ICD-10:

Q21.1 Atrial septal defect
http://www.who.int/classifications/apps/icd/i...

Q21.1 Vorhofseptumdefekthttp://www.dimdi.de/static/de/klassi/diagnose...

should be "septal" rather than "septum"

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company.
"atrial septal defect
n.
A defect in the interatrial septum of the heart, due to failure of the embryonic foramen to close normally."
http://www.answers.com/atrial+septal+defect&r=67
 
British Heart Foundation
"Heart Conditions
Atrial septal defect
What is it?
An atrial septal defect is a hole in the wall (septum) between the two upper chambers of the heart - the left atrium and the right atrium. Some of the blood from the left atrium flows through the hole to the right atrium. This increases the amount of blood flowing to the lungs."
http://www.bhf.org.uk/hearthealth/index.asp?s...

"In a person with an atrial septal defect (ASD), there's an opening in the wall (called the septum) between the right atrium and the left atrium. (You might hear this type of defect also referred to as a "hole in the heart.")
http://www.kidshealth.org/parent/medical/hear...

Roche Lexikon Medizin 5. Auflage:
Vorhofseptumdefekt
Syn.: ASD(Abk.)
E: atrial septal defect
Lückenbildung im Vorhofseptum als angeborener Herzfehler.
http://www.gesundheit.de/roche/

Kinderherzzentrum Kiel
"Der Vorhofseptumdefekt tritt mit einer Häufigkeit von 7 bis 12 % aller angeborenen Herzfehler auf. Zusammen mit dem Ventrikelseptumdefekt macht er damit etwa die Hälfte aller angeborenen Herzfehler aus."
http://www.kinderherzzentrum-kiel.de/html/vor...