# Incidence of ventricular arrhythmias after implantable cardioverter-defibrillator implantation or replacement, and driving restriction consequences

Thomas Marc, Karim Benali, Pierre Groussin, Redwane Rakza, Joana Brito, Nathalie Behar, Philippe Mabo, Dominique Pavin, Christophe Leclercq, Vincent Galand, et al.

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## To cite this version:

Thomas Marc, Karim Benali, Pierre Groussin, Redwane Rakza, Joana Brito, et al. "Incidence of ventricular arrhythmias after implantable cardioverter-defibrillator implantation or replacement, and driving restriction consequences." Archives of cardiovascular diseases, 2024, 118 (1), pp.35-42. 10.1016/j.acvd.2024.10.005. hal-04833437

HAL Id: hal-04833437

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Clinical Research

# Incidence of ventricular arrhythmias after implantable cardioverter-defibrillator implantation or replacement, and driving restriction consequences ☆

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Thomas Marcª, Karim Benaliª,ᵇ, Pierre Groussinª, Redwane Rakzaª, Joana Britoª, Nathalie Beharª, Philippe Maboª, Dominique Pavinª, Christophe Leclercqª, Vincent Galandª, Raphaël P. Martinsª,\*

## INFO ARTICLE

Historique de l'article :
Reçu le 30 mai 2024
Reçu sous la forme révisée
le 2 octobre 2024
Accepté le 3 octobre 2024
Disponible sur Internet le 6 November 2024

Keywords :
Implantable cardioverter-defibrillator
Driving
Driving restriction
Arrhythmias

## ABSTRACT

**Background.** – Following implantation/replacement of an implantable cardioverter-defibrillator, patients are legally subjected to variable lengths of driving restrictions based on the indication (1 and 3 months after primary and secondary prevention, respectively; 1 week after device replacement).

**Aim.** – To assess the incidence of ventricular arrhythmia during the theoretical driving restriction period in a large cohort of patients.

**Methods.** – Patients who underwent implantable cardioverter-defibrillator implantation for primary or secondary prevention or device replacement between 2015 and 2021 were included retrospectively. The primary endpoint was the occurrence of ventricular arrhythmia during the theoretical driving restriction period, as defined by guidelines.

**Results.** – A total of 914 patients were analysed, including 654 first implantations (438 and 216 for primary and secondary prevention, respectively) and 260 device replacements. The primary outcome occurred in 2/438 patients (0.004%) during the 1-month period following device implantation for primary prevention and in 25/216 patients (11.5%) during the 3-month period following device implantation for secondary prevention; it did not occur in the 1-week period following device replacement. The monthly calculated risk of harm remained below the accepted threshold of 0.005% for each group.

**Conclusions.** – Primary prevention patients, such as those who have undergone device replacement, have a low risk of ventricular arrhythmia, which could lead to a reduction in their driving restriction period. Secondary prevention patients experienced a higher risk of recurrent ventricular arrhythmia, supporting the 3-month driving restriction period.

© 2024 Les Auteurs. Publié par Elsevier Masson SAS. Cet article est publié en Open Access sous licence CC BY (http://creativecommons.org/licenses/by/4.0/).

## 1. Abbreviations

Ac probability of an accident leading to injury or death to other road users or bystanders

CI confidence interval

ICD implantable cardioverter-defibrillator

SCD sudden cardiac death

SCI yearly risk of sudden cardiac incapacitation

VA ventricular arrhythmia

## 2. Background

Implantable cardioverter-defibrillators (ICDs) have proven their efficacy in significantly reducing the risk of death as a result of ventricular arrhythmias (VAs) in various clinical trials, and have become a standard of care for selected patients [1–3]. Although ICDs are effective in preventing sudden cardiac death (SCD), they do not prevent the occurrence of VA, which may result in transient loss of consciousness. Therefore, patients with ICD are subject to driving restrictions.

