.³⁹ There appears to be an increased incidence of postcardiopulmonary bypass renal dysfunction in adults with longstanding cyanosis.⁴¹

Neurologic

Adults with persistent or potential intracardiac shunts remain at risk for paradoxic embolism. Paradoxical emboli can occur even through shunts that are predominantly left to right because during the cardiac cycle there can be small transient reversals of the shunt direction. It has been said that, unlike in children, adults with cyanotic CHD are not at risk for the development of cerebral thrombosis despite the hematocrit.^20,42 However, this assertion has been challenged by Ammash and Warnes,⁴³ who suggested an association of stroke not with red cell mass, but with iron deficiency and repeated venesection. Adults do, however, remain at risk for the development of brain abscess. A healed childhood brain abscess can provide the nidus for the development of seizures throughout life.

Prior thoracic surgery can result in permanent peripheral nerve damage. Surgery at the apices of the lungs is particularly associated with the risk for nerve damage. These operations would include Blalock–Taussig shunts, ligation of patent ductus arteriosus (PDA), banding of the pulmonary artery, and repair of aortic coarctation. Nerves that are susceptible to injury include the recurrent laryngeal nerve, the phrenic nerve, and the sympathetic chain. The incidence of migraine headaches is greater in adults with CHD compared with a control group with acquired heart disease (45% vs. 11%) and is increased in left-to-right, right-to-left, and no-shunt groups.⁴⁴

Vasculature

Vessel abnormalities can be congenital or iatrogenic. They can affect the suitability of vessels for cannulation by the anesthesiologist or measurement of correct pressures. These abnormalities are described in Table 20-3.

TABLE 20-3 Potential Vascular Access Issues

Pregnancy

The physiologic changes of pregnancy, labor, and delivery can significantly alter the physiologic status of women with CHD. Several texts are available that specifically discuss issues of the pregnant woman with CHD in more detail than is possible here,^45–47 and there has been a recent review of generic cardiac surgery in the parturient.⁴⁸ Management and clinical outcomes during pregnancy and delivery for several cardiac lesions are included under the later discussions of those lesions.

Although cardiac complications, spontaneous abortions, premature delivery, thrombotic complications, peripartum endocarditis, and poor fetal outcomes can occur,⁴⁹ successful pregnancy to term with vaginal delivery is possible for most patients with congenital defects.⁵⁰ High-risk factors for mother and fetus are shown in Box 20-4. Eisenmenger physiology is a particular risk factor. Up to 47% of cyanotic women have worsening of functional capacity during pregnancy.⁵¹ Hematocrits greater than 44% are associated with birth weights in less than the 50th percentile, and fetal death is about 90% or more with hemoglobin levels greater than 18 gm/dL or oxygen saturation less than 85%, with most losses in the first trimester. The increases in stroke volume and cardiac output during pregnancy can stress an already pressure-overloaded ventricle. The decrease in systemic vascular resistance that accompanies pregnancy is better tolerated by women with regurgitant lesions and typically offsets the added insult of pregnancy-related hypervolemia. The decrease in systemic vascular resistance can, however, increase right-to-left shunting. Hypervolemia can be problematic in patients with poor ventricular function. Maternal cyanosis is associated with increased incidences of prematurity and intrauterine growth retardation. Profound cyanosis is associated with a high rate of spontaneous abortion.⁵² Endocarditis prophylaxis is not currently recommended for vaginal deliveries.⁵³ The recurrence risk rate of any congenital cardiac defect in a newborn is 2.3% with one affected older sibling (any defect), 7.3% with two, 6.7% if the mother has a congenital cardiac defect, but only 2.1% if the father is affected.² However, it has become apparent that recurrence risk can be specific to the type of maternal defect and the underlying genetic basis. If possible, pregnancies in mothers with CHD should be managed in a high-risk obstetric center with cardiologists experienced with the care of adult CHD, and with early consultation with the obstetric anesthesia service. Women on long-term anticoagulation will likely need peripartum modifications, and postpartum thromboembolism is a potential significant problem.

