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.