Congenital Anomalies of the Atrium

This chapter will cover a group of rare congenital anomalies of the atrium that are not discussed in the chapters on atrial septal defects, sinus venosus defects, atrioventricular septal defect (AVSD), and systemic and pulmonary venous anomalies. This group of rare diseases includes atrial wall and atrial appendage aneurysms, atrial diverticula, right venous valve anomalies, and double-outlet atrium. The terminology of these malformations has been unclear, and some terms have been used interchangeably, e.g., congenital enlargement of the right atrium, right atrial aneurysm, and diverticulum have been used to describe the same lesion. These terms will be used consequently in this chapter, and we strive to give definitions based on morphology and anatomopathological findings of patients. The clinical spectrum of these anomalies can vary significantly from manifestations in fetal life to incidental findings in asymptomatic patients at an advanced age. The prevalence of these rare diseases in the general population is not known, since for most diseases only a limited number of patients have been reported in the literature which ranges from a few case reports to less than 100 patients summarized in systematic reviews on the subject. In addition, some patients are completely asymptomatic, leading to an underestimation of the true prevalence.