|
The high-resolution electrocardiogram (Hi-Res
ECG) allows analysis of signals that are too small to be detected by routine
measurement techniques. Among such signals are those which arise from areas of
slow and inhomogeneous conduction in diseased ventricular myocardium (usually
referred to as late potentials).
In 1991, a Task Force of the American College of Cardiology, the American Heart
Association, and the European Society of Cardiology published standards for
acquisition, analysis, and clinical indications for the Hi-Res ECG. These
recommendations were recently updated by an American College of Cardiology
Expert Consensus Document. The most important applications of the Hi-Res ECG
include: 1) risk stratification for future arrhythmic events in survivors of myocardial
infarction, and 2) prediction of malignant ventricular tachyarrhythmias in patients
with coronary artery disease and syncope, or asymptomatic non-sustained ventricular
tachycardia. Numerous studies have convincingly shown that the Hi-Res ECG is a useful
noninvasive test for risk stratification for malignant ventricular tachyarrhythmias,
especially in survivors of myocardial infarction. It has a very high negative predictive
accuracy but a relatively low positive predictive accuracy. This is why efforts to
optimize the overall predictive value of the test are ongoing. Two general approaches
have shown promising results. One, is the realization that varying abnormality criteria
may be required for different clinical indications. Second, is the observation that
combined time- and frequency-domain analysis of the Hi-Res ECG can significantly
improve its predictive accuracy. Finally, even if efforts to increase the prognostic value
of the Hi-Res ECG are successful, optimal risk stratification for arrhythmic events
dictates that the test be utilized as part of an algorithm in conjunction with other
risk stratifiers.
|
