Morphologic classification of the right auricule on 256-slice computed tomography.

Purpose: To investigate the shape of right auricule on 256-slice computed tomography (CT).

Materials And Methods: Five hundred people (250 men, age range 16-84 years) who had cardiac multidetector CT angiography were recruited in this study. All patients had normal sinus rhythm with normal blood pressure (<140/90 mmHg for systolic/diastolic pressure). The morphology of the right auricule was studied and compared after reconstruction of the raw images.

Results: All patients successfully had cardiac CT angiography (100%), and the right auricule morphology was divided into five types and nine subtypes, including Type I of triangular shape (Ia and Ib), Type II of M shape (IIa and IIb), Type III of L shape (IIIa and IIIb), Type IV of reverse L shape (IVa and IVb), and Type V of balanced shape. The most common type of right auricule is Type IV (28.4%) followed by Type II (24.0%), whereas the least common is Type V (11.0%). Type Ia was present significantly (P < 0.0001) more frequently in females than in males, whereas Type IIa significantly (P = 0.042) more frequently in males than females. No other significant (P > 0.05) sex difference existed in the constitution ratio of the types. The normal angle was greater in Type Ib than in Ia. The greater the normal angle in Type I, the greater the deviation of the right auricule tip towards the left.

Conclusion: A good understanding of the right auricule anatomical morphology can better guide atrial pacing, radiofrequency ablation and other surgical procedures while preventing possible intra-procedural complications.