Discussion
Intra-atrial reentrant tachycardia is a well-known complication after
open heart surgery with atriotomy. 1-4 Typical atrial
flutter is the most commonly presenting arrhythmia in this patient
population, often combined with incisional AT associated with
postoperative scars due to atriotomy and/or
cannulation.1,2 The STS approach provides excellent
exposure for mitral valve reconstruction. However, this method may be
proarrhythmic compared with the other left atrial approach because the
it involves an extensive series of incisions.3 The
incision line acts as the central obstacle during incisional AT, and a
postoperative myocardial conduction delay between the incision line and
other structures (tricuspid valve and/or IVC) is believed to facilitate
the formation of the reentrant circuit after this
approach.4 Therefore, typical atrial flutter is the
most frequent circuit of postoperative AT in this patient population.
Incisional AT, which develops around the right atrial part of the
incision by the STS approach, is likely to occur subsequently. In the
present case, four resumption points across the surgical incision were
observed; however, two penetrations were involved in the tachycardia
circuit. The other two areas between these points are likely to present
functional conduction block during tachycardia (Figure 3 ).
Although the precise mechanism of electrical propagation across a
theoretically inexcitable surgical suture line is unknown, three
possible mechanisms (mechanical coupling, electronic influence, and
direct electrical conduction) are proposed.5 It is
certain that conduction across the contralateral side of the incision
line can occur, as shown by studies regarding AT between the donor and
recipient hearts after heart transplantation.6-8 It is
reasonable to consider that the same phenomenon can occur in an
autologous heart. In a case series of 16 patients by Lukac et
al.,4 the activation wavefront circulating around the
entire right atrial part of the incision was confirmed in all but one
patient with incisional AT. In this paper, incisional AT that revolved
around the incision line with one penetration point was shown. However,
incisional AT with multiple penetrating points on one surgical incision
has not been reported so far.
The recurrence rate after AT ablation following open heart surgery is
relatively high (20%-25%).9,10 Kanagasundram et al.
reported the importance of complete block from the lateral incision to
IVC of the right atrium to prevent recurrence after ablation of
incisional AT following the STS approach.11 It is also
important to assess the presence or absence of reconduction along the
incision line, and if present, additional radiofrequency application may
help prevent future AT recurrences.