Anesthesiologists will generally encounter pregnant patients well into the last trimester. Most of the major physiologic changes associated with pregnancy occur before the third trimester, and if the patients have maintained good functional status to this point, they will have declared themselves to be in a relatively low-risk group. Pregnancy is a stress test, and if they have successfully arrived at the mid-to-late third trimester, it is more likely that they will successfully tolerate delivery. Also, many high-risk women will have been counseled to avoid pregnancy. There is no a priori reason to favor an instrumented or Caesarean delivery over a vaginal one. This is an obstetric, not cardiologic decision. A functioning epidural makes uterine contractions easy to tolerate. Bearing down, associated with the second stage, requires close observation. The third stage can be accompanied by an autotransfusion of placental blood, or potentially with hypovolemia with uterine atony and hemorrhage Oxytocin will decrease systemic vascular resistance and increase heart rate and pulmonary vascular resistance. Methylergonovine will increase systemic vascular resistance. These rapid changes in loading conditions can be poorly tolerated in mothers with fixed cardiac output and pulmonary edema, or heart failure can develop.

Some mothers will be taking medications for their cardiac condition, including antiarrhythmics. In general, these are safe for the infant.⁵⁴ Exceptions include β-blockers that can interfere with fetal growth and the response of the fetus to the stress of labor, as well as amiodarone that can affect fetal thyroid function. Maternal cardioversion would appear to be safe for the fetus at all stages, because of the low intensity of the electrical field at the uterus. However, the fetus should be monitored throughout the procedure. Women with implanted internal defibrillators have carried successfully to term.⁵⁵ Should cardiopulmonary bypass (CPB) be required during pregnancy, it carries with it increased fetal risk, particularly if hypothermia is used.

Psychosocial

Teenagers with CHD are certainly no different from other teenagers in that issues of denial, a sense of immortality, and risk-taking behavior can affect optimal care for these youngsters. Bodies that carry scars from prior surgery and physical limitations can complicate the body-conscious teenage years. Although most adolescents and adults with CHD function well, adults with CHD are less likely to be married or cohabitating and are more likely to be living with their parents.⁵⁶ There are several series of adolescent and adult patients and psychosocial outcome, but there are no well-done controlled studies.^57–64 It has been suggested that depression is common and can exacerbate the clinical consequences of the cardiac defect.

Adolescent CHD patients have higher medical care expenses than the general population, and they can have difficulty in obtaining life and health insurance after they can no longer be covered under their parents’ policies.^65–67 Life insurance is somewhat more available to adult CHD patients than in the past; however, policies vary widely among insurers.⁶⁸

Aortic Stenosis

Most aortic stenosis in adults is due to a congenitally bicuspid valve that does not become problematic until late middle age or later, although endocarditis risk is lifelong. Congenital aortic stenosis can, on some occasions, however, become severe enough to warrant surgical correction in adolescence or young adulthood, in addition to those severely affected valves that present in infancy. Once symptoms (angina, syncope, near-syncope, heart failure) develop, survival is markedly shortened. Median survival is 5 years after the development of angina, 3 years after syncope, and 2 years after heart failure.⁷⁴ Anesthetic management of aortic stenosis does not vary whether the stenosis is congenital (most common) or acquired (see Chapter 19).

Most mothers with aortic stenosis can successfully carry pregnancies to term and have vaginal deliveries. Severe stenosis (valve area < 1.0 cm²) can result in clinical deterioration and maternal and fetal mortality. Hemodynamic monitoring during delivery with maintenance of adequate preload and avoidance of hypotension are critical. When surgical intervention is required during pregnancy, percutaneous balloon valvuloplasty appears to carry lower risk than open valvotomy.