<footnote>ª Inserm, LTSI – UMR 1099, CHU de Rennes, Rennes University, 35000 Rennes, France</footnote>

<footnote>ᵇ CHU de Saint-Étienne, 42000 Saint-Étienne, France</footnote>

<footnote>☆ X post (Tweet): Check out our latest article diving into ventricular arrhythmia in ICD recipients and their driving restrictions consequences. Essential insights for patient care. @Thomas_Marc35 @MartinsRaphae15 @galand.vincent.</footnote>

<footnote>\* Corresponding author: Service de cardiologie et maladies vasculaires, CHU de Rennes, 2, rue Henri-Le-Guilloux, 35000 Rennes, France.</footnote>

<footnote>Adresse e-mail : raphael.martins@chu-rennes.fr (R.P. Martins).</footnote>
Driving is an essential activity for most individuals, as it provides mobility and independence. Driving licences are categorized as private drivers (group 1), who do not earn a living from driving, and commercial drivers (group 2) [4]. As this activity carries a risk, an acceptable “risk of harm” was developed in 1992 to stratify this driving-specific risk [5]. As a result of the occurrence of VA-linked losses of consciousness, patients with an ICD have an increased risk of causing injury to themselves and bystanders [6]. Consequently, the first driving restriction guidelines for ICD recipients were published in 1997, and were updated in 2009 because of the growing number of ICD implantations in primary prevention [7,8]. The 2009 guidelines, currently still relevant in Europe, recommend a 3-month and 1-month driving restriction for private drivers after ICD implantation in secondary and primary prevention, respectively [9–12]. Whereas driving restrictions are intended to ensure patient safety, they can also significantly impact their quality of life [13,14]. Patients may experience decreased mobility and increased dependence on others, leading to social isolation and reduced participation in daily activities. Additionally, driving restrictions may have economic implications, such as the loss of employment or the need for alternative transportation, which can be financially burdensome [15]. Reassessing the risk of sudden incapacitation in those different groups of private drivers would have an impact in terms of adherence and psychosocial impact, as almost one third of patients do not respect the actual recommendations [16].

Accordingly, this study aimed to assess the incidence rate of VA during the theoretical driving restriction period, as defined in the guidelines, and to compare the results with the current length of driving restriction.

# 3. Methods

## 3.1. Study design

We conducted a retrospective single-centre observational study of patients scheduled for ICD implantation (endovascular or subcutaneous ICD) for primary or secondary prevention or device replacement at Rennes University Hospital, France, between January 2015 and June 2021. Patients who underwent transplantation or implantation of a left ventricular assist device within the first year of follow-up were excluded.

## 3.2. Data collection and study population

Baseline and follow-up data of all enrolled patients were collected from local hospital records. Our local protocol requires patients to attend a clinical visit 2–3 months and 1 year after implantation. The overall population was monitored remotely. ICD-specific data were collected using electronic medical records at the time of the follow-up visit and with the remote monitoring system. The data collected included demographic characteristics, cardiac disease, indication for ICD implantation, heart failure medical therapy, type of ICD and clinical outcomes. This study adhered to the Declaration of Helsinki guidelines for ethical research.

## 3.3. Endpoints

The primary endpoint was the incidence of VA during the theoretical driving restriction period, as defined in the guidelines, i.e., 1 month for ICD implantation for primary prevention, 3 months for secondary prevention and 1 week for device replacement. VA was defined as an episode requiring appropriate therapy delivered by the ICD (i.e., antitachycardia pacing and electrical shock) or any sustained and symptomatic episode occurring in a monitored zone without delivered therapy. The secondary endpoints were inappropriate therapies and the assessment of the risk of harm.

The overall follow-up was 1 year after the ICD procedure, regardless of the patient groups.

## 3.4. Risk of harm

The “risk of harm” formula was defined in 1992 by the Canadian Cardiovascular Society Consensus Conference to assess the risk level of driving with a medical condition, and specifically with a heart disease [17]. This formula, still relevant today, is used as a tool to calculate the yearly risk of harm for the driver with an ICD, and also to estimate the risk for passengers and others. An annual risk of death or injury to others of 5 in 100,000 (0.005%) has been proposed to be acceptable [18].

