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biventricular pacing in CHF
Dr Eric Prystowsky
Director
Clinical Electrophysiology Laboratory
St Vincent Hospital, Indianapolis
Dr Leslie Saxon
Chief, Electrophysiology Laboratory and Implantable
Device Services
University of California in San Francisco
San Francisco, CA
Dr Angelo Auricchio
Director, Cardiac Catheterization Laboratory
University of Magdeburg
Magdeburg, Germany
Pacing in heart failure
While only 5-10% of advanced heart failure
patients have traditional indications for
bradycardia pacemakers, many of them have
conduction disease – prolonged PR intervals or
bundle branch blocks.
In early, non-randomized trials, programming the
AV delay to about 100 ms in standard RA and RV
pacemakers in decompensated class IV heart
failure patients resulted in dramatic improvements
in pump function.
In controlled clinical trials, no universal right-sided
delay was found to improve pump function.
Improving left- and right-sided
delays
A subset of patients with marked prolongation of
their PR interval and mitral regurgitation may
benefit from an ultra-short AV delay in the range of
100 ms.
It was also thought that the 30% of patients with
dilated heart failure who have a left bundle branch
block might benefit from pre-excitation, reducing
the delay in left sided activation contraction.
Current studies in biventricular stimulation are now
ongoing.
PATH-CHF
Pacing therapies for congestive heart failure
In an original substudy, patients with class III and
IV heart were implanted with ventricular
resynchronizers (VRs). They were treated for 1month with pacing, 1-month with the VR turned
off (without the patient’s knowledge), and a
further 1-month with stimulation. Investigators
measured heart rate, heart rate variability, and
oxygen consumption.
A second study looked at left ventricular pacing
alone compared to biventricular pacing.
PATH-CHF
Pacing therapies for congestive heart failure
Measurement of acute hemodynamic responses
revealed 2 different patient populations with
regard to the effect on the QRS complex.
Patients with a wide QRS complex, wider than 150
ms, all behave as responders.
Other patients may not respond acutely to any
shortening of the AV delay, and may even
demonstrate substantial hemodynamic worsening.
Biventricular pacing
Transvenous approach to epicardial pacing
A lead may be passed through the coronary sinus
and into the venous system, obviating the need
for screw-in epicardial lead implants.
Approximately 5-10% of patients have some
anatomical aberrancy and cannot be implanted
using the transvenous approach.
The ability to lodge the lead in the terminal vessels
to get adequate LV pacing down far enough off the
AV groove is also an issue.
This technology still needs refinement so that
these leads can be implanted widely and safely.
Pacing as therapy for CHF
To date, the patients who improve the most have
the widest QRS intervals and more advanced heart
failure. In these patients, improvements in VO2
and walking distance up to 20-25% have been
noted.
Early echo data shows that chronic pacing for as
short as 3 months prevents the progressive
remodeling of the ventricle.
Insufficient data currently exist regarding the
effects of pacing in right bundle branch block.
Pacing as preventive therapy for CHF
“I guess the question Leslie is throwing on the
table, and I've heard it from others, and I
think it's intriguing…if you take somebody who
has class II heart failure with a left bundle, or
left IVCD, and prophylactically pace them, will
you prevent the development of class III
failure?”
Dr Eric Prystowsky
Director
Clinical Electrophysiology Laboratory
St Vincent Hospital, Indianapolis
Additional randomized trials in
biventricular pacing
The COMPANION trial looks at mortality and
hospitalization in CHF patients using biventricular
stimulation alone, or biventricular therapy coupled
with an ICD, compared to standard drug therapy.
The MUSTIC trial (Multisite Stimulation in
Cardiomyopathy) randomized 58 heart failure
patients into 2 study arms using a cross-over,
single-blinded design. The first arm started with
BVP, the second with no BVP - after 3 months the
pacing modes were switched.
MUSTIC trial results (i)
Overall results of BVP vs no BVP
BVP vs no BVP
Distance walked in 6-minute period*
Peak VO2 (mL/min/kg)†
Quality of life†
BVP biventricular pacing
* primary endpoint
† secondary endpoint
Percentage
change
p value
+ 23%
0.0001
+ 8%
0.0158
+ 30%
0.0002
MUSTIC trial results (ii)
The MUSTIC trial had a 5% mortality rate during
the 6-month crossover period.
2 deaths were classified as sudden death: 1
occurred after 26 days in the BVP mode, 1
occurred after switching the pacemaker from
inactive to active mode.
The third death was due to heart failure
decompensation.
No data have yet shown that biventricular pacing
promotes arrhythmic death.
PACMAN trial
The PACMAN trial is a randomized trial with 2
arms, comparing biventricular stimulation versus
no stimulation over time. Therapy is maximized for
ACE inhibitors, beta-blockers and diuretics.
Endpoints include improvement in exercise
capacity, oxygenation and changes in total
comorbidities.
Follow-up will be at least 1 year per patient.