In recent years, cardiac resynchronization therapy or biventricular pacing has been proved to be effective in alleviating congestive heart failure in 70% of patients. For patients who have bradycardia devices in place before presentation of heart failure and the devices are well before end of life, the RV pacing system can be effectively, efficiently and safely upgraded to bi-ventricular pacing through a bipolar IS-1 Y adaptor converting the single ventricular output of the original pacemaker to dual outlets conjoining the two ventricular leads in parallel. Patients who are successfully upgraded enjoy benefits similar to those of de novo implantation of bi-ventricular pacemaker. At implantation, the pacing threshold of the newly implanted unipolar left ventricular lead should be measured in the Y adaptor-on or LV lead cathode tip to RV anode ring configuration to allow for additional resistance elements.