Clinical Practice Guideline
Developed for the
Aerospace Medical Association
by their constituent organization
Overview: Coronary artery (CAD) disease is considered disqualifying for all flying duty classes in both the military and civilian flying populations. It is the leading cause of death and premature, permanent disability of American males and females. In spite of tremendous progress regarding CAD therapy, about 50% of initial and recurrent acute events are fatal. Initial symptoms may include incapacitating angina, altered consciousness or sudden death. Heat stress, hypoxia, high +Gz maneuvers and other features of the unique military cockpit/aircraft environment may provoke ischemia in individuals with pre-existing coronary artery lesions.
Clinically significant CAD is defined as one or more lesions with >50% stenosis (diameter reduction) by coronary angiography. In the clinical literature, such disease is nearly always symptomatic, since it would rarely be identified otherwise. When treated medically, patients with this degree of disease are reported to show >5% per year annual cardiac event rates in favorable prognostic subgroups. Although the term significant coronary artery disease (SCAD) has historically also been applied to aviators discovered to have a maximal stenosis >50%, event rates encountered in the clinical population may not accurately predict prognosis in the younger and relatively healthier aviator population with asymptomatic disease.
To evaluate the actual risk associated with asymptomatic CAD, the US Air Force Aeromedical Consultation Service (ACS) analyzed initial and long-term follow-up data from approximately 1,500 asymptomatic military aviators with coronary angiography. For aviators with SCAD as defined above, average annual cardiac event rates exceeded 2.5% per year at 2, 5 and 10 years of follow-up. To further stratify risk, the SCAD group was divided into two subsets of SCAD severity, SCAD50-70 (worst lesion 50-70%) and SCAD>70 (worst lesion >70%). Detailed examination of the SCAD50-70 subset revealed that extent of disease (aggregate of lesions) at the time of index coronary angiography identified low-risk versus high-risk subjects. Aggregate of lesions is the arithmetic sum of all graded lesions, e.g. 60% lesion + 20% lesion + 30% lesion = aggregate of 110%. Aggregate <120% identified a low-risk SCAD50-70 subgroup with an average annual event rate <1% per year at ten years of follow-up. Subsequent analysis of the group with minimal coronary disease (MCAD, defined at that time as maximal stenosis <50%) also showed that aggregate was significantly predictive of events.
Because aggregate successfully stratified cardiac risk, the combined SCAD50-70 and MCAD groups, consisting of all aviators with a maximal lesion <70%, was submitted to a similar analysis. In this combined group, aggregate was highly predictive of event-free survival (p<0.00004). Specifically, aviators with an aggregate <50% showed an average annual event rate of 0.6% per year, while those with an aggregate >50% but <120% had an average annual event rate of 1.1% per year. (Although a rate of 1.1% slightly exceeds the 1%/yr threshold, the data reviewed predated the routine use of lipid-lowering therapy for secondary prevention, which would be expected to reduce events by an additional 30-40%.)
By way of comparison, clinical literature reports annual cardiac event rates of about 0.5% per year in general population studies of apparently healthy asymptomatic males aged 35-54 years; follow-up studies of male subjects with normal coronary angiography, who in most cases presented with a chest pain syndrome, report annual cardiac event rates of 0.2-0.7% per year. Annual cardiac event rates in apparently healthy USAF aviators have been reported as <0.15% per year for males aged 35-54 years.
From this database analysis, the current aeromedical classification of asymptomatic CAD is based on aggregate, with minimal CAD (MinCAD) defined as an aggregate <50%, and moderate CAD (ModCAD) defined as an aggregate >50% but <120%. Significant CAD is now defined as an aggregate >120%. Maximum lesion >70% is also considered SCAD.
Graded lesions in the left main coronary artery are treated more cautiously due to the unfavorable prognosis associated with left main disease. Left main coronary artery lesions <50% stenosis are defined as ModCAD, assuming that other criteria for that classification are met. Left main lesions >50% stenosis are considered SCAD.
An additional category of CAD was more recently identified from the ACS database – luminal irregularities (LI) only. LI only describes coronary angiography with irregular arterial edges due to atherosclerotic plaque but less than gradable 10-20% stenosis (diameter reduction). LI only represents a subset of CAD with event rates higher than those with truly normal coronary angiography (smooth arterial edges). A review of the ACS database showed that aviators with LI only on coronary angiography had no events in the first five years after diagnosis. However, between 5 and 10 years follow-up, cardiac event rates were 0.54% per year compared to 0.1% per year for those with truly normal coronary angiography. This represents a risk similar to minimal CAD in the first five years of follow-up.
