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Presentation Time:
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11/9/2004 4:15:00 PM
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Title:
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Electrical Remodeling Caused by Brief Ventricular Ectopy Increases T
Wave Alternans
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Keywords:
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Ventricular arrhythmia,Sudden death,Pacing,Electrophysiology
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Author Block:
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William R Lewis, Ottorino Costantini, MetroHealth Med Ctr,
Cleveland, OH; Jennifer E Cummings, Cleveland Clinic Foundation, Cleveland,
OH; Kara J Quan, David S Rosenbaum, MetroHealth Med Ctr, Cleveland, OH
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Disclosure Block:
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W.R. Lewis, None; O. Costantini,
None; J.E. Cummings, None; K.J. Quan, None; D.S.
Rosenbaum, Cambridge Heart E. Consulting fees or other remuneration.
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Unlabeled/unapproved:
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There are no unlabeled/unapproved uses of drugs or products
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Background: Ventricular
ectopy (e.g.: PVCs) alters ventricular depolarization and repolarization
and is associated with arrhythmia vulnerability in the setting of left
ventricular dysfunction. An altered activation sequence also produces
ventricular electrical remodeling (VER), often ascribed to “T wave memory”.
T Wave Alternans (TWA) testing is a technique used to evaluate ventricular
repolarization and arrhythmia risk. Therefore, we hypothesized that VER
caused by ventricular ectopy increases susceptibility to TWA. Methods
and Results: Microvolt-level TWA was measured in 22 patients
during controlled atrial pacing using a 10 minute ramp protocol (a gradual
increase in heart rate from 100 to 120 bpm, and then a gradual deceleration
back to 100 bpm). Then, 10 minutes of PVCs (paced single extrastimuli) were
delivered from the right ventricular apex to simulate bigeminy, and the
atrial pacing ramp protocol was then repeated. TWA levels were compared
before and after the period of VER by PVCs. Mean age was 58 +/- 8 years. There
were 21 men, 45% had diabetes, and 73% had hypertension. The mean ejection
fraction was 32 +/-13%. Ischemic cardiomyopathy was seen in 77%, and 54%
had undergone CABG. The duration of TWA was 2.0 +/-3.9 min at baseline,
which increased significantly to 2.6 +/-4.4 min after PVCs (p=0.037). There
was a trend towards an increase in TWA amplitude from 5.4 +/-3.0 to 6.4
+/-3.9 microvolts after PVCs (p=0.08). Overall, 15 of 22 (68%) patients
exhibited an increase in TWA after simulated PVCs. A subset of patients
underwent sequential atrial pacing protocols without PVCs and did not
demonstrate any change in TWA amplitude or duration. Conclusion:
Surprisingly brief periods of ventricular ectopy increase T wave alternans
in patients with left ventricular dysfunction. These data suggest a
mechanism by which ectopy-induced Ventricular Electrical Remodeling may enhance
susceptibility to ventricular arrhythmias.
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