Effect of different interventions on heart rate variability after heart transplantation: Non-autonomic vs autonomic factors

1. The human transplanted heart is initially denervated, hence any fluctuation present in the RR interval variability can be either due to reaquired innervation, or to the effect of some non autonomic activity, such as a direct effect of respiration on atrial (sinus node) stretch. 2. In order to distinguish between sympathetic, vagal and non autonomic factors we examined the effects of various physical and pharmacologic manoeuvres on the respiratory and non-respiratory components of heart rate variability. 3. We found that sinusoidal neck suction appears a useful, noninvasive tool to characterise the relative importance of the different factors, which can influence heart rate variability in the transplanted heart.