1.
Acute Causes of AF
AF
may be related to acute, temporary causes, including
alcohol intake ("holiday heart syndrome"),
surgery, electrocution, MI, pericarditis, myocarditis,
pulmonary embolism or other pulmonary diseases, and
hyperthyroidism or other metabolic disorders. In such
cases, successful treatment of the underlying condition
may eliminate AF. AF that develops in the setting of
an acute MI portends an adverse prognosis compared with
preinfarct AF or sinus rhythm (171).
AF may be associated with another supraventricular tachycardia,
the WPW syndrome, or AV nodal reentrant tachycardias,
and treatment of these primary arrhythmias reduces the
incidence of recurrent AF (87).
AF is a common early postoperative complication of cardiac
or thoracic surgery.
2.
AF Without Associated Heart Disease
The
concept that AF is not a disease by itself and should
instead be considered a sign of underlying cardiac disease
is reinforced by the fact that it has so many causes.
Arguing to the contrary, approximately 30% to 45% of
paroxysmal cases and 20% to 25% of persistent cases
of AF occur in younger patients without demonstrable
underlying disease (lone AF) (19,21,22).
AF can present as an isolated (48)
or familial (172)
arrhythmia, although an underlying disease may appear
over time. Although this may reduce the relative incidence
of lone AF in the elderly, development of heart disease
in older patients may be coincidental and unrelated
to AF.
3.
AF With Associated Heart Disease
Specific
cardiovascular conditions associated with AF include
valvular heart disease (most often mitral valve disease),
coronary artery disease (CAD), and hypertension, particularly
when LV hypertrophy is present. In addition, AF may
be associated with HCM or dilated cardiomyopathy or
congenital heart disease, especially atrial septal defect
in adults. Sinus node disease, ventricular preexcitation,
and supraventricular tachycardias may also underlie
AF. The list of etiologies also includes restrictive
cardiomyopathies (such as amyloidosis, hemochromatosis,
and endomyocardial fibrosis), cardiac tumors, and constrictive
pericarditis. Other heart diseases, such as mitral valve
prolapse even without mitral regurgitation, calcification
of the mitral annulus, cor pulmonale, and idiopathic
dilation of the RA, have been associated with a high
incidence of AF. AF is commonly encountered in patients
with the sleep apnea syndrome, but whether the arrhythmia
is provoked by hypoxia or other biochemical abnormality
or mediated by changes in pulmonary dynamics or RA factors
has not been determined. Table
3 shows a list of associated heart diseases in the
contemporary population of the ALFA study (21).
4.
Neurogenic AF
The
autonomic nervous system may trigger AF in susceptible
patients through heightened vagal or adrenergic tone.
Many patients experience onset of AF during periods
of enhanced parasympathetic or sympathetic tone, and
Coumel described a group of patients that he characterized
in terms of a vagal or adrenergic form of AF (173).
Vagal AF is characterized by 1) a prevalence
that is approximately 4 times greater in men than in
women; 2) age approximately 40 to 50 years
at onset; 3) frequent association with lone
AF; 4) little tendency to progress to permanent
AF; 5) occurrence at
night, during rest, after eating, or after ingestion
of alcohol; and 6) antecedent progressive bradycardia.
Because heart rate is relatively slow during the episode
of AF, most patients complain of irregularity rather
than dyspnea, lightheadedness, or syncope. Importantly,
both adrenergic blocking drugs and digitalis may increase
the frequency of vagally mediated AF.
Like
vagal AF, the age of patients with adrenergic AF is
usually about 50 years at onset, and most do not exhibit
structural heart disease. In contrast, as originally
described by Coumel (173)
and subsequently verified by others, adrenergic AF has
the following features: 1) a lower incidence
than vagally mediated AF; 2) onset predominantly
during the daytime; 3) provocation by exercise
or emotional stress; 4) polyuria as a common
correlate; 5) onset typically associated
with a specific sinus rate for a given patient; and
6) no gender differences. In contrast to
vagally induced AF, beta-blockers are usually the treatment
of choice for AF of the adrenergic type.
