Editorial: Developments in cardiac implantable electronic device therapy: how can we improve clinical implementation?

Since their first introduction cardiac pacemakers and later implantable cardioverterdefibrillators (ICDs) have advanced remarkably. By the early 2000s, one might have the feeling that significant changes in this field could no longer be expected. Although, the next revolution in the development of the cardiac implantable electronic device (CIED) therapy was just waiting in front of the door. It started with the introduction of extravascular and leadless devices and most recently conduction system pacing (CSP) is looking for its place and awaits for more experience, evidence and improved tools to further improve clinical implementation. The current research topic (RT) presents valuable papers to physicians with interest for novel clinical and scientific aspects of CIED therapy.The first section of this series is focused on risk stratification and reduction of complications in patients receiving a transvenous CIEDs. Both echocardiography and cardiac magnetic resonance imaging (MRI) may be used to assess left ventricular ejection fraction (LVEF) before implantation of a primary prophylactic ICD. Marcos-Garcés et al. explored the role of these two imaging modalities in 52 patients receiving an ICD following ST-elevation myocardial infarction at a single center in Spain. Their study suggests that compared with assessment by echocardiography, LVEF determined by cardiac MRI may be a better predictor for appropriate ICD therapy.Natriuretic peptides are powerful biomarkers in cardiovascular disease. Plasma levels of Nterminal pro-B-type natriuretic peptide (NT-proBNP) are essential for the diagnosis of heart failure and a strong predictor of mortality in this context [1,2]. Risk stratification of patients receiving an ICD may help identify optimal candidates. Deng et al. explored the association of NT-proBNP with all-cause mortality and time to first appropriate shock in a cohort of 500 patients undergoing de novo implantation of a transvenous single-or dual-chamber ICD at a single center in Beijing, China. In analyses adjusted for clinical covariates and potential confounders, higher levels of NT-proBNP were independently associated with mortality, but not with time to first appropriate shock.Accelerometer sensor of contemporary CIEDs may be used to derive surrogate data on physical activity. Using data from a prospective, multicenter registry in China, Sun et al. to quadripolar LV leads. In the cohort of 81 patients, no difference in implantation success or CRT-response was observed, but PNS was significantly lower in patients with bipolar active fixation leads (13% vs. 0%; p<0.05). Although single-center and retrospective, this is the first study suggesting that LV active fixation leads might not only be used in case of large target veins, but also in CRT candidates at high risk for PNS.As the Achilles' heel of modern CIED therapy seems to be the intracardiac and intravascular presence of leads, major improvements have been observed in the last decade to avoid mechanical lead fractures and to minimize CIED related infection risks. Although there are no randomized studies showing superiority of the new subcutaneous defibrillators (S-ICD) or leadless pacemakers (LMP) over conventional technologies, several studies prove the noninferiority of these.A real-life comparison of patients underwent S-ICD or conventional ICD implantations revealed no differences in a composite clinical endpoint including survival, freedom of hospitalization and device associated events. The decision to implant S-ICD showed a trend towards patients with more complex diseases, measured by the Charlson comorbidity Index (CCI). Compared with previous studies the observed mortality of patients with similar CCI was much lower in the study of Kattih et al., which raises the question to use the CCI to predict patient mortality in patients needing an ICD.where the decision to extract the ICD lead and implant a new conventional ICD system (62 patients) or abandon the lead and implant an S-ICD (43 patients) was left to the clinician. There was no difference observed in major or minor complications in the two patient groups, however in 4 patients the lead extraction has failed, and a crossover to S-ICD strategy was performed.Another Italian multicenter study investigated the use of single chamber LPM in 73 "non-AF" patients with sinus node disfunction or sinus rhythm and atrioventricular block. There were no major differences in the perioperative or late complications and in the combined clinical endpoint of syncope, pacemaker syndrome, cardiac hospitalization and all-cause death compared with permanent atrial fibrillation patients receiving LPM. Although the non-AF patients had a higher percentage of ventricular pacing (52±36 vs. 40±29%; p=0.002) there were no patients reported with pacemaker syndrome. This highlights the option to choose LMP instead of conventional dual chamber pacemaker in patients with sinus rhythm.All these results