Case report
A 54-year-old man was referred to our hospital because of palpitation
attacks. He had a history of mitral annuloplasty with a superior
transseptal (STS) approach for mitral valve prolapse at the age of 49
years. Atrial flutter was recognized by 12-lead echocardiography (ECG);
thus, catheter ablation was performed. When both atria were mapped using
the CARTO3 system (Biosense Webster, Diamond Bar, CA) during
tachycardia, double potentials, indicating an incision line connecting
the right atrial free wall to the septum and then to the left atrial
roof, were observed (Figure 1A ). The typical counterclockwise
atrial flutter with a cycle length of 260 ms was mapped and terminated
during cavotricuspid isthmus (CTI) ablation. Subsequently, atrial
tachycardia (AT) with a cycle length of 272 ms was induced. The
entrainment and activation mapping revealed a macroreentrant circuit
associated with the right atrial part of the incision line from the STS
approach. The activation wavefront circulated clockwise around the
incision with two penetration points along the surgical incision in
right atrium (Figure 1B ). AT was rapidly terminated after 2
seconds of the first radiofrequency application (30 W, 60 seconds in
total) at the conduction site across the incision of the right atrial
free wall. AT was not induced thereafter. Another conduction point
across the incision was also ablated. In addition, a linear ablation
connecting the incisional scar with the inferior vena cava (IVC) was
created. Then, pacing from the low lateral right atrium (anterior side
of the incision line) showed residual conduction beyond surgical
incision at 10 O’clock and 11 O’clock positions viewing the annulus as a
clockface (Figure 2, A and B ). Radiofrequency application at
these sites was performed, and complete conduction block was verified
(Figure 2, C ). The excitation of sinus rhythm propagates behind
the incision, then turns to the tricuspid annulus (anterior side of the
incision) and ascends in a counterclockwise manner to the free wall. The
two block lines (incision to IVC and CTI) make the posterolateral wall
of the tricuspid annulus the most delayed site of propagation during
sinus rhythm in the right atrium. The patient has been free of
recurrence of tachycardia for three years after ablation.