Cardiac implantable electronic devices (CIEDs), including permanent pacemakers (PMs), implantable cardioverter defibrillators (ICDs), and cardiac resynchronization therapy devices with or without defibrillators (CRT-Ds or CRT-Ps), are standard therapy for bradyarrhythmia, tachyarrhythmia, and systolic heart failure [1,2]. Their use has increased over the last decade [3,4]. However, CIED implantation comes with a considerable burden of complications, leading to elevated patient morbidity, health care costs, and mortality [5-8]. The most recent consensus on device implantation and replacement by the European Heart Rhythm Association [9] has been significantly influenced by the invaluable contributions of various international registries. One of the most prominent among them is the “Replace” registry [10], which has played a pivotal role in advancing our understanding of this crucial aspect of cardiac care.

A comprehensive understanding of post-CIED implantation complications and their predictive factors is essential for patient management when considering CIED implantation. Therefore, a survey of patients undergoing CIED implantation in Tunisia is crucial to identify specific CIED complications due to the demographic and epidemiological specificities of the patients, as well as the conditions of the local health care system.

This study aims to assess the incidence, characteristics, and predictors of complications arising in the initial 12 months following the implantation of CIEDs, describe the demographic and epidemiological profiles of a national cohort of consecutive patients with CIED, and provide insights into the level of compliance exhibited by Tunisian electrophysiologists with international guidelines pertaining to cardiac pacing and the prevention of sudden cardiac death.

NATURE-CIED (National Study of Cardiac Implantable Electronic Devices) is a nationwide, multicenter, prospective observational study with a 1-year follow-up period. The study’s steering committee extended invitations to all electrophysiologists, interventional cardiologists, and cardiovascular surgeons with experience in CIED implantation, regardless of whether they are practicing in the Tunisian public or private sectors, to participate in the study.

Patients’ enrollment occurred between January 18, 2021, and February 18, 2022, at all Tunisian public and private CIED implantation centers that agreed to participate in the study. Eligibility screening was conducted during hospitalization.

The study population consisted of consecutive patients undergoing primary CIED (conventional PMs, ICDs, and cardiac resynchronization: CRT-P–CRT-D) implantation, generator replacement, and upgrade procedure. To be enrolled, eligible patients have to provide written informed consent. All enrolled patients entered a 1-year follow-up period with 4 consecutive visits at 1, 3, 6, and 12 months after the CIED implantation. Exclusion criteria are nonconsenting patients and those operated exclusively for lead dysfunction.

A steering board with 2 main investigators pre-established a specific case report form (CRF) for each type of CIED. Baseline data included patient demographics, ethnic specificity, medical history, cardiovascular history, cardiovascular risk factors, the CIED implantation indication, vital signs, laboratory measurements, electrocardiographic and echocardiographic findings, details of medical management, and results of eventual invasive and noninvasive investigations prior to CIED implantation (echocardiography, Holter monitoring, treadmill exercise stress test, and electrophysiological study).

The form also includes data regarding the technical aspects of the CIED implantation procedure and the occurrence of any periprocedural complications. Finally, the form specifies data on the clinical follow-up and device electrical testing parameters, as well as the eventual major incident events and CIED complications during the follow-up period. Investigators (electrophysiologists and interventional cardiologists) who agreed to participate in the study were asked to complete the pre-established form (CRF) for each type of implanted device at the enrollment visit and each scheduled visit.

Collected data were electronically recorded on a clinical suite platform (DACIMA software), which complies with international standards including US FDA 21 CRF part 11 (Food and Drug Administration 21 Code of Federal Regulations Part 11), US HIPAA (Health Insurance Portability and Accountability Act) and ICH (International Conference on Harmonisation), and Medical Dictionary for Regulatory Activities. The main investigators and the DACIMA consulting team periodically validated recorded data. The clinical suite platform generates alerts and requests in case of inconsistencies and missing data. Throughout the planned duration of the study, the steering board supervises the inclusion of patients, checks the data sources, and prepares the study’s statistical analysis plan.

Patient enrollment and data collection began on January 18, 2021, and continued until February 18, 2022. Follow-up continued until all patients had 1-year data. The end of the study was therefore scheduled for February 18, 2023 (Figure 1).

If patients missed a scheduled follow-up visit, they or their relatives were contacted by phone to assess any adverse event and to reschedule a follow-up appointment.

The main objective of this observational study is to assess the incidence, characteristics, and predictors of major and minor complications arising in the initial 12 months following the implantation of CIEDs.

The complications were characterized as major when life-threatening or requiring surgical reintervention for correction, and minor when suitable for treatment on an outpatient basis, involving device reprogramming, or requiring exclusive clinical observation [11]. Major complications include implantation failure, lead-related reinterventions, tamponade or myocardial perforation, pneumothorax requiring drainage, hematoma requiring evacuation, wound or pocket infection, systemic infections or endocarditis, Twiddler syndrome, and procedure-related deaths. Minor complications include pacing threshold increase, phrenic nerve stimulation, heart failure or left ventricular ejection fraction decrease, pericardial effusion, and conservatively treated hematoma and pneumothorax.

