MARON
AND MCKENNA et al., ACC/ESC Expert Consensus Document on Hypertrophic
Cardiomyopathy
JACC 2003; 42:
000-000
American
College of Cardiology/European Society of Cardiology Clinical
Expert Consensus Document on Hypertrophic Cardiomyopathy
A
Report of the American College of Cardiology Foundation Task
Force on Clinical Expert Consensus Documents and the European
Society of Cardiology Committee for Practice Guidelines
Atrial
Fibrillation
Atrial
fibrillation is the most common sustained arrhythmia in HCM
and usually justifies aggressive therapeutic strategies (30,38,161–163,249)
(Fig. 1). Paroxysmal episodes or chronic
AF ultimately occur in 20% to 25% of HCM patients (30,163,249),
linked to left atrial enlargement and an increasing incidence
with age (163). Furthermore,
it is possible that subclinical AF (i.e., identified only
by Holter recording) may be even more common. Clinical cohort
studies show that AF is reasonably well tolerated by about
one-third of patients and is not an independent determinant
of sudden unexpected death (163);
however, it is possible that in certain susceptible patients,
AF may trigger life-threatening ventricular arrhythmias (244,254).
Nevertheless, AF is independently associated with heart failure-related death, occurrence of fatal and nonfatal stroke, as
well as long-term disease progression with heart failure symptoms
(38,161,163);
transient episodes occur in about 30% of patients immediately
following septal myectomy, often in patients with a prior
history of AF (202). Risk
for complications of AF is enhanced when the arrhythmia becomes
chronic, onset is before 50 years of age, and outflow obstruction
is present (163).
Paroxysmal
episodes of AF may also be responsible for acute clinical
deterioration, with syncope or heart failure resulting from
reduced diastolic filling and cardiac output—as a consequence
of increased ventricular rate and with loss of atrial contraction
(and its contribution to ventricular filling) in a hypertrophied
LV with pre-existing impaired relaxation and compliance (161–163).
Atrial fibrillation in HCM should be managed generally in
accordance with the ACC/AHA guidelines (272).
In particular, electrical or pharmacologic cardioversion are
indicated in those patients presenting within 48 h of onset,
assuming that the presence of atrial thrombi can be excluded
with a reasonable degree of certainty. Although comparative
data regarding the efficacy of antiarrhythmic drugs are not
available for HCM patients, amiodarone is generally regarded
as the most effective antiarrhythmic agent for preventing
recurrences of AF, based largely on extrapolation from its
use in other heart diseases (272,273).
A
generally aggressive strategy for maintaining sinus rhythm
is warranted in HCM because of the association of AF with
progressive heart failure and mortality, as well as stroke
(38). In chronic AF, beta-blockers,
verapamil (and digoxin) have proved effective in controlling
heart rate, although A-V node ablation and permanent ventricular
pacing may occasionally be necessary in selected patients.
Anticoagulant therapy (with warfarin) is indicated in patients
with either paroxysmal or chronic AF (7,11,38,163).
Because even one or two episodes of paroxysmal AF have been
associated with increased risk for systemic thrombo-embolization
in HCM, the threshold for initiation of anticoagulant therapy
should be low and can include patients after the initial AF
paroxysm (7,38,163).
Since warfarin has proved superior to aspirin in other cardiac
conditions associated with AF, it is the recommended anticoagulant
agent in HCM patients judged to be at risk for thromboembolism.
While anticoagulation reduces the risk of thromboembolic events
in patients with AF and HCM, it is also recognized that anticoagulation
does not completely abolish the risk of stroke (38,163).
Such clinical decisions should be tailored to the individual
patient after considering the risk for hemorrhagic complications,
lifestyle modifications, and expectations for compliance.
The
most appropriate management for patients with asymptomatic
nonsustained supraventricular tachycardia (detected only on
ambulatory [Holter] ECG or exercise-testing), and associated
with left atrial enlargement is presently unresolved. Also,
at present, there is little experience specifically in HCM
patients with emerging and novel alternative treatment strategies
for AF such as pulmonary vein radio-frequency ablation, the
surgical MAZE procedure, or implantable atrial defibrillators
to warrant definitive recommendations at this time.
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