Przemyslaw Guzik

Heart Rate Turbulence: Standards of Measurement, Physiological Interpretation, and Clinical Use: International Society for Holter and Noninvasive Electrophysiology Consensus

This consensus statement has been compiled on behalf of the International Society for Holter and Noninvasive Electrophysiology. It reviews the topic of heart rate turbulence (HRT) and concentrates on technologies for measurement, physiologic background and interpretation, and clinical use of HRT. It also lists suggestions for future research. The phenomenon of HRT refers to sinus rhythm cycle-length perturbations after isolated premature ventricular complexes. The physiologic pattern of HRT consists of brief heart rate acceleration (quantified by the so-called turbulence onset) followed by more gradual heart rate deceleration (quantified by the so-called turbulence slope) before the rate returns to a pre-ectopic level. Available physiologic investigations confirm that the initial heart rate acceleration is triggered by transient vagal inhibition in response to the missed baroreflex afferent input caused by hemodynamically inefficient ventricular contraction. A sympathetically mediated overshoot of arterial pressure is responsible for the subsequent heart rate deceleration through vagal recruitment. Hence, the HRT pattern is blunted in patients with reduced baroreflex. The HRT pattern is influenced by a number of factors, provocations, treatments, and pathologies reviewed in this consensus. As HRT measurement provides an indirect assessment of baroreflex, it is useful in those clinical situations that benefit from baroreflex evaluation. The HRT evaluation has thus been found appropriate in risk stratification after acute myocardial infarction, risk prediction, and monitoring of disease progression in heart failure, as well as in several other pathologies.

Heart rate asymmetry by Poincaré plots of RR intervals.

Abstract 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.

A phenomenon of heart-rate turbulence, its evaluation, and prognostic value.

Identification of high-risk cardiac patients is crucial for stratification strategies and prevention of cardiovascular events, including death. Single ventricular premature beat triggers some oscillations in cardiac cycle duration (the shortening followed by the lengthening of the cycle intervals) in healthy subjects and low-risk patients with ischaemic heart disease and/or heart failure. This phenomenon is called heart-rate turbulence (HRT). It was shown in retrospective and prospective studies that the absence of HRT is associated with increased risk of subsequent mortality in cardiac patients. HRT can be quantified by two variables: turbulence onset (TO), describing an early acceleration phase, and turbulence slope (TS), describing a late deceleration phase of heart rate after ventricular premature beat. Both TO and TS are independent one from another and from other conventional risk predictors. The combination of TO and TS seems to be the strongest Holter-based risk predictor and has some addictive predictive value to left ventricular ejection fraction, heart rate variability, and the averaged diurnal heart rate and baroreflex sensitivity. In addition, HRT has a predictive value in patients treated with beta-blockers and amiodarone. Moreover, it is thought that HRT is mediated by baroreflex and therefore can be used as a non-invasive measure of its sensitivity and autonomic nervous system function. Blunted HRT can be observed in diabetic patients with autonomic dysfunction and in patients with atropine-blocked vagal nerve activity. Moreover, it seems that a diurnal variation of HRT exists because it is better expressed during sleep. However, the use of HRT is limited to patients with dominant sinus rhythm and the presence of single ventricular beat. Nevertheless, the assessment of HRT is an inexpensive and simple method and can be performed with a routine ambulatory 24-hour ECG recording.

