The purpose of this study is to evaluate whether treatment with ISIS CRP Rx can reduce AF (Atrial Fibrillation) burden (percentage of time spent in AF) in subjects with paroxysmal AF

Inclusion Criteria:

• Male of female; age over 18 years
• Dual chamber permanent pacemaker implanted
• Confirmed diagnosis of paroxysmal atrial fibrillation with an AF burden of 1 to 50%, as derived from pacemaker diagnostic algorithms
• Able to have pacemaker antiarrhythmic algorithms turned off for the duration of the study
• Able to discontinue all Class I and III antiarrhythmic medication for the duration of the study
• Therapeutically anticoagulated with warfarin or dabigatran, and anticipated to be for duration of the study
• High sensitivity C-Reactive Protein (hsCRP) between 2 and 10 mg/L (inclusive)

Exclusion Criteria:

• Clinically significant abnormalities in medical history, physical examination, or screening laboratory results that would render a subject unsuitable for inclusion
• NYHA class III/IV heart failure
• Impaired left ventricular function of less than 45% determined by echocardiography within 3 months of screening
• Moderate or greater mitral regurgitation assessed by echocardiography within 3 months of screening
• Permanent AF
• Continuous Amiodarone therapy within 90 days prior to Study Day 1
• Treatment with another Study Drug, biological agent, or device within one-month of screening, or five half-lives of study agent, whichever is longer
• Use of systemic corticosteroids or other anti-inflammatory medications including non-steroidal anti-inflammatory drugs (NSAIDs)
• Use of statins, ACE inhibitors or AT-receptor antagonists unless on a stable regimen for at least 3 months prior to dosing and will remain on a stable regimen for the duration of the study
• Uncontrolled hypertension (BP >160/100)
• Current or expected use of any anticoagulant apart from warfarin or dabigatran