Beat-to-beat QRS variability of 12-lead ECG in patients with scintigraphic signs of infarction and ischemia

The aim was to study beat-to-beat QRS variability in resting 12-lead ECG in patients with ischemia and myocardial infarction. The variability analysis was based on a refined technique for time alignment of the beats and included means for compensating the influence of respiration. A group with normal myocardial scintigraphy (called NO) was compared to a group with signs of both myocardial infarction and exercise-induced ischemia (called ISCINF). The mean QRS variability was smaller in lead I in ISCINF than in NO but there was no significant difference in QRS variability in the other leads. The joint variance in all leads was calculated and ROC curves constructed. The sensitivity to detect coronary artery disease (CAD) was 75% at a specificity of 50%. It is concluded that QRS variability does not discriminate between presence and absence of CAD well enough to be of clinical value.