Circulation, Vol 74, 1280-1289, Copyright © 1986 by American Heart Association
DL Kuchar, CW Thorburn and NL Sammel
The risk of developing spontaneous ventricular tachycardia (VT) and/or
sudden death ("arrhythmic events") was prospectively assessed in 165
patients who survived acute myocardial infarction. Signal-averaged
electrocardiograms (ECGs) were performed before hospital discharge and then
serially at regular intervals over the following year. In addition, 24 hr
Holter monitoring was performed and left ventricular ejection fraction was
determined. Sixty-five patients (group 1) had abnormal signal-averaged ECGs
(voltage in the last 40 msec of the filtered QRS less than 20 microV or
filtered QRS duration greater than 120 msec), 92 had normal signal-averaged
ECGs (group 2), and eight had bundle branch block (excluded from analysis).
In group 1, spontaneous normalization of the voltage in the last 40 msec of
the QRS complex occurred in 30% of patients after 12 months, although total
filtered QRS duration did not change overall. During follow-up of up to 20
months (median 11), seven patients died suddenly and six presented again
with spontaneous, symptomatic VT. Eleven of 65 (17%) group 1 patients had
an arrhythmic event compared with one of 92 patients (1%) in group 2 (p
less than .001). The sensitivity of the signal-averaged ECG as a predictor
of arrhythmic events was 92% with a specificity of 62%. Patients with
subsequent arrhythmic events had considerably lower voltage in the last 40
msec of the QRS (11.0 +/- 8.3 vs 32.0 +/- 21.9 microV; p less than .001)
than those without such events, and longer filtered QRS complexes (121 +/-
14 vs 105 +/- 12 msec; p less than .001). Multivariate logistic regression
determined that the signal- averaged ECG provided independent prognostic
information from the presence of complex ventricular ectopy and the degree
of left ventricular dysfunction assessed at the time of hospital discharge.
Signal-averaged ECGs provide important prognostic information in
identifying patients at risk of arrhythmic events after myocardial
infarction. Dynamic changes in the terminal QRS voltage are observed during
the first year after myocardial infarction.
ARTICLES
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