Aortopulmonary Shunts

Depending on their age, adult patients may have had one or more of several aortopulmonary shunts to palliate cyanosis during childhood. These are shown in Figure 20-1. Although life saving, there were considerable shortcomings of these shunts in the long term. All were inherently inefficient, as some of the oxygenated blood returning through the pulmonary veins to the left atrium and ventricle would then return to the lungs through the shunt, thus volume loading the ventricle. It was difficult to quantify the size of the earlier shunts such as the Waterston (side-to-side ascending aorta to right pulmonary artery) and Potts (side-to-side descending aorta to left pulmonary artery). If too small, the patient was left excessively cyanotic; if too large, there was pulmonary overcirculation with the risk for development of pulmonary vascular disease. The Waterston, in fact, could, on occasion, stream blood flow unequally, resulting in a hyperperfused, hypertensive ipsilateral (right) pulmonary artery and a hypoperfused contralateral (left) pulmonary artery. There were also surgical issues when complete repair became possible. Takedown of Waterston shunts often required a pulmonary arterioplasty to correct deformity of the pulmonary artery at the site of the anastomosis, and the posteriorly located Potts anastomoses could not be taken down from a median sternotomy. Patients with a classic Blalock–Taussig shunt almost always lack palpable pulses on the side of the shunt. Even if there is a palpable pulse (from collateral flow around the shoulder), blood pressure obtained from that arm will be artifactually low. Even after a modified Blalock–Taussig shunt (using a piece of Gore-Tex tubing instead of an end-to-side anastomosis of the subclavian and pulmonary arteries), there can be a blood pressure disparity between the arms. Preoperative blood pressure should be measured in both arms to ensure a valid measurement (Box 20-5).

Figure 20-1 Various aortopulmonary anastomoses.

The illustrated heart is one with tetralogy of Fallot. The anastomoses are: 1, modified Blalock-Taussig; 2, classic Blalock-Taussig; 3, Waterston (Waterston-Cooley); and 4, Potts.

(From Baum VC: The adult with congenital heart disease. J Cardiothorac Vasc Anesth 10:261, 1996.)

Atrial Septal Defect and Partial Anomalous Pulmonary Venous Return

There are several anatomic types of ASD. The most common type, and if otherwise undefined the presumptive type, is the secundum type located in the midseptum. The primum type at the lower end of the atrial septum is a component of endocardial cushion defects, the most primitive of which is the common atrioventricular canal (see later). The sinus venosus type, high in the septum near the entry of the superior vena cava (SVC), is almost always associated with partial anomalous pulmonary venous return, most frequently drainage of the right upper pulmonary vein to the low SVC. An uncommon atrial septal–type defect is when blood passes from the left atrium to the right via an unroofed coronary sinus. For purposes of this section, only secundum defects are considered, although the natural histories of all of the defects are similar (Box 20-6).

Both the natural history and the postoperative outcome of ASDs and the physiologically related partial anomalous venous return are similar.^75–77 Because the symptoms and clinical findings of an ASD can be quite subtle and patients often remain asymptomatic until adulthood, ASDs represent approximately one third of all CHD discovered in adults. Although asymptomatic survival to adulthood is common, significant shunts (_p/_s > 1.5:1) will probably cause symptoms over time, and paradoxical emboli can occur through defects with smaller shunts. Surgical repair of restrictive lesions 5 mm or smaller in size does not impact the natural history. Thus, surgical closure of small lesions is not indicated in the absence of paradoxical emboli. Effort dyspnea occurs in 30% by the third decade, and atrial flutter or fibrillation in about 10% by age 40.⁷⁵ The avoidance of complications developing in adulthood provides the rationale for surgical repair of asymptomatic children. The mortality for a patient with an uncorrected ASD is 6% per year after 40 years of age, and essentially all patients older than 60 years are symptomatic.^75–77 Large, unrepaired defects can cause death from atrial tachyarrhythmias or right ventricular failure in 30- to 40-year-old patients.⁷⁸ With the decreased left ventricular diastolic compliance accompanying the systemic hypertension or coronary artery disease that is common with aging, left-to-right shunting increases with age. Pulmonary vascular disease typically does not develop until after the age of 40, unlike ventricular or ductal level shunts, which can lead to it in early childhood. Mitral insufficiency can be found in adult patients and is significant in about 15% of adult patients.⁷⁹ Paradoxical emboli remain a lifelong risk.

