J J Says to Buy Guidant for \$25.4 Billion  PHILADELPHIA (Reuters) - Johnson   Johnson &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=JNJ.N target=/stocks/quickinfo/fullquote"&gt;JNJ.N&lt;/A&gt; on  Wednesday said it agreed to buy Guidant Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=GDT.N target=/stocks/quickinfo/fullquote"&gt;GDT.N&lt;/A&gt;, for  \$25.4 billion in cash and stock, giving the healthcare products  maker a foothold in the fast-growing market for implantable  devices that regulate heartbeats.