Disclosed is an implantable medical device including a connector block that allows varied lead configurations to be used with a single connector block and implantable medical device assembly. The connector block is configured with one or more lead insertion lumens that are open at both ends, such that each end of the lead insertion lumen may receive a separate lead. The circuitry within the implantable medical device is configured to allow the delivery of electrical pulses from a pulse generator within the implantable medical device to two separate leads inserted within opposite ends of a single lead insertion lumen.