**8.2 Left ventricle**

Even without associated left ventricular morphological abnormalities, left ventricular function may be compromised due to compression from a dilated atrialized right atrium (**Figure 3b**). Angiographic analysis of 26 patients with Ebstein's anomaly demonstrated seven patients with a decrease in left ventricular diastolic volume (LVEDV <60 ml/m<sup>2</sup> ); 12 patients had increased LVEDV (>80 ml/m<sup>2</sup> ). Eight patients 29 (31%) either with normal or increased LVESV had decreased left ventricular ejection fraction in this study. Patients with a decrease in LVESV had normal left ventricular ejection fraction in this study [71]. Abnormalities of left ventricular morphology involving the myocardium or valves were noted in 39% of Ebstein's anomaly [71], with 18% of patients demonstrating an association with left ventricular noncompaction [72]. Mitral valve prolapse, bicuspid aortic valve, and mitral valve dysplasia, as well as left ventricular systolic dysfunction (7%) and diastolic dysfunction (34%), can be associated with Ebstein's anomaly [72]. A hemodynamically significant left ventricular outflow tract obstruction secondary to the systolic anterior motion of the mitral valve and severe mitral regurgitation was noted in a 52-year-old patient following tricuspid valve replacement and was resolved with esmolol administration [73]. Using three-dimensional models, a global or regional decrease in left ventricular ejection fraction (LVEF) was noted in patients with Ebstein's anomaly (LVEF 41 7% VS 57 5%) [74]. In addition, tricuspid regurgitation is negatively correlated with the left ventricular ejection fraction by cardiac magnetic resonance imaging [75]. Rarely, non-apex forming left ventricular anatomy is associated with Ebstein's anomaly, in which, heart transplantation is the only surgical option [76].

### **8.3 Arrhythmia**

The downward displacement of the septal leaflet of the tricuspid valve is associated with direct muscular connections in the septal atrioventricular ring resulting in a potential connection for an accessory atrioventricular pathway [77]. Accessory pathways are noted in 10–36% of patients with Ebstein's anomaly [78–80] and most accessory connections are located around the orifice of the malformed tricuspid valve [45, 81]. Delayed ventricular activation with the appearance of a right bundle branch block pattern can be seen in up to 93% of patients with Ebstein's anomaly [80]. In a series of 52 patients with Ebstein's anomaly from Mayo clinic, 34 patients (65%) had arrhythmias preoperatively (supraventricular tachycardia, atrial fibrillation, ventricular arrhythmias, and high-degree atrioventricular block) with perioperative and postoperative arrhythmias noted in 42% of the patients (14 patients had atrial tachyarrhythmia and eight had ventricular arrhythmias) s [82]. Maintenance of sinus rhythm is important to maintaining adequate cardiac output and may necessitate the use of epicardial pacing postoperatively.

#### **8.4 Respiratory management**

Tanaka et al. reported lung autopsy results from four neonates with Ebstein's anomaly or tricuspid valve dysplasia. Lung hypoplasia or immaturity was not seen in full-term neonates with tricuspid abnormalities unless patients had a concomitant diaphragmatic hernia [83]. Despite an increased cardiothoracic ratio to 92% [83], surgical intervention to relieve tricuspid regurgitation and atrial plication may improve respiratory function by decreasing cardiomegaly and associated lung compression. Strategies to reduce pulmonary vascular resistance and minimize postoperative right ventricular distention and tricuspid regurgitation include the use of supplemental oxygen, inhaled nitric oxide, and ventilation to minimize hypercarbia. Early extubation, if feasible, will reduce intrathoracic pressure and right ventricular afterload.
