Clinical Practice Guideline

for

HYPERLIPIDEMIA

Developed for the

Aerospace Medical Association

by their constituent organization

American Society of Aerospace Medicine Specialists

Overview: Although National Cholesterol Education Program (NCEP) guidelines have been available since 1988, these National Institutes of Health guidelines had been openly debated, particularly because of the lack of clinical trials showing that primary prevention of coronary disease was efficacious in reducing all-cause mortality. However, with the availability of the highly efficacious statin drugs, and with newer clinical trials showing a profound effect of those drugs in primary and secondary prevention of coronary disease, there is now widespread agreement that primary treatment of hyperlipidemia is indicated. With coronary disease representing the second most common cause of in-flight incapacitation (or most common, depending on the data referenced), prevention of coronary disease by control of hyperlipidemia is particularly indicated.

The patient should satisfy the following criteria for an accurate lipid profile determination: the patient should fast for 14 hours, with water or fat free fluids allowed; he or she should have been following a normal diet for the preceding two weeks; he or she should not have had an illness, operation, or injury during the preceding four weeks. While fasting is not required for total cholesterol or high-density lipoprotein (HDL) cholesterol levels, consumption of fat-containing foods will significantly affect triglyceride and therefore calculated low-density lipoprotein (LDL) levels.

Aeromedical Concerns: Hyperlipidemia itself is not disqualifying, but based on convincing evidence that lipid lowering results in a decreased risk of coronary heart disease, it should be treated seriously nonetheless. Waiver is not required for hyperlipidemia controlled by diet and exercise. Resin binding agents such as cholestyramine and colestipol may be prescribed by the flight surgeon without removal from flying duty, and once the potential for idiosyncratic reaction has been excluded; waiver is not required. Statins appear to be the most effective medications in the flying pharmacopoeia; lovastatin and pravastatin are waiverable in the military for full aviation duties. Patients on lovastatin or gemfibrozil require liver function tests at least quarterly.

In civil aviation in the USA abnormal lipids is not a ground for denying medical certification. A Lipid Panel is required on all cardiovascular evaluations for a majority of cardiac conditions where medical certification is granted. This includes myocardial infarction, coronary artery disease that has been treated, CABG, PTCAs, and stent insertions. If the cholesterol or LDL are elevated this could be a discriminator in case where the granting of medical certification is questionable.

Medical Work-up: In the military service at present, lipid guidelines have been adapted from NCEP recommendations, which have been altered where necessary to fit into the physical exam process. Since diabetes is grounding, it is not listed among risk factors. In the US Air Force, a fasting lipid panel is obtained at five-year intervals. At any age, a Step I diet should be recommended for an LDL greater than or equal to 130 mg/dl. A Step 1 diet involves an intake of saturated fat constituting 8-10% of total calories, and less than 300 mg of cholesterol per day. At the first lipid panel upon reaching age 40, an LDL greater than or equal to 190 mg/dl, or an LDL greater than or equal to 160 mg/dl together with one or more risk factors, should prompt a repeat fasting lipid panel for confirmation. Risk factors consist of: a family history of coronary disease, with an event earlier than age 55 in a first degree male relative or earlier than age 65 in a first degree female relative; current smoking; hypertension, whether treated or not; a low HDL cholesterol of less than 35 mg/dl. A high HDL, defined as greater than or equal to 60 mg/dl, is considered a negative risk factor and should be subtracted from any sum of positive risk factors. If the repeat lipid study reveals an average LDL greater than or equal to 190 mg/dl, or 160 mg/dl with one or more risk factors, the flight surgeon should prescribe a Step II diet, with saturated fat less than 7% of total calories, and less than 200 mg per day of cholesterol. Lipid panels should be repeated at three months for reinforcement, and at six months for reassessment. If LDL is not under threshold values at six months, pharmacologic therapy should be begun with lovastatin, resin-binders, or combination therapy, all of which are acceptable for unrestricted military Flying Class II waiver after a 30-day ground trial. Gemfibrozil, considered a minor hypolipidemic agent, is waiverable for military Flying Class IIA duties alone or in combination with resin-binders. Combination therapy with gemfibrozil and lovastatin is not waiverable due to an unacceptable incidence of myopathy. Lipid panels should be repeated again at three and six months, with a preferred target of 160 mg/dl, or 130 mg/dl with risk factors. Continued elevation of the LDL suggests either difficulty with compliance or a resistant problem. In either case, the military aviator whose LDL after six months of therapy remains above 190 mg/dl, or 160 mg/dl with risk factors, should be evaluated with an exercise tolerance test and coronary fluoroscopy, with the results sent to the ACS.

Aeromedical Disposition (military and civilian): The aviator must show an acceptable response to a standard dose of drug, without unacceptable side effects. It is left up to the treating physician to monitor tests such as liver function in statins.

Waiver Experience (military): Waivers can be considered in most cases of hyperlipidemia in the military services. The type of waiver granted depends on the method of control, described in the preceding paragraphs.

Waiver Experience (civilian): All medications that are used in the treatment of hyperlipidemia are acceptable with requirement for waiver in civil aviation. Waivers are not required for elevated cholesterol or LDL or low HDL. It is likely that some evidence of successful treatment would be required in any civil airman who had a triglyceride level elevated above 1000 mg/dl.

References:

Summary of the second report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation, and treatment of high blood cholesterol in adults (Adult Treatment Panel II). JAMA, 1993;269:3015-23.

Shepherd J, Cobbe SM, Ford I, et al. Prevention of coronary heart disease with pravastatin in men with hypercholesterolemia. N Engl J Med, 1995;333:1301-7.

Scandinavian Simvastatin Survival Study Group. Randomised trial of cholesterol lowering in 4444 patients with coronary heart disease: the Scandinavian Simvastatin Survival Study (4S). Lancet, 1994;344:1383-9.

July 9, 2002