Physical Activity Measured by Implanted Devices Predicts Atrial Arrhythmias and Patient Outcome: Results of IMPLANTED (Italian Multicentre Observational Registry on Patients With Implantable Devices Remotely Monitored)

Abstract

Background: To determine whether daily physical activity (PA), as measured by implanted devices (through accelerometer sensor), was related to the risk of developing atrial arrhythmias during long-term follow-up in a population of heart failure (HF) patients with an implantable cardioverter defibrillator (ICD).

Methods and results: The study population was divided into 2 equally sized groups (PA cutoff point: 3.5 h/d) according to their mean daily PA recorded by the device during the 30- to 60-day period post-ICD implantation. Propensity score matching was used to compare 2 equally sized cohorts with similar characteristics between lower and higher activity patients. The primary end point was time free from the first atrial high-rate episode (AHRE) of duration ≥6 minutes. Secondary end points were: first AHRE ≥6 hours, first AHRE ≥48 hours, and a combined end point of death or HF hospitalization. Data from 770 patients (65±15 years; 66% men; left ventricular ejection fraction 35±12%) remotely monitored for a median of 25 months were analyzed. A PA ≥3.5 h/d was associated with a 38% relative reduction in the risk of AHRE ≥6 minutes (72-month cumulative survival: 75.0% versus 68.1%; log rank P=0.025), and with a reduction in the risk of AHRE ≥6 hours, AHRE ≥48 hours, and the combined end point of death or HF hospitalization (all P<0.05).

Conclusions: In HF patients with ICD, a low level of daily PA was associated with a higher risk of atrial arrhythmias, regardless of the patients' baseline characteristics. In addition, a lower daily PA predicted death or HF hospitalization.

Keywords: atrial fibrillation; heart failure; implanted cardioverter defibrillator; physical exercise.

Figure 1

Two examples of calculation of baseline daily physical activity (PA). Baseline daily PA was calculated as the mean daily activity (in h/d) recorded in the period from 30 to 60 days after device implantation (activity window). A, Patient enrolled in the Boston Scientific Latitude Patient Management System (Boston Scientific, St Paul, MN). The mean daily PA recorded during the activity window was 1.2 h/d (lower‐activity patient). B, Patients enrolled in the Medtronic CareLink Network (Medtronic Inc, Minneapolis, MN). The mean daily PA recorded during the activity window was 4.8 h/d (higher‐activity patient).

Figure 2

Study flow with derivation of the study population. AF indicates atrial fibrillation; AHRE, atrial high‐rate episode; ICD, implantable cardioverter defibrillator; IMPLANTED, Italian Multicentre Observational Registry on Patients With Implantable Devices Remotely Monitored.

Figure 3

Forest plot showing the risk of AHREs lasting ≥6 minutes in the whole study population (n=770) by quintiles of daily physical activity after multivariable analysis. AHRE indicates atrial high‐rate episode; CI, confidence interval; HR, hazard ratio.

Figure 4

Kaplan‐Meier estimates of the cumulative time free from first atrial high‐rate episodes (AHREs) detected by the device, and from clinical events in the low and high physical activity propensity score–matched groups (n=446). A, First AHRE lasting ≥6 minutes. B, First AHRE lasting ≥6 hours. C, First AHRE lasting ≥48 hours. D, All‐cause death or heart failure (HF) hospitalization. E, All‐cause death. F, HF hospitalization. Events are counted after closure of the activity window used to determine baseline physical activity level.