QRS scoring with the Mason‐Likar lead system at rest and during ischaemia

Abstract

The stability of the post-infarction simplified 29-point Selvester QRS score during maximal exercise testing was studied using both standard 12 and Mason-Likar (modified standard, M-L) ECG lead systems. Thirty-eight patients participated in the standard exercise test (mean interval after single infarction 4 months) and a total of 54 patients underwent exercise 201thallium emission tomography with M-L lead system 2 months later. None had electrocardiographic features complicating the scoring. There were no significant differences between the (paired) mean QRS scores, except between the M-L score at rest (2.3 +/- 2.4) and at exercise (3.2 +/- 2.6, P less than 0.01). The correlation coefficient (r) between resting scores was 0.87, between rest and exercise 0.90 (standard leads) and 0.80 (M-L leads). In 78% nuclear imaging revealed ischaemia, but this had no significant effect on the mean scores or correlation between rest and exercise scores. It is concluded that the QRS score is relatively stable during exercise with standard leads if the limb leads are recorded immediately after the exercise. Scoring with the M-L lead system is somewhat inaccurate, especially during exercise, and is not recommended for stratification of clinical risk. The QRS score is protected against ischaemia, which emphasizes its value as an independent prognostic tool.