All concepts, explanations, trials, and studies have been
re-written in plain English and may contain errors. I am
not a doctor
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Cardiac Resynchronization Therapy (CRT)
This means using a BiV (biventricular or 3-lead) pacemaker.

About one in 3 CHFers receiving a CRT pacer don't benefit.
Pacer implant does have risk and it is expensive, so
selecting patients who will benefit is important. People
with uncoordinated beating between right and left heart
chambers may be helped most.
	The most promising measurement for spotting these
patients so far is made by echo. An echo using an EKG as a
reference can measure the delay between when blood leaves
the pulmonary artery and when it leaves the aorta. Such an
echo can also measure the delay between motion in different
parts of the heart's wall.

One trial showed that using echo to calculate "septal to
posterior wall motion delay" or SPWMD, predicts long-term
improvement in heart function with CRT pacing.
	This study included 25 class 3 CHFers with EFs
under 35%. All patients had normal heart rhythm and had
left bundle branch block, with QRS duration over 140 ms.
	Before pacer implant, an echo was done. Left heart
size and SPWMD were measured. Patients were followed up at
one month and again at one year.
	After one year, left heart size, EF, and mitral
valve regurgitation all improved. An SPWMD over 100 ms
predicted all patients who responded by better than 15%
to CRT pacing. The worse the uncoordinated beating of the
heart's chambers, the more EF improved.
	This trial suggests that measuring SPWMD by echo
can help select CHFers who will get definite improvement
from CRT pacing.

Longer-term results from MIRACLE, MIRACLE ICD, and InSync
III trials show that most improvement from CRT pacing
shows up within 3 months after device implant, with very
little further improvement later on. Improvements do seem
to last.

Source: Medscape.
Source: American Heart Association Scientific Sessions 2003.
Author: Dr. Ileana Pina.