Measuring Behavior 2005: Goedhart et al.

Temporal stability of ambulatory stroke volume and cardiac out-put measured by impedance cardiography

A.D. Goedhart, N. Kupper, G. Willemsen, D.I. Boomsma and E.J.C. de Geus

Department of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands

Ambulatory recording of heart rate and blood pressure has furthered our understanding of how repeated or chronic cardiovascular activation in response to naturalistic events can contribute to cardiovascular disease. The assessment of cardiac output would further complete this picture of hemodynamic regulation in naturalistic settings. Recently, devices have become available that allow non-invasive measurement of stroke volume and cardiac output through ambulatory thorax impedance recording. If such recordings have adequate temporal stability, they offer great potential to further our understanding of how repeated or chronic cardiovascular activation in response to naturalistic events may contribute to cardiovascular disease. An important question is whether ambulatory impedance-derived stroke volume and cardiac output show acceptable temporal stability. In this study, 24-hour ambulatory impedance-derived stroke volume, cardiac output and systolic time intervals were measured in 65 healthy subjects across an average time span of 3 years and 4 months. Because significant increases in stroke volume were seen during sleep, coupled to a decrease in heart rate and cardiac output, intraclass correlations were computed separately for sleep and daytime recordings. Intraclass correlations were moderate for stroke volume (.30–.39) and cardiac output (.32–.40) and good for systolic time intervals (.53–.82). Stroke volume derived from the dZ/dt(max) value based on the B-point in the impedance signal resulted in higher correlations to that derived from the dZ/dt=0 baseline, particularly during sleep. We conclude that moderate long-term temporal stability was found for individual differences in ambulatory stroke volume and cardiac output measured by impedance cardiography.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.