TARGET: Individualized assessment
improves results of cardiac resynchronization therapy
In the first randomized clinical trial to report the
benefits of using echocardiography - the most common non-invasive tool for diagnostic
imaging of the heart - to guide placement of pacemaker leads, researchers found
that a patient-tailored approach using software to analyze left ventricle function
and guide placement of lead wires can significantly boost clinical benefits from
pacemakers, according to research presented at the American College of Cardiology's
60th Annual Scientific Session.
"Optimal placement of pacemaker leads is determined by the location of
cardiac scar tissue and areas of delayed heart muscle contraction, which vary
considerably among patients," said Fakhar Z. Khan, M.D., clinical research
fellow, Cambridge University, Cambridge, U.K. "Our improved results with
an individualized approach should change the way pacemaker leads are implanted
in this population of patients."
Researchers used speckle tracking echocardiography (STE) to conduct cardiac
assessments of 220 patients scheduled for cardiac resynchronization therapy. STE
is a technological advance that refines echocardiography. Several studies have
confirmed that STE is a simple, inexpensive, quick and accurate way to measure
strain and function in the myocardium.
For the 110 patients randomly assigned to the test group, STE measurements
guided placement of the lead wire implanted in the left ventricle. Leads for the
control group were implanted conventionally, without reference to the STE data.
The test group had better results than the control group on all clinical endpoints,
including rates of response by reverse remodeling of the left ventricle, a measure
of improvement in heart function (70 percent vs. 55 percent), and improvement
on a standard scale for heart failure (83 percent vs. 65 percent).
Clinical results correlate with degree of success in directing the lead to
the optimal site identified by STE. Across both groups, patients with a concordant
lead - placed exactly at the target site - had the lowest combined rate of death
from any cause and hospitalization related to heart failure (8 percent) and better
results overall. That rate was doubled (16 percent) for patients with a lead adjacent
to the optimal site and 4.5 times higher (36 percent) for those with a lead remote
from the optimal site. A much higher proportion of patients in the test group
had concordant lead placement (61 percent vs. 47 percent).
"STE software can be applied to any existing echocardiographic image at
no additional risk to the patient," Khan said. "It makes targeting of
the lead feasible at any facility that's already performing echocardiography and
has the software in their system to analyze the images. That makes it widely accessible,
even for small centers and non-university hospitals, where more and more pacemakers
are being implanted."
Study participants were recruited from Papworth and Addenbrooke's Hospitals,
Cambridge, U.K, and will continue to have ongoing follow-up. The study was sponsored
by Papworth Hospital Foundation Trust and funded through charitable funds and
the UK National Institute for Health Research.
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