Elsevier

International Journal of Cardiology

Volume 168, Issue 2, 30 September 2013, Pages 1127-1130
International Journal of Cardiology

Validity of cardiac implantable electronic devices in assessing daily physical activity

https://doi.org/10.1016/j.ijcard.2012.11.050Get rights and content

Abstract

Background

Data on physical activity assessed by cardiac implantable electronic devices (ICD/CRT) have been used for prognostic implications in heart failure patients, but no study has ever compared these data to validated external accelerometers.

Methods

73 ICD/CRT recipients (age 60 ± 20 years, 21% female) received a validated external accelerometer over a period of 7 days. Thereafter, data on physical activity of both ICD/CRT and external accelerometers were retrieved and compared using Spearman's rank correlation coefficient and Bland Altman plots.

Results

Mean total daily activity was 276 ± 85 min (range 72–462) as assessed by the external accelerometers and 237 ± 105 min (28–575) as assessed by the ICD/CRT activity sensors (p < 0.001). A strong, significant intra-individual correlation (r > 0.7) between the two measurements was observed in a majority (70%) of patients (p < 0.05 each). However, a Bland Altman plot revealed a broad variation of total daily activity between both methods (95% limits of agreement − 225 to 147 min), resulting in differences in the duration of daily activity up to several hours. In multivariate regression analysis, no influence of age, NYHA functional class, left ventricular ejection fraction, underlying disease or type of device on these differences was observed.

Conclusions

As compared to a validated external accelerometer, daily physical activity assessed by ICD/CRT devices shows strong intra-individual correlations, but differs substantially regarding the absolute amount of daily activity. Thus, using ICD/CRT activity data for more precise clinical or prognostic information without prior validation is of limited value.

Introduction

Regular physical activity and exercise improve quality of life and exercise tolerance in heart failure patients, whereas a decrease in physical activity indicates disease progression [1], [2], [3], [4], [5], [6]. Hence, monitoring physical activity is important in the clinical management of these patients. Implantable cardioverter-defibrillators and cardiac resynchronization therapy devices (ICD/CRT) are routinely equipped with activity sensors in order to adjust heart rates during patient activity. Thus, data on daily physical activity assessed by these sensors can easily be obtained on ICD/CRT interrogation. This information is available irrespective of the activation of the rate response function. Several studies have used these data to monitor physical activity and to derive prognostic information [7], [8], [9], [10]. However, no study has so far evaluated the activity amounts assessed by ICD/CRT devices regarding their clinical applicability. Therefore, the aim of this study was to compare data on daily physical activity assessed by ICD/CRT devices to activity data measured by a validated external accelerometer [4], [11] in heart failure patients.

Section snippets

Materials and methods

The study was a prospective analysis of consecutive male and female heart failure patients of all ages who had received Medtronic ICD/CRT devices for primary or secondary preventive purposes ≥ 6 months earlier. Participants were recruited in the outpatient clinic of the German Heart Center in Munich from June to December 2010. Only clinically stable, medically optimally treated patients were included; no cut-off value for left ventricular ejection fraction was used. Patients with physical

Results

A total of 73 patients were included; baseline characteristics are shown in Table 1. Mean total daily activity of all participants was 276 ± 85 min as assessed by the AiperMotion and 237 ± 105 min as assessed by the ICD/CRT activity sensor, resulting in a mean difference between both measurements of 39 ± 83 min (p < 0.001). The average time spent in the different activity modes of the AiperMotion was distributed as follows: “active” 177 ± 54 min, “slow walking” 82 ± 36 min, “fast walking” 6 ± 12 min, “running” 0 

Discussion

This study compared activity data of a validated external accelerometer to activity data deriving from ICD/CRT devices in heart failure patients. Although the intra-individual correlation was strong, Bland Altman plot revealed broad variations of activity measurements between the two methods with differences up to several hours per day. Differences were not predicted by NYHA functional class, age, ejection fraction, underlying disease or type of device. Thus, non-validated ICD/CRT activity

Acknowledgments

The authors wish to thank Michaela Herold and Markus Renner from Medtronic, Neuss, Germany and Martin Ertlmeier of Aipermon, Munich, Germany for their continuous, friendly and professional support and for reading and approving the manuscript.

Funding

None.

Conflicts of interest

Author Christof Kolb has received lecture fees from Medtronic and performs other studies which are financially supported by Medtronic. All other authors report no conflict of interest.

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