BLOCK-HF was conducted by Medtronic, Inc from December 2003 until November 2011.  The study was conducted here March 2009 until November 2011.  Our hospital was able to enroll 28 patients in that time to become one of the highest enrolling centers in the study.  In total there were 758 patients implanted with the device at 60 centers in the US and Canada.

All patients who met the inclusion criteria were implanted with a 3 lead system.  The third lead was an LV pacing lead that was being studied to see if implanting and using it on the study population would decrease the amount of heart failure hospitalizations and ultimately early death.

All study participants were implanted with the third (LV) lead and were randomized 50:50 to either have it turned on and functioning or left programmed off for the study.

After the analysis of the data it was determined that patients with AV block and LV systolic dysfunction  (LVEF < 50%), BiV pacing compared to RV pacing leads to a significant 26% reduction in the combined endpoint of mortality, heart-failure related urgent care, and increase in LVESVI.

Furthermore, there is a 27% relative risk reduction in the composite endpoint of heart-failure urgent care and all-cause mortality.

At the end of the study all the patients in the trial were able to have the LV lead programmed on without having another procedure to implant that lead.  The FDA (Food & Drug Administration) approved the use of the Cardiac Resynchronization Therapy (3 lead System) devices for use in all patients with the same heart problems of the study patients as listed below.

When is it used? CRT-P and CRT-D devices have been approved for many years for patients with poorly synchronized right and left ventricles to improve their heart failure symptoms. Based on the results of a new clinical study called BLOCK HF, FDA is now expanding who is eligible (or “indicated”) for CRT. The new, added patients must have EACH of the following:

  • MUST have slow or absent ventricular heart beating (heart block) with symptoms that would traditionally require a conventional pacemaker
  • PLUS mild to moderate heart failure symptoms
  • PLUS at least mild heart muscle damage