Late closure of the defect, after 5 years of age, has been associated with incomplete resolution of right ventricular dilation.⁸⁰ Left ventricular dysfunction has been reported in some patients having defect closure in adulthood, and closure, particularly in middle age, may not prevent the development of atrial tachyarrhythmias or stroke.^81–84 Survival of patients without pulmonary vascular disease has been reported to be best if operated on before 24 years of age, intermediate if operated on between 25 and 41 years of age, and worst if operated on thereafter.⁸⁴ However, more recent series have shown that even at ages older than 40, surgical repair provides an overall survival and complication-free benefit compared with medical management.⁸⁵ Surgical morbidity in these patients is primarily atrial fibrillation, atrial flutter, or junctional rhythm.⁸² Current practice is to close these defects in adults in the catheterization laboratory via transvascular devices if anatomically practical (Figure 20-2). For example, there needs to be an adequate rim of septum around the defect to which the device can attach. Device closure is inappropriate if the defect is associated with anomalous pulmonary venous drainage. The indications for closure with a transvascular device are the same as for surgical closure.⁸⁶

Figure 20-2 Closure of an atrial septal defect in an adult with use of a transvascular device (the Amplatzer septal occluder).

A, Radiograph. B, Transesophageal echocardiogram. The device is clearly visualized spanning and occluding the atrial septal defect. LA, left atrium; RA, right atrium.

(Courtesy of Dr. Scott Lim.)

An otherwise uncomplicated secundum ASD, unlike most congenital cardiac defects, is not associated with an increased endocarditis risk.⁸⁷ Presumably, this is because the shunt, although potentially large, is low pressure and unassociated with jet lesions of the endocardium.

Although some discussion is given to onset times with intravenous or inhalation induction agents, clinical differences are hard to notice with modern low-solubility volatile agents. Thermodilution cardiac output reflects pulmonary blood flow, which will be in excess of systemic blood flow. Pulmonary arterial catheters are not routinely indicated. Patients generally do tolerate any appropriate anesthetic; however, particular care should be taken in patients with pulmonary arterial hypertension or right-sided failure.

Most women with an ASD tolerate pregnancy well. However, the normal hypervolemia associated with pregnancy can result in heart failure in women with large defects. Hypovolemia accompanying delivery can result in right-to-left shunting through the defect, and there is a risk for pulmonary thromboembolism or paradoxical embolism.

Coarctation of the Aorta

Unrepaired coarctation of the aorta in the adult brings with it significant morbidity and mortality. Mortality rate is 25% by age 20, 50% by age 30, 75% by age 50, and 90% by age 60.^78,88–90 Left ventricular aneurysm, rupture of cerebral aneurysms, and dissection of a postcoarctation aneurysm all contribute to the excessive mortality. Left ventricular failure can occur in patients older than 40 with unrepaired lesions. If repair is not undertaken early, there is incremental risk for the development of premature coronary atherosclerosis. Even with surgery, coronary artery disease remains the leading cause of death 11 to 25 years after surgery.⁹¹ Coarctation is accompanied by a bicuspid aortic valve in the majority of patients. Although endocarditis of this abnormal valve is a lifelong risk, these valves often do not become stenotic until middle age or later. Coarctation can also be associated with mitral valve abnormalities (Box 20-7).

Aneurysms at the site of coarctation repair can develop years later (Figure 20-3), and restenosis as well can develop in adolescence or adulthood. Repair includes resection of the coarctation and end-to-end anastomosis. Because this sometimes resulted in recoarctation when done in infancy, for many years a common repair was the Waldhausen or subclavian flap operation, in which the left subclavian artery is ligated and the proximal segment opened and rotated as a flap to open the area of the coarctation. Aneurysms in the area of repair are a particular concern in adolescents and adults after coarctectomy. Persistent systemic hypertension is common after coarctation repair.⁹² The risk for hypertension parallels the duration of unrepaired coarctation. Adult patients require continued periodic follow-up for hypertension. A pressure gradient of 20 mm Hg or more (less in the presence of extensive collaterals) is an indication for treatment.⁹³ Recoarctation can be treated surgically or by balloon angioplasty with stenting.⁹⁴ Surgical repair of recoarctation or aneurysm in adults is associated with increased mortality and can be associated with significant intraoperative bleeding because of previous scar or extensive collateral vessels. It requires lung isolation for optimal surgical exposure and placement of an arterial catheter in the right arm. Endovascular repair by ballooning/stenting has proved useful for these patients.^95,96

