Scripties UMCG - Rijksuniversiteit Groningen
 
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Determinants and prognostic value of QT and HR phenotypes in 44,866 individuals of the UK Biobank

(2017) Vegte, Y. van de (Yordi)

Cardiovascular disease (CVD) is the most important cause of morbidity and mortality all over the world. QT and Heart rate (HR) phenotypes, such as QT at rest, QT corrected by Fridericias formula (QTcF), achieving age-predicted submaximal heart rate (APSHR), heart rate reserve (HR-Res) and heart recovery (HR-rec), are a) thought to reflect beneficial effects of regular exercise (possibly mediated by the autonomic nervous system (ANS)), b) thought to differ between men and women and c) thought to be of predictive value for CVD as primary cause of death, all-cause mortality and (events from) coronary artery disease (CAD). This thesis focuses on finding these relations in a large cohort of the general population.
We therefore measured HR and QT intervals of 65,854 three lead exercise ECG’s and subsequently used 44,866 of those that are part of the baseline visit in subsequent analyses. Linear regressions were performed to validate our delineation method and to assess differences in QT and HR phenotypes between regularly active and sedentary individuals and between men and women. Cox regressions were performed to assess the predictive value of QT and HR phenotypes on death from CVD, all-cause mortality and events from (CAD).
Most important, this thesis provides evidence for a valid method of assessment of QT and HR phenotypes from exercise ECG’s. Furthermore, it provides evidence that some QT and HR phenotypes (QTcF, RHR, HR-rec) to be an independent predictor of all-cause mortality and others (Resting QT and QTcF) to be an independent predictor of mortality of CVD as primary cause in the general population. QT and HR phenotypes were not predictive for events of CAD. Higher QT and HR phenotypes were found in women, supporting and adding evidence to previous literature on the need to account for gender-related differences in heart rate dynamics. Differences between regularly active and sedentary individuals were found for all QT and HR phenotypes except QTcF and we can therefore conclude that only QTcF can’t be changed by participating in regular physical activity. A lower RHR and a higher HR-rec, possibly mediated by underlying changes in the ANS, were found in physically active individuals, which we suspected based on previous literature. Interestingly, the effects of regular physical activity on the decrease of RHR and the increase of HR-rec were higher in men than in women, suggesting a higher effect of regular physical activity on RHR and HR-rec in men. The effects of regular physical activity on RHR and HR-rec underline the importance of regular physical activity, with lower chances of all-cause mortality in the physically active group mediated by a lower RHR and a higher HR-rec.






 
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