br Conflict of interest br Acknowledgments br Introduction C

Conflict of interest
Acknowledgments
Introduction Compared to the traditional right atrial appendage (RAA) pacing, inferior interatrial septum (IAS) pacing around the coronary sinus ostium significantly reduces paroxysmal atrial fibrillation (AF) burden and recurrence and slows the progression to chronic AF [1–5]. Previous studies reported that inferior IAS pacing produces synchronous bi-atrial excitation resulting in shorter P-wave durations and reduces unnecessary right ventricular (RV) pacing by shortening the atrioventricular conduction time during atrial pacing [6–9]. Both the outcomes have a positive impact with regard to AF prevention. Moreover, IAS pacing has a potential benefit in patients who have undergone cardiac resynchronization therapy (CRT) by resynchronizing both atria and maintaining an appropriate balance of atrioventricular and left ventricular (LV) synchrony [10,11]. However, in certain cases, the insertion of an active fixation lead in the inferior IAS is difficult and time-consuming. Although a few useful devices and techniques have been introduced [12–14], positioning of the atrial lead around the inferior IAS can be challenging.
Case report A 68-year-old man presented to our hospital with sustained ventricular tachycardia (VT) that was complicated with congestive HG-9-91-01 failure (CHF). He had experienced a broad anteroseptal myocardial infarction at the age of 56 years; at that time, five bare metal stents were implanted in his left coronary artery. Subsequently, he experienced symptoms of CHF (New York Heart Association [NYHA] functional classification class III) despite undergoing optimal medical therapy, including 5mg of carvedilol and 5mg of enalapril. Immediately after admission, the sustained VT spontaneously terminated. The patient was orally administered 200mg of amiodarone, which effectively suppressed the recurrence of sustained VT. Echocardiographic examination indicated the presence of LV dilatation with generalized severe hypokinesia. The LV end-diastolic dimension and LV ejection fraction were 68mm and 27%, respectively. No significant valvular deficiency was observed. An electrocardiogram showed a regular sinus rhythm with a complete right bundle-branch block with right axis deviation. QRS and PQ widths were prolonged to 200ms and 260ms, respectively. For the purpose of secondary prevention, we recommended the implantation of an implantable cardiac defibrillator. However, since a high percentage of RV pacing is believed to be unavoidable due to the first-degree atrioventricular block, we eventually decided to implant a CRT device with defibrillator (CRT-D) after informed consent was obtained from the patient. The patient\'s height was 155.0cm and weight was 57.5kg. A 5-cm-wide skin incision was made, along the Langer\'s cleavage line of the cutis at the left subclavian space, 3cm caudal to the left clavicle and 1.5cm medial to the left pectodeltoid sulcus. Three 9.0 Fr ×15cm sheaths (Medikit Co., Tokyo, Japan) were smoothly introduced from the left subclavian vein after extrathoracic punctures were made. An 8.6 Fr ×65cm shock lead (Sprint Quattro™; Medtronic Inc., MN, USA) was inserted in the RV apex using the standard method. We used a 6.0 Fr ×60cm bipolar atrial fixation straight lead (Siello S™ 60; BIOTRONIK SE & Co., Berlin, Germany) for inferior IAS pacing. After several unsuccessful attempts to insert the lead in the inferior IAS by the standard method involving manually bent stylets, as described by Acosta et al. [14], we used a 9.0 Fr (7.2 Fr inner) ×45cm GC (Attain Command™ 6250-MPR; Medtronic), because its shape appeared to be suitable for manipulation around the inferior IAS (Fig. 1). After a 0.035-in. ×220-cm hydrophilic J-wire (DRAGON™; Goodman Co., Nagoya, Japan) was inserted in the RV apex, the GC was delivered into the right atrium (RA). After pulling back the J-wire, the GC tip was directed toward the IAS with gentle counter-clockwise torque, and it was easily placed at the inferior IAS, in an upper and dorsal location to the coronary sinus ostium. The placement was confirmed by both the right and left anterior oblique views (Fig. 2). An active fixation RA lead with an inner straight stylet was then inserted into the GC without any torque manipulation. It proceeded into the GC without any resistance (Fig. 3a) and attached to the inferior IAS at the tip of the GC (Fig. 3b). A screw-in maneuver was easily performed using the right index finger. We did not need to provide any counter-clockwise torque to the lead and stylet during the fixation maneuver (Fig. 4). The protrusion of the screw from the tip of the GC was smooth and was clearly visible (Fig. 3c). The firm fixation of the lead was confirmed by proximally pulling back the GC (Fig. 3d). Subsequently, the GC was peeled away. A 6.2 Fr ×88cm over-the-wire LV epicardial lead (Attain OTW™ 4194; Medtronic) was delivered into the lateral branch of the posterolateral coronary vein using the standard method involving a 9.0 Fr ×50cm (7.2 Fr inner) GC (Attain Command™ 6250-EH; Medtronic). A CRT-D (Protecta XT™ CRT-D; Medtronic) was then implanted. Far-field R-wave sensing was not observed. The P-wave duration in the lead II was shortened from 118 to 84ms. The total operation time was 98min. The patient\'s post-operative course was uneventful. One week after the procedure, the patient underwent trans-thoracic echocardiography-based optimization. Ten days after the procedure, he was discharged and his symptoms had improved (NYHA class II).