INDICES OF VASCULAR STIFFNESS AND WAVE REFLECTION IN RELATION TO BODY MASS INDEX OR BODY FAT IN HEALTHY SUBJECTS

1 Obesity appears to influence vascular stiffness, an important cardiovascular risk factor. An accurate picture of arterial stiffness may be obtained when a combination of various techniques is used. 2 The purpose of the present study was to assess whether the body mass index (BMI) and body fat content obtained by bioimpedance were of equal value in estimating the influence of body fatness on various indices of vascular stiffness and wave reflection. 3 A total of 175 healthy subjects was studied. Anthropometric measurements and total body bio‐impedance analysis were performed to assess fat mass as a proportion of total body composition. Arterial stiffness and wave reflection were assessed using digital volume pulse analysis and tonometric measurement of the wave reflection indices and central haemodynamics. 4 Significant differences in the stiffness index (SIDVP; P < 0.0001), peripheral augmentation index (pAIx; P < 0.0001), central augmentation index (cAIx; P < 0.0001), peripheral pulse pressure (pPP; P = 0.026) and central pulse pressure (cPP; P < 0.0001) were found when the population examined was divided accordingly to tertile of body fat content. However, subdividing various indices of arterial stiffness according to the tertile of BMI did not reveal any significant differences between groups, except for pPP and cPP. 5 Body fat content was significantly correlated with SIDVP, pAIx, cAIx, pPP and cPP. The BMI correlated weakly with SIDVP, pPP and cPP. 6 In conclusion, the BMI is not very useful in predicting changes in arterial stiffness and wave reflection due to obesity. However, stiffness and wave reflection indices derived from digital volume pulse analysis, the characteristics of radial and aortic pressure waveforms and peripheral and aortic pulse pressure are all related to body fat content, as estimated by bioimpedance.

Arterial stiffness in relation to subclinical atherosclerosis.

Background  Increased arterial stiffness or arteriosclerosis, represents a physiological part of ageing. Atherosclerosis is a process that does not affect the arterial bed uniformly but has a variable local distribution and is frequently superimposed on stiffened vessels. We therefore addressed the question of whether any correlation exists between the general characteristics of arterial stiffness or wave reflection and subclinical atherosclerosis as assessed by carotid intima‐media thickness (IMT) in a sample of healthy subjects.

Acquisition and analysis of cardiovascular signals on smartphones: potential, pitfalls and perspectives By the Task Force of the e-Cardiology Working Group of European Society of Cardiology

Smartphones, mobile applications (‘apps’), social media, analytics, and the cloud are profoundly changing the practice of medicine and the way health decisions are made. With the constant progress of technology, the measurement of vital signals becomes easier, cheaper, and practically a standard approach in clinical practice. The interest in measuring vital signals goes beyond medical professionals to the general public, patients, informal caregivers, and healthy individuals, who frequently lack any formal medical training. On smartphone platforms such as iOS and Android, a proliferation of health or medical ‘apps’ acquire and analyse a variety of vital signs through embedded sensors, interconnected devices or peripherals utilising on occasion analytics and social media. Smartphone vendors compete with traditional medical device manufacturers in the grey area between health care, wellness, and fitness, as US and EU regulatory bodies are setting and revising rules for these new technologies. On the other hand, in the absence of robust validation results, clinicians are hesitant to trust measurements by apps or recommend specific apps to their patients, partly also due to lack of a cost reimbursement policy. This review focuses on the acquisition and analysis on smartphones of three important vital signs in the cardiovascular and respiratory field as well as in rehabilitation i.e. heart or pulse rate, blood pressure, and blood oxygenation. The potential, pitfalls, and perspectives on mobile devices and smartphone apps for health management by patients and healthy individuals are discussed.

Heart rate deceleration runs for postinfarction risk prediction

UNLABELLED A method for counting episodes of uninterrupted beat-to-beat heart rate decelerations was developed. METHODS The method was set up and evaluated using 24-hour electrocardiogram Holter recordings of 1455 (training sample) and 946 (validation sample) postinfarction patients. During a median follow-up of 24 months, 70, 46, and 19 patients of the training sample suffered from total, cardiac, and sudden cardiac mortality, respectively. In the validation sample, these numbers were 39, 25, and 15. Episodes of consecutive beat-to-beat heart rate decelerations (deceleration runs [DRs]) were characterized by their length. RESULTS Deceleration runs of 2 to 10 cycles were significantly less frequent in nonsurvivors. Multivariate model of DRs of 2, 4, and 8 cycles identified low-, intermediate-, and high-risk groups. In these groups of the training sample, the total mortalities were 1.8%, 6.1%, and 24%, respectively. In the validation sample, these numbers were 1.8%, 4.1%, and 21.9%. CONCLUSION Infrequent DRs during 24-hour Holter indicate high risk of postinfarction mortality.

Asymmetric properties of long-term and total heart rate variability

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,

Asymmetrical properties of heart rate variability in type 1 diabetes

{\text {SD1}}_{\rm d}, {\text {SD1}}_{\rm a},