The study was performed according to the ethical principles for medical research involving human subjects specified in the Declaration of Helsinki and the ICH Good Clinical Practices. Ethics approval was obtained from the human research ethics committees at Abderrahmen Mami Hospital in Tunis (04/2021). Written informed consent was obtained from all the patients who participated in the study. The protocol of NATURE-CIED was approved by the Tunisian Society of Cardiology and Cardiovascular Surgery. The NATURE-CIED study was submitted to ClinicalTrials.gov (NCT05361759).

The DACIMA Clinical Suite platform enables the collection of web-based data and their extraction in SAS (SAS Institute) or SPSS (IBM Corp) format. The statistical analysis is exploratory, involving the calculation of 95% CI. The data will be described for the whole analyzed population. Continuous variables will be described by mean and SD or median and IQR. Categorical variables will be described by the size and frequency of every modality. Mean comparison will be performed by analysis of variance or by nonparametric tests if the hypothesis of normality is rejected.

The normality of continuous variables will be verified with the Shapiro-Wilk test. The statistical tests are bilateral with a 95% CI. A chi-square test will be performed for categorical variables. Yates correction or the Fisher exact test will be used if the conditions of validity for the chi-square test are not met.

A multivariate analysis will be performed with each complication as a dependent factor. The independent variables will be age, gender, ethnic specificity, BMI, CIED type, procedure type, procedure priority, implantation center (private and public), and CIED implanting operator whether he is an electrophysiologist or not (interventional cardiologist or cardiac surgeon).

Univariate logistic regression will be carried out with a 10% output threshold. The final model will be performed with the parameters selected by the backward stepwise method of Wald. The selected variables in the final model will be tested at the 5% threshold. The interaction between selected parameters is tested at the 10% threshold. The intermediate analyses will be carried out after formulating the statistical analysis plan.

NATURE-CIED is the first national and North African study that will (1) provide validated data on short- and medium-term complications and their predictors, which will allow us to individualize high-risk patients for optimal care, (2) identify the epidemiologic and demographic characteristics of Tunisian patients undergoing CIED implantation, and (3) clarify the contemporary CIED indications in Tunisia and their compliance with international guidelines.

To the best of our knowledge, NATURE-CIED is the first National study of CIEDs in North Africa to provide the combination of large numbers of patients and devices and diverse implanting physicians. Twenty-seven cardiologists (electrophysiologists and interventional cardiologists) enrolled 1500 patients who underwent CIED implantation.

According to the second report from the Pan African Society of Cardiology working group on cardiac arrhythmias and pacing [12], Tunisia had the highest implant rates, with 164.3 PMs per million inhabitants and 2.16 PM implantation practitioners per million inhabitants in 2018, which makes it rank in the second position after Mauritius [12].

However, there is still a gap concerning patients’ demographics, CIED indications, and conformity to recent European Society of Cardiology guidelines [2] and CIED-related complications [12-14].

Both patient-related and procedure-related predictors of complications may identify patients with a particularly high risk of complications [15]. Previously reported incidences of complications after CIED implantation varied widely because of differences in the definitions of complications and length of follow-up [15-18]. Several previous studies in the 2000s reported that complication rates for PM were 4%-10% [13,17-19] and 3%-10% for ICDs and CTRDs [6,20]; however, an analysis of US Medicare states that data in 2014 showed much lower complication rates [21].

In 2010, the “Replace” registry, comprising data from a substantial cohort of 1744 patients who underwent device replacement procedures, yielded pivotal insights into predictive factors for complications [10]. This comprehensive analysis has, in turn, informed the development of practical and evidence-based procedural recommendations. By identifying the key determinants of complications, the registry has empowered health care professionals to more effectively anticipate and mitigate risks, ultimately leading to improved patient outcomes.

Therefore, the NATURE CIED study aims to offer detailed and comprehensive data on the predictors of CIED complications during the perioperative and 1-year follow-up period, which are derived from real-world data in Tunisia. The information generated by this study will prove valuable in the development of a national peri-implantation management protocol and the assessment of overall health care costs [11,12,14,22].

This study presents some limitations that must be considered in the interpretation of the results. This study is voluntary for both investigators and patients, and there is no routine audit to monitor the proportion of enrolled patients by participating electrophysiologists or cardiologists. This currently limits our ability to examine exact implant rates and to examine equity of access to PM therapy across the country. Some patients were lost to follow-up.

We identified all complications documented in patients during hospitalization and follow-up. We believe that this approach is the most accurate and comprehensive way to detect complications. In addition, this study was not designed to assess the effects of each investigator’s experience level and the volume of procedures performed individually. Therefore, the electrophysiologists’ or interventional cardiologists’ positions on their learning curve may influence the rate of complications mainly in teaching hospitals.

NATURE-CIED study will fill an important gap in the management of patients undergoing CIED implantation both perioperatively and during follow-up and will identify patients at particularly high risk of complications for optimal management.

In Tunisia, this study will yield the largest contemporary longitudinal cohort of patients undergoing CIED implantation and will provide real-world data regarding heart rhythm diseases’ epidemiology and management with insights into the degree of adherence to international guidelines.