Aeromedical Concerns: The aeromedical concern is myocardial ischemia presenting as sudden cardiac death, acute myocardial infarction, stable or unstable angina or ischemic dysrhythmias, any of which could cause sudden incapacitation or significantly impair flying performance. At present, there is no reliable method of detecting asymptomatic progression of CAD short of frequent noninvasive monitoring, combined with periodic invasive testing.
Medical Work-up: Medical evaluation for coronary artery disease does not differ between aviators and non-aviators. Appropriate non-invasive and invasive tests need to be done to determine the diagnosis and extent of disease.
Aeromedical Disposition (military): For most cases, all three military services do not allow their pilots to fly after they have had a cardiac event, even if a lesion has been corrected by means of some procedure. In the US Air Force, a waiver may be considered for categorical duties (non high-performance aircraft) depending on the severity and extent of disease. All individuals with suspected CAD or CAD diagnosed locally are evaluated by their prospective military consultation services prior to a waiver being recommended. Necessary evaluation should include local work-ups, which indicate an aeromedical summary, abnormal test reports, and all associated films and tracings. All individuals with a waiver for MCAD will require repeat examination every year with a repeat cardiac catheterization performed every 3 years. These waiver considerations apply to asymptomatic aviators/aircrew who have not had a coronary artery revascularization procedure (e.g. stent, angioplasty, bypass surgery). Military pilots with SCAD are currently not granted waivers in any service.
Aeromedical Disposition (civilian): This condition makes up 3 of the FAA’s 15 Specifically Disqualifying Medical Conditions. These are Myocardial Infarction, Angina Pectoris and Coronary Artery Disease that is symptomatic or has required treatment. The FAA allows all the treatments that are currently available. This includes coronary bypass grafting, percutaneous transluminal angioplasty, stent insertion and atherectomy. Civilian airmen who wish to be granted medical certification must wait for 6 months prior to any attempt at gaining certification. For First and Second Class airmen the requirements are that they must have a 6 month post event cardiac catheterization, a current status evaluation by their treating physician, a maximal Bruce Protocol Stress test off beta blockers along with a radionuclide scan, a lipid panel and a fasting blood sugar. The airman is then presented to a panel of aviation cardiologists who review the case and make a recommendation. Third class private pilots are also required to wait 6 months after an event or treatment. They are only required to provide a current status from the treating physician, maximal Bruce Protocol Stress Test and the laboratory work. All medications are permitted in the treatment of CAD in civilian airmen with the exception of nitrates. Long acting nitrates are felt to mask the angina that could occur or lead to adverse side effects for aviation purposes. Airmen with ejection fractions of less that 35% are usually not granted certification.
Waiver Experience (military): A low performance aircraft only waiver may be considered for military aviators with MCAD. Any drug therapy, other than prophylactic aspirin, is disqualifying. Interventional treatment such as catheter based techniques or coronary artery bypass is also disqualifying in almost all cases. Aircrew with single lesions > 40%, left main disease, with an aggregate of lesions > 120%, or who have a history of myocardial infarction or angina are disqualified from flying. MCAD is also disqualifying when found in conjunction with left bundle branch block, ventricular tachycardia of any degree, or sustained SVT.
In the US Air Force, 52 aviators have applied for a flying waiver from May 2001 to present. Of that total, 37 were granted an unrestricted or categorical waiver for an acceptance rate of 71%.
Waiver Experience (civilian): For myocardial infarction as of calendar year 2005 there have been 440 first- 418 second- and 2,938 third-class airman granted medical certification. For percutaneous transluminal angioplasty as of calendar year 2005 there were 370 first- 286 second- and 1,682 third-class airmen medically certified. In those airmen who had one or more coronary stents inserted during the same time frame, there were 548 first-, 437 second- and 2,940 third-class airmen granted medical certification. In the case of coronary artery bypass grafting currently issued medical certificates for calendar year 2005 were 368 first-, 381 second- and 3,178 third-class airmen.
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April 23, 2007