ANALYSIS OF ABNORMAL INTRA-QRS POTENTIALS - IMPROVED PREDICTIVE VALUEFOR ARRHYTHMIC EVENTS WITH THE SIGNAL-AVERAGED ELECTROCARDIOGRAM

Background Using the signal-averaged ECG (SAECG), this study developed a new electrical index for predicting arrhythmic events: abnormal int ra-QRS potentials (AIQP). Methods and Results We studied 173 patients followed after myocardial infarction for a mean duration of 14+/-7 mon ths. Sixteen arrhythmic events occurred, defined as sudden cardiac dea th, documented sustained ventricular tachycardia, or non-fatal cardiac arrest, Noninvasive indices of arrhythmia risk were measured, includi ng AIQP, conventional SAECG, Holter, and left ventricular ejection fra ction (LVEF), Abnormal intra-QRS potentials were defined as abnormal s ignals occurring anywhere within the QRS period. They were estimated w ith a lead-specific, parametric modeling method that removed the smoot h, predictable part of the QRS. AIQPs are characterized by the remaini ng transient, unpredictable component of the QRS and manifest as low-a mplitude notches and slurs. A combined XYZ-lead AIQP index exhibited h igher specificity (95%) and predictive value (PV) (+PVI 47%; -PV, 94%) than the conventional SAECG in combination with Holter and LVEF (spec ificity, 89%; +PV, 25%; -PV, 93%). Conclusions AIQP improved specifici ty and predictive value, compared with conventional tests, for predict ion of arrhythmic events. AIQP emerged as the best noninvasive univari ate predictor of arrhythmic events after myocardial infarction in this study. A review of several other reports shows that AIQP in the prese nt study outperformed the conventional predictive indices reported in those other data sets.