Session P81.3

Evidence for Respiration Influence on the Heart Rate Variability after Human Heart Transplantation: Effect of Observation Model

G Laouini*, A Cabasson, G Blain, P Bonizzi,
O Meste, S Bermon

University of Nice
Sophia Antipolis, France

From the pioneering work of Bernardi, it is known that the heart rate variability signal exhibits oscillation at the respiration frequency, even at high workload exercise. Although it has been demonstrated in a non continuous dynamic manner, recent works show the persistence of this phenomenon during continuously increasing exercise. Heart transplanted patients records provide interesting data since modulation of the heart rate is not due to neural activity, although the reinnervation is still nowadays questionable. Studying these patients reveals the so called mechanical modulation (MM) that is increased as the exercise intensity is higher. In a recent paper we have introduced the PFM model that relates the observed amplitude of the MM to the ventilation and the mean heart rate, with a set of non transplanted subjects. In this paper we use a time-frequency representation added to a student’s t-test to show whether the HRV signal, or tachogram, contains or not power in the respiration frequency band. This approach is well adapted to the purely dynamic condition corresponding to increasing exercise. Observation models such as PFM and IPFM can be accounted in the analysis since there is no evidence of a linear interaction between observed values from the heart rate variability signal and physiological input such as the ventilation. The aforementioned models are compared regards our proposed student’s t-test. We measured the HRV of 14 heart transplant patients with age ranging from 27 to 70 years and time since transplantation ranging from 3 to 171 months. For all patients, the presence of power in the respiration frequency band after a PFM correction is proven (P<0.001), in contrast to the IPFM correction or without correction. The interest of such correction is also demonstrated with simulated signals. It is also shown that from the 14 subjects, 8 exhibit raising MM amplitude as the exercise, and accordingly the ventilation, increases. In conclusion, we have shown that mechanical modulation of the heart rate is present not only in healthy subject but also in heart transplanted patients in purely dynamical conditions. This finding is supported by a correct selection of the heart rate observation model.

(Abstract Control Number: 151)