The “risk of harm” formula is defined as follows: risk of harm = TD × V × SCI × Ac [5,19]. TD is the proportion of time spent behind the wheel; whereas a commercial driver spends approximately 25% of their time driving, a private driver spends approximately 4% of their time driving. V is the type of vehicle driven, and is given a value of 0.28 for a private driver and 1 for a commercial driver; it is based on the large number of commercial vehicles and heavy trucks involved in fatal injuries. SCI is the yearly risk of sudden cardiac incapacitation, and was calculated from the yearly incidence of sudden disabling events; for patients with an ICD, it was supposed that SCI was equal to the cumulative incidence of VA multiplied by the accepted standard risk of syncope of 31% in literature [11]. Ac is the probability that such an event results in a fatal or injury-producing accident, defined as 0.02 for all drivers [20,21].

For this study, we estimated the monthly risk of harm. SCI variables were calculated by multiplying the monthly incidence of VA by the 31% risk of syncope.

## 3.5. Statistical analysis

Qualitative variables are expressed as absolute numbers and percentages, and were compared using the $\chi^2$ test or Fisher’s exact test; continuous data are expressed as mean ± standard deviation or median (interquartile range), depending on their distribution, which was assessed using the Kolmogorov-Smirnov test. Continuous variables were compared using Student’s t test or the Mann-Whitney U-test for two-group comparisons. Survival rates were summarized using Kaplan-Meier estimates, and log-rank tests were used to compare the groups. Incidence rates of VA are presented with their respective 95% confidence intervals (95% CIs). Statistical significance was set at $P<0.05$. The prespecified subgroups included ischaemic and non-ischaemic cardiomyopathy. The analyses were performed with the SPSS statistical package, version 29.0 (SPSS Inc., Chicago, IL, USA).

# 4. Results

## 4.1. Study population

From January 2015 to June 2021, 914 patients underwent ICD implantation in our centre, including 654 first implantations (438 and 216 in primary and secondary prevention, respectively) and 260 device replacements. Patient characteristics are described in Table 1. Briefly, patients were mostly male (78.3%), with a mean age of 59.4 ± 13 years. The mean follow-up duration was 359 ± 34 days, corresponding to 215,871 patient-days. Ischaemic and non-ischaemic cardiomyopathies were the most common aetiologies (42.8 and 42.1%, respectively). Most patients (46.9%) received a single-chamber ICD, and 11.4% received a subcutaneous ICD.

As expected, patients implanted in primary and secondary prevention mainly differed in terms of left ventricular ejection fraction (31.3% in primary prevention vs. 46.1% in secondary prevention)
<table><caption>**Table 1**
Baseline characteristics.</caption><thead><tr><th></th><th>Total (n=914)</th><th>Primary prevention (n=438)</th><th>Secondary prevention (n=216)</th><th>Replacement (n=260)</th></tr></thead><tbody><tr><td>Age (years)</td><td>59.4 ± 13</td><td>60.3 ± 12</td><td>57.5 ± 15</td><td>62.2 ± 15</td></tr><tr><td>Male sex</td><td>716 (78.3)</td><td>335 (76.5)</td><td>174 (80.5)</td><td>207 (79.6)</td></tr><tr><td>LVEF (%)</td><td>36.2 (20–51)</td><td>31.3 (18–44)</td><td>46.1 (31–61)</td><td>43.0 (27–59)</td></tr><tr><td>Chronic kidney disease</td><td>145 (15.8)</td><td>78 (17.8)</td><td>32 (14.8)</td><td>35 (13.5)</td></tr><tr><td>Cardiopathy</td><td></td><td></td><td></td><td></td></tr><tr><td>Ischaemic</td><td>391 (42.8)</td><td>198 (45.2)</td><td>96 (44.6)</td><td>97 (37.3)</td></tr><tr><td>Non-ischaemic</td><td>385 (42.1)</td><td>200 (45.7)</td><td>76 (35.3)</td><td>109 (41.9)</td></tr><tr><td>Hypertrophic</td><td>44 (4.8)</td><td>29 (6.6)</td><td>9 (4.2)</td><td>6 (2.3)</td></tr><tr><td>Arrhythmogenic</td><td>94 (10.3)</td><td>11 (2.5)</td><td>35 (16.3)</td><td>48 (18.5)</td></tr><tr><td>Treatment</td><td></td><td></td><td></td><td></td></tr><tr><td>Antiarrhythmic drug</td><td>97 (10.6)</td><td>31 (7.1)</td><td>25 (11.6)</td><td>41 (15.8)</td></tr><tr><td>Beta-blocker</td><td>824 (90.1)</td><td>405 (92.5)</td><td>190 (88.0)</td><td>229 (88.0)</td></tr><tr><td>ACEI/ARB/ARNI</td><td>715 (78.2)</td><td>394 (90.0)</td><td>133 (61.6)</td><td>188 (72.3)</td></tr><tr><td>Mineralocorticoid antagonist</td><td>324 (35.4)</td><td>211 (48.2)</td><td>46 (21.3)</td><td>67 (25.8)</td></tr><tr><td>ICD type</td><td></td><td></td><td></td><td></td></tr><tr><td>Single chamber</td><td>429 (46.9)</td><td>174 (39.7)</td><td>119 (55.1)</td><td>136 (52.3)</td></tr><tr><td>Dual chamber</td><td>125 (13.7)</td><td>36 (8.2)</td><td>34 (15.7)</td><td>55 (21.1)</td></tr><tr><td>Resynchronization</td><td>250 (27.3)</td><td>176 (40.2)</td><td>17 (7.9)</td><td>57 (21.9)</td></tr><tr><td>Subcutaneous ICD</td><td>104 (11.4)</td><td>51 (11.6)</td><td>45 (20.8)</td><td>8 (3.0)</td></tr></tbody></table>

