Randomized Trial of Anticoagulation Guided by Remote Rhythm Monitoring in Patients With Implanted Cardioverter-Defibrillator and Resynchronization Devices - IMPACT


Patients with paroxysmal atrial fibrillation (AF)/atrial tachycardia (AT) have a thromboembolic risk that is directly correlated to its duration and burden. Implanted cardioverter-defibrillator (ICD) and resynchronization (CRT-D) devices have the ability to discriminate atrial tachyarrhythmias (ATs). The current trial sought to study the safety and efficacy of remote monitoring with these implanted devices in the management decision of anticoagulation for AT.


Remote monitoring for AT with a predefined anticoagulation plan would be superior to in-office identification of AT with oral anticoagulation (OAC) directed by the treating physician.

Study Design

  • Randomized
  • Blinded
  • Parallel

Patient Populations:

  • CHADS2 risk score ≥1
  • Implanted ICD or CRT-D with Home Monitoring® technology
  • Able and willing to begin anticoagulation therapy, if needed
  • Acceptable P-wave amplitude documented (≥1.0 mV sinus rhythm, ≥0.5 mV AF)
  • Age ≥18 years and able to provide informed consent

    Number of enrollees: 2,718
    Duration of follow-up: 5 years (median 2 years)
    Mean patient age: 65 years
    Percentage female: 26%


  • Permanent AF
  • History of stroke, transient ischemic attack, or systemic embolism and documented AF or atrial flutter
  • Currently requiring OAC or known contraindication to OAC
  • <3 months of OAC therapy after successful AF ablation
  • Platelet count <100,000/mm3

Primary Endpoints:

  • First stroke, systemic embolism, or major bleed

Secondary Endpoints:

  • All-cause mortality, stroke rate, AT burden

Drug/Procedures Used:

Patients with an implanted ICD or CRT-D were randomized in a 1:1 fashion to remote monitoring of AT or in-clinic assessments. The decision to anticoagulate was based on the CHADS2 score. In patients randomized to remote monitoring, AT was defined as 36 of 48 beats with a rate ≥200 bpm.

For patients with a CHADS2 score of 1 or 2, anticoagulation was started if AT persisted for ≥48 hours, and then subsequently discontinued if there was no further AT for 30 days. For patients with CHADS2 scores of 3 and 4, anticoagulation was started if AT persisted for ≥24 hours in 2 days, and then subsequently discontinued if there was no further AT for 90 days.

Patients with a higher CHADS2 score or with prior thromboembolic events were started and maintained on anticoagulation once they had any evidence of AT. In the control arm, in-clinic assessments were made regarding prevalent AT with anticoagulation based on the treating physician’s decision.

Concomitant Medications:

Aspirin (32%), other antiplatelet (32%)

Principal Findings:

The trial was terminated early due to futility. At this time, a total of 2,718 patients were randomized, 1,357 to remote monitoring and 1,361 to control. Baseline characteristics were similar between the two arms. The median CHADS2 score at baseline was 2, with evidence of left ventricular dysfunction on chronic heart failure (CHF) in nearly 90% of patients. Approximately 9% had evidence of prior stroke, and nearly two-thirds had an ICD, whereas the remainder had a CRT-D device. The most commonly used anticoagulant was warfarin. Time in therapeutic range was approximately 60% for anticoagulated patients.

During the course of the trial, 36.3% of patients in the remote monitoring arm had AT, compared with 33.2% in the control arm. Adjudication results found that 60.5% of AT events were AF, 30% were atrial flutter, and 9.5% were false positive. A total of 13.4% of patients in the remote monitoring arm started OAC, and 7.1% subsequently stopped it, compared with 11.6% and 5.2%, respectively, in the control arm.

The primary outcome of thromboembolic or bleeding event was similar between the two arms at 5 years of follow-up (2.4/100 patient-years [PY] vs. 2.3/100 PY; p = 0.78). Individual components including thromboembolism (1.2/100 PY vs. 1.4/100 PY; p = 0.59), hemorrhagic stroke (0.1/100 PY in both), and other major bleeding (1.6/100 PY vs. 1.2/100 PY; p = 0.15) were similar between the two arms. Mortality was also similar (5.4/100 PY vs. 5.1/100 PY; p = 0.66).


The results of the IMPACT trial indicate that home monitoring for AT in patients with CHF and an implanted ICD/CRT-D device (and starting and stopping OAC based on these findings) is not superior to in-office assessments of AT and anticoagulation based on physician discretion. This is an interesting concept, and may have utility in select patient populations (for example, older patients who may not be able to come for frequent clinic visits).

This trial adds to the list of several other home monitoring trials that have been performed over the past few years. However, the majority of these trials, including the current one, have been negative.


Presented by Dr. David T. Martin at the American College of Cardiology Scientific Session, Washington, DC, March 29, 2014.

Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure

Keywords: Stroke, Defibrillators, Follow-Up Studies, Warfarin, Tachycardia, Thromboembolism, Heart Failure, Medical Futility, Ventricular Dysfunction, Left, Atrial Flutter, ACC Annual Scientific Session

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