help clinicians to have more alternative options to treat patients with specific conditions. However, there is still lack of randomized trials on S-ICD or LPM which would confirm the superiority of these new technologies with defintely higher costs.One of the most relevant changes of the last years in device therapy is the break-in of CSP into the daily clinical practice. However, some concerns limiting its faster and wider spread should be acknowledged: technically challenging implantation, reduced success rate, elevated pacing thresholds, lack of data on long-term outcomes. The papers submitted to the RT nicely represent that the leading technique for CSP is no longer the His bundle, but the left bundle branch (area) pacing (LBB(A)P). Wang et al. found in their single center, observational comparative study of consecutive bradycardia patients that procedure and fluoroscopy time is higher when performing LBBAP compared to conventional right ventricular pacing (RVP). Although, they also found that these parameters could be significantly reduced by increasing procedure volume, reflecting for a learning curve effect of this finding. Nonetheless, their overall implantation success rate was high (92.6%) and comparable with that was reported by Li et al. from a multicentre collaboration (95.5%). This latter group could also demonstrate lower occurrences of HF hospitalization or upgrading to biventricular pacing in patients with LBBAP compared to patients with RVP. Notably, this benefit was predominantly observed in patients with ventricular pacing >40% or with baseline LVEF <60%. Slightly lower implantation success rate (90.9%) was reported in 22 patients undergoing LBBAP following prosthetic cardiac valves by Wei et al. Furter important lessons were learnt from this publication regarding the anatomic landmarks of optimal LBBAP.A systematic review summarizing the criteria for differentiating left bundle branch pacing and left ventricular septal pacing by Zhu at al. serves as a valuable practical guide to physicians who are learning this technique. We can see that there is unfortunately no one-fits-all concept, personalized criteria are needed in some cases. For note, further novel criteria are also published since this review (for example the V6-V1 interpeak interval)(4), which may further help the reliable identification of left bundle branch capture. Shen and colleagues join with their case report to the experts who recommends a continuous pacing and screwing during LBBAP instead of the interrupted method. Beyond the advantage of the continuous monitoring of the current of injury, further concepts also support this method (i.e. detection of screw-in-beats, better mechanical penetration of the lead body, etc.) (5). To use this method also with lumenless leads, a dedicated tool connecting the lead to the analyzer/EP-system during screwing is still awaited from the industry. In a research article Shen et al. drew the attention to the optimal setting of the high-pass filter to identify the morphology of the discrete local ventricular components in the intracardiac EGM as a marker of selective LBBP. The relevance of the detection of the discrete local ventricular EGM in LBBP needs further confirmation.Most recently LBBAP appeared also as an alternative of classical CRT. Hua et al. presents an interesting concept for choosing between these two modalities based on the electroanatomical mapping of the left ventricle. They describe this method feasible in 71 CRT recipients to differentiate between true left bundle branch block (candidates for LBBP) and pseudo-left bundle branch block (candidates for conventional CRT). Whether this method will spread in clinical practice requires further research. Zheng et al. report also LBBAP as an alternative in a unique case of patient with a giant atrium with standstill and inability of atrial capture. This rare situation also highlights that CSP may be a good option in case of narrow QRS and bradypacing indication.Remote monitoring of CIED patients has not only evolved as a technology to unburden daily clinical routine from growing patient contacts but also shown to lower HF worsening rates during the COVID-19 pandemic [6]. Xiong et al. expand the idea of remote monitoring to remotely control and reprogram a device in real-time using a 5G-cloud technology system. In their case series, they present three everyday emergency settings that require immediate CIED interrogation and potential reprogramming. Long et al. describe their experience with the 5G-cloud technology during two dual-chamber pacemaker and one CRT-P implantation which enabled to conduct remote parameter testing and programming by a device specialist without entering the cath lab. Although, remote device programming offers promising innovative approaches as demonstrated in these case reports, further prospective evaluationpredominantly due to safety issues -is warranted.The authors confirm being the only contributors of this work and approved it for publication.

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