A Retrospective Analysis of the Use of ACE-inhibitors and Angiotensin Receptor Blockers
Condition: Atrial Fibrillation; Atrial Flutter
MeSH terms: Atrial Fibrillation; Atrial Flutter
Study type: Observational

Summary: 
      It is well known that atrial fibrillation (AF) and atrial flutter occur frequently after most
      types of cardiac surgeries.(1-4) Postoperative AF is associated with significant morbidity,
      longer hospital stay, and higher related costs. Currently, it is common procedure to
      premedicate patients with antiarrhythmic drugs for elective cardiac surgeries. Treatments
      such as beta blockers, Amiodarone, and electrical pacing are used to help prevent the
      morbidity associated with pot-operative AF.(5)

      Renin-angiotensin system (RAS) activation may contribute to AF. Several clinical trials have
      suggested that inhibitors of this system may reduce the incidence of AF.(6-12) Patients with
      AF are known to have increased levels of angiotensin converting enzyme (ACE) and some types
      of angiotensin receptors.(13-15) Data from animal studies performed by our group suggest that
      cardiac ACE overexpression may lead to arrhythmic ion channel changes.(16;17) Although not
      studied in this group yet, it would be reasonable to conclude that the use of ACE inhibitors
      and angiotensin receptor blockers (ARBs) would decrease the incidence of AF in post-operative
      patients, too
    

Detailed description: 
      2.0 Objectives

      Based on the discussion above, we hypothesize that patients premedicated on ACE Inhibitors
      and ARBs will have a decreased incidence of post-operative AF or atrial flutter. This study
      will be a retrospective cohort analysis of all patients that underwent elective cardiac
      surgeries between 2000-2005 at Emory University Hospital, Crawford Long Hospital, or the
      Atlanta Veterans Affairs Medical Center to evaluate the relationship of pre-operative ACE
      inhibitor or ARB use to the incidence of post-operative atrial arrhythmias.. This study is
      undertaken in preparation for a funding proposal for a prospective trial.

      3.0 Patient Selection 3.1 Eligibility criteria:

      1. All patients that patients who underwent elective cardiac surgery in the Emory University
      Hospital, Crawford Long Hospital, or the VA Medical Center between 2000-2005.

      3.2 Ineligibility criteria:

        1. Emergent operations.

        2. The presence of AF or atrial flutter at the time of surgery.

        3. Patients without adequate documentation of atrial rhythm following surgery.

        4. New York Heart Association (NYHA) class IV heart failure at the time of surgery.

        5. Hyperthyroidism

        6. Implanted devices for designed for active management of atrial arrhythmias by pacing or
           defibrillation

        7. Known illicit drug use

        8. Known ethanol abuse

        9. Electrophysiological ablation for atrial tachycardia within 6 months of the operation.

      4.0 Registration and randomization: none

      5.0 Therapy: none

      6.0 Pathology: none

      7.0 Patient assessment: none

      8.0 Data collection: Data will be collected from review of the patient's hospital charts,
      from telemetry recordings, and ECGs to document the presence or absence of AF or atrial
      flutter during the hospital admission for cardiac surgery. The presence or absence of atrial
      fibrillation will be diagnosed on the basis of an electrocardiographic recording and
      confirmed by a cardiologist. Demographic data collected will include: age, race, sex, body
      mass index, blood pressure, NYHA classification, Killip classification, and the history of
      previous myocardial infarction, hypertension, diabetes, smoking, alcohol use, antiarrhythmic
      drug use, presence and type of pacemaker if any, history of AF or atrial flutter, previous
      cardiovascular events, type of operation, and length of operation. Patients enrolled in this
      study will be given unique study numbers. No follow up data will be required from patients.

      9.0 Statistical considerations: This study design is a retrospective chart review of a cohort
      of patients undergoing cardiac surgery to determine if there is an association between
      pre-operative ARB or ACE inhibitor use and the incidence of post-operative atrial
      fibrillation or atrial flutter. The null hypothesis is that there is no association between
      the preoperative use of ACE Inhibitors and ARBs and postoperative AF and atrial flutter.
      Within the cohort, those patients with AF or atrial flutter will be compared to those without
      these atrial arrhythmias in the post-operative period. Baseline data for the two groups will
      be expressed as mean ± standard deviation for continuous variables, and frequencies for
      categorical variables. Differences in baseline characteristics between the groups will be
      examined by use of Fisher exact and Mann-Whitney tests for categorical and continuous
      variables, respectively. Quantification of any association between pre-operative ACE
      Inhibitors and ARBs and the presence of atrial fibrillation will modeled by logistical
      regression analysis after adjusting for other variables that may affect arrhythmia frequency.
    

Intervention name(s): ACE-Inhibitors and Angiotensin Receptor Blockers
Intervention type(s): Procedure
Intervention description(s): Retrospective study - no intervention as part of study.
Intervention MeSH terms: Angiotensin-Converting Enzyme Inhibitors; Angiotensin Receptor Antagonists
Observational model: Case-Only
Time perspective: Retrospective
Sampling method: Probability Sample
Study population: 
        All patients, 18 years or older up to and including 65 years of age, who underwent elective
        cardiac surgery in the Emory University Hospital, Crawford Long Hospital, or the VA Medical
        Center between 2000-2005.
      
Keywords: Atrial Fibrillation; Atrial Flutter; Angiotensin Converting Enzyme Inhibitor; Angiotensin Receptor Blocker