Data are expressed as mean ± standard deviation, number (%) or median (interquartile range). ACEI: angiotensin-converting enzyme inhibitor; ARB: angiotensin II receptor blocker; ARNI: angiotensin receptor neprilysin inhibitor; ICD: implantable cardioverter-defibrillator; LVEF: left ventricular ejection fraction.

and use of chronic heart failure medical therapy. Regarding ICD programming, for patients implanted in primary prevention (including the first implantation and device replacement groups), the mean ventricular tachycardia and ventricular fibrillation detection rates were programmed at 177 ± 6 beats/min and 225 ± 9 beats/min, respectively. For those implanted in secondary prevention, the mean ventricular tachycardia and ventricular fibrillation detection rates were 170 ± 17 beats/min and 224 ± 8 beats/min, respectively. Lastly, patients who received a subcutaneous ICD were programmed with a conditional zone of 217 ± 9 beats/min and a shock zone of 246 ± 7 beats/min. These programming strategies were concordant with latest European Society of Cardiology guidelines [22,23].

The 260 patients included in the device replacement group (79.6% male, mean age 62.2 ± 15 years, 135 and 125 primary and secondary prevention, respectively) had a median left ventricular ejection fraction of 43.0% (interquartile range 27.0–59.0%). Ischaemic and non-ischaemic were the most common underlying aetiologies (37.3 and 41.9%, respectively). Single-chamber ICDs were the implanted most frequently (52.3%).

Of note, among the 914 patients, 38 were seen at 3 months in our institution, but were thereafter lost to follow-up because they were followed in other centres. Loss to follow-up occurred in all the patients after the theoretical driving restriction period.

Five patients died (primary prevention group, n = 1; secondary prevention group, n = 1; replacement group, n = 3). All the deaths occurred after the theoretical driving restriction period, and did not affect the analysis of the primary endpoint of the study.

## 4.2. Occurrence of VAs in the overall population

Among the 914 patients and over 1 year of follow-up, 65 (7.1%, 95% CI 5.4–8.8) experienced at least one VA event, including 14 of 438 (3.2%, 95% CI 1.6–4.8) in the primary prevention group, 39 of 216 (18.1%, 95% CI 12.9–23.2) in the secondary prevention group and 12 of 260 (4.6%, 95% CI 2.1–7.2) in the device replacement group.

## 4.3. Occurrence of VAs in the primary prevention group

In the primary prevention group, among the 14 patients (3.2%, 95% CI 1.6–4.8) experiencing a VA event, eight received an appropriate shock, five were treated with antitachycardia pacing and one was untreated for a sustained arrhythmia occurring in the monitor

zone. Notably, seven episodes were associated with syncope. These events were evenly distributed over the first year, with four events occurring during the first trimester, three in the second trimester, three in the third trimester and four in the fourth trimester: event incidences of 0.92% (95% CI 0.02–1.8), 0.69% (95% CI 0.0–1.5), 0.69% (95% CI 0.0–1.5) and 0.92% (95% CI 0.02–1.8) for trimesters 1–4, respectively (Fig. 1).

