Hi Friend,
As per below KB, it seems you even can go for below path
VMware ESXi 5.5, Patch Release ESXi550-201404001
Apply this patch on ESXi 5.5 hosts to resolve all issues fixed in ESXi 5.5 Update 1, and additionally the OpenSSL Heartbleed issue.
VMware KB: Resolving OpenSSL Heartbleed for ESXi 5.5 - CVE-2014-0160
You will another option as well in above KB
On your query, can you please point me to the KB that you are referring to?
For VC 5.1, you can directly go for upgrading VC 55U1a.