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Presentation Number:
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924-129
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Abstract Title:
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Effect of Bundle Branch Block on Microvolt T-Wave Alternans
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Presentation Start/End Time:
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Sunday, Mar 12, 2006, 3:30 PM - 4:30 PM
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Topic:
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Clinical Electrophysiology -Ventricular Arrhythmias
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Author Block:
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Daniel P. Morin, Steven M.
Markowitz, Suneet Mittal, Sei Iwai, Bindi K. Shah, Jim Cheung, Vivian Tan,
David P. Dobesh, Dmitry Nemirovsky, Sandhya Dhruvakumar, Bruce B. Lerman,
Kenneth M. Stein, Cornell University Medical Center, New York, NY
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Background: Microvolt T wave
alternans (TWA) has been proposed as a means of risk stratification for
sudden cardiac death (SCD). It is unknown whether bundle branch block
influences TWA.
Methods: We evaluated 317 consecutive pts with CAD, NSVT, and LVEF <
40% (254 [80.1%] men, age 66.5+10.7 years). Pts underwent TWA
testing and EPS with up to three ventricular extrastimuli (VES) from two
right ventricular sites. Positive EPS was defined as inducibility of
sustained monomorphic VT with up to triple VES, or VF or polymorphic VT
with up to double VES. A physician blinded to the results of TWA and EPS
examined each pt’s ECG for evidence of conduction delay.
Results: There was no difference in the TWA indeterminacy rate
between normals and pts with left hemiblock (HB), LBBB, RBBB, or IVCD (all
p>0.05). Excluding indeterminates, more pts with LBBB than normals had
positive TWA (80% vs. 54%, p=0.02). There was a nonsignificant increase in
the EPS positivity rate in the LBBB group (p=0.07). There was no
significant difference in the TWA positivity rate between normals and pts
with left hemiblock, IVCD, or RBBB (p=0.56, 0.39, and 0.79 respectively),
nor in EPS results between normals and pts with left hemiblock, IVCD, or
RBBB (p=0.86, 0.33, and 0.42).
Conclusions: Compared with normals, TWA is more often positive in
pts with LBBB, but not in pts with left hemiblock, IVCD, or RBBB. This may
reflect either increased sensitivity or diminished specificity of TWA
testing in the setting of LBBB.
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QRS width, ms
(mean, SD)
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EF, %
(mean, SD)
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TWA Pos
(n, %)
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TWA Neg
(n, %)
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TWA Ind
(n, %)
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TWA
Pos/(Pos+Neg)
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EPS Pos
(n, %)
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EPS Neg
(n, %)
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Normal (n=179, 56.5%)
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97.1 (11.5)
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29.7 (7.8)
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69 (38.5)
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59 (33.0)
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51 (28.5)
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0.539
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85 (47.5)
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94 (52.5)
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HB (n=42, 13.2%)
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100.5 (10.5)
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31.8 (7.0)
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16 (38.1)
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18 (42.9)
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8 (19.0)
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0.471
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21 (50.0)
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21 (50.0)
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LBBB (n=37, 11.7%)
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148.3 (17.7)
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25.2 (7.5)
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20 (54.1)
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5 (13.5)
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12 (32.4)
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0.800
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24 (64.9)
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13 (35.1)
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IVCD (n=31, 9.8%)
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126.7 (14.1)
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26.7 (8.9)
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17 (54.8)
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9 (29.0)
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5 (16.1)
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0.654
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18 (58.1)
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13 (41.9)
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RBBB (n=28, 8.8%)
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145.2 (19.0)
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28.7 (8.4)
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9 (32.1)
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6 (21.4)
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13 (46.4)
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0.600
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16 (57.1)
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12 (42.8)
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Keywords:
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Sudden death,Rhythm disorders,Risk prediction
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