Author + information
- Sudhi Tyagi, MD,
- Michael Curley, MD,
- Marcie Berger, MD,
- Judith Fox, APNP,
- Scott J. Strath, PhD,
- Jason Rubenstein, MD,
- James Roth, MD and
- Michael E. Widlansky, MD, MPH∗ ()
- ↵∗Division of Cardiovascular Medicine, Medical College of Wisconsin, 9200 West Wisconsin Avenue, FEC E5100, Milwaukee, Wisconsin 53226
There is growing recognition that physical inactivity in the general population is an important risk factor for cardiovascular disease and death (1–3). To date, there are limited data as to the predictive value of physical activity in individuals with pacemakers and preserved left ventricular (LV) function. Implanted cardiac pacemakers provide a unique opportunity to collect precise quantitative longitudinal data with respect to physical activity level in this at-risk population.
We retrospectively reviewed records of individuals who underwent de novo implantation of a Medtronic EnRhythm or Revo device (Medtronic, Minneapolis, Minnesota) between January 1, 2005, and December 31, 2012, at 1 academic medical center. Physical activity profiles were obtained from routine interrogation data downloaded at 3-month intervals and averaged over a 1-year time period following a 6-month post-implantation blanking period. We divided subjects qualifying for study inclusion into 4 activity categories: <1 h/day, 1 to <2 h/day, 2 to <3 h/day, and >3 h/day (reference category).
A total of 149 subjects were screened, and 53 subjects were excluded due to their procedure being a generator change rather than a new implant, or incomplete follow-up. Subjects were divided into 4 groups based on average active minutes and followed for an average of 4.1 ± 2.2 years after pacemaker implant. There were a total of 18 deaths during the follow-up period.
All-cause mortality significantly increased as active minutes decreased (7%, 9%, 29%, and 42% all-cause mortality in order from highest to lowest active minute category; p = 0.004). Kaplan-Meier analysis demonstrated total mortality was significantly higher as pacemaker-quantified active minutes decreased (Figure 1). In age- and sex-adjusted analyses, patients with an average of <1 h/day of active time had a nearly 7.5-fold increased risk of death during follow up compared to those who were active >3 h/day (odds ratio [OR]: 7.44; 95% confidence interval [CI]: 1.88 to 29.43; p = 0.007). Patients who averaged 1 to 2 h/day of active time had nearly 3.5 times the risk of death compared to the reference group, but this OR fell short of statistical significance (OR: 3.47; 95% CI: 0.84 to 14.39; p = 0.09). No significant increase in the risk of death was seen comparing those who completed 2 to 3 h/day of active time versus the reference group (OR: 1.06; 95% CI: 0.11 to 10.22; p = 0.96).
The use of implantable cardiac devices to assess an individual’s activity level has unique advantages. It represents an objective measurement of movement and removes recall bias and inaccuracies. Furthermore, as patients with pacemakers are typically followed on a quarterly basis, regular follow-up, and access to activity data is easily obtainable.
Two prior studies using accelerometer data from implanted cardiac devices found a correlation between survival and physical activity as measured by accelerometers in patients with impaired LV ejection fractions (4,5). Our data significantly extend these findings to a population without a reduction in LV ejection fraction, which in itself may be related to reduced activity levels. Further, our data account for activity levels well outside the peri-implantation window, which mitigates the impact of periprocedural complications on the relationship between activity time and mortality.
Our study is limited by the relatively small study population. We did not include other pacing devices with accelerometers as their algorithms for determining active time may differ from the 2 devices included in this study. We elected not to include patients with defibrillators so as to reduce the confounding effects of impaired cardiac function on activity levels. Balanced against these limitations are the quantitative nature of our data, the novelty of the findings and their potential impact on the care of patients post-pacemaker implantation.
Physical activity as measured by an implanted accelerometer is correlated with mortality—those who are less active have decreased survival independent of other risk factors. Our findings support the notion that care providers following patients with pacemakers could use these readily available data for risk stratification, to encourage increased physical activity, and to follow patient compliance with physical activity recommendations. Whether interventions to decrease inactive time can impact survival needs to be prospectively studied.
Please note: Dr. Widlansky has received grant support from the National Institutes of Health, Merck Sharp & Dohme Corp., and the Doris Duke Foundation. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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