QRS duration measurement using high-frequency electrocardiography: Applications and limitations of a new technique

Abstract

Accurate, objective measurement of QRS duration is of central importance in clinical electrocardiography. The applicability of a new computer technique based on the observation that the QRS, unlike other ECG waveforms, contains significant frequencies >50 Hz was studied. Accordingly, a microprocessor-based ECG system was adapted with a signalaveraging program to reduce noise and a 50- to 300-Hz phaseless digital filter which permitted direct “extraction” of the QRS complex from surrounding low-frequency PR and ST segments. The hypothesis first tested was that, owing to greater cardiac mass, QRS duration in men should be slightly greater than in women. High-frequency QRS duration measurements were performed in 30 healthy adult men and 28 healthy adult women from simultaneously acquired orthogonal leads I and a VF. QRS duration in men (85.5 ± 12.3 msec, X ± SD ) was significantly ( p < 0.05) greater than in women (78.7 ± 11.0 msec). Furthermore, after pooling these two groups of healthy subjects ( n = 58), modest but significant ( p < 0.001) correlations were noted between QRS duration and height ( r = 0.51), weight ( r = 0.46), and body surface area ( r = 0.48). The question then addressed was whether QRS duration in patients with myocardial infarction (after excluding those with apparent conduction delays, hypertension, or axis deviation) is greater than normal due to myocardial scarring or conduction system involvement. QRS duration in 25 men with prior transmural infarction (90.6 ± 14.2 msec) was slightly greater than normal; however, this difference was not statistically significant. Furthermore, in 7 of the 25 cases (28%) QRS duration was <86 msec, the mean for normal men. These results indicate that (1) high-frequency electrocardiography provides a useful new technique capable of detecting subtle (<10 msec) differences in QRS duration between men and women; (2) body size and therefore cardiac mass is one determinant of QRS duration; and (3) QRS duration in patients with infarction overlaps with normals. Therefore, QRS duration criteria cannot be used to exclude previous infarction.