Abstract
The normal physiologic range of QRS complex duration spans between 80 and 125 ms with known differences between females and males which cannot be explained by the anatomical variations of heart sizes. To investigate the reasons for the sex differences as well as for the wide range of normal values, a technology is proposed based on the singular value decomposition and on the separation of different orthogonal components of the QRS complex. This allows classification of the proportions of different components representing the 3-dimensional representation of the electrocardiographic signal as well as classification of components that go beyond the 3-dimensional representation and that correspond to the degree of intricate convolutions of the depolarisation sequence. The technology was applied to 382,019 individual 10-s ECG samples recorded in 639 healthy subjects (311 females and 328 males) aged 33.8 ± 9.4 years. The analyses showed that QRS duration was mainly influenced by the proportions of the first two orthogonal components of the QRS complex. The first component demonstrated statistically significantly larger proportion of the total QRS power (expressed by the absolute area of the complex in all independent ECG leads) in females than in males (64.2 ± 11.6% vs 59.7 ± 11.9%, p < 0.00001—measured at resting heart rate of 60 beats per minute) while the second component demonstrated larger proportion of the QRS power in males compared to females (33.1 ± 11.9% vs 29.6 ± 11.4%, p < 0.001). The analysis also showed that the components attributable to localised depolarisation sequence abnormalities were significantly larger in males compared to females (2.85 ± 1.08% vs 2.42 ± 0.87%, p < 0.00001). In addition to the demonstration of the technology, the study concludes that the detailed convolution of the depolarisation waveform is individual, and that smoother and less intricate depolarisation propagation is the mechanism likely responsible for shorter QRS duration in females.
Highlights
As well known, the physiologically normal adult QRS complex is 80–125 ms w ide[1,2]
Adult heart sizes are less variable compared to the QRS duration[11] and while heart size reasonably correlates with body size[12], the QRS duration does n ot[9]
While showing substantial inter-subject differences, QRS complex duration is reasonably stable within each healthy subject, especially when considering repeated measurements at
Summary
The physiologically normal adult QRS complex is 80–125 ms w ide[1,2]. The contribution of the differences in myocyte geometric composition and of the details in Purkinje fibre distribution must be rather substantial to explain the appreciable spread of myocardial depolarization duration Considering these histology factors, the inter-subject differences in the QRS width have to be largely caused by heterogeneity in the propagation of the depolarization sequence including the anisotropic differences between longitudinal and cross-fibre excitation transmission combined with gap junction discontinuities[13,14]. In addition to testing the application of the technology, we aimed at investigating whether the SVD signal analysis would help explaining the differences in QRS complex duration among healthy subjects and whether, similar to the differences in the QRS duration, it would show differences in QRS composition between the sexes We have researched this using data that have previously been collected in a battery of clinical pharmacology studies
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