you could concatenate the discription onto the name that is passed to authorize.net.
on the confirm page, look for code similar to:
$AuthNet_itemized[0][$nextIndex] = "Name";
$AuthNet_itemized[1][$nextIndex] = "".trim($yourCartName->DisplayInfo("Name")) ."";
where "yourCartName" is the name of your eCart object.
and change that to:
$AuthNet_itemized[0][$nextIndex] = "Name";
$AuthNet_itemized[1][$nextIndex] = "".trim($yourCartName->DisplayInfo("Name")) ." - ". trim($yourCartName->DisplayInfo("Description")) ."";