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Abstract
Title:
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The
Influence of Atrial and Ventricular Pacing on T Wave Alternans
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Presentation
Start:
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Sunday,
Mar 07, 2004, 10:00 AM -11:00 AM
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Topic:
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ECG/Ambulatory
Monitoring Signal Averaging
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Author
Block:
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Aneesh
V. Tolat,
Matthew R. Reynolds, Panos Papageorgiou, Allison W. Richardson, Peter
Zimetbaum, Mark E. Josephson, Beth Israel Deaconess Medical Center, Boston,
MA
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Background:
T Wave
Alternans (TWA) is a novel technique of risk stratification for sudden
cardiac death. Exercise and atrial pacing have been studied with regards to
their influence on TWA. In the present study, we investigated the
differential effect of atrial and atrioventricular pacing on TWA outcome
(TWA-O) and TWA magnitude (TWA-M) and examined their correlation with
outcome of standard electrophysiology study (EPS) in patients with coronary
disease and left ventricular dysfunction.
Methods: Atrial and atrioventricular pacing at 5 rates (80, 90, 100,
110, 115 bpm) for 1.5 minutes was performed followed by EPS in 34 patients
with a history of coronary disease and mean ejection fraction 28% referred
for risk stratification. A Cambridge Heart, Heartwave system was used to
analyze TWA-O (+ or - ) according to standard guidelines. TWA analysis was
based on recordings from 6 precordial leads and 4 orthogonal leads.
Results: Atrioventricular pacing resulted in higher TWA-M when
compared to atrial pacing alone, but both sites yielded similar TWA-O
(p=0.02; Sign Test; kappa=0.61). Monomorphic ventricular tachycardia was
inducible in 20/34 patients. TWA was positive in 16 patients during atrial
pacing and in 13 patients during atrioventricular pacing but TWA-O did not
correlate with EPS outcome. The ECG lead distribution of TWA was
independent of pacing site. Leads V2-V4 demonstrated 100% sensitivity for
positive TWA
Conclusion: 1. Increased TWA-M during ventricular pacing suggests
that ventricular pacing may be proarrhythmic. 2. TWA and EPS measure
different indices of electrical instability and could be used in
combination. 3. The use of the anterior precordial leads may allow for a
simplified approach in recording TWA. 4. Ventricular pacing may be
alternative method to assess TWA in patients with atrial fibrillation.
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