Heart rate variability and QT interval: their relationships with the cardiac frequency

Abstract

The influence of the autonomic nervous system (ANS) on cardiac functions can be evaluated in ambulatory surface ECG recordings by two different approaches; the heart rate variability (HRV) and the QT interval dynamicity. HRV specifically evaluates the modulation of the sinus node automatism by the ANS, whereas QT dynamicity is related to the ANS influence on the ventricular myocardium. One expects that under physiological conditions in normal hearts the indications yielded by these two approaches will probably be consistent. However, this is probably no longer the case when a structural heart disease is present. As a matter of fact, HRV is only affected by the impact of the heart disease on the ANS, whereas QT dynamicity is involved by the disease itself.