Potential Influence of Timing of Low-Density Lipoprotein Cholesterol Evaluation in Patients with Acute Coronary Syndrome

Michele A. Faulkner, Pharm.D., Daniel E. Hilleman, Pharm.D., Christopher J. Destache, Pharm.D., and Aryan N. Mooss, M.D.

Disclosures

Pharmacotherapy. 2001;21(9) 

In This Article

Abstract and Introduction

Objective. To determine the significance of timing of low-density lipoprotein (LDL) cholesterol evaluation in patients with chest pain as it relates to subsequent National Cholesterol Education Program (NCEP) treatment decisions.
Design. Prospective, observational study.
Setting. A university-affiliated tertiary care hospital.
Patients. Sixty-two patients with coronary heart disease who were not receiving lipid-lowering therapy and whose LDL levels were obtained 25-48 hours after onset of chest pain.
Intervention. We evaluated laboratory test results of patients with chest pain admitted to the cardiac care unit to determine risk to patients when LDL levels obtained inappropriately are used to make decisions regarding antihyperlipidemic therapy.
Measurements and Main Results. Inpatient and outpatient LDL levels were compared, and changes in NCEP treatment decisions analyzed. Differences between inpatient and outpatient LDL levels were significant (p<0.05), which frequently resulted in changes in therapy using the NCEP guidelines. The LDL levels of most inpatients were consistent with NCEP goals for patients with coronary heart disease, whereas the outpatient levels showed a need for drug therapy.
Conclusion. Lipid values obtained 25-48 hours after hospital admission in patients with acute coronary syndromes do not represent baseline values and may significantly alter the treatment approach; thus, they should not be used to direct drug therapy.

Hyperlipidemia is a major risk factor for development of coronary heart disease (CHD). Exercise, smoking cessation, and drug therapy are treatment strategies to reduce the prevalence of hyperlipidemia. Which therapeutic option or options should be used depends on blood cholesterol values and concomitant risk factors such as age, obesity, tobacco use, diabetes, hypertension, and family history of coronary artery disease.[1] The current version of the National Cholesterol Education Program (NCEP) expert panel recommendations for treatment of adults with elevated blood cholesterol defines a low-density lipoprotein (LDL) cholesterol level of 100 mg/dl or less as an appropriate goal for people with existing coronary heart disease.[1] In this population, drug treatment is recommended for those with LDL levels of 130 mg/dl or greater.

Several identifiable barriers prevent implemen-tation of appropriate therapy for hyperlipidemia. Physicians report that despite the widely accepted belief that treatment for this condition is important to prevent adverse cardiovascular events, many believe they lack ability to significantly alter patient behavior. Some physicians also believe they are not prepared to provide appropriate and effective counseling.[2] Other barriers, such as time limitations, patient's perceived lack of desire to change, and lack of communication among physicians in the inpatient and outpatient settings have been cited.[2,3] Another potential barrier to imple-menting therapy is inappropriate evaluation of serum lipids in patients with acute coronary syndrome.

Studies have demonstrated that LDL levels begin to decline within hours of an acute ischemic cardiac event and continue to do so, reaching significantly reduced levels in the days following.[4,5,6,7,8,9,10] Reasons for this decrease are not completely understood. Myocardial injury precipitates an acute-phase response that results in increased cholesterol synthesis. A concomitant increase in activity of the LDL receptor and subsequent heightened rate of LDL catabolism may be responsible for the dip in LDL levels seen in patients with acute coronary syndrome.[5] These alterations typically are significant enough to complicate patient evaluations and subsequent decisions about starting appropriate lipid-lowering therapy. Timing of laboratory assessment of serum lipids for a patient hospitalized because of an ischemic event is therefore crucial in determining the appropriate method of treatment for hyperlipidemia. The American College of Cardiology/American Heart Association (ACC/AHA) guidelines for lipid analysis after myocardial infarction specify that lipoprotein analysis be performed within 24 hours of onset of chest pain.[11] When this goal is not met, therapy may be based on a previous LDL value or on a value that was determined after serum lipid levels had returned to normal. Study outcomes regarding the appropriate amount of time that must elapse before lipoprotein levels have returned to baseline range from 10 days to several months.[4,5,9,12] The ACC/AHA guidelines recommend a minimum waiting period of 4 weeks after myocardial infarction before lipid levels are evaluated.[11] When these guidelines are not followed, patients may be at risk. Misleading laboratory values can mask patient eligibility for therapy and cause necessary treatment to be withheld.

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