Analysis of heart rate variability (HRV), available through routine Holter ECG monitoring, provides additional possibilities to assess the patient’s well-being after a heart transplant (HTX). It is unclear if, and if so, how the graft hypertrophy can be surveilled by HRV.
The 44 HTX patients, in a stable condition within 14 months post HTX, were divided into three groups: with a left ventricle of normal geometry (NG), concentrically remodeled (CR) and hypertrophic (H). Forty three measures were applied in estimates of HRV in nocturnal Holter signals obtained from HTX patients. Segmented heart rate variability (sHRV) is proposed for (1) preprocessing long recordings of 20000 points to series of equal size s signal segments (s=10,...400), (2) mapping it into series of HRV of segments and then (3) evaluating HRV series by sample entropy. The method offers insight into the relationship between HRV in successive elements of segmented recordings.
Heart contraction rhythms of patients in the CR group show the lowest short-term HRV, i.e., the frequency and variety of alternating acceleration and deceleration patterns are lower than in the signals of patients in the other groups. The short-term HRV of these signals, when transferred to sHRV signals, are highly unpredictable. Signals from the NG group are characterized by high values of short-term HRV and high predictability of sHRV. Group H signals show high HRV but sHRV often presents the greatest randomness.
HRV is a prognostic indicator of the deveopment of hypertrophy of the graft. Moreover, it may be hypothesized that sHRV follows couplings to other oscillatory functions of the organism.