Cardiac vulnerability assessment from electrical microvariability of high-resolution electrocardiogram

Patients susceptible to malignant arrhythmias often have an increased beat- to-beat variation of the T-wave of the electrocardiogram. Variability analy sis of the T-wave is increasingly used for non-invasive risk assessment The aim of this study is to evaluate intra-ORS beat-to-beat signal variation a nd to compare it to ST-T variation. The beat-to-beat, microvolt variation o f the QRS and the ST-T segment from 44 patients with coronary heart disease at high risk of suffering from malignant arrhythmias and from 51 healthy v olunteers are compared. Variation analysis is carried out on 250 consecutiv e sinus beats from high-resolution electrocardiograms. The individual beats are filtered using a waveform-independent, cubic spline-filter. A variabil ity index of the ORS and ST-T segments is calculated as the integrated stan dard deviation of corresponding samples inside the area of interest. Patien ts at risk of suffering from malignant arrhythmias have a significantly hig her variability index of both the QRS (median 44.5ms against 34.7ms, p<0.00 1) and the ST-T segment (median 20.5ms against 9.8ms, p<0.001 compared to t he group of healthy subjects. The discriminative ability of the odds variab ility indices of the QRS and ST-T segments are not statistically different, the ratios being 7.8 (QRS) and 12.6 (ST-T). We conclude that patients at h igh risk of suffering from malignant arrhythmias are characterised by an in creased beat-to-beat microvolt variation of both the QRS and the ST-T segme nt Further studies are necessary to evaluate the prognostic potential of de polarisation variability.