The primary outcome, i.e. the incidence rate of VA during the theoretical driving restriction period, as defined in the guidelines, corresponding to 1 month in this group, occurred in 2 out of 438 patients (0.004%, 95% CI 0.0–1.1).

## 4.4. Occurrence of VAs in the secondary prevention group

In the secondary prevention group, 39 patients (18.1%, 95% CI 12.9–23.2) experienced arrhythmia during follow-up: 21 were treated with appropriate shock; 16 were treated with antitachycardia pacing; and one was untreated because it occurred in the monitor zone. Fifteen of these episodes were associated with syncope. Of note, one patient was driving his scooter when an appropriate shock was delivered for a fast ventricular tachycardia, 2 days after ICD implantation. This episode was not syncopal.

The primary outcome, corresponding to 3 months in this group, occurred in 25 (11.5%, 95% CI 7.3–15.8) patients. The incidence was lower in the second, third and fourth trimesters: 1.4% (95% CI 0.0–3.0), 2.4% (95% CI 0.3–4.3) and 2.9% (95% CI 0.6–5.0), respectively (Fig. 1).

## 4.5. Occurrence of VAs in the device replacement group

Among the 260 patients who underwent generator replacement, 12 events were recorded in 12 patients (4.6%, 95% CI 2.1–7.2), including six appropriate shocks, three antitachycardia pacing and three untreated VA in the monitor zone. These episodes were equally distributed over time: event incidences of 1.2% (95% CI 0.0–2.5), 1.92% (95% CI 0.3–3.6), 0.77% (95% CI 0.0–1.8) and 0.77% (95% CI 0.0–1.8) for trimesters 1–4, respectively (Fig. 2). The primary outcome, corresponding to 1 week in this group, did not occur in all 260 patients.
<figure><img src="image_5.png" /><figcaption>**Fig. 1.** Incidence of ventricular arrhythmias in the primary (grey) and secondary prevention (red) groups. A. Number of events in each trimester after implantation. B. Cumulative incidence of ventricular arrhythmias.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>**Fig. 2.** Incidence of ventricular arrhythmias in the replacement group. A. Number of events in each trimester after implantation. B. Cumulative incidence of ventricular arrhythmias.</figcaption></figure>

## 4.6. Risk of harm

The risk of harm score was calculated for each ICD implantation group and evaluated every month after the ICD procedure. As defined in the Methods section (cf. Section 3), the acceptable level of risk is consensually defined at 0.005% (i.e., 5 in 100,000 road users). As shown in Fig. 3, for all groups, the risk of harm was low and acceptable during the follow-up period, systematically below the 0.0005% cut-off. For the group with the higher risk – the secondary prevention group – the risk of harm was higher during the first trimester, although below the acceptable level of 0.005%, followed by a steady low risk during the subsequent months.

As inappropriate shocks may also cause light-headedness or syncope, leading to safety issues while driving, we conducted a

comprehensive risk of harm assessment, incorporating inappropriate shocks, to evaluate their impact on the acceptable risk levels (Fig. A.1). Notably, in the secondary prevention group, there was a significant increase in inappropriate events during the second month, which substantially raised the risk score. However, despite this increase, the overall risk remained within acceptable levels across all groups.

## 4.7. Inappropriate shocks

During the follow-up period, 14 of the 914 patients experienced inappropriate shock: 4 (0.9%, 95% CI 0.0–1.8), 6 (2.8%, 95% CI 0.6–5.0) and 4 (1.5%, 95% CI 0.0–3.0) in the primary prevention, secondary prevention and device replacement groups, respectively.
<figure><img src="image_7.png" /><figcaption>**Fig. 3.** Risk of harm score for the primary prevention (left panel), secondary prevention (middle panel) and device replacement (right panel) groups. The risk of harm per 100,000 patients, based on sudden cardiac incapacitation risk, was estimated monthly by calculating the incidence of ventricular arrhythmias, multiplied by the standard risk of syncope (0.31), time driven (0.04 for private drivers), probability of death or injury-producing accident (0.02). The red line defines the acceptable risk of harm (0.005%).</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Fig. 4.** Number of inappropriate shocks in the study population.</figcaption></figure>

vely (Fig. 4). Inappropriate shocks mostly occurred during the first trimester (n = 8) and were mainly associated with supraventricular tachycardia (n = 10/14). None of the inappropriate shocks was syncopal.

