Echocardiographic Risk Factors of Stroke in Patients With Atrial Fibrillation

Atrial fibrillation is the most common heart rhythm disorder seen in clinical practice.
Patients with atrial fibrillation are at increased risk for stroke. This risk is determined
by several factors. Congestive heart failure, hypertension, age, diabetes, female sex,
previous history of heart attack or vascular disease, and previous history of stroke all
increase a patients' risk for clot formation and stroke. These risk factors have been
formulated into a scoring system called the CHA2DS2-VASc score. A score of greater than 2 on
this scale indicates a moderate to high risk for clot formation and stroke. Anticoagulation
medications are recommended in these patients. Non-traditional risk factors such as left
atrial size and left ventricular hypertrophy have also been associated with increased stroke
risk. These factors have not yet been routinely incorporated into treatment decisions
regarding anticoagulation and stroke prevention.

This study is an expansion of an initial pilot conducted at Pen Bay Medical Center of patient
records from 2014-2017. This pilot found 19 patients with a recorded stroke or TIA, history
of atrial fibrillation, and CHA2DS2-VASc score of 2 or lower within that time period. This
study will be an expansion of that pilot to include patient data from Maine Medical Center.

This study aims to look at these non-traditional risk factors in patients who have an
otherwise low stroke risk based on the CHA2DS2-VASc score.

Our specific aims are:

1. Assess left atrial volume using volumetric measurements and left ventricular septal and
posterior wall thickness from 2-D transthoracic echocardiography studies in patients
with known atrial fibrillation who suffered a stroke or TIA. We would then compare these
data to control patients with atrial fibrillation with matched CHA2DS2-VASc scores, age
(+/- 5 years), and gender who have no history of stroke or TIA. Our hope is to identify
higher risk patients with alternate anatomy who otherwise would be considered lower risk
using traditional risk scoring methods. Identifying these individuals may lead to more
aggressive interventions and subsequently may help in reducing the risk of stroke.

2. Assess stroke outcome in the population of patients with atrial fibrillation who
suffered a stroke to identify any potential differences associated with structural
changes. If structural changes are associated with stroke severity, echocardiogram
findings again may aid in guiding treatment decisions for patients with atrial
fibrillation.

Hypothesis: Patients with atrial fibrillation and a history of stroke or TIA will have
alternate anatomy when compared to patients with atrial fibrillation with matched
CHA2DS2-VASc scores who have not had a stroke or TIA.

This is a retrospective matched case-control study of data collected at Pen Bay Medical
Center (PBMC) and Maine Medical Center (MMC) from 2014-2017. Patient records that met the
criteria as a case from PBMC have already been collected from existing data housed in the
American Heart Association's "Get with the Guidelines" registry as a pilot project. These
data will be included in this study and combined with controls identified from PBMC, and
cases and controls identified from existing EPIC data for MMC patients.

Inclusion Criteria:

- 1. A case is defined as a patient from either PBMC or MMC within the years of 2014-2017
who had a stroke or TIA, atrial fibrillation, a documented transthoracic echocardiogram,
and who had a CHA2DS2-VASc score of 0, 1, or 2. Cases from Pen Bay Medical Center have
already been ascertained from the American Heart Association "Get with the Guidelines"
registry, and will be included in this study. Cases from Maine Medical Center will be
identified from EPIC.

2. Controls from both PBMC and MMC will be obtained. Controls are patients from 2014-2017
with matched age (+/- 5 years), gender, and CHA2DS2-VASc score who had atrial fibrillation
and had not had a documented stroke or TIA in EPIC or the "Get with the Guidelines"
registry maintained at PBMC.

Exclusion Criteria:

- 1. Patients with a CHA2DS2-VASc score greater than 2.