Page 2416 - Hematology_ Basic Principles and Practice ( PDFDrive )

2156 Part XII Hemostasis and Thrombosis

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TABLE The SAMe-TT 2R 2 Score lower risks of major bleeding. Additionally, VKAs have numerous
147.3 interactions with vitamin K–containing foods and other medicines,
and the anticoagulant activity of NOACs is not influenced by dietary
Acronym Definitions Points vitamin K intake and there are few drug–drug interactions. Because
S Sex (female) 1 they produce a more predictable anticoagulant effect than VKAs,
NOACs do not require routine coagulation monitoring. A specific
A Age (less than 60 years) 1
issue with NOACs is the lack of routinely-available antidotes for
M Medical history a 1 patients who suffer major bleeding or require reversal in preparation
e for urgent surgery. However, there is no evidence that the outcome
of major bleeds is worse in patients treated with NOACs than it is in
T Treatment (interacting drugs e.g., 1 those receiving VKAs. NOACs should not be used in patients with
amiodarone for rhythm control)
prosthetic heart valves.
T Tobacco use (within 2 years) 2
R Race (non-white) 2
Maximum points 8 Secondary Stroke Prevention
a Two of the following: hypertension, diabetes mellitus, coronary artery disease/
myocardial infarction, peripheral artery disease, congestive heart failure, The highest risk of recurrent stroke is in the early phase after a first
previous stroke, pulmonary disease, hepatic or renal disease. stroke or transient ischemic attack. Prevention of recurrent stroke
with anticoagulation is effective but requires a multidisciplinary
approach with stroke physicians, hematologists, and cardiologists to
carefully select appropriate patients and minimize the risk of hemor-
Case 2: Interventional Approach to Atrial Fibrillation rhagic transformation. All NOACs are associated with a lower risk of
intracranial bleeding than VKAs; hence if a patient suffers a stroke
A 66-year-old man was referred to a cardiac electrophysiologist with a while on warfarin, clinicians may consider switching to an NOAC.
6-month history of irregular palpitations that cause considerable dis-
tress. He had presented to his local emergency department twice and
on both occasions was found to be in rapid atrial fibrillation (AF) that Nonpharmacologic Strategy
reverted spontaneously. Treatment with beta-blockers had not reduced
the frequency of symptoms and the patient had developed profound
lethargy with higher dosage. He was treated with two antihypertensive Left atrial appendage occlusion can be used to reduce the risk of
agents. The family doctor had already commenced warfarin, with a stroke for patients with AF that are unable to tolerate anticoagula-
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target international normalized ratio (INR) of 2.5. The patient elected tion. The US Food and Drug Administration (FDA) has recently
to have catheter ablation after a discussion of alternative pharmaco- approved the Watchman device for this indication, although it should
logical options and the procedural risks. He underwent radiofrequency be remembered that antiplatelet or anticoagulant therapy is often
ablation, achieving isolation of the four pulmonary veins, accessed required in the initial stage of endothelialization. Surgical approaches
through the femoral vein with a transseptal puncture of the interatrial to ligate or excise the LAA may be considered for patients with AF
septum. Warfarin was continued without interruption, maintaining an undergoing cardiac surgery or thoracoscopic maze surgery. However,
INR of 2.0 to 3.0. The procedure was uncomplicated and the patient
was discharged the following day. At 3 months he remained free of in most cases it is advisable to continue oral anticoagulation (based
symptoms. The CHA 2 DS 2 -VASc score was 2 and the patient elected to on the CHA 2 DS 2- VASc risk score), as not all SSE in AF arise from
switch to a non–vitamin K antagonist (VKA) oral anticoagulant (NOAC) the LAA.
to reduce the need for regular blood tests.
Comment Periprocedural Anticoagulation
In some patients, AF can substantially reduce quality of life, and a
strategy of rhythm control is the most appropriate choice. The number
of catheter ablation procedures is rapidly increasing worldwide, and it Interruption of anticoagulation temporarily increases thromboem-
can be offered as first-line therapy in place of antiarrhythmic drugs in bolic risk, whereas continuing anticoagulation increases the risk of
selected patients. Complication rates are low in experienced centers, bleeding associated with surgical procedures. Individuals undergoing
with 1 in 100 risk of cardiac tamponade and 1 in 500 risk of stroke. low bleeding risk procedures (e.g., dental and cutaneous procedures)
The procedure is frequently performed without interruption of VKAs can continue anticoagulation (warfarin within the target INR range
and with only brief or no interruption of NOACs. There is mounting and probably NOACs as well). Individuals at high or moderate
evidence that uninterrupted anticoagulant therapy periprocedurally thromboembolic risk should limit the period without anticoagulation
is safer than stopping the anticoagulant and bridging with heparin. to the shortest possible interval, with or without bridging with
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Long-term freedom from AF is 50% to 80% after catheter ablation, but low-molecular-weight heparin (LMWH). For individuals undergoing
this is variable and multiple ablation procedures may be necessary.
Regardless of the apparent restoration of sinus rhythm, anticoagula- major surgery or those with a high bleeding risk procedure, full-dose
tion should continue in patients with two or more CHA 2 DS 2 -VASc risk LMWH bridging should be delayed for 2 to 3 days after hemostasis
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factors. In this patient, a CHA 2 DS 2 -VASc score of 2 is equivalent to an has been secured.
estimated stroke rate of 3% to 4% per year. Details on the pharmacologic properties of available anticoagu-
lants are provided in Chapter 149.
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reduce the overall risk of stroke from 4.5% to 1.4% per year). A ANTICOAGULANT-RELATED BLEEDING
key consideration in the use of warfarin is the TTR (maintaining the
INR between 2.0 and 3.0 in nonvalvular AF). To achieve optimal Risk of Bleeding
reduction in SSE, TTR should be maintained above 65%–70%.
Antiplatelet agents such as aspirin are inferior to oral anticoagula- Risk management of anticoagulation-related bleeding is complicated
tion for stroke prevention and are associated with similar bleeding because many of the risk factors for bleeding are also risk factors for
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risks; hence their use for primary prevention of SSE in AF is now stroke. The HAS-BLED score (see Table 147.2) was derived and
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discouraged. Recently, four NOACs have become available, including validated in the Euro Heart survey population, with scores ≥3
the oral direct thrombin inhibitor dabigatran and the oral factor Xa indicating a high risk of bleeding and the requirement for atten-
inhibitors apixaban, edoxaban, and rivaroxaban. All have shown equal tion to minimize bleeding complications. Of note, the HAS-BLED
or greater efficacy than warfarin in reducing SSE and generally have score should not be used to withhold anticoagulation, but rather