The 59 modifier is not used based on the number of codes being billed, but rather on whether or not codes would normally be bundled. If you are billing for two services where one is considered inclusive of another, but there is a reason that it should be allowed separately you would use the 59 modifier. In the example you gave, you should not need a 59 modifier on the 93000 (EKG) because the EKG is not considered inclusive of any of the other procedures being billed and should therefore be allowed separately without a modifier. The same with the 81000. An example of when the 59 modifier would be used:
99213 724.2 401.0 250.00 (office visit for low back pain, HTN, & DM)
90804 59 304.00 (along with a 20-30 min counseling for opioid dependency)
With all that said, the insurance companies are going to do what they are going to do and sometimes modifiers are needed when they shouldn't be.
Hope that helps
Michele