The AHA Guidelines and Scientifi c Statements Handbook
mapping (ECGI) and solving the inverse relation-
ship appear promising [30]. Other studies have
focused on use of adenosine to determine the tachy-
cardia mechanism. Adenosine appears to terminate
triggered rhythms, depress automatic rhythms and
appears to have no effect on those with micro re-
entry [31]. In addition, efforts to improve tech-
niques for ablation of anteroseptal foci include
introduction of a technique to ablate anteroseptal
foci from the noncoronary cusp of the aortic valve
[32].
Atrial fl utter
Atrial fl utter is rapid macro re-entrant atrial tachy-
cardia with atrial rates between 250 and 350 beats/
minute. Atrial fl utter usually involves the muscles
around the tricuspid annulus. The most common
form is counter clockwise activation (LAO projec-
tion) around the annulus with the crista terminalis
and subeustachian ridge acting as the posterior
barrier. A less common form involves clockwise
activation around the annulus. Both of these forms
involve the cavotricuspid isthmus and this area
serves as the target for ablation.
Non-CTI dependent fl utter is most often seen
after corrective surgery for congenital cardiac disease
or following left atrial ablation for atrial fi brillation.
These circuits involve activation around scars and/
or pulmonary venous sites. In addition, atypical
fl utter may involve the muscles around the mitral
annulus or over the left atrial septum.
Treatment
Acute therapy is dictated by the patient’s hemody-
namic status. Emergency intervention includes use
of atrial overdrive pacing or low energy (20–50
watts) direct current cardioversion. In more urgent
situations use of AV nodal blocking agents for rate
stabilization is indicated. This is especially impor-
tant for those in whom Class 1 C drugs are contem-
plated, since IC drugs may slow the atrial rate and
result in paradoxical increase in the ventricular
response unless nodal conduction is attenuated.
The most effective drug for acute conversion of
atrial fl utter is intravenous ibutilide (38–76%
effi cacy rate). Acute therapy is summarized in
Table 16.7.Chronic therapy
Chronic drug therapy is often ineffective. Class III
agents especially dofetilide appear to be more effec-
tive than Class 1 C drugs, since the latter appear to
stabilize the fl utter circuit by decreasing atrial con-
duction velocity.
Catheter ablation has proved to be 95% effective
for those with CTI dependent fl utter and has become
the cornerstone of treatment for this arrhythmia.
Ablation for nonisthmus dependent fl utter is less suc-
cessful since multiple circuits involving multiple scars
are often found. The success rate will be governed by
circuit numbers and complexity. See Table 16.8.
Since publication of the guidelines, a number of
studies comparing drug therapy or drug vs. ablative
therapy have been reported. In two multicenter
double-blind randomized trials [33], the effi cacy of
dronedarone (amiodarone derivative) was evaluated
for patients treated with 400 mg twice per day vs.
409 patients treated with placebo. The patients had
either atrial fi brillation and/or atrial fl utter. In both
trials there was a signifi cant increase in time to fi rst
recurrence of either atrial fi brillation or fl utter. This
study provides evidence for a new drug approach for
management of patients with atrial fl utter.
A recent prospective randomized study by Kafkas
et al. [34] compared conversion rates of recent onset
atrial fi brillation or atrial fl utter in patients treated
with IV amiodarone vs. IV ibutilide. For the patients
with atrial fl utter, ibutilide was signifi cantly superior
to amiodarone (87% vs. 29%) (P < 0.003) in conver-
sion to sinus rhythm. This study strengthens guide-
line recommendations for acute treatment of atrial
fl utter.
A randomized prospective study [35] compared
amiodarone treatment vs. ablation after only the
initial episode of symptomatic cavotricuspid isthmus
fl utter. The study included 104 patients who were
randomized to the two treatment arms. Better long-
term success rates (in terms of maintenance of sinus
rhythm) were achieved for the group treated with
ablation.
A number of studies have focused on long-term
follow-up of patients treated with radiofrequency
ablation of the cavotricuspid isthmus for typical