Slew Rate As a Predictor for Optimal Lead Fixation

During the implantation of transvenous pacemakers and implantable cardiac defibrillators, the placement of active fixation leads requires the measurement of standard electrical parameters (sensing, impedance, and capture threshold) to identify the optimal pacing site before helix deployment into the cardiac muscle. Selecting the optimal site at the time of implantation is crucial to ensure long-term lead performance and to prevente potential device malfunctions secondary to threshold elevation or sensing reduction.

Two additional electrical parameters-slew rate and the current of injury-may aid in selecting the optimal pacing site. However, these parameters have been poorly studied in the literature and exhibit significant differences. While the slew rate is easily measurable, as it is automatically determined by the pacing system analyzer (PSA), the current of injury requires non-standardized, complex, operator-dependent, and time-consuming manual measurements. Additionally, the slew rate can be assessed before helix deployment, whereas the current of injury can only be measured after helix fixation. While the current of injury generally indicates adequate helix fixation, at least in the acute setting, the significance of slew rate in predicting long-term lead stability remains uncertain.

The study hypothesis is that the slew rate significantly correlates with sensed electrical activity at 12 months post-implantation and may therefore serve as a predictor of optimal long-term lead fixation and performance.

This is a prospective, observational, single-arm, investigator-initiated, multicenter, non-profit cohort study. Four Italian centers are participating: Ospedale di Fidenza, Arcispedale Santa Maria Nuova di Reggio Emilia, Ospedale Civile di Piacenza, and Azienda Ospedaliero-Universitaria di Ferrara.

Patients undergoing pacemaker or ICD implantation with active-fixation atrial or ventricular leads, either for pacing or defibrillation, will be enrolled. The lead fixation site (right ventricular apex or septum) and pacing modality (traditional right ventricular pacing or conduction system pacing) will be determined at the physician's discretion.

Electrical parameters at implantation-including slew rate, current of injury, sensing, impedance, and capture threshold-will be measured in all participating centers using the same pacing system analyzer (PSA) model (Medtronic, Model 2290). Slew rate, sensing, impedance, and capture threshold will be assessed before and after helix deployment, as well as after lead fixation.

The current of injury is defined as an increase in ST-segment elevation of at least 5 mV for ventricular leads and 1 mV for atrial leads compared to baseline in the intracardiac electrogram (EGM).

All characteristics of the current of injury-including total intracardiac EGM duration, maximum ST elevation, and maximum ST elevation 80 msec after the first EGM deflection-will be assessed immediately after helix deployment, as the current of injury is a dynamic and time-dependent electrical phenomenon.

Following implantation-after device connection and prior to discharge-and throughout the follow-up period, electrical parameters (sensing, impedance, and capture threshold) will be assessed using the device programmer provided by the manufacturer of the implanted device.

Follow-up visits are scheduled at 1 and 12 months post-implantation and may be conducted either as in-person ambulatory visits or via remote monitoring, according to the standard clinical practice of each center. During these visits, lead dislodgement and any significant variations in electrical parameters will also be assessed. The total follow-up duration is 12 months from implantation.

• Current of injury of active fixation leads (pacing or defibrillator leads) measured at the time of implantation [Time frame: After the enrollment, at the time of implantation, immediately following helix deployment for active lead fixation]
• Sensing of active fixation leads (pacing or defibrillator leads) [Time frame: From enrollment at the time of implantation to the end of follow-up at 12 months]
• Capture threshold of active fixation leads (pacing or defibrillator leads) [Time frame: From enrollment at the time of implantation to the end of follow-up at 12 months]
• Impedance of active fixation leads (pacing or defibrillator leads) [Time frame: From enrollment at the time of implantation to the end of follow-up at 12 months]