1. CAD: ACS, Post MI, Stable Angina, and CABG Surgery

Question 1: In persons who have had an MI, or have stable angina, and/or have had coronary revascularization in the form of percutaneous coronary intervention (PCI) or CABG surgery and survived to discharge and with follow-up, what is the risk of sudden cardiac death (SCD) within 1 year? Where possible, stratify according to sex, age, and left ventricular ejection fraction (LVEF). In this section, SCD serves as the surrogate for SCI.

ACS—STEMI and NSTEMI

The risk of incapacitation after ACS is predominately related to the risk of SCD. More contemporary reports provide mortality rates but not the rate of sudden deaths. Significantly reduced LVEF, rather than type of ACS (ST segment elevation MI [STEMI] vs non-STEMI [NSTEMI]), is the most widespread clinical identifier of patients at increased risk for SCD after ACS.^[9] Recommendations for driving after ACS are summarized in Table 1.

Patients with LVEF ≤ 40%. The Valsartan in Acute Myocardial Infarction (VALIANT) trial enrolled > 14,000 post-MI patients between 1998 and 2001 with LVEF ≤ 40% according to radionuclide ventriculogram or ≤ 35% according to echocardiogram and/or clinical or radiological signs of HF.^[10] The 30-day and 1-year incidence of SCD was 1.4% and 2.17%, respectively. Similarly, a post-MI registry of nearly 3000 patients from 1997 to 2005 showed the incidence of SCD to be 1.2% and 3.0% at the same time points.^[11] However, considering the time frame, less than half received definitive revascularization (PCI or CABG) for their ACS; this might not necessarily reflect contemporary care. In contrast, in the more recent Vest Prevention of Early Sudden Death Trial (VEST) 2302 participants with LVEF ≤ 35% were randomly assigned to a wearable cardioverter-defibrillator in a 2:1 fashion within 7 days after MI discharge.^[12] The incidence of SCD remained relatively high at 2.4% at 90 days. In contrast, a contemporary observational study of > 120,000 patients from the Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies (SWEDE-HEART) registry, which enrolled patients from 2009 to 2017 (77% revascularized) showed that the incidence of SCD among patients with LVEF ≤ 40% to be 0.76% at 3 months.^[13] Therefore, because rates of SCD remain high (exceeding the acceptable threshold of 1% annually) even in the modern era among patients with LVEF ≤ 40%, it is reasonable to continue to restrict commercial driving for 3 months post-MI.

Patients with LVEF > 40%. Contemporary registries comprising post-MI patients with normal EF (or most with normal EF) and high rates of revascularization have shown that the risk of SCD ranged from 0.5% to 0.6% at 1 year.^[14],[15] Secondary analyses of recent clinical trials with most patients having a normal or mildly reduced EF, have shown that the risk of SCD ranged from 0.6% to 1.1% at 1 year, but that approximately 25% of SCD occurred in the first month, suggestive that monthly rates were much lower thereafter.^[16],[17] In the contemporary SWEDEHEART registry, the rate of SCD was approximately 0.2% after 1 month and remained similar at 3 months.^[13] This suggests that the rate of SCD between 1 and 3 months was far below the 0.083% per month (1% annually) acceptable threshold and favours an easing of driving restrictions in the subgroup of post-MI patients with LVEF > 40%.

ACS—unstable angina

Although the incidence of SCD after hospitalization for unstable angina compared with STEMI or NSTEMI has not been recently reported, the differential risk across types of ACS can be extrapolated from studies that evaluated overall or cardiovascular death. Rates of SCD among patients admitted with unstable angina are likely low. Data from the Global Registry of Acute Coronary Events (GRACE) study of 19,122 patients from 2004 to 2007 showed that 6-month mortality was 4.0% (700 of 17,598 patients), with most (71.3%) due to cardiovascular causes. At 2-year follow-up, the incidence of cardiovascular death (which includes SCD) among patients with unstable angina (28% of the cohort) was 2.6% compared with 5.2% for NSTEMI or 3.7% for STEMI.^[18] The relatively lower risk of death in patients with unstable angina compared with other forms of ACS is consistent with findings from another 6-month postdischarge GRACE study cohort.^[19] Considering the low event rate, the consensus opinion was to proscribe driving only for 48 hours out of an abundance of caution for patients with a new ACS (likely having been hospitalized) who underwent an intervention and for 7 days in those without an intervention.

Chronic CAD and stable angina

The rates of SCD in patients with stable angina are also likely low, and driving recommendations in the setting of chronic CAD are summarized in Table 1. In the Prevention of Events with Angiotensin Converting Enzyme Inhibition (PEACE) trial, which enrolled patients with stable CAD and normal left ventricular function, the rate of SCD was 1.5% after a median follow-up of 4.8 years.^[20] Similarly, the Innovation to Reduce Cardiovascular Complications of Diabetes at the Intersection Study (ARTEMIS), which enrolled consecutive Finnish patients who had undergone coronary angiography 3-6 months earlier (> 3 months post-ACS), showed a rate of SCD of 2.5% after a median follow-up of 6.3 years.^[21] There is a paucity of contemporary Canadian registry data on SCD, as opposed to all-cause or cardiovascular death, but reported rates of mortality in Canadians with stable CAD suggest that the risk for SCD is likely well < 1% per year.^[22],[23] Pivotal clinical trials on the role of PCI among patients with stable CAD did not explicitly evaluate the incidence of SCD in follow-up.^[24]–[26] As such, no restrictions are suggested for patients with stable or asymptomatic coronary disease.

CABG surgery

The Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery (SYNTAX) trial, which compared the causes of death after PCI (n = 871) vs CABG (n = 805) in patients with complex CAD, showed that patients who underwent CABG had a 0.9% 30-day risk of SCD, a 1.5% 1-year risk of SCD, and a 1.9% risk of SCD at 5 years.^[27] The relatively low rate of use of implantable cardioverter defibrillators (ICDs) in SYNTAX might have contributed to these findings. Other studies showed lower rates of SCD post CABG surgery. The Coronary Revascularization Demonstrating Outcome Study in Kyoto (CREDO-Kyoto) PCI/CABG registry study showed that rates of SCD were only 0.3% at 1 year after CABG for multivessel CAD (n = 2910). In a separate cohort of the CREDO-Kyoto PCI/CABG registry study, on 5-year outcomes of PCI vs CABG,^[28] rates of SCD at 5 years were 2.2% for triple-vessel CAD (n = 1154) and 1.6% for unprotected left main disease post CABG (n = 640). In the Bypass Angioplasty Revascularization Investigation in Type 2 Diabetes (BARI 2D) study,^[29] which included > 7.7 years of follow-up for 2239 patients after CABG surgery, the rate of SCD was 2.4%.

Studies of patients with LVEF of < 35% who underwent CABG include the Surgical Treatment for Ischemic Heart Failure (STICH) trial,^[30] which showed that among 1411 patients who underwent CABG that the risk of SCD was 0.35% at 30 days, 1.2% at 3 months, 2.0% at 6 months, and 2.8% at 1 year. In a national study of post-CABG individuals with wearable cardioverter defibrillators and an LVEF ≤ 35% (n = 243), the percentage who experienced SCD at 1 month was 0.09%, 0.10% at 3 months, and 0.26% at 1 year. A report on an aggregate national experience of individuals with wearable cardioverter defibrillators reported on the SCD of post-CABG patients with an LVEF ≤ 35% (n = 243); extrapolating from the survival charts the percentage who experienced SCD at 1 month was 0.09%, 0.10% at 3 months, and 0.26% at 1 year.