W.A. Dijk

Heart rate dependent changes in spectral analysis

Analysis of heart rate variability (HRV) is used to study the influence of the autonomic nervous system on the heart For appropriate spectral analysis using fast Fourier transformation (FFT), resampling techniques like linear interpolation are often used. Some of these techniques however, introduce significant bias. We compared FFT using three different resampling techniques with discrete Fourier transformation (DFT) and concluded that spectral power is reproduced more accurately by DFT than by FFT using resampling techniques.<<ETX>>

Pacemaker registration by E-mail

In the Netherlands, many pacemaker clinics use a computer to store their implant and follow-up data in a database. Still, there are quite a number of clinics that only use their computer for word processing. In order to improve the accuracy of the received data, we developed a data entry package where the data is checked, after which it is sent to the central registry by E-mail.

The influence of recording length on time and frequency domain analysis of heart rate variability

Analysis of Heart Rate Variability (HRV) is used to assess autonomic control of the heart. Many technical aspects may influence the outcome of HRV analysis. One of these aspects is recording length. Ambulatory monitoring recordings are frequently used as a data source. Because of their mathematical properties, some HRV variables are influenced by recording length. Further more, recording length may play a role, since, in clinical practice, hook-up times of ambulatory monitoring are not randomly distributed over time. In order to test recording-length related changes of HRV the authors tested three groups: 1. healthy subjects (n=24); 2. congestive heart failure patients (n=24); and 3. patients with coronary artery disease (n=21). Results revealed that although the average normal to normal interval already changed after 1 hour reduction, most time domain variables differed statistically significantly after 4 hours reduction in length. Frequency domain variables proved to be less sensitive to recording-length changes. The extent of length related changes of HRV was shown to vary in different patient categories. It is concluded that ambulatory monitoring recordings less than 20 hours long should not be used for HRV analysis.

Central Pacemaker Patients Registration in the Netherlands-a ten year evaluation

The setup and organization of the computerized Central Pacemaker Patients Registration in the Netherlands are described. Over a ten-year period (1979-88), information on 39000 pacemaker patients and their pacemakers and leads has been stored. It is emphasized that the registration is a valuable tool in the nationwide management of pacemaker patient care. Until 1989 the information was sent by mail on a standardized registration card. Starting in 1989, electronic transmission of the data was introduced, expanding the functionally of the system.<<ETX>>

Applicability and performance of heart rate variability methods

Heart rate variability (HR V) may be measured using different measurement techniques. Almost all of these techniques deal with ectopic beats. Either these beats are excluded from the analysis or they are required. To access the functional character and easiness of use of several HRV techniques we compared Holter registrations in three patient groups: normal subjects, post infarction patients and patients with heart failure. Analysis speed, sensitivity to non sinus intervals, applicability and accuracy were investigated. Time as well as frequency domain techniques, heart rate turbulence and a non linear measure of HRV were studied. The results of the analysis suggest that non linear analysis is as least as potent as conventional HRV techniques in discriminating between patient groups. This technique can be applied in all patients with minimal computational effort and without the need for accurate analysis of the ECG.

The Groningen ambulance study

This paper describes the effects of a treatment protocol for patients with ST elevation myocardial infarction, which was introduced in 2004. The setup of the new approach is described. The principle goal is to minimize time between onset of symptoms associated with acute myocardial infarction and reperfusion through primary percutaneous coronary intervention. Preliminary results are discussed

Computer simulation of atrial arrhythmias, including paroxysmal atrial fibrillation

To study initiation and termination of atrial arrhythmias, especially atrial fibrillation, a simulation environment was designed, based on previously published models. Two different aspects of atrial electrophysiology are currently studied using these simulation models. Firstly whether or not, depending on the electrophysiological properties, electrical activity originating in the sinus node can reach the fibrillating atrium. In a second study a spiral wave rotating in a piece of atrial tissue is conducted back from the border zone to the core of the spiral wave over subendocardial muscle structures. The influence of various parameters on the disturbance of the spiral wave is under investigation.

The influence of lead selection on the correlation dimension for quantification of the chaotic attractor underlying polymorphic tachyarrhythmias

Currently the correlation dimension is frequently used to quantify the non-linear properties of the electrocardiogram recorded in rest or during various tachyarrhythmias. In this study the influence of lead selection and embedding dimension on the correlation dimension was evaluated. In nine dogs presented with Torsade de Pointes tachyarrhythmias the correlation dimension was determined using the commonly applied method of Grassberger and Procaccis, for the embedding dimension 3, 4, 5 and 8. Between dogs the average correlation dimension varied from 1.37-2.12, 1.42-2.39, 1.45-2.63, and 1.55-3.03 respectively. Within dogs the difference between those two leads with the minimal and maximal dimension varied from 0.17-0.67, 0.19-0.95, 0.24-1.00 and 0.32-1.14. The study suggests that the correlation dimension should not be used to compare the non-linearity between patients but should be limited to longitudinal comparison in one patient.

Effects of metronome breathing on the assessment of autonomic control using heart rate variability

Analysis of Heart Rate Variability is a non-invasive quantitative tool to study the influence of the autonomic nervous system on the heart. Rapid variations in heart rate, related to breathing are primarily mediated by the vagal limb of the autonomic nervous system. The resulting variations in heart rate are usually referred to as respiratory sinus arrhythmia. Metronome breathing (MB) is often advocated to assess more accurately vagal control. However, the additional value of MB over SB has never been established. The authors studied the effect of MB (0.25 Hz) on HRV variables in 12 healthy male subjects under stable conditions using pharmacological autonomic blockade. During MB several variables showed a lower absolute value, however a strong correlation existed between variables computed during spontaneous breathing (SB) and MB. MB offers some, but no important advantages over spontaneous breathing.

Chaotic behavior in a deterministic model of circus movement tachycardia in the WPW syndrome

In most studies the chaotic properties of the cardiac rhythm are related to different situations like infarction, sudden death, heart failure etc. In this study the possibility of chaotic behavior of cardiac arrhythmias, without the influence of factors like the autonomic nervous system, hormonal influence etc., was studied. In a simulation model of a reentrant tachycardia using an accessory pathway, chaotic behavior was demonstrated. This finding might have important implications on further analysis of life-threatening arrhythmias.