curtis_2008.qxp 5/8/08 12:23 Page 78
Heart Block
Figure 1: Detrimental Effects of Chronic Right Ventricular Pacing
AF, HF hospitalization,
3–5,10
and ventricular arrhythmias.
11
This reality has
prompted clinicians to evaluate the role of CRT in patients with AVB who
do not have indications for CRT according to current guidelines.
RV pacing
The Post-AV Nodal Ablation Evaluation (PAVE) trial compared chronic
biventricular (BiV) pacing with RV ventricular pacing in 184 patients
Altered ventricular activation undergoing ablation of the AV node for management of AF. The study
end-points were change in the six-minute walk test, quality of life, and
LVEF. Patient characteristics were similar in both groups. At six months
Delayed papillary
post-ablation, patients treated with CRT had a significant improvement in
Delayed LV contraction
muscle contraction
Abnormal septal motion
six-minute walk distance and LVEF. Patients with an EF ≤45% or with
NYHA class II/III symptoms receiving a BiV pacemaker appeared to have a
greater improvement in six-minute walk distance than patients with
LV–RV asynchrony Septal EF
Mitral regurgitation
normal systolic function or class I symptoms.
19
Leon et al.
20
evaluated the effects of a BiV upgrade in 20 patients with
LV diastolic filling Global EF
severe HF (EF ≤35%, NYHA functional class III or IV) who had previously
LA/LV remodeling undergone AV junction ablation and RV pacing for management of AF.
Mean follow-up was 17.3 months. There were significant improvements
in NYHA functional classification, LVEF, reverse remodeling indices, and
EF = ejection fraction; LA = left atrial; LV = left ventricular; RV = right ventricular.
hospitalizations after BiV upgrade. In the Homburg Biventricular Pacing
Evaluation (HOBIPACE) study, 30 patients with a standard indication for
Table 1: Clinical Trials of Cardiac Resynchronization Therapy in
Patients with Atrioventricular Block
permanent ventricular pacing for AVB and LV dysfunction defined by an
LV end-diastolic diameter ≥60mm and an EF ≤40% were randomized to
Study (Population) Pacing Modality Mean Follow-up Findings/Comments
RV or BiV pacing. BiV stimulation was associated with a significant
PAVE trial
19
RV versus BiV 6 months The BiV group had a
decrease in LV end-diastolic and end-systolic volumes, N-terminal
(n=184) significantly greater LVEF fragment of B-type natriuretic peptide (NT-proBNP) level, and the
(AF and AV than the RV group Minnesota Living with Heart Failure score compared with RV pacing. BiV
junction ablation)
stimulation was associated with a significant increase in LVEF and
Leon et al.
20
Upgrade from RV 17.3 months Significant improvements in
exercise capacity.
21
(n=20) to BiV pacing NYHA class, LVEF, reverse
(AF and AV remodeling indices, and HF
Hay et al.
22
reported the acute hemodynamic effects of different pacing
junction ablation)
techniques in nine patients with HF, AF, and severe AVB. Ventricular
HOBIPACE trial
21
RV versus BiV 3 months Significant improvements in
(n=30) cross-over reverse remodeling indices,
stimulation was applied to the RV (apex or outflow tract), LV free wall, and
(AVB and LVEF <40%) LVEF, and exercise capacity
both sites (BiV). BiV improved systolic function more than either site alone,
OPSITE trial
23
RV versus LV 3 months Modest changes in quality of
and LV pacing was significantly better than RV pacing. However, only BiV
(n=186) (phase1) cross-over life and exercise capacity,
improved diastolic function (isovolumic relaxation).
(NYHA class II ICD RV versus BiV non-clinically significant
patients with (phase2) The Optimal Pacing Site (OPSITE) study was a three-month cross-over
QRS >130ms)
randomized clinical trial comparing RV with LV pacing (phase 1) and RV
BLOCK HF
24
CRT on versus Ongoing Evaluate role of CRT in
with BiV pacing (phase 2) in 56 patients undergoing AV junction ablation
(n=1,636) CRT off patients with LVEF
for AF. Mean EF was 39% at baseline. Only a modest improvement was
<50% and symptomatic
observed in quality of life and exercise capacity, and was not clinically
bradycardia with different
significant. Moreover, the improvement in quality of life observed with
degrees of AVB
BIOPACE Trial
25
RV versus BiV Ongoing Evaluate role of CRT in
rhythm regularization was three to 10 times higher than that obtained
(n=1,200) patients with different
using RV to LV or BiV pacing. Interestingly, BiV pacing but not LV pacing
degrees of AVB; normal and
was slightly superior to RV pacing in the subgroup of patients with
<50% LVEF will be included
preserved systolic function and a narrow QRS interval.
23
PREVENT HF
26
RV versus BiV Ongoing Evaluate role of CRT in
(n=100) patients with high These findings suggest that patients with AVB, LVEF <45%, and NYHA
probability of 80% of VP;
functional class II–IV appear to benefit from CRT rather than RV pacing
normal and <50% LVEF will
alone. These data also suggest that in patients with AVB, BiV pacing may
be included
be superior to LV pacing. The benefit of CRT is not yet clear in patients
with AVB and a normal LVEF. The results of the OPSITE study seem to differ
AF = atrial fibrillation; AV = atrioventricular; AVB = atrioventricular block; BiV = biventricular;
CRT = cardiac resynchronization therapy; EF = ejection fraction; HF = heart failure; LV = left
from the other clinical studies. This discrepancy can probably be explained
ventricular; NYHA = New York Heart Association; RV = right ventricular; VP = ventricular pacing.
by the study design (BiV pacing only after completion of phase 1, RV
78 US CARDIOLOGY
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