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Objective The persistence of a left superior vena cava(LSVC) has been observed in 0.3% of the general population asestablished by autopsy. In the adult population, it is an importantanatomic finding if a left superior approach to the heart isconsidered. The aim of the study was to evaluate the prevalence of aLSVC in patients undergoing pacemaker (PM) andcardioverter-defibrillator (CD) implantation. Design We observed the prevalence of LSVC during a 10-year period; eachpatient undergoing PM or transvenous CD implantation received a leftcephalic/left subclavian venous approach to the heart. With thistechnique, LSVC persistence is easily diagnosed during leadplacement. Results A total of 1,139 patientsconsecutively underwent PM implantation during 10 years: 4 patients hadpersistent LSCV (0.34%). Among 115 patients undergoing CDimplantation, 2 patients with LSVC (1.7%) were observed. Overall LSVCpersistence was found in 6 of 1,254 patients (0.47%). Two patients, one of whom had no right superior vena cava (RSVC), received aleft-sided PM, whereas two other patients received right-sided devices. Both CD patients received a left-sided active-can device: the firstpatient with a right-sided lead tunneled to the left pectoral pocket, as a result of poor catheter handling through the LSVC and coronarysinus, and the second patient with a screw-in lead from LSVC. Long-termfollow-up of these patients (average ± SD, 41 ± 26 months)revealed absence of lead dislodgment and appropriate device functionregardless of lead implantation site. Conclusions Persistence of LSVC in adults undergoing PM/CD implantation is similarto that of the general population (0.47% in our study). The left-sidedimplant can be achieved by stylet shaping and by use of active fixationleads in most patients, with a reliable outcome at short term inaddition to appropriate device performance at follow-up. Assessment ofthe RSVC is advisable when planning a right-sided implantation, since aminority of patients lacks this vessel.

Introduction Electrical shocks delivered for atrial cardioversion (CV) may cause myocardial damage. The aim of this study was to assess the extent of myocardial injury caused by repeated intracardiac shocks delivered for low-energy internal atrial CV. Methods and results Thirty-five patients with chronic persistent atrial fibrillation (AF) of different etiologies underwent CV with delivery of synchronized biphasic shocks (3.0/3.0 ms) between two catheters positioned in the right atrium and the coronary sinus. Shocks were delivered according to a step-up protocol (50 V, 180 V, then steps of 40 to 56 V up to 500 V, if necessary). In 23 patients, AF was reinduced after baseline CV, and CV was repeated. Myocardial injury was monitored by measuring cardiac troponin I (cTnI) serum concentrations in blood samples taken at baseline and at 2, 4, 8, 12, and 24 h after the procedure, by means of an immunoenzymologic assay (normal values, ≤ 0.6 ng/mL). A mean (± SD) of 6.9 ± 3.4 shocks per patient were delivered (range, 2 to 17). Shocks delivered in each patient had a maximal energy of 7.3 ± 4.0 J (range, 1.7 to 15.7). In 20 patients (57%), no evidence of myocardial injury (cTnI level, ≤ 0.6 ng/mL) was found. In 13 patients (37%), mildly elevated cTnI levels (range, 0.7 to 1.4 ng/mL) in samples taken 4 to 12 h after CV suggested minor myocardial injury. In two patients (6%), higher cTnI levels were found in samples taken 4 to 8 h after CV (peak, 1.7 and 2.4 ng/mL), indicating a necrotic damage. Patients with no cTnI elevation, with mild cTnI elevation, or with cTnI levels≥ 1.5 ng/mL did not differ significantly with respect to the total number of shocks delivered, the mean amount of energy delivered, and the cumulative amount of energy delivered. No clinical complications were observed. Conclusions Following internal CV with the delivery of repeated shocks, minor elevations of cTnI serum levels could be detected in a significant proportion of patients, and this suggests subtle asymptomatic minor myocardial injury. The elevations of cTnI levels do not appear to be related to the number of shocks or to the amount of energy delivered.