Rethinking ASCVD screening, management in commercial drivers, pilots
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The evaluation and management of CAD has critical implications in certain populations. A recently published review addresses this topic for two high-risk populations, commercial motor vehicle drivers and commercial pilots.
Current requirements
Both commercial motor vehicle (CMV) drivers and pilots must undergo screening exams as part of the licensure process.
The Federal Motor Carrier Safety Administration (FMCSA) requires that CMV drivers undergo an exam at least every 2 years by a certified examiner. Applicants are classified into one of three categories based on estimated 10-year atherosclerotic CVD risk: asymptomatic low risk (< 20% 10-year risk), asymptomatic high risk ( 20% 10-year risk) or symptomatic based on self-reported symptoms.
Drivers are asked to self-report symptoms that may affect their employment status. Asymptomatic high-risk applicants undergo further evaluation, such as an exercise treadmill test (ETT), at the discretion of the examiner. For symptomatic applicants with angina or those with recent MI, PCI or CABG, additional requirements include yearly exams and an ETT every 2 years.
Exams for pilots are conducted by certified aviation medical examiners. Similar to CMV operators, pilots are classified into asymptomatic low-risk, asymptomatic high-risk and symptomatic-risk groups.
Asymptomatic high-risk pilots (10-year ASCVD risk > 10%) must undergo either coronary artery calcium scoring or CAC plus coronary CT angiography (CCTA). If CAC score is greater than 100, left main stenosis greater than 30% or any stenosis on CCTA greater than 50% is present, pilots must undergo functional stress imaging and invasive coronary angiography. To obtain certification, some pilots with stable coronary disease may be required to undergo revascularization.
Pilots who undergo coronary revascularization must undergo assessment for recurrence of symptoms, exercise tolerance and determination of ejection fraction. Additionally, there must be no ischemia on myocardial perfusion imaging by single-photon emission CT before regaining certification.
Rethinking licensure requirements
The guidelines put forth by the FMCSA and Federal Aviation Administration are not entirely reflective of current American Heart Association/American College of Cardiology guidelines for the general population. For pilots, licensing agencies maintain that guidelines for the general population cannot be uniformly applied to pilots working in high-stress situations with unique environmental conditions, such as g-forces and relative hypoxia. Still, recent paradigm shifts in the prevention and management of ASCVD have been driven by large trials demonstrating improved outcomes that would benefit CMV drivers and pilots as well.
CV medicine practitioners are increasingly utilizing an anatomic imaging approach in patients at low or intermediate risk for obstructive CAD. The FAA does employ CAC scoring and potentially CCTA for asymptomatic individuals with greater than 10% 10-year ASCVD risk and may require functional imaging for additional workup. Licensing requirements for pilots require yearly stress testing if there is a history of prior revascularization.
Total atherosclerotic disease burden, which can be assessed with CAC score or CCTA, is useful to predict adverse CV outcomes. Anatomic imaging modalities such as CCTA are more sensitive than stress testing for detection of nonobstructive CAD, as many patients with nonobstructive disease will have a normal stress test. Several recent, large trials have demonstrated that CCTA could improve outcomes by detecting CAD and increasing implementation of secondary prevention measures.
Another benefit of CCTA over functional testing is its ability to provide information about high-risk plaque characteristics, including left main coronary artery plaque and low-attenuation plaque. Knowledge of these features could inform decision-making about further invasive testing and intervention. Guidelines exist in the United Kingdom for incorporating fractional flow reserve with CCTA as a noninvasive means of selecting patients who are more likely to benefit from invasive angiography.
Requirements for revascularization for pilots is another area that warrants revisiting. Per current guidelines, there are various situations in which stable, asymptomatic pilots may be required to undergo revascularization and situations in which pilots may not regain a first-class certificate without revascularization of ischemia-causing stenoses.
The ISCHEMIA trial found that routine revascularization among patients with stable ischemic heart disease and moderate to severe reversible ischemia did not reduce risk for CV events compared with optimal medical therapy alone. The FAA should consider revising its approach in the context of the ISCHEMIA findings, given that a conservative approach was found to be as safe as an invasive approach.
Promotion of prevention strategies
The FMCSA and FAA rely heavily on routine stress testing and have a lower threshold for requiring invasive angiography and revascularization than what is recommended for the general public, arguing that more aggressive risk mitigation is warranted because of the high-stakes environments in which CMV drivers and pilots work. While these strategies have not been shown to improve outcomes, successful implementation of preventive strategies has been shown to reduce adverse outcomes. Future iterations of these guidelines should focus on implementing strategies to increase rates of attainment of diet and lifestyle recommendations and adherence to optimal medical therapy.
Truck drivers have elevated ASCVD risk compared with the general population, due in part to high concomitant rates of obesity, hypertension, diabetes and tobacco use, as well as lack of regular brisk physical activity and high rates of fast-food consumption. Licensing exams represent an important opportunity to focus on prevention strategies.
A more evidence-based approach to risk-stratifying CMV drivers and pilots is an important starting place. The licensing exam for both groups includes stratification into asymptomatic low risk, asymptomatic high risk and symptomatic.
Challenges and future directions
Estimations that rely heavily on self-report may affect one’s ability to work and could incentivize underreporting of symptoms. Additionally, there is no standardization as to what calculator should be used to estimate ASCVD risk. The 10-year Pooled Cohort Equation is the most widely validated, but it has not been validated in individuals younger than 40 years. Validation of a risk stratification tool that can be applied to younger drivers and pilots would be beneficial. The risk stratification algorithm could also include guidelines for use of CAC scoring in refining risk estimates.
Thresholds could be established to guide implementation of statin therapy and antihypertensive medications, in addition to referral for additional testing such as CCTA or invasive angiography when appropriate. Intervals for reassessing risk and monitoring for improvement in cholesterol, HbA1c and weight in individuals at elevated risk could also be established. Attainment of adequate physical activity and healthy diet should be incentivized.
Evidence-based changes needed
The FMCSA and FAA are tasked with quantifying and mitigating ASCVD risk in CMV drivers and pilots through licensing exams. Assuring the safety of drivers, pilots and civilians should remain the top priority. Recent research has led to several paradigm shifts in the field of CV medicine, and these new guidelines for licensing drivers and pilots should be promptly implemented.
Licensing boards should consider results from new anatomic imaging modalities such as CAC scoring and CCTA when making recommendations for operating both over road and through air commercial travel. Additionally, the strategy of employing revascularization as a form of risk mitigation should be revisited based on the ISCHEMIA trial. Prevention should be emphasized through creation of improved tools for assessing risk and guidelines for implementation of optimal medical therapy.
References:
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For more information:
Roger S. Blumenthal, MD, is the director of the Ciccarone Center for the Prevention of Cardiovascular Disease and professor of medicine at Johns Hopkins University School of Medicine. He is also the editor of the Prevention section of the Cardiology Today Editorial Board. Twitter: @rblument1.
Chloe Duvall, MD, is a resident at Johns Hopkins Hospital.
Garima Sharma, MD, is assistant professor of medicine at Johns Hopkins University School of Medicine. Twitter: @garimavsharmamd.
Nadia R. Sutton, MD, is an interventional cardiologist and assistant professor of internal medicine at the Frankel Cardiovascular Center of the University of Michigan Health System. Twitter: @nadia_sutton.
The authors can be reached at Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease, Division of Cardiology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Halsted 560, Baltimore, MD 21827.
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