Left ventricular (LV) leads positioned in the apical region when compared to the mid-ventricular or basal regions are associated with a significantly increased risk of heart failure (HF) and death in patients receiving cardiac resynchronization therapy (CRT) according to a sub-study of the Multicenter Automatic Defibrillator Implantation Trial-CRT (MADIT-CRT). The late-breaking clinical trial was presented at Heart Rhythm 2010, the Heart Rhythm Society's 31st Annual Scientific Sessions. It is the first trial to evaluate clinical outcomes based on the LV lead position within a mildly symptomatic CRT patient population.

In MADIT-CRT, patients were randomly assigned to receive CRT-D or implantable cardioverter defibrillators (ICD) therapy. A total of 1,820 patients were enrolled in 110 centers and a significant portion of the patient population was women (25 percent). The results of the MADIT-CRT study showed that over a two-year follow up period, CRT-D was associated with a 34 percent overall reduction of death and HF in minimally symptomatic patients, and that CRT-D was more effective in women than men.

Led by Jagmeet P. Singh, M.D. Ph.D. from Massachusetts General Hospital, this sub-study of the MADIT-CRT study sought to evaluate the impact of left ventricular (LV) lead location on outcomes in 799 patients randomized to CRT-D in MADIT-CRT. The LV lead location was classified along the short axis into an anterior, lateral or posterior position, and along the long axis into a basal, mid-ventricular or apical region. The location of the left ventricle lead was analyzed by a core-lab review of coronary venograms and chest x-rays recorded at the time of device implantation.

Results showed that 22 percent of patients with apical lead position had a significantly increased risk of HF and mortality compared to an average of 12 percent for patients with the mid-ventricular or basal position. In addition, the placement of LV leads along the anterior, lateral or posterior wall in CRT-D patients showed similar outcomes and extent of benefit from resynchronization therapy.

"The results of this MADIT-CRT sub-study are a major step forward towards understanding the impact of LV lead implantation on CRT response and clinical outcomes," stated lead author Jag Singh, M.D. Ph.D. "We can look back at patient groups who may not have previously responded positively to CRT and consider alternate lead positions. These findings could also enhance the overall response rate to CRT for future patients by simply avoiding the apical position altogether."

The method by which the study data and venous angiograms was collected and evaluated is unique and has not been done in any prior CRT study to date. Based on the significant outcome variance in patients within this study, the results suggest that pacing the apical region of the left ventricle should be avoided in future patients receiving cardiac resynchronization therapy.