The advent of reliable software access to beat-by-beat QT interval series opened a novel insight to sympathetic control of ventricular myocardium.
Experimental measurement of time constant in the RR-QT system (
) using pharmacological or electrophysiological manipulations of heart rate (HR) has documented that
size may introduce in borderline subjects in normal life settings episodes of functional long-QT syndrome.
In type I young diabetics in the earliest phase of autonomic dysfunction, spectral QT and RR analyses suggest preferential vagal down-regulation but preservation of sympathetic responsiveness of ventricles to life challenges.
Both findings signal an early risk worth to be dealt with by specific preventive steps.