Biomedical Engineering Reference
In-Depth Information
6.3.1.6 The Multicenter InSync Randomized
Clinical Evaluation (MIRACLE)
The randomized, controlled, double-blind MIRACLE study
was conducted from 1998 to 2000. It included 266 patients.
The inclusion criteria were chronic heart failure, an
LVEF
on echocardiography, and a QRS width > 120 ms. The
patients were randomized into a group treated with pharma-
cotherapy and biventricular pacing (409 patients) and a group
with pharmacological medication only (404 patients). In the
CRT group, lower rates of hospitalization for cardiovascular
causes and all-cause mortality were reported compared with
the control group.
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35 %, an LVEDD
³
55 mm, NYHA class III/IV, and
a QRS
130 ms. The aim of the study was to assess the
change in the quality of life, NYHA class, and 6-min walk
test following the implantation of a biventricular system.
Patients who had received standard medication for more than
1 month underwent implantation and were randomized to the
group with resynchronization therapy (n = 134) or the con-
trol group (n = 132) for a period of 6 months. Afterward,
CRT was programmed to be turned on in all the patients. The
6-min walk test and questionnaire-assessed quality of life in
the CRT group were evaluated as superior to those in the
control group. In addition, there was an improvement in
NYHA class and a reduction in LVEDD.
³
6.3.1.10 Resynchronization Reverses Remodeling
in Systolic Left Ventricular Dysfunction
(REVERSE)
This prospective, randomized, double-blind study, conducted
in the period from 2004 to 2006, randomized 610 patients.
Its aim was to assess whether CRT along with optimal phar-
macological therapy can alleviate the development of heart
failure compared with optimal pharmacological therapy
alone. The inclusion criteria were mild heart failure of NYHA
class I/II, a QRS width > 120 ms, an LVEF
40 %, and an
LVEDD > 55 mm. The patients were randomized to optimal
pharmacological therapy and CRT turned on (n = 419) or
optimal pharmacological therapy and CRT turned off (n =
191). At 12 months, no statistically significant differences
were found in the quality-of-life questionnaire or the 6-min
walk test. An improvement in echocardiographic parameters
was reported in the CRT group.
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6.3.1.7 Multicenter InSync ICD Randomized Clinical
Evaluation (MIRACLE ICD)
The MIRACLE ICD study, conducted from 1999 to 2001,
included 639 patients who met the inclusion criteria from the
MIRACLE study as well as indications for ICD implanta-
tion. After CRT-D implantation, the patients were random-
ized to the CRT group or the control group. The following
parameters were assessed again: quality of life, changes in
the NYHA class, 6-min walk test, echocardiographic param-
eters, and pharmacological medication. After 6 months,
resynchronization therapy was activated in the control group.
Improvements in the parameters observed were more
significant in the group with active resynchronization ther-
apy; however, no difference was found between the two
groups in the 6-min walk test.
6.3.1.11 MADIT with Cardiac Resynchronization
Therapy (MADIT-CRT)
Since 2005, this international, multicenter study included a
total of 1,820 patients from 110 centers in 14 countries. It is
the largest randomized CRT-D study of NYHA class I and II
patients. The aim was to ascertain whether CRT-D implanta-
tion in high-risk patients with an LVEF < 30 %, a QRS > 130 ms,
and mild heart failure of NYHA class I/II will reduce all-cause
mortality or mortality from heart failure compared with ICD
treatment alone. The patients were randomized into two
groups in a 3:2 ratio (CRT-D vs. ICD). The study showed that
early CRT-D implantation reduced the risk of mortality by
34 % compared with ICD implantation alone. Resynchronization
also increased LVEF and reduced LVEDD.
The results of the above-mentioned studies, as well as
others not described here, suggest a benefit from biventricu-
lar pacing. Still, according to some data, approximately
20-30 % of patients show no improvement following this
therapy. These patients are referred to as nonresponders.
Assessment of the efficacy of resynchronization therapy
should be performed based on objective data obtained from
echocardiographic or hemodynamic measurements and not
only by assessing the NYHA functional class, which is sub-
jective. However, which parameters are sufficient to assess
the success of CRT is not yet fully clear.
6.3.1.8 Comparison of Medical Therapy, Pacing
and Defibrillation in Heart Failure
(COMPANION)
See the description of this study in the “Secondary Prevention
Studies” section included earlier in the chapter.
6.3.1.9 Cardiac Resynchronization in Heart Failure
(CARE-HF)
This international, multicenter, controlled, single-blind
study, conducted from 2001 to 2003, included a total of 813
patients from 83 centers in 12 countries. The aim of the study
was to determine the effect of CRT on the morbidity and
mortality of patients with moderate to severe heart failure.
The inclusion criteria were heart failure persisting for more
than 6 weeks, NYHA class III/IV despite optimal pharmaco-
logical therapy, an LVEF
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35 %, LV dilatation as evidenced
