Clinical applications of signal-averaged electrocardiography in patients after myocardial infarction.
In conclusion, signal-averaged electrocardiography is a useful, noninvasive technique to identify patients after myocardial infarction at risk for future arrhythmic events, especially in conjunction to existing tools, such as 24 hour ambulatory monitoring, echocardiography, nucleotide angiography and coronary angiography. It has a limited positive predictive value, but has an excellent negative predictive value. The optimum time to do signal-averaged electrocardiograms after myocardial infarction is unclear, 6 to 14 days after myocardial infarction has the highest sensitivity. Time domain analysis remains the most common method used to record late potentials. The definition of late potential and the scoring of a high resolution electrocardiogram as normal and abnormal have not yet been resolved. The criteria proposed by the Task Force Committee of the European Society of Cardiology, the American Heart Association and the American College of Cardiology (see introduction) should be observed at present. Many studies on signal-averaging were done in the prethrombolytic era. In patients who have received thrombolytic therapy, the positive predictive value of signal-averaged electrocardiograms has decreased. There are other limitations in applying signal averaging technique. The faster the ventricular tachycardia is induced in electrophysiological studies, the shorter is the late potential. Thus, a faster tachycardia which causes sudden cardiac death may not be detected by late potentials. The management strategies for patients who have abnormal signal-averaged electrocardiograms after myocardial infarction have not be defined. One should note that any management strategy has to prove that it improves prognosis. More prospective, randomized clinical trials are required to address these issues.
Wong
C B
CB
Department of Cardiology, University of Nebraska Medical Center.
Windle
J R
JR
D001145:Arrhythmias, Cardiac / Q000175:diagnosis* / Q000503:physiopathology; D016757:Death, Sudden, Cardiac / Q000209:etiology; D004562:Electrocardiography / Q000295:instrumentation*; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000503:physiopathology; D012307:Risk Factors; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D013610:Tachycardia / Q000175:diagnosis / Q000503:physiopathology