'Sweet Spot' for Echo-Guided CRT Lead Placement Explored in Trial

May 14, 2012

May 14, 2012 (Boston, Massachusetts) — Patients are more likely to respond to cardiac resynchronization therapy (CRT), clinically and in terms of reverse remodeling, if speckle-tracking echocardiography guides the placement of their pacing leads, suggests a randomized study [1].

For echo guidance in the trial, called Speckle Tracking Assisted Resynchronization Therapy for Electrode Region (STARTER), leads were positioned at or close to the myocardial site of latest mechanical activation for each patient individually. Those whose lead positions were tailored that way, compared with standardized positioning without echo guidance, benefited with significantly improved ventricular end-systolic volumes and survival without heart-failure hospitalization.

"A substantial proportion of patients, about one-third, do not respond to CRT therapy, and we don't know who those people are," Dr Samir Saba (University of Pittsburgh, PA) told heartwire . "Now we are starting to understand better. Once we know where the leads should be appropriately placed, for that specific patient, we achieve better results."

Dr Samir Saba

Saba presented STARTER here at the Heart Rhythm Society 2012 Scientific Sessions. Its findings support the earlier TARGET trial of CRT lead positioning guided by the same echo technique, which led to similar significant improvements in end-systolic volumes and clinical outcomes.

STARTER further clarifies how important it is to position the pacing leads precisely at the echo-determined target region — as it turns out, according to Saba, "not very important."

The trial, he said when presenting the study, "would suggest that adjacent or exact [placement] are equally good, we don't have to be precise; there is potentially a large sweet spot."

Even so, he said when interviewed, "There are at least a good 15% of patients in whom you can't even achieve the close vicinity of the site of latest mechanical activation. And in those, we may need to consider other routes, down the line." One of the study's implications for the future, according to Saba, is that alternatives like epicardial or transseptal lead placement may be needed to achieve optimal CRT results for patients in whom the echo-guided best position can't be achieved transvenously.

The trial randomized 187 patients eligible for CRT based on LVEF and QRS-duration criteria, in NYHA class 2–4 heart failure, to device implantation with lead placement guided or not guided by speckle-tracking echocardiography. In each case, the site of latest mechanical activation was determined by assessing the time to peak radial strain associated with myocardial wall thickening.

Procedure time and fluoroscopy time were similar in the two groups whether or not leads were placed under echo guidance. But echo-guided placement at the exact myocardial target or adjacent to it was possible 85% of the time. Lead placement at the optimal site "happened fortuitously" without echo guidance two-thirds of the time (p=0.009).

Matching of lead positions to targets and clinical outcomes, by echo guidance or no echo guidance

Parameter Echo guided, n=110 (%) Standard, n=77 (%) P
Concordance of LV lead with site of latest mechanical activation      
Exact concordance 30 12 0.006
Exact concordance or adjacent 85 66 0.009
Remote 15 33 0.009
Events (mean follow-up 1.8 y, median 1.95 y)      
Death 14 19 0.192
HF hospitalization 11 22 0.031
Transplantation 1 1 0.655
LVAD implantation 3 4 0.480

 

Over a follow-up averaging 1.8 years, the rate of heart-failure hospitalization was significantly lower in the echo-guided group (p=0.031), but there were no such significant differences for mortality, rate of transplantation, or rate of receiving a left ventricular assist device (LVAD).

However, the intention-to-treat primary end point of death or heart-failure hospitalization according to lead position was significantly reduced when leads were placed at or near the target vs remote from the target (p=0.006). Hitting or nearly hitting the lead target similarly led to a reduced rate of death, transplantation, or LVAD use (p=0.002).

Echocardiographic structural effects at one year by randomization (method of lead positioning) and by concordance of lead position and site of latest mechanical activation

Parameter Echo-guided (%) Standard (%) p Concordant or adjacent (%) Remote (%) p
LVESV change -30 -20 0.04 -30 -11 0.005
LVESV decrease ≥15 and no primary clinical event 59 41 0.043 57 29 0.010
LVEF change +13% +9 0.12 +13 +6 0.014
LVEF increase ≥5% and no primary clinical event 59 36 0.009 55 26 0.008

LVESV=left ventricular end-systolic volume

Both echo-guided lead placement and positioning of the leads at or near the target site, considered separately, significantly improved reverse myocardial remodeling by several measures of left ventricular end-systolic volume at one year.

One variable not included in the current analysis, Saba said when interviewed, was the effect of myocardial scarring on the success of speckle-tracking echo guidance. Scars would vary widely in position and quantity among patients with ischemic cardiomyopathy, who made up 62% of the cohort.

"Scar could be part of the equation, and that's why we will be doing that analysis on the STARTER data. There was a significant improvement in outcomes even without taking scar into account. But whether there would be an additional benefit to the information on site of latest mechanical activation if we add information on scar remains to be seen."

Saba discloses receiving research grants from Boston Scientific, Medtronic, St Jude Medical, and Biotronik; consulting for Spectranetics and St Jude Medical; and having intellectual property rights with Medtronic.

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