Introduction

In 1992, the Canadian Cardiovascular Society (CCS) consensus conference document, “Assessment of the Cardiac Patient for Fitness to Drive,” was published.^[1] Four years later, as a result of significant advances in the investigation and management of arrhythmias and syncope, an update was deemed necessary by the CCS Task Force that penned the original document.^[2] In 2002, after receiving suggestions from the CCS membership, the CCS Council selected “fitness to drive and fly” as the consensus conference topic for 2003-2004.^[3],[4] In 2012, a CCS focused position statement on left ventricular assist devices (LVADs) was published, to respond to new evidence that event rates in this population were lower than previously believed.^[5] Most recently, the CCS membership perceived that a further update was required, because significant developments had again occurred in the evaluation and treatment of cardiac disorders, rendering some of the recommendations outdated or obsolete.

Physicians and some other health care professionals in many Canadian jurisdictions are required by law to report patients who are potentially unfit to drive because of their disease or condition. Legislation in 7 of 10 provinces and all 3 territories requires that physicians report to the regulatory authorities, patients who might pose a risk on the road because of their medical condition (the remaining jurisdictions have discretionary reporting systems). Reporting has become an integral part of the risk assessment process for most Canadian physicians and other health care professionals who provide care for cardiac patients. These guidelines are formulated on the best evidence available to guide risk assessment and reporting, as legally required. Furthermore, these guidelines fill a gap in knowledge synthesis pertaining to the risk of sudden incapacitation across cardiovascular conditions. The updated recommendations have taken into consideration estimates of risk in patients on contemporary therapy for cardiovascular diseases. Risk is estimated on the basis of the best available estimated event rates observed in registries, administrative data sets, and the “control groups” of pragmatic trials. Some of the event rates that were studied are by necessity surrogates for sudden incapacitation and include sudden death, malignant ventricular arrythmias, defibrillator therapy, and syncopal episodes. When insufficient evidentiary data were available, recommendations were made on the basis of common best practices and historical deference to caution with writing subgroup expert consensus (this is particularly true for postprocedural recommendations). When possible, sex differences in risk estimates are provided.

These guidelines are not a substitute for physicians using their clinical judgement and assessment of risk in clinical settings with appropriate regard to the individual circumstances, values and preferences of the patient, and the diagnostic and treatment options available. Adherence to these recommendations will reduce, but not eliminate risk.

The 2023 Fitness to Drive guidelines follow a series of virtual meetings of cardiovascular researchers and clinicians. The members were selected on the basis of contributions to previous guidelines and current areas of clinical and research expertise, with a view to representativeness across cardiac subspecialties, gender, generation, and geography.

Risk of Harm Formula

Under the leadership of Dr Jim Brennan, the original task force developed the ground-breaking “Risk of Harm” formula (which, for the first time, allowed the assignment of a quantitative level of risk to drivers with cardiac disease). The development of this quantitative approach included definition of the risk that society had historically considered to be acceptable. This standard of acceptable risk served as the benchmark against which all other drivers with cardiac disease could be measured. Although arbitrary, this benchmark of acceptable risk has stood the test of time, from a general acceptability point of view, and remains, to our knowledge, the only quantitative estimate of society’s tolerance for risk in the medical fitness to drive literature.

The reader is encouraged to refer to the original document for the derivation of the Risk of Harm formula.^[3],[4] On the basis of the available literature, it was determined that a commercial driver (a tractor trailer operator, for example) who faces a 1% risk of sudden cardiac incapacitation (SCI) in the next year poses a 1 in 20,000 risk of death or serious injury to other road users or bystanders. Set as the standard, this annual 1 in 20,000 risk can be applied in turn to a private driver to determine the annual risk of SCI that would pose the same overall risk to society. Because private drivers spend much less time on the road, and because they drive vehicles that are less likely to cause harm in the event that an accident actually does occur, it can be calculated that a private driver with a 22% annual risk of SCI also poses a risk to society of 1 in 20,000. Therefore, a private driver with a 22% chance of having a suddenly incapacitating event in the next year poses no greater risk to society than does a tractor trailer driver with a 1% chance of having a suddenly incapacitating cardiac event over the same time period.

Because no licensing jurisdiction has quantified the acceptable risk in legislation or regulations, any standard risk threshold used in any expert guidance might be considered as somewhat arbitrary. However, arriving at a standard risk threshold has allowed us to apply consistent and fair recommendations across different cardiac conditions and across different classes of licenses. In addition, the standard risk threshold, originally calculated by the CCS in 1996,^[2] has remained consistent over time as evidenced by its uptake by successive published editions of the Canadian Medical Association Drivers Guide^[6] and the Canadian Council of Motor Transport Administrators National Safety Code^[7] (documents widely used by government regulatory authorities to adjudicate individual fitness to drive). To our knowledge, no other quantified “acceptable” level of risk has been suggested, tested, or accepted. For these reasons, the panel opted to continue with the use of this historical standard risk threshold in the development of this updated guideline.

The current recommendations reflect new information that has become available in the literature over the intervening years, but the Risk of Harm formula remains the major assessment tool. In addition to assessing level of risk compared with a standard level of acceptable risk, it also allows for consistency across the breadth of recommendations.

Level of Evidence

Literature reviews were undertaken to generate risk estimates, and data sources for these estimates were selected on the basis of consensus of experts in each cardiovascular field. There are no prospective, controlled studies in which patients had been randomized to permit or to proscribe the driving privilege nor where patients had been randomized to receive or not to receive physician advice not to drive. Furthermore, the acceptable threshold of risk used in this document (although sensibly derived as previously described herein) is consensus-based. For this reason, the current guidelines do not follow the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Additionally, we have chosen to formulate general, overarching clinical questions as an introduction to each section because structured population, intervention, control, and outcomes (PICO) questions did not apply to the available data.

The recommendations for driving eligibility are made on the basis of a comparison with the previously stated threshold, but the risk estimates are made on the basis of the best and most recent available evidence. This evidence was used to estimate risk of sudden incapacitation or a reasonable surrogate, as described in the introductory section, when this evidence was lacking. However, the evidence does not speak to the actual risk of driving or collision rates associated with the cardiac diagnosis, the benefit of driving cessation, or the effect of the system of mandatory reporting of and formal license suspension for such patients.

The panel has made an effort to consider the inherently subjective nature of society’s tolerance for risk, while also applying a scientifically based risk assessment mechanism in an effort to make the recommendations not just acceptable to society, but also consistent and justifiable. It is noteworthy, however, that existing guidelines for other medical conditions outside those considered in these guidelines (ie, for noncardiac medical conditions) have been developed by other experts and associations using different approaches and methodologies. The consistency with these other recommendations has not been assessed.

Important Considerations in the Fitness to Drive Guidelines

1. Because there are no prospective, randomized trials on fitness to drive and risk of sudden incapacitation, the recommendations are mostly on the basis of observational data from studies on various cardiac conditions, making the level of evidence moderate.
2. When evidence was not available, consensus-based recommendations were made by each of the individual subgroups on the basis of best practices, historical practice, and deference to safety.
3. In many instances, because no specific data on SCI exist, best reasonable surrogates such as sudden death, ventricular arrhythmias (VAs), defibrillator therapies, and syncope were used to estimate risk.
4. The Risk of Harm formula was used to describe an acceptable threshold level of risk for private and commercial drivers (22% risk of SCI within the year and 1% risk of SCI within the year, respectively).
   Because of these particularities, it was decided to forego the GRADE methodology and PICO questions because these were not deemed applicable with the available evidence and the structure of our recommendations.