CRNI (infusion) certification is not entry-level. You have to have 1600 hours of infusion experience to be eligible for the certification exam. It's a pricey exam. Here's the info. About INCC - Infusion Nurses Certification Corporation
I don't believe that there is a national certification for cath lab. You could go with a PCCN certification (from AACN) PCCN - Certification for Progressive Care Nurses
- similar to CCRN, but not as hard core with technical skills and patient management that would only be required in ICU. Or, you could take a look at the CRN certification... CRN Certification | C-NET | Center For Nursing Education & Testing
It is for nurses who work in interventional radiology, which is the basic function of cath labs. Neither are entry-level certifications. CRN is less expensive.
Bottom line - you have to actually be practicing in one of these specialty areas for some time before you are eligible to sit for the certification exam. Don't bother with any 'quickie' certificate (as opposed to the nationally recognized certifications listed above) - they may not require any prep except writing the check, but they don't add any value to your resume.