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. Furthermore 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 we tested tree groups: 1. Healthy subjects(n=24) 2. Congestive heart failure patients(n=24) 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 significant 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. Ambulatory monitoring recordings less than 20 hours should not be used for HRV analysis

A low cost DICOM review station for cardiac surgery

A low-cost PC based DICOM multi modality review station for cardiac surgery has been developed for use during Minimally Invasive Coronary Surgery. This system is a Windows 95 networked PC for review of DICOM coronary catheterization, ultrasound and MRI cine's stored at a departmental image server. For fast review a specific one-heartbeat sequence out of a coronary catheterization run is automatically selected by an application and copied to the departmental image sewer. The Ultrasound studies, acquired by Vingmed System 5 and stored in an Echopac archive, are exported as DICOM files to the same sewer. The MRI studies are pushed as DICOM messages from an Agfa Picture Archiving and Communication System (PACS) to this image file sewer and automatically converted to DICOM file format. The RuboMed v 1.00 DICOM PC DICOM viewer is used to review the multi-modal cine's and the patient data. The review station does not require expensive hardware and software to provide for easy, direct and transparent review of multi-modal DICOM cines stored at a central departmental image file server