Scant
data are available on neurogenic AF, which is relatively
rare as a pure entity. Although patients with pure vagal
or adrenergic AF are uncommon, when the clinical history
reveals a pattern of onset of AF that has features of
one or the other of these syndromes, the clinician may
be able to select agents that are more likely to prevent
recurrent episodes.
B.
Clinical Manifestations
AF
may be symptomatic or asymptomatic, even in the same
patient. The dysrhythmia may present for the first time
with an embolic complication or exacerbation of HF,
but most patients with AF complain of palpitations,
chest pain, dyspnea, fatigue, lightheadedness, or syncope.
The association of polyuria with AF may be mediated
by release of atrial natriuretic peptide. AF may be
associated with a fast ventricular response, leading
to tachycardia-mediated cardiomyopathy, especially in
patients who are unaware of the arrhythmia. Syncope
is an uncommon but serious complication that is usually
associated with sinus node dysfunction or hemodynamic
obstruction, such as valvular aortic stenosis, HCM,
cerebrovascular disease, or an accessory AV pathway.
Symptoms vary with the ventricular rate, underlying
functional status, duration of AF, and individual patient
perceptions.
C.
Quality of Life
Although
strokes certainly account for much of the functional
impairment associated with AF, the rhythm disturbance
can also decrease quality of life directly. In the SPAF
study cohort, Ganiats et al. (174)
found the New York Heart Association functional classification,
developed for HF, to be an insensitive index of quality
of life in patients with AF. In another study (175),
47 (68%) of 69 patients with paroxysmal AF considered
the dysrhythmia disruptive of their lives, but this
perception was not associated with either the frequency
or duration of symptoms.
Little
is known of the direct effects of antiarrhythmic and
rate control therapy on quality of life. In the Canadian
Trial of Atrial Fibrillation (CTAF) study, quality of
life improved after pharmacological treatment, whether
this involved amiodarone, propafenone, or sotalol (176).
The postcardioversion EMERALD (European and Australian
Multicenter Evaluation Research on Atrial Dofetilide)
study (177)
showed that dofetilide improved quality of life 1 month
after electrical cardioversion. The AFFIRM trial (Atrial
Fibrillation Follow-up Investigation of Rhythm Management),
still in progress, is comparing maintenance of sinus
rhythm with rate control in patients with AF and addressing
many facets of quality of life, as has been done in
the smaller PIAF (Pharmacological Intervention in Atrial
Fibrillation) study (178,179).
In
selected patients, radiofrequency catheter ablation
of the AV node and pacemaker insertion decreased subjective
symptoms of AF and improved quality-of-life scores compared
with medical therapy (180-185).
Baseline quality-of-life scores appear to be lower for
patients with atrial flutter and fibrillation than for
those with other arrhythmias who are undergoing radiofrequency
ablation (186).
A meta-analysis of 10 published studies of patients
with AF (187)
found improvement in both symptoms and quality-of-life
scores after ablation and pacing. Although these studies
followed highly selected patients who remained in AF,
such consistent improvement suggests that quality of
life was impaired at baseline (before intervention).
Two studies have described improvement in symptoms and
quality of life after radiofrequency catheter ablation
of atrial flutter (188,189).
Long-term
oral anticoagulant therapy, which involves frequent
blood testing and multiple drug interactions, is another
factor with important implications for the quality of
life of AF patients. Gage et al. (190)
quantified this as a mean 1.3% decrease in utility,
a measure of quality of life used in quantitative decision
analysis. Eleven patients (16%) felt that their quality
of life would be greater with aspirin than with oral
anticoagulants, despite its lesser efficacy. Protheroe
et al. (191),
using decision analysis to assess patient preferences,
found that only 59 (61%) of 97 patients preferred anticoagulation
therapy to no treatment, a considerably smaller proportion
than that for whom treatment has been recommended according
to published guidelines. These comparisons could be
influenced in the future by the development of more
convenient approaches to antithrombotic therapy.
Copyright
© 2001 by the American College of Cardiology, American
Heart Association, Inc., and the European Society of
Cardiology
Published
by Elsevier Science Inc.
