Page 2415 - Hematology_ Basic Principles and Practice ( PDFDrive )

Chapter 147 Atrial Fibrillation 2155

I V1

II V2

II V3

aVR V4

aVL V5

aVF V6

Fig. 147.2 ELECTROCARDIOGRAM OF ATRIAL FIBRILLATION.

factors for SSE, even if the patient appears to be in normal sinus TABLE Risk Stratification for Incident Stroke and Systemic
rhythm.
147.2 Thromboembolism and Bleeding
CHA 2 DS 2 -VASc Score for SSE HAS-BLED Score for Bleeding
PREVENTION OF STROKE AND THROMBOEMBOLISM Prediction Prediction
Clinical Characteristic Points Clinical Characteristic Points
The risk of SSE in AF varies, depending on several clinical factors,
including age, gender, previous embolic events and vascular disease, CHF or LVEF ≤40% 1 Hypertension 1
hypertension, diabetes mellitus, and heart failure. In most cases of Hypertension 1 Abnormal renal/liver 1 or 2
AF related to valvular heart disease (such as mitral stenosis), there are function
rarely any reasons not to anticoagulate patients due to the high Age ≥75 2 Stroke 1
baseline risk of SSE, regardless of other patient characteristics. Risk
stratification scores can be helpful in clinical practice in nonvalvular Diabetes 1 Bleeding 1
AF to initially identify those patients at lowest risk of SSE that do Stroke/TIA/TE 2 Labile INRs 1
not require antithrombotic therapy (i.e., a CHA 2 DS 2 -VASc score 0 Vascular disease 1 Elderly (age >65 1
in men, 1 in women; Table 147.2). Subsequent to this step, effective years)
stroke prevention (oral anticoagulation) can be offered to patients
with one or more additional stroke risk factors (i.e., CHA 2 DS 2 -VASc Age 65–74 1 Drugs or alcohol 1 or 2
score ≥1 in males, ≥2 in females). This approach is better than a Sex category (female) 1
categorical approach to stroke risk (i.e., low/moderate/high) and Cumulative score Range 0–9 Cumulative score Range 0–9
basing treatment decisions on these artificial risk categories, given
that stroke risk is a continuum and because clinical risk scores have For the CHA 2 DS 2 -VASc score, estimated stroke and thromboembolism event
rates at 1 year follow-up are 0.78% (0 points), 2.01% (1 point), 3.71% (2
limited predictive value for identifying “high-risk” subjects. points), 5.92% (3 points), 9.27% (4 points), 15.26% (5 points), 19.74% (6
Oral anticoagulation can be achieved using a well-controlled, points), 21.50% (7 points), 22.38% (8 points), 23.64% (9 points); see Olesen
adjusted-dose vitamin K antagonist (VKA, e.g., warfarin), with time JB, Lip GY, Hansen ML, et al: Validation of risk stratification schemes for
in therapeutic range (TTR) >70%, or one of the non-VKA oral predicting stroke and thromboembolism in patients with atrial fibrillation:
nationwide cohort study. BMJ. 342:d124, 2011.
anticoagulants (NOACs) (see later). Deciding between a VKA and Hypertension = systolic blood pressure >160 mmHg; vascular disease = prior
23
an NOAC can be assisted using the SAMe-TT 2 R 2 score, which is a myocardial infarction, peripheral artery disease, and/or aortic plaque; abnormal
simple clinical risk score to help identify those patients likely to do renal function = dialysis, transplant, creatinine >2.6 mg/dL or >200 µmol/L;
well on a VKA (patients with a high TTR [SAMe-TT 2 R 2 score 0–2]), abnormal liver function = cirrhosis or bilirubin >2× normal with AST/ALT/AP
>3× normal; labile INR = unstable/high INRs, time in therapeutic range <60%;
or those for whom an NOAC would be a better treatment option drugs = antiplatelet agents, nonsteroidal antiinflammatories; alcohol = eight or
(less likely to achieve a good TTR (SAMe-TT 2 R 2 score >2]) 24,25 more drinks/week.
(Table 147.3). Although in some health care systems NOACs are AST, Aspartate aminotransferase; ALT, alanine aminotransferase; AP, alkaline
routinely used as first-line therapy, the majority of patients with AF phosphatase; CHF, congestive heart failure; INR, international normalized ratio;
LVEF, left ventricular ejection fraction; SSE, stroke or systemic
globally are still treated with VKAs. thromboembolism; TE, thromboembolism; TIA, transient ischemic attack.
Anticoagulants
The most commonly used anticoagulants in AF are VKAs such as
warfarin, which reduce the risk of stroke by nearly two-thirds (i.e.,