Page 2413 - Hematology_ Basic Principles and Practice ( PDFDrive )

Chapter 147 Atrial Fibrillation 2153

Key Investigations
TABLE Symptom Scoring in Atrial Fibrillation
147.1
Cardiac ultrasound (echocardiography) in AF contributes to risk
mEHRA score Symptoms Description stratification, diagnosis of complications, and management of associ-
1 None ated conditions. Transthoracic echocardiography is a noninvasive
method that provides a comprehensive assessment of cardiac structure
2a Mild Normal daily activity not affected
and function. In patients where exclusion of the left atrial appendage
2b Moderate Normal daily activity not affected, thrombus is required, transesophageal echocardiography is the
but patient troubled by modality of choice; in addition to visualization of dense spontaneous
symptoms echo contrast, LAA-emptying velocities of <20 cm/s are strongly
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3 Severe Normal daily activity affected associated with incident SSE. Other imaging techniques, such as
computed tomography and magnetic resonance imaging, are being
4 Disabling Normal daily activity discontinued
used more frequently and have complementary roles in the manage-
mEHRA, Modified European Heart Rhythm Association score. ment of patients with AF.
Blood tests are important in the initial assessment of AF, and
should include tests for thyroid, renal, and hepatic function, in addi-
Case 1: Concomitant Atrial Fibrillation and Risk of Stroke tion to serum electrolytes, full blood count, and global tests of coagu-
lation, such as prothrombin time/international normalized ratio
A 77-year-old woman with syncope, progressive exertional breathless- (INR) and activated partial thromboplastin time. Biomarkers (such
ness, and a systolic murmur was referred for urgent cardiology opinion as troponin, B-type natriuretic peptide, and D-dimer) have the
by her family doctor. Past medical history included type 2 diabetes. potential for refining risk prediction for SSE, but their role in man-
On transthoracic echocardiography, the aortic valve was critically agement requires further evaluation before routine measurement can
stenosed, with good biventricular function. She denied any history of 16
palpitations and multiple electrocardiograms (ECGs) confirmed sinus be recommended.
rhythm. She was reviewed by a cardiac surgeon and urgently listed for a
bioprosthetic aortic valve replacement. During all preoperative assess-
ments, she remained in sinus rhythm. On the day of operation she Differential Diagnoses
was noted to be in atrial fibrillation (AF). Intraoperative transesophageal
echocardiogram revealed a large thrombus arising from her left atrial Other atrial rhythms may resemble AF on an ECG, but these can often
appendage (LAA), measuring over 5 cm. The surgeon modified the be distinguished by the presence of discrete P waves (e.g., atrial tachy-
approach and first opened the left atrium, physically removed the cardias). Atrial flutter, in the typical form, is characterized by a sawtooth
thrombus, surgically amputated the LAA, and overstitched the orifice, pattern of regular atrial activation, visible as flutter waves in leads II,
before proceeding to aortic valve replacement. The patient made a
good recovery and was commenced on long-term warfarin due to a III, aVF, and V1. Atrial flutter commonly occurs with 2 : 1 AV block,
CHA 2DS 2-VASc score of 4. resulting in a ventricular rate of approximately 150 beats/min (unless
rate control medications have been taken). It should be remembered
Comment that persistent atrial flutter is also associated with SSE, and hence
In the context of other cardiovascular conditions, identifying symptoms requirements for anticoagulation are similar to those for AF. Supraven-
of AF can be difficult. AF frequently complicates other conditions, tricular tachycardias can be readily distinguished from other narrow
particularly those that have a structural impact on the heart, such as complex tachycardias (and often effectively treated) by the use of
heart failure and valve disease. This patient most likely had paroxysmal
AF that was not detected despite numerous preoperative ECGs. The intravenous adenosine. Broad complex tachycardia should be treated
large thrombus in the LAA would have placed her at high risk of a urgently as ventricular tachycardia, unless there is good reason to
fatal stroke. Surgical amputation of the LAA is a viable option during suspect a bundle-branch block pattern (for example, hemodynamically
cardiac surgery; however, as more than 10% of clots arise from outside stable irregular AF with preexisting left bundle branch block).
the LAA, patients still require long-term anticoagulation depending on
predicted risk. In this patient, a CHA 2DS 2-VASc score of 4 is equivalent
to an estimated stroke rate of 4%–5% per year. HEART RATE AND RHYTHM CONTROL

Aside from anticoagulation (see later), management of AF involves
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patients with heart failure is associated with increased mortality, control of the rapid heart rate in the majority of patients and therapy
irrespective of the type of heart failure (whether systolic or diastolic to restore sinus rhythm in selected individuals. Compared with rate
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dysfunction). Regardless of the development of heart failure, control therapy, rhythm control does not appear to reduce adverse
AF is linked with higher mortality in women (1.9-fold) and men outcomes; hence the strategy for managing patients with AF is
(1.5-fold). 14 dependent on the presence of ongoing symptoms. 17,18 Thus, modern
management of AF is largely patient-centered and symptom-directed.
DIAGNOSIS AND DIFFERENTIALS
Rate Control
Diagnosing Atrial Fibrillation
Rate control can be achieved with beta-blockers, non–dihydropyridine
Advances in diagnostic technology are leading to more decisive thera- calcium channel blockers (CCB; diltiazem and verapamil), and
peutic approaches. Among the various diagnostic tools, the simplest cardiac glycosides (digoxin and digitoxin). Unfortunately there are
method of detecting AF is the electrocardiogram (ECG), which is few robust randomized trials in this field, leaving the choice of
often prompted by an irregular pulse. Diagnostic ECG criteria therapy up to individual clinicians based on patient factors such as
include absence of P waves, fibrillatory waves between QRS com- the presence of heart failure or hypertension. Traditionally beta-
plexes, and irregular R-R intervals (Fig. 147.2). In paroxysmal AF, blockers have been the preferred therapy due to a presumption of
ambulatory ECG monitors are helpful, with longer-term monitoring improved prognosis in patients with concomitant heart failure.
now easily achieved with loop recorders implanted using a local Recent data, however, suggest that unlike their effect in patients with
anesthetic. In cases of embolic stroke with undetermined source sinus rhythm, beta-blockers do not reduce mortality or cardiovascular
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(previously called cryptogenic stroke), implantable loop recorders are hospitalization in heart failure patients with AF. CCB are typically
recommended to capture episodes of silent AF that would benefit avoided in patients with reduced ejection fraction due to negative
from anticoagulation. inotropic effects, but can be useful drugs in those with preserved