The German Wikipedia page for Inflektiv also provides a synonym—Erikativ—which is "named for Erika Fuchs, who translated Mickey Mouse comics into German and used the form frequently". Going by Google's results, Erikativ (or Ericativ, sometimes with an 'e' at the end) appears to be just as popular as Inflektiv.
There is an interesting (and exhaustive) paper by a Mark Lindsay [PDF] on the subject of the Erikativ from a linguistic point of view. He states:
The German Erikativ construction (also known as the Inflektiv (Teuber 1998)) is a phenomenon that existed prior to the mid-twentieth century, but first developed widespread prominence through the German-language translations of Disney comics during the 1950’s. The translator, Erika Fuchs, used this form to describe sounds and actions of the characters (not unlike English crash! or pow!); eventually, these words evolved beyond onomatopoeic use, expanding to phrases like stare (starr) or dancing while sitting (sitzendtanz). Unlike onomatopoeias, these new forms followed a predictable pattern.
It should be noted that Teuber (1998, p. 8) describes the Inflektiv as a verb form that is non-inflected (German: nicht-flektiert); therefore, the German term Inflektiv should be translated into English as Uninflective. To avoid the confusion this causes, I shall use the alternative term, Erikativ.
Teuber (1998) argues convincingly that the Erikativ is a true verb form, as it has semantic and morphological restrictions that distinguish it from the freeform nature of interjections. Noting the common similarity between the Erikativ form and the verbal stem, he coins the term Inflektiv (‘uninflective’) to describe its lack of overt inflection.
The Erikativ is essentially the same as "actions" or "emotes" (WP) seen in most IRC channels and other chat rooms such as
*rolls his eyes*,
In comic lettering, emotes, when inserted within dialogue, are punctuated differently. These punctuations are called breath marks, crow's feet, cat's whiskers, or fireflies. I am unaware of any standard term that describes the "breath words" themselves.