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Major advances in the field of pediatric cardiology and cardiac surgery over the last several decades have led to an improvement in survival rates of the patients with congenital heart disease. During this period, improvements in surgical and medical treatments have been accompanied by developments in a spectrum of diagnostic modalities. Integration of different modalities in clinical and research environments is being used for better understanding and better managing of complex cardiac conditions.

Ideally, few noninvasive imaging modalities should be able to delineate all aspects of the anatomy and evaluate physiologic consequences of the lesion(s) in patients with congenital heart disease. Moreover, the imaging modalities used should be cost effective and portable, not cause excessive discomfort and morbidity, and not expose patients to harmful effects of ionizing radiation. To limit the number of imaging modalities used in diagnosis and therapy, research is being performed to evaluate and validate techniques that could potentially serve as noninvasive or minimally invasive imaging modalities that would replace those which are invasive and less available.

The aim of this chapter is to present a model of how noninvasive multimodal imaging can improve the understanding of pathophysiology and increase the accuracy of the diagnosis of the specific congenital heart disease. The focus is on the heart with atrioventricular septal defect (AVSD).

Appropriate diagnosis and detailed assessment of the anatomic and functional features of AVSD presents challenges. Particularly, accurate preoperative assessment of the atrioventricular valve component is crucial since long-term outcomes for surgical repairs of AVSDs depend on the successful repair of the left atrioventricular valve. Moreover, surgical destruction of the conduction system may occur in cases of inappropriate diagnosis because AVSDs have different conduction pathways compared with defects that have separate atrioventricular valves.1

Understanding the electroanatomic and functional relationships in hearts with AVSDs is suggested to permit differentiation of atrioventricular defects from other similar abnormalities.

AVSD is anatomically characterized by abnormal development of the atrioventricular valve junction.2-6 In addition, the overall atrioventricular valve complex including valve leaflets and papillary muscles is abnormally developed. Figure 18–1 schematically depicts main differences in the normal (Fig. 18–1A) and primum AVSD heart (Fig. 18–1B) anatomy. Atrioventricular valve leaflets are different from normal mitral and tricuspidal leaflets because atrioventricular valve leaflets guard a common atrioventricular junction and are displaced. In addition, valve leaflets may be asymmetric, the mural leaflet may be abnormally small. Displacement and sometimes even dysfunction of the papillary muscles is present. Those changes are often associated with pre- and postoperative regurgitation of the valve.7-9 Left ventricular papillary muscles are positioned further from the septum compared with normal, with the posterior papillary muscle more so than the anterior papillary muscle.1 Thus, specifically, the posterior papillary muscle is a marker of distinction between AVSDs and other similar defects such as defects with mitral clefts.1

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