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Author
Block:
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Kenneth
M. Stein, Sei
Iwai, Suneet Mittal, Steven M. Markowitz, Ravi K. Yarlagadda, Bindi K. Shah,
Amit B. Guttigoli, Bruce B. Lerman, Cornell University Medical Center, New York,
NY
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Background: Retrospective analysis of the
MADIT-2 database has suggested that the population with a narrow QRS complex
derives less benefit from ICD implantation than the population with a wide
QRS complex. We sought to determine whether the results of EP-testing (EPS)
and T wave alternans testing (TWA) in a population with severe left
ventricular dysfunction and prior myocardial infarction were consistent with
this hypothesis.
Methods: We prospectively evaluated 67 patients (53 men, mean age 68±9
yrs) who were referred for EPS for risk stratification (n=59) or due to a
history of syncope or presyncope (n=8). All patients had documented coronary
artery disease and a prior myocardial infarction and all had an LVEF ≤
30% (mean: 25±5%). All pts underwent TWA testing during rapid atrial pacing
(550 msec) with the Cambridge Heart CH2000 system or HearTwave system at the
time of EPS. TWA was interpreted using standard criteria by two physicians
blinded to the results of EPS. The EPS protocol used programmed stimulation
at two ventricular sites with up to triple extrastimuli with and without
isoproterenol or dobutamine. Positive EPS was defined as the induction of
sustained monomorphic ventricular tachycardia with up to triple ventricular
extrastimuli. A wide QRS was defined as a QRS duration ≥ 120 msec.
Results: Among the 31 patients with a wide QRS, 65% had positive EP
studies vs. 67% among the 36 patients with a narrow QRS (p=NS). Among
patients with a wide QRS 58% had a positive TWA test vs. 47% with a narrow
QRS (p=NS). Excluding patients with indeterminate TWA tests the positivity
rates were 72% and 59% respectively (p=NS). In fully 90% of wide QRS patients
and 81% of narrow QRS patients at least one of the 2 tests (EPS, TWA) was
positive (p=NS).
Conclusion: The likelihood of a positive electrophysiologic study
and/or TWA test is remarkably high in a population with ischemic
cardiomyopathy and LVEF ≤ 30%, irrespective of whether the baseline QRS
is wide or narrow. These data do not support the concept that a narrow QRS
identifies a low-risk subpopulation of "MADIT-2"-type patients.
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