Figure 20-3 Magnetic resonance image of a 37-year-old man showing descending thoracic aortic pseudoaneurysm at the site of a coarctation that had been repaired years earlier. This patient also has a bicuspid aortic valve and an aneurysm of the ascending aorta that was later repaired.

(Courtesy of Dr. Christopher Kramer.)

Half of patients operated on after age 40 have persistent hypertension, and many of the remainder have an abnormal hypertensive response to surgery. Long-term survival is worse for patients having repair later in life. Patients older than 40 undergoing repair have a 15-year survival rate of only 50%.⁹¹

Blood pressure should be obtained in the right arm unless pressures in the left arm or legs are known to be unaffected by residual or recurrent coarctation. Postoperative hypertension is common after repair of coarctation and often requires treatment for some months. Postoperative ileus is also common, and patients should be maintained NPO for about 2 days.

Pregnancy can exacerbate preexisting hypertension in women with unrepaired lesions, increasing the risk for aortic dissection or rupture, heart failure, angina, and rupture of a circle of Willis aneurysm. Adequate blood pressure control during pregnancy is paramount in these women. Most aortic ruptures during pregnancy occur during labor and delivery. Presumably, epidural analgesia would moderate hypertension during delivery.

Congenitally Corrected Transposition of the Great Vessels (l-Transposition, Ventricular Inversion)

“Transposition” in this context refers solely to the fact that the aorta arises anterior to the pulmonary artery. It bears no reference to the origin of blood in the aorta or pulmonary artery, or to the ventricle of origin of those vessels. In l-transposition, as a consequence of the embryonic heart tube rotating to the left rather than to the right, the flow of blood is through normal vena cavae to the right atrium, through a mitral valve to a right-sided anatomic left ventricle, to the pulmonary artery, through the pulmonary circulation, to the left atrium, through a tricuspid valve to a left-sided anatomic right ventricle, and thence to the aorta (Figure 20-4) Although anatomically altered, the physiologic flow of blood is appropriate and there are no associated shunts. l-Transposition of the great arteries (L-TGA) is frequently associated with other cardiac lesions, most commonly a ventricular septal defect (VSD), subpulmonic stenosis, heart block, or systemic atrioventricular (tricuspid) valve regurgitation. In the absence of any of these associated cardiac defects, L-TGA will usually be asymptomatic through infancy and childhood. When l-transposition is an isolated lesion, most patients maintain normal biventricular function through early adulthood, and can attain a normal life span.

Figure 20-4 Diagram of the anatomy of L-TGA.

Note that the atrioventricular valves are associated with the “usual” ventricle. Ao, aorta; LA, left atrium; LV, anatomic left ventricle; MV, mitral valve; PA, pulmonary artery; RA, right atrium; RV, anatomic right ventricle; TV, tricuspid valve.

Systemic atrioventricular (tricuspid) valve insufficiency may not develop until later in life, resulting in approximately 60% of patients being diagnosed as adults.⁹⁷ Dysfunction of the right or systemic ventricle can develop with aging, and asymptomatic aging is relatively uncommon.⁹⁸ By age 45, heart failure will be present in 67% of those patients with associated lesions and 25% of those without.⁹⁹ These patients can be born with congenital heart block, which can progress in degree. Second- or third-degree heart block occurs at a rate of about 2% per year. More than 75% of patients develop some degree of heart block, although the intrinsic pacemaker remains above the His bundle with a narrow QRS complex. l-Transposition can be associated with an Ebstein-like deformity of the systemic atrioventricular (tricuspid) valve, and there can be a bundle of Kent causing the Wolff-Parkinson-White syndrome associated with that abnormal valve. There is a significant incidence of tricuspid valve insufficiency in the systemic ventricle, and this is greater still in patients with an Ebstein’s deformity of the valve.¹⁰⁰ Anesthetic management depends on the presence of any associated lesions and the adequacy of right (systemic) ventricular function.

