ACC: Speckle echo can better TARGET lead placement
NEW ORLEANS—Targeted left ventricular (LV) lead placement via speckle tracking echo can improve cardiac resynchronization therapy (CRT) response and concordant LV lead placements, dyssynchrony and pacing away from areas of scar, and can also improve outcomes, according to the results of the TARGET study presented April 5 at the annual meeting of the American College of Cardiology.

While cardiac resynchronization therapy is an established treatment for patients with advanced heart failure (HF), 30 to 40 percent of patients fail to see clinical benefit. Left ventricular (LV) lead position can determine response.

Fakhar Z. Khan, MD, of the Cambridge University in Cambridge, England, who presented the study, said that “higher response rates are seen when pacing the latest site of contraction” and lower response rates are seen when the area of the scar is paced."

The researchers evaluated whether a targeted LV lead placement at the latest site of contraction and away from scar areas could enhance CRT response compared to unguided treatments.

Khan et al set out to evaluate the impact and feasibility of targeted lead placement on CRT outcomes by enrolling 220 patients. Patients were then randomized to receive either standard CRT (n=110) or targeted LV lead placement with speckle tracking echo (STE), which was used to identify optimal site and LV lead targeted to the site (n=110).

STE software allows electrophysiologists to evaluate LV function and better guide lead placement.

The researchers used four steps for LV lead targeting:
  • Identify optimal site as the latest site with an amplitude >10 percent to signify freedom from scar;
  • Coronary sinus venography in steep left anterior oblique (LAO) view (50-90 degrees) and coronary vein closest to optimal site identified;
  • LV lead placed to optimal site (anterior, lateral, posterior or inferior in LAO view and basal or mid LV in the RAO view); and
  • LV lead position correlated with echocardiographic data and described as: Concordant (pacing the optimal site); Adjacent (1 segment away); Remote (2 segments away from the optimal site).

The researchers used response rates—more than 15 percent reduction of LV end-systolic volume at six months—as the study's primary endpoint.

Response rates were significantly higher in the TARGET group compared with the control group, 70 percent vs. 55 percent. “What we found was an almost 15 to 16 percent difference to position the lead in the right place when STE was used compared to that which was placed in the right place due to chance,” noted Khan.

And while implant-related complications occurred at a rate of 13 percent in the TARGET group and 14 percent in control group, researchers also found that the improvement on a standard scale for HF was 83 percent in the TARGET group and 65 percent in the control arm.

Khan said that freedom from scar at the LV site was associated with reduced mortality and the combined endpoint.

In both groups, placing a concordant lead at the exact target site showed the lowest combined rate of death from any cause and hospitalization related to HF (8 percent). This rate was doubled to 16 percent for patients with a lead placed adjacent to the optimal site and 4.5 times higher for patients with a lead remote from the optimal site.

Compared to the control group, patients within the TARGET group had a higher number of concordant lead placements, 47 percent vs. 61 percent.

“The study advances our understanding a little bit about what happens when you try to target lead placements,” said Khan.

Co-chair of the panel Byron Kwock Lee, MD, of the University of California, San Francisco, called the trial “impressive in light of the fact that other studies like this one, have had difficulty showing clinical significance because even though the cardiac imager is going to tell the electrophysiologist where to place the lead sometimes it's difficult to place the lead there. So to be able to show a clinically significant outcome is impressive.”

Khan concluded that the “STE software can be applied to any existing echocardiographic image at no additional risk to the patient.” However, Khan offered that patients who have enlarged hearts or other conditions may be unsuitable for STE due to the fact that it will not track heart segments and images cannot be evaluated—this usually affects 10 percent of patients. Khan noted that the “simplicity of the technology will allow it to be rolled out to other centers; however, these evaluations must be done in an appropriately measured way.”