Magnetic resonance imaging in patients with a subcutaneous implantable cardioverter-defibrillator.

AIMS: Our aim was to evaluate the potential for safely imaging patients with a new type of implantable cardioverter-defibrillator called the subcutaneous implantable cardioverter-defibrillator (S-ICD) in a 1.5 T magnetic resonance imaging (MRI) scanner. With the increasing number of patients with cardiac implantable devices who are indicated for MRI, there is a growing need for establishing MRI compatibility of cardiac implantable devices. METHODS AND RESULTS: Patients with implanted S-ICD systems underwent one or more types of anatomical MRI scans. The S-ICD was programmed off and patients were monitored throughout the imaging procedure. Device function was evaluated pre- and post-scan. Patients were asked to report immediately any pain, torqueing movement, or heating sensation in the area of the pocket or electrode. Fifteen patients underwent a total of 22 examinations at 1.5 T. Scans included brain, spine, knee, and heart. Two patients were re-scanned due to complaints of heating over the can during lumbar scans, which was caused by a thermistor probe placed on the skin to measure skin temperature. All the remaining scans occurred without incident. No evidence of device malfunction was observed. CONCLUSION: This study is the first to domonstrate the feasibility of exposing S-ICD patients to MRI using the scanning and monitoring protocol described. More data are required to support S-ICD as a MRI conditional device.

Left ventricular mechanical activity detected by impedance recording.

AIMS: Recording and analysing impedance fluctuation along the cardiac cycle in the right (RV) and left ventricles (LV). METHODS AND RESULTS: During a biventricular (BiV) implantation procedure, impedance was sequentially derived between the atrial ring electrode and either electrode (tip or ring) of the RV lead [transvalvular impedance (TVI)], and between the atrial ring and either the tip or ring electrode of a coronary sinus lead, positioned in a cardiac vein [left ventricle impedance (LVI)]. The LVI signal was also recorded by the implanted pacemaker at the 1 day and 3 months follow-ups. With intrinsic conduction, TVI showed an average increase of 53 +/- 29 ohm during ventricular systole, whereas at the same time, LVI decreased by 45 +/- 21 ohm (25 and 23 patients, respectively, out of 28 tested cases). Transvalvular impedance and LVI displayed a similar time course, which appeared to be related to the systolic timing in the RV and LV. Both LVI amplitude and duration decreased as a function of the cardiac rate. The LVI deflection started immediately after LV stimulation, and often anticipated the R-wave sensing after contralateral pacing. At the 3-month follow-up, LVI amplitude was decreased in 70% of cases and increased in the remainder, with a non-significant average change of -5 +/- 85% with respect to the acute recordings. CONCLUSION: Transvalvular impedance properties are consistent with the assumption of an inverse relationship with RV volume. Though LVI requires a different physical interpretation, the waveform duration might reflect the timing of LV myocardial contraction. In this hypothesis, the relationship between TVI and LVI could provide insight into the effects of BiV pacing on mechanical synchronization.

Pacemaker and ICD lead extraction with electrosurgical dissection sheaths and standard transvenous extraction systems: results of a randomized trial.

AIMS: The purpose of this prospective randomized study was to evaluate the safety and efficacy of transvenous pacemaker and implantable cardioverter-defibrillator (ICD) lead extraction with an electrosurgical dissection sheath (EDS) system in a single-centre experience. Methods Over 10 years, 462 patients have undergone transvenous lead extraction in our institution. From these, 120 consecutive patients (with 161 leads) were randomized to either radiofrequency (RF) current supported extraction or standard countertraction lead removal (60 patients in each arm, 96 men and 24 women). The mean age of randomized patients was 62.7 +/- 9.6 years. In 16 patients, we explanted 17 ICD leads. The average time from the date of implantation to the extraction procedure was 73.4 +/- 15.7 months. The most common reason for lead extraction was infection (95.6%). Results The complete extraction of 78 leads (93%) was achieved in the RF group and 56 leads (73%) with the standard transvenous lead extraction system by counter-traction (P < 0.01). Among these leads, we successfully removed nine of 10 ICD leads (90%) in the RF group and only four of seven ICD leads (57%) in the standard group. We also observed a significant reduction in the time taken for the successful removal of pacemaker and ICD leads using the RF system (9.6 +/- 6.2 min versus 21 +/- 9 min, P < 0.01). Partial success was achieved in six patients with the RF system and in 11 with standard sheaths. In those cases where we failed to remove the lead from the body we sent all but one patient to cardiac surgery. Serious complications were associated with the standard system in two patients, both of whom developed septic pulmonary embolization. Serious bleeding occurred in three patients, one with standard and two with the EDS lead extraction system. CONCLUSION: The EDS extraction system is significantly more effective and quicker. However, the standard counter-traction method is still an effective alternative when used in a highly experienced centre.