**7. Pathophysiology**

The broad spectrum of anatomic severity in EA is due to the wide spectrum of clinical and hemodynamic manifestations. The pathophysiologic changes are related to the RV functional impairment and the degree of TV regurgitation or, rarely, stenosis; the size of the interatrial communication; LV dysfunction and other associated congenital cardiovascular malformations. The aRV acts as a passive reservoir during contraction of the atrium due to the decreasing volume of ejected blood. The overall effect on the right atrium is dilatation and an increase in size of the interatrial communication. Tricuspid regurgitation increases with perogressive annular dilatation. To a lesser degree, the pathologic substrates predisposing to tachyarrhythmias produce an additional dimension contributing to the pathophysiology.

of RV myopathy, tricuspid regurgitation, and elevated pulmonary resistance can lead to poor pulmonary perfusion when the arterial duct constricts or closes. Venous pressures rise, leading to right-heart failure and cyanosis due to right-to-left shunting across the foramen ovale. Until the pulmonary resistance decreases, and the pulmonary flow increases, these infants present a diagnostic and therapeutic dilemma. Patency of the pulmonary outflow tract and valve must be confirmed [42]. This can be achieved by demonstrating the opening of the pulmonary valvar leaflets by cross sectional echocardiographic scans, or by documenting either forward or more commonly regurgitant flow across the valve using Doppler techniques.

Ebstein's Anomaly

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http://dx.doi.org/10.5772/intechopen.78067

The manifestations of EA are cyanosis, right-sided heart failure, arrhythmias, and sudden cardiac death. The hemodynamic variations and clinical presentation depend on the age at presentation, anatomic severity, hemodynamics, and the degree of right-to-left interatrial

Patients with EA may present at any age and the majority is diagnosed in infancy or childhood, but a small percentage with less severe malformations present in adulthood. The most severe cases present prenatally or as newborns. Prenatal diagnosis is dependent upon ultrasonic screening examinations. The mortality rate is higher in the patients with severe EA. In the severe forms of EA, cardiomegaly, hydrops, and tachyarrhythmias may be seen in the fetal echocardiography. Marked cardiac enlargement may lead to pulmonary parenchymal hypoplasia in the most severe cases. Prenatal arrhythmia is not common. Neonates usually present with cyanosis and heart failure and secondary TV regurgitation resulting from decreased pulmonary blood flow, depressed RV function, and low cardiac output [42]. Murmurs and arrhythmias are frequently encountered presenting complaints in children, adolescents and adults. Adults also present with progressive cyanosis, decreasing exercise tolerance, fatigue, or right-sided heart failure. Palpitations in a cyanotic child should raise the possibility of EA [38, 41, 42]. In the presence of an interatrial communication, the risk of paradoxical embolization, brain abscess, and sudden death increases. Exercise tolerance is dependent on the

Growth and development are generally normal. Physical signs vary depending on the severity of pathology and magnitude of the right-to-left atrial shunt, which may lead to cyanosis and digital clubbing in patients with interatrial communication. Cyanosis is typically pronounced in the neonate and infants, whereas it is milder (sometimes only exertional) in older children. Many have an unusual facial coloration, described as violaceous hue, red-cheeked, or malar rush. Usually these patients have an associated mild polycythemia. Asymmetry of the chest is a frequent finding secondary to the right heart dilatation. Arterial and venous pulsations are

**8. Clinical presentation**

cardiac function and oxygen saturation [43, 44].

**9. Physical findings**

shunting [38, 41].

Dysfunction of the RV myocardium, and the abnormalities of the TV contribute to the impaired flow into the right heart and the pulmonary circulation. The dilated right atrium and RVa decrease the right heart flow. There is no valvar tissue separating this area from the true atrial chamber and the great veins. This results in increased venous pressure, which leads to an elevation in resistance to forward flow. A larger volume of RA due to RA distension results in right to left shunting at the atrial level in the presence of an ASD. When the aRV relaxes, it will expand, and can even balloon outwards during true atrial contraction. This creates a reservoir for venous blood and decreases the amount of effective forward flow that crosses the abnormal TV. This to-and-fro flow pattern between the right atrium and the aRV not only decreases effective output from the right heart but also provides an ongoing stimulus for atrial dilatation and atrial arrhythmias. The degree of functional impairment has been directly related to these anatomic and physiologic abnormalities. A small fRV and large aRV, extreme displacement or absence of the septal leaflet, the degree of displacement or tethering of the anterosuperior leaflet, and the aneurysmal dilation of the RVOT were all associated with a reduced functional state of the New York Heart Association [40]. A small fRV and large aRV, and extreme displacement of the septal leaflet is shown in https://mts.intechopen.com/ download/index/process/176/authkey/53ae2bbd4b7866a29632305139289c32.

Although the primary focus in patients with EA has been on right-sided structures, there have been an increasing number of reports of left-sided abnormalities, especially in LV size, shape, and function [35–37]. Radionuclide scans and cineangiograms have shown disturbed LV function at rest in nonoperated patients. During formal exercise testing, these patients show an appropriate increase in LV ejection fraction due to a reduced end-systolic volume and unchanged end diastolic volume [37]. EA is related to the abnormal echocardiographic appearance of the LV myocardium: myocardial noncompaction and hypertrabeculated segments. Most patients have satisfactory LV function; a small percentage show severe systolic and diastolic dysfunction even if patients have LV myocardial abnormalities [41]. These leftsided myocardial abnormalities, although seen in only a few patients, support the concept that EA is actually a global myocardial disorder that primarily manifests itself within the RV and TV. Pulmonary vascular resistance is always high immediately after birth and usually decreases rapidly in the first days of life. It is highly difficult for the infant with severe EA to deal with neonatal circulation due to the high pulmonary vascular resistance. The combination of RV myopathy, tricuspid regurgitation, and elevated pulmonary resistance can lead to poor pulmonary perfusion when the arterial duct constricts or closes. Venous pressures rise, leading to right-heart failure and cyanosis due to right-to-left shunting across the foramen ovale. Until the pulmonary resistance decreases, and the pulmonary flow increases, these infants present a diagnostic and therapeutic dilemma. Patency of the pulmonary outflow tract and valve must be confirmed [42]. This can be achieved by demonstrating the opening of the pulmonary valvar leaflets by cross sectional echocardiographic scans, or by documenting either forward or more commonly regurgitant flow across the valve using Doppler techniques.
