Cardiac Pacing in Cardioinhibitory Reflex Syncope: Clinical Use of Closed-loop Stimulation

Cardiac pacing has been studied extensively in patients with reflex syncope over the past two decades. The heterogeneity of the forms and clinical manifestations of reflex syncope explain the controversial results of older randomised clinical trials. New evidence from recent trials has changed medical practice, now leading to clear indications for pacing in patients with asystolic syncope documented during carotid sinus massage, implantable cardiac monitoring or tilt testing. Given that recent trials in reflex syncope have been performed using the closed-loop stimulation algorithm, the authors will briefly discuss this pacing mode, review hypotheses about the mechanisms underlying its activation during syncope and provide practical instructions for programming and troubleshooting.

714 Effects of direct irradiation on cardiac implantable electronic devices

Aims Cardiac implantable electronic devices (CIEDs) may sustain damages during a course of radiation therapy, especially when the beam is directed onto the pulse generator, with device electrical reset and/or sudden battery drain. 2010 HRS/ASA expert consensus, and all CIEDs manufacturers, recommend to avoid devices direct irradiation with an accumulated dose that exceed five grays (Gy). In our prospective study, we tested the effects of direct irradiation on CIEDs with different radiation doses, also higher than 5 Gy. Methods and results Thirty-seven CIEDs of Medtronic, Abbott, Biotronik, and Boston Scientific were collected during system upgrading or lead extraction procedures. All devices were considered if they had at least 80% of residual battery capacity. All CIEDs were programmed with same default electrical parameters. Depending by CIED type, pacing mode was configured in VVI, VVIR, VDDR, or DDDR, and biventricular stimulation was activated, if present. ICDs electrical therapies were set-up with a pre-determined configuration. All devices were singularly placed in a 30 cm × 30 cm plastic bowl containing 2 l of deionized water that was placed over 5 cm Rockwool to simulate the backscatter and irradiated by a linear accelerator (Elekta Synergy®). CIEDs were divided into two groups depending on irradiation dose delivered: 5 Gy and 10 Gy. No significant differences in battery drainage were observed after irradiation respect to baseline in 5 Gy as well 10 Gy group [7.9 ± 3.1 vs. 7.5 ± 2.1 (years) battery longevity, P = 0.693; 7.7 ± 3.1 vs. 7.4 ± 2.1 (years) battery longevity, P = 0.677, respectively) (Figure). Moreover, all CIEDS saved the baseline program setting, without device reset events (Table). Conclusions Our data confirm that CIEDs direct irradiation of 5 Gy is safe, of note, direct irradiation up to 10 Gy seems to be similarly safe concerning the risk of CIEDs electrical reset and/or unexpected battery drain.

Cardiac implantable electronic devices in Bulgaria: results from the electronic registry BG-Pace for the period 2019-2021

The current study analyses the activity in cardiac pacing in Bulgaria in 2019, 2020 and 2021 based on data derived from a national registry of patients with cardiac electronic implantable devices (CIEDs). Materials and methods. Data from the national registry BG-Pace in the period 08.2019-06.2021 was retrospectively studied. Demographic data, procedure and device type, pacing mode, etiology, symptoms, preimplantation ECG, number of implantations and centre and operator volumes were analysed. Results. Six thousand nine hundred forty-nine devices were implanted by 47 operators in 28 centres for the study period. Median age was 75 (IQR 68-81, 21-103) years in males and 77 (IQR 71-82, 17-98) years in females, P< 0.05. The largest number of devices were implanted in the age group 70-79 years. The most commonly implanted CIEDs were antibradycardia devices with a total of 486.7/million implantations for the period 08.2019-08.2020 and 353.9/million for the period 08.2020-06.2021. Implanted cardioverter-defibrillators demonstrated a growth from 14.1/million to 20.1/million in the period 08.2020 – 06.2021. The number of all implantations dropped signifi cantly during the two epidemic waves of COVID-19. The mean number of implantations per centre and per operator for the whole period was 232.3±204 (2-705) and 148±139.1 (2-660), respectively. Dual chamber device implantations were more prevalent, representing 65.8% of implantations in AV block I and II degree, 63.5% in complete AV block, 59.8% in intraventricular conduction disturbances and 60.9% in sick sinus syndrome. Pacing modes with atrial sensing represented more than 55% of the implantations for all indications. Increasing age was associated with signifi cantly more common use of VVI pacing mode (P < 0.001). Conclusion. The national registry BG-Pace includes systematic clinical, demographical and procedural data for CIED implantations in Bulgaria. Results demonstrate lower number of implantations compared to the average European volume. There was a signifi cant drop in the implantation rate during the two waves of COVID-19.

Electrical characteristics of pacing different portions of the His bundle in bradycardia patients

Aims His-bundle pacing (HBP) can be achieved in either atrial-side HBP (aHBP) or ventricular-side HBP (vHBP). The study compared the pacing parameters and electrophysiological characteristics between aHBP and vHBP in bradycardia patients. Methods and results Fifty patients undergoing HBP implantation assisted by visualization of the tricuspid valvular annulus (TVA) were enrolled. The HBP lead position was identified by TVA angiography. Twenty-five patients were assigned to undergo aHBP and compared with 25 patients who underwent vHBP primarily in a prospective and randomized fashion. Pacing parameters and echocardiography were routinely assessed at implant and 3-month follow-up. His-bundle pacing was successfully performed in 45 patients (90% success rate with 44.4% aHBP and 55.6% vHBP). The capture threshold was lower in vHBP than aHBP at implant (vHBP: 1.1 ± 0.5 vs. aHBP: 1.4 ± 0.4 V/1.0 ms, P = 0.014) and 3-month follow-up (vHBP: 0.8 ± 0.4 vs. aHBP: 1.7 ± 0.8 V/0.4 ms, P &lt; 0.001). The R-wave amplitude was higher in vHBP than in aHBP at implant (vHBP: 4.5 ± 1.4 vs. aHBP: 2.0 ± 0.8 mV, P &lt; 0.001) and at 3-month follow-up (vHBP: 4.4 ± 1.5 vs. aHBP: 1.8 ± 0.7 mV, P &lt; 0.001). No procedure-related complications and aggravation of tricuspid valve regurgitation were observed in most patients and echocardiographic assessment of cardiac function remained in the normal range in all patients during the follow-up. Conclusion This study demonstrates that vHBP features a low and stable pacing capture threshold and high R-wave amplitude, suggesting better pacing mode management and battery longevity can be achieved by HBP in the ventricular side.