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In this report we present a case of subcutaneous cardioverter defibrillator (S–ICD) implantation complicated by pneumothorax (PNX), in the absence of alteration of electrical parameters nor lung parenchyma involvement. After implantation in secondary prevention (1995) of an abdominal transvenous defibrillator (TV–ICD) via the left subclavian vein, a replacement (2009) with a new contralateral TV–ICD system, and the withdrawal of the proximal edge of the right ventricular (RV) lead in the abdominal region, a 78–years–old man presented in our center for pocket erosion. The trans–esophageal echocardiography was suspect for vegetations, while PET/CT and blood cultures were negative. Transvenous extraction of the right–sided ICD system was performed (the original RV lead was left in place due to his complex course), then the patient underwent implantation of a S–ICD with the intermuscular 2–incision technique. In the end of this well tolerated procedure the electrical parameters were optimal, the defibrillation test was effective and the position of the S–ICD was judged correct on the chest X–ray. Few hours later, the patient complained for local pain and progressive respiratory failure. A chest CT showed a PNX at the lateral insertion of the lead, which reached the pleural space, along the left scissure (Fig.1). During lead repositioning, programmed with stand–by thoracic surgery, the lead was easily disconnected from the generator through the lateral incision, pulled–back through the subxiphoid one and tunneled in the correct plane without complications (Fig.2). Serial chest CT confirmed PNX resolution. The patient was discharged in 8 days. At the 1–month follow–up visit electrical parameters were stable, in absence of infective complications. In literature there are few cases of PNX, so that it’s challenging to define their risk factors. We assume that, despite a correct implantation technique, a barrel chest configuration and the aging of the fascia favored the wrong tunnelling. In conclusion, PNX is a rare and unexpected complication of S–ICD implantation and can go unnoticed when of limited dimensions, in the absence of clinical and radiological signs nor alteration of electrical parameters. Fluoroscopic and CT imaging is recommended for diagnosis. Thoracic surgery is useful during repositioning of the lead, which can also be performed by simple traction. CT imaging is of utmost importance for planning such a procedure and predicting its complexity.

Background The biatrial trans-septal approach (BTSa) ameliorates mitral valve (MV) exposure in difficult cases when routine left atriotomy doesnt"t allow it. Main steps are an oblique incision on the right atrium (RA), reaching medially the right pulmonary veins (PV), a septal incision from the fossa ovalis, extended up to reach the first incision, then on the left atrium (LA). Purpose We aim to study the arrhythmic burden in this post-surgical context, focusing on atrial tachycardia (AT), to investigate the complexity of several possible circuits. Methods All patients (>18yo) with previous MV surgery via BTSa for MV repair or replacement, who underwent ablation of AT from January 2017 to September 2019, were enrolled. Patients ablated for persistent or paroxysmal AF, or with AF during the index procedure were excluded. Patients with associated surgery on other valves or congenital defects, coronary, surgical or percutaneous rhythm interventions weren’t excluded. Electroanatomical mapping was created using 2 different high-density mapping system. Substrate and activation map and radio-frequency (RF) ablation (25-50W, Ablation Index target 400) were realized. Cartographies were analysed to evaluate AT re-entry circuit, critical isthmus (CI) location and characterization, atrial vulnerability. Procedural outcomes (AT termination, sinus rhythm (SR) restoration, anti-arrhythmic drugs (AAD) withdrawal), and peri-procedural complications were also evaluated. Results We enrolled 49 patients (median age 57 ± 15), finding a maximum of 5 AT per procedure (2 ± 1). A total of 112 AT were mapped: the majority (72%) were persistent AT, 8,2% common atrial flutter. Cycle length was 314 ± 74 msec, with proximal-distal activation of coronary sinus (78%). A multiple re-entry circuit was observed in 70% of index AT. We identified 152 critical isthmus (maximum 5 per procedure). Only 27,9% of our patients had a single CI; CTI was the most frequent one (n = 37), envolved in 33% of all AT, while BTS scars altogether were envolved in 65% AT. A complete AT circuit was mapped in the RA, the LA and both atria in respectively 49%, 11,5% and 39%AT. The distribution of CIs is shown in figure 1. Biatrial and left AT leads to superior procedure, RF and fluoroscopy duration (p Conclusions AT occurring after a BTSa have a high prevalence of multiple re-entry circuits with multiple critical isthmus. Ablation in this context is feasible and safe but often requires a left atrial access. Mapping of both atria should be considered to identify critical isthmus and tailored ablation strategy. Abstract Figure 1. Critical Isthmus Distribution