# 5. Discussion

## 5.1. Major results

The results of our study provide valuable insights into the incidence and distribution of appropriate and inappropriate ICD therapies in different groups of patients with ICDs during the theoretical driving restriction period. The major results are as follows: (1) patients implanted in secondary prevention have a high risk of recurrent VA during the first trimester, although the risk of harm remained below the acceptable 0.005% threshold; (2) a steady and low risk of harm was observed for patients implanted in primary prevention, specifically during the first month after implantation; and (3) the risk of arrhythmias during the week following device replacement was negligible.

## 5.2. VAs following ICD implantation

Over the past two decades, major advances in therapeutics and revascularization interventions have considerably improved the prognosis of patients with heart disease, resulting in a 44% decline in the rate of SCD among those with symptomatic heart failure, and a 70% decline in patients with ischaemic heart disease [24,25]. Many landmark studies have also proven their efficacy in significantly reducing the risk of SCD [1–3], which remains, however, a major medical and societal challenge [26]. Although ICDs are effective in preventing SCD, they do not prevent the occurrence of VA. The evolution of ICD programming has decreased the rate of appropriate therapies [27], but if they occur, they may result in transient loss of consciousness, subjecting ICD recipients to driving restrictions [9,11]. In our study, we observed a relatively large proportion of VAs during the first trimester after ICD implantation, particularly in the secondary prevention group (11.5% of patients), which is consistent with the current literature. Indeed, the DREAM-ICD-II study, investigating the incidence of appropriate device therapies in patients receiving an ICD for secondary prevention, showed a 34.4% incidence of appropriate ICD events in the first
90 days following implantation, with a 17.8% total incidence in the first year of follow-up [28]. Similar results were found in the light-headedness OMNI registry [29]. In patients implanted in primary prevention or after ICD replacement, the risk of SCD is lower, and the restriction is mostly related to the necessity of recovery after the procedure [10,12]. Indeed, we observed that the incidence of VA remained low (< 1% per trimester) during the first year, with no increase in risk during the first month. This rate is similar to the low incidence reported in a trial from 2011 involving 1718 patients who underwent primary prevention ICD implantation [30].

### 5.3. Driving restrictions and risk of harm

Our study, supported by several other trials, highlights the difference between the actual guidelines and available data on driving restrictions.

For the secondary prevention group, our findings showed a low risk of harm during the first trimester, which never exceeded the reasonable and approved risk of harm cut-off of 5 per 100,000 patients. This result is consistent with the DREAM-ICD-II study, which showed that the rate of appropriate ICD therapy decreased significantly after the first 3 months, and was always under the risk of harm threshold. Similarly, in a prospective observational study, Thijseen et al. observed that in a cohort of 2786 patients implanted in primary and secondary prevention, the accepted risk of harm was under the threshold of 0.005% [30]. In the light of this result, the authors suggested that, for private drivers, no driving restriction should be warranted, contrasting with the European recommendations allowing secondary prevention patients to drive 12 weeks after implantation. Importantly, USA guidelines are more restrictive, with a 6-month restriction period [18].

As explained above, for private drivers implanted in primary prevention or scheduled for device replacement, driving restrictions are primarily based on the necessity of recovery of the wound after the procedure, rather than the immediate risk of sudden cardiac incapacitation [8]. Epstein et al. demonstrated that the likelihood of an ICD discharge while driving was very low, in the range of 0.15% of patients per year (i.e. during the short- and long-term follow-up after ICD implantation) [17]. Our findings are consistent with a low risk of harm during the first year following device implantation, especially during the immediate postimplantation period. Currently, a 1-month restriction period after primary ICD implantation prevention is typically advised in the current guidelines. However, considering the low risk of harm and the very low risk of VAs observed in several studies, including ours, this group of patients may benefit from a potentially shorter driving restriction after the procedure. Indeed, the psychological impact of ICD and driving restrictions is significant, and it could be beneficial to reduce the restriction period in this population [31,32]. However, in case of early driving authorization, patients should be careful in order to avoid postimplantation complications (i.e., pocket haematoma or ICD lead dislodgment).

