Abstract
On standard electrocardiogram (ECG) PQ interval is known to be moderately heart rate dependent, but no physiologic details of this dependency have been established. At the same time, PQ dynamics is a clear candidate for non-invasive assessment of atrial abnormalities including the risk of atrial fibrillation. We studied PQ heart rate dependency in 599 healthy subjects (aged 33.5 ± 9.3 years, 288 females) in whom drug-free day-time 12-lead ECG Holters were available. Of these, 752,517 ECG samples were selected (1256 ± 244 per subject) to measure PQ and QT intervals and P wave durations. For each measured ECG sample, 5-minute history of preceding cardiac cycles was also obtained. Although less rate dependent than the QT intervals (36 ± 19% of linear slopes), PQ intervals were found to be dependent on underlying cycle length in a highly curvilinear fashion with the dependency significantly more curved in females compared to males. The PQ interval also responded to the heart rate changes with a delay which was highly sex dependent (95% adaptation in females and males after 114.9 ± 81.1 vs 65.4 ± 64.3 seconds, respectively, p < 0.00001). P wave duration was even less rate dependent than the PQ interval (9 ± 10% of linear QT/RR slopes). Rate corrected P wave duration was marginally but significantly shorter in females than in males (106.8 ± 8.4 vs 110.2 ± 7.9 ms, p < 0.00001). In addition to establishing physiologic standards, the study suggests that the curvatures and adaptation delay of the PQ/cycle-length dependency should be included in future non-invasive studies of atrial depolarizations.
Highlights
Previous studies only examined simple linear relationships between the PQ interval durations and either underlying heart rate or the simultaneously measured RR intervals
40 (6.26%, 23 females) had to be subsequently excluded since the optimization algorithms for the calculation of PQ/RR hysteresis profile did not converge
While the QT/RR hysteresis constants were marginally albeit significantly shorter in females compared to males (115.7 ± 21.3 s vs 123.7 ± 21.9 s, p = 0.00009), the sex difference of the PQ/RR hysteresis constants was reversed and more substantial (114.9 ± 81.1 s vs 65.4 ± 64.3 s, p < 0.00001)
Summary
Previous studies only examined simple linear relationships between the PQ interval durations and either underlying heart rate or the simultaneously measured RR intervals. Very limited data exist on the possible sex and age differences in the PQ/heart rate relationship This limited understanding of the character of PQ dynamics prevents the development of more accurate non-invasive methods for the assessment of intra-atrial conduction abnormalities including the risk of atrial fibrillation. To address these knowledge gaps, we used large sets of ECG data obtained in healthy subjects both to develop and test methodology of the intra-subject characterization of the PQ/heart rate relationship, and to statistically summarize the results in terms of the age dependency and of the differences between healthy females and males. Since substantial experience exists with the dynamics of the QT interval and with intra-subject assessment of the QT/heart rate relationship, we compared the PQ interval dependency on heart rate with that of the QT interval assessed in the very same population
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