Although women generally do well with pregnancy,¹⁰¹ the physiologic stresses of pregnancy and delivery can result in ventricular or valvular dysfunction, particularly with baseline dysfunction and/or an insufficient systemic atrioventricular valve; but even if these develop, pregnancy can be successfully managed.^101–104 The decrease in systemic vascular resistance associated with both pregnancy and neuraxial analgesia might be advantageous to women with tricuspid (systemic) valve insufficiency. The acute autotransfusion associated with delivery could potentially cause problems for women with existing diminished systemic ventricle function.

Ebstein’s Anomaly of the Tricuspid Valve

Ebstein’s anomaly, one of arrested or incomplete delamination of the embryonic tricuspid valve from the right ventricular myocardium, resulting in apically displaced valve tissue, is the most common cause of congenital tricuspid insufficiency. The septal leaflet tends to be the most dysplastic. The anterior leaflet tends to be large and redundant. The defect is associated with a patent foramen ovale or a secundum ASD. There is “atrialization” of part of the right ventricle. The displacement of the tricuspid valve toward the right ventricular apex results in a portion of the right ventricle being above the tricuspid valve and becoming functionally part of the right atrium. Apicalization of the tricuspid valve results in a portion of the heart above the valve having a ventricular intracardiac electrogram (it is ventricular myocardium) but atrial pressures (it lies above the tricuspid valve). The right atrium can be massively enlarged (Figure 20-5), and the right ventricle, lacking the inflow portion that is now part of the right atrium, is smaller than usual with varying degrees of pulmonic stenosis. Patients with l-transposition (see earlier) can have Ebstein’s anomaly of a left-sided tricuspid valve.

Figure 20-5 Ebstein’s anomaly of the tricuspid valve.

This echocardiogram shows the apically displaced redundant tricuspid valve tissue and a massively enlarged right atrium with bowing of the atrial septum to the left. LA, left atrium; LV, left ventricle; MV, mitral valve; RA, right atrium; RV, right ventricle; TV, tricuspid valve.

(From Baum VC: Abnormalities of the atrioventricular valves. In Lake CL, Booker P [eds]: Pediatric cardiac anesthesia, 4th ed. Philadelphia, 2004: Lippincott Williams & Wilkins.)

Symptoms will vary based on the amount of displacement of the valve and the size of the smaller than normal right ventricle. Cyanosis from atrial-level right-to-left shunting can be a neonatal phenomenon, resolving with the normal postnatal decrease in pulmonary vascular resistance, only to recur in adolescence or adulthood. Very mild disease is quite compatible with asymptomatic survival into adulthood, although overall earlier reports suggested a mean age at death of about 20 years, with about one third dying before 10 years of age and only 15% survival rate by 60 years.^105–107 About half of patients experience development of arrhythmias, typically supraventricular tachyarrhythmias. Once symptoms develop, disability rapidly progresses.

Valve repair is currently the approach of choice, and only uncommonly will tricuspid valve replacement be required.¹⁰⁸ Additional intervention may be required for progressive insufficiency, stenosis, prosthetic valve failure, or valve replacement with growth. After valve replacement, up to 25% of patients experience development of high-grade atrioventricular block. Ebstein’s valves are often associated with a right-sided bypass tract, causing Wolff-Parkinson-White syndrome. This is of concern because 25% to 30% of patients experience development of supraventricular tachyarrhythmias. The dilated right atrium is ready substrate for the development of atrial fibrillation. In addition to a decrease in cardiac performance, atrial fibrillation is also potentially dangerous in patients with underlying Wolff-Parkinson-White syndrome because very high atrial rates can be conducted to the ventricle through the bypass tract.

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