### 5.4. Inappropriate shocks

Despite the development of complex algorithms, current data still report an annual inappropriate shock rate of between 2 and 5% [33,34]. In our study, 0.9 and 3.7% of the primary and secondary prevention groups, respectively, experienced inappropriate ICD therapies during the first year of follow-up. Of note, in the secondary prevention group, the occurrence of inappropriate shocks was higher during the first trimester (2.6%), mostly as a result of supraventricular tachycardia, which was the most common cause of inappropriate therapy [35]. Previous works attributed this higher risk to aggressive ICD programming in secondary prevention patients who are at risk of atrial fibrillation or other

supraventricular arrhythmias, leading to a misdiagnosis of VA [36,37]. However, in our study, both primary and secondary prevention groups had similar ICD programming. Nevertheless, the 2.6% risk of inappropriate shock during the first trimester in secondary prevention patients could also influence the driving restriction time, owing to the negative psychological impact and safety issues caused by an ICD shock delivered during driving.

### 5.5. Clinical implications

Driving restriction is mainly driven by the need for local recovery in patients implanted for primary prevention or those undergoing device replacement. Importantly, our study did not find a higher risk of VA during the postimplantation period, and a shorter driving restriction time (less than 1 month) could be proposed for selected patients implanted for primary prevention. For the secondary prevention group, despite a risk of harm below the acceptable threshold during the first 3 months, our study showed an 11.5% risk of VA during this period, representing an important proportion of patients at risk of syncope. Additionally, we described more inappropriate ICD shock events during the first 3 months following implantation. Based on these results, and despite a relatively low risk of harm, we believe that a driving restriction time of 3 months seems justified to ensure the safety of these individuals and other road users.

Furthermore, given the high risk of recurrent VA in the secondary prevention group following ICD implantation, a more aggressive antiarrhythmic treatment strategy could be implemented to avoid recurrences (pharmacological treatment, radiofrequency ablation) [38,39]. Further studies are needed to establish an optimal therapeutic strategy during this high-risk period.

### 5.6. Study limitations

Our study has some limitations, including its single-centre and retrospective design, which may have affected the results. This is particularly true for the occurrence of syncope, which may have been underestimated. Additionally, the main issue is more general, and involves the risk of harm assessment in patients with ICD. Indeed, the risk of harm formula is oversimplified, and potentially does not reflect actual practice, as the different variables included in the formula are extracted from historical reports. For example, the probability of an accident leading to injury or death to other road users or bystanders (the "Ac" factor) is considered to be 2%, and was issued in a 1970s report (Ontario Road Safety Annual Report). Similarly, the risk of harm threshold of 0.005% was based on data from more than 30 years ago. Lastly, the cornerstone for estimating the risk of sudden cardiac incapacitation variable is related to the risk of syncope estimated at 31% during ICD therapy, but recent studies suggest a lower value (< 15%) [40,41].

## 6. Conclusions

This study reports an acceptable risk of harm for both the primary and secondary prevention group during 1-year follow-up after the first ICD implantation. For the primary prevention group, a shorter driving restriction time could be proposed after the intervention. However, more than 10% of secondary prevention patients present with VA recurrence during the first trimester, a finding supporting the current guidelines regarding the driving restriction period in this population (Central Illustration).
Cumulative incidence of appropriate therapies
after device implantation or replacement during
the theoretical driving restriction period

<figure><img src="image_9.png" /></figure>

**Central Illustration.** Incidence of appropriate therapies for ventricular arrhythmias after device implantation or replacements during the theoretical driving restriction period.

Funding

None.

Disclosure of interest

R.P.M. has received lecture fees from Biosense Webster. The other authors declare that they have no competing interest.

**Appendix A. Supplementary data**

Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.acvd.2024.10.005.

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