JUXTAPOSITION OF THE MORPHOLOGICALLY RIGHT ATRIAL APPENDAGE IN SOLITUS AND INVERSUS ATRIA - A STUDY OF 35 POSTMORTEM CASES

Juxtaposition of the atrial appendages has previously been classified positionally, left sided being more frequent than right sided. In our study of 35 postmortem cases, juxtaposition was analyzed morphological ly for the first time. juxtaposition of the morphologically right atri al appendage (JRAA) was always left sided with solitus atria (34 cases ) but was right sided with inversus atria (1 case), the latter patient being the first documented case of JRAA with atrial inversion. Thus i n patients with JRAA, the sidedness of the juxtaposition depends on th e type of atrial situs that coexists. frequent associated malformation s included tricuspid valve anomalies (21 [60%] of 30), hypoplasia of t he right ventricular sinus (26 [74%] of 35), and an abnormal conus (su baortic or bilateral) in 100%. Hypoplasia of the right ventricular sin us, plus malformation of the conus, appears to be important in the mor phogenesis of JRAA.