To analyze the correlation of the Poincaré plot descriptors of RR intervals with standard measures of heart rate variability (HRV) and spontaneous baroreflex sensitivity (BRS). A physiological model of changing respiratory rates from 6 to 15 breaths/min provided a wide range of RR intervals for analysis. Beat-to-beat finger blood pressure, ECG, and respiratory curves were recorded noninvasively in 15 young healthy volunteers (19-25 years old; 7 females) breathing for 5 min at 4 different respiratory rates of 6, 9, 12, and 15 breaths/min. Four descriptors of the Poincaré plot (SD1, SD2, S, and SD2/SD1), time and frequency domain HRV, and spontaneous BRS (cross-correlation method) were calculated for each 5-min recording. The values of SD1 characterizing short-term HRV, SD2 describing long-term HRV, and S measuring total HRV were significantly correlated with BRS and time and frequency domain measures of short, long, and total HRV. The LF/HF significantly correlated with SD2 and SD2/SD1 representing the balance between long- and short-term HRV. None of the Poincaré plot descriptors was correlated with the mean RR interval. The increased respiratory rate caused a significant reduction of BRS, measures of total and long-term HRV, and an increase of HF that peaked at 12 breaths/min. The descriptors of the Poincaré plot of RR intervals are significantly correlated with measures of BRS and time and frequency domain HRV, but not with heart rate. A faster respiratory rate reduces long-term HRV measures and temporarily increases HF.

The geometry of the Poincaré plot of RR intervals is considered and its basic descriptors are defined in terms of the second moment of a distribution of points in a plane. One of the standard descriptors, SD1, is redefined and used to define two new descriptors, SD1(UP) and SD1(DOWN), whose squares partition SD1(2) (the variance corresponding to short-term heart rate variability) into contributions from decelerations and accelerations of heart rate. It is shown that there is a visible and statistically highly significant asymmetry in the Poincaré plot, with the upper part, corresponding to decelerations of heart rate, larger than the lower part, which corresponds to accelerations. The effect is shown in one hundred 30 min long time series of RR intervals derived from the ECG recordings of 100 young (19-32 years old) and healthy adults. After shuffling the data to random order the asymmetry disappears, which shows that this is a genuine physiological phenomenon rather than an artefact of the method.

The Poincaré plot is a widely used method for visualizing and calculating heart rate variability and for investigating the oscillatory nature of heart action. We show that the Poincaré plot produced using physiological data for RR intervals is asymmetric. This suggests that the processes of heart rate acceleration (shortening of consecutive RR intervals) and deceleration (prolongation of successive RR intervals) might be asymmetric. To investigate this phenomenon, we define descriptors quantifying the heart rate asymmetry and present the results of a study involving 5-min ECG recordings of 50 healthy subjects in which, despite of the shortness of the recordings, the asymmetry is clearly visible.

The Declaration of Helsinki is a set of ethical principles to be followed by scientists involved in medical research with humans or human cells and tissues. This Declaration defines how scientific research should be planned, carried out, documented, analysed, and published. We summarise and discuss some ethical issues related to publishing original articles, including clinical trials, review papers, and case reports based on the seventh revision of the Declaration of Helsinki. The principles of the Declaration of Helsinki refer most strongly to the publication of medical research results, in particular clinical trials, as original articles. Such papers must meet several ethical requirements, especially the study protocol transparency and the presentation of the results. For case reports, the bioethical aspects related to their publication are twofold - they must include informed and voluntary consent and the confidentiality of study participants. The review papers are of the least bioethical concern. However, whether patients' agreements with specific studies are valid if the data are used in meta-analyses is uncertain. Adherence to ethical policies and standards helps to ensure the highest possible quality of scientific publications. Responsibility for compliance with the Declaration of Helsinki lies not only with the authors preparing their manuscripts but also with the editorial board and reviewers, who must evaluate the ethical soundness of the submitted papers. The additional guidelines for the different types of studies facilitate the implementation of the Declaration principles.

We report on two new physiological phenomena: the long-term and total heart rate asymmetry, which describe a significantly larger contribution of heart rate accelerations to long-term and total heart rate variability. In addition to the existing pair of indices, \({\text {SD1}}_{\rm d}, {\text {SD1}}_{\rm a},\) which are based on partitioning short-term variance, we introduce two other pairs of descriptors based on partitioning long-term (\({\text {SD2}}_{\rm d}, {\text {SD2}}_{\rm a}\)) and total (\( {\text {SDNN}}_{\rm d}, {\text {SDNN}}_{\rm a}\)) heart rate variability. The new asymmetric descriptors are used to analyze RR intervals time series derived from the 30-min ECG recordings of 241 healthy subjects resting in supine position. It is shown that both new types of asymmetry are present in 76% of the subjects. The new phenomena reported here are real physiological findings rather than artifacts of the method since they vanish after data shuffling.