Assuming you can break alt
text in new line (meaning it's not generated dynamically) a simple idea to have alt
text in new line is :
<img src="foo.jpg" alt="Line 1
Line 2" /> <br > // new line here is next line for alt text
So for your case :
<img src="invalid url" border="0" alt="AAA BBBB
AAA BBBB
123456789" style="width:237px;height:100px;">
Reference : Newline in alt text