Physiologic heart rate dependency of the PQ interval and its sex differences

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 daytime 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. The electrocardiographic (ECG) interval between the onset of the P wave and the onset of the QRS complex is frequently called the PR interval but should be more accurately termed the PQ interval. As well known, the duration of this interval represents the combination of the intra-atrial conduction and of the excitation delay within the atrioventricular node. Abnormalities of the PQ interval are associated not only with the atrioventricular node pathologies but also with intra-atrial anomalies. In addition to the diagnosis of atrioventricular conduction pathologies, monitoring of the PQ interval is therefore useful for the assessment and device programming of cardiac resynchronization therapy 1-3 as well as for clinical follow-up of heart failure patients 4,5. Prolongation of the PQ interval was also found predicting adverse outcome in general population 6,7. More recently, a number of studies showed that PQ interval may be used as a risk indicator of subsequent development of atrial fibrillation or of its recurrence after ablation therapy 8-11. Similarly, risk of atrial fibrillation was reported to relate to the P wave duration 12,13. Similar to the ventricular conduction system, intra-atrial conduction is influenced by the autonomic nervous system 14. It is therefore not surprising that PQ interval duration also exhibits autonomically modulated changes and that the interval is heart rate dependent 15,16. Also not surprisingly, s...

Heart Rate Dependency and Inter-Lead Variability of the T Peak – T End Intervals

“…A collection of Holter recordings previously analyzed for a different purpose was used (Toman et al, 2020). Altogether, 639 healthy adult subjects participated at six clinical pharmacology studies.…”

“…As previously described (Toman et al, 2020), each of the studies included repeated 12-lead day-time Holter recordings. In each participant, the recordings were made during multiple baseline days when the subjects were off any medication, did not smoke, and refrained from consuming caffeinated drinks.…”

“…Using previously developed technology combining computerized signal processing with visual checks and manual corrections of the measurements (Malik et al, 2008a(Malik et al, , 2012Toman et al, 2020), multiple 10-s segments were extracted from each of the Holter recordings aiming at the inclusion of segments with different underlying heart rates. For each extracted segment, a 5-min history of preceding RR intervals was obtained.…”

Spatial distribution of physiologic 12-lead QRS complex

“…A collection of Holter recordings previously analysed for a different purpose was used 24 . Altogether 639 healthy subjects participated at six different clinical pharmacology studies.…”

“…As previously described 24 , each of the studies included repeated 12-lead day-time Holter recordings in each participant. The recordings were made during multiple baseline days.…”