Lipid Levels in ACS
Lipid Levels in ACS
Abstract & Commentary
By Michael H. Crawford, MD, Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco. Dr. Crawford is on the speaker's bureau for Pfizer. This article originally appeared in the June 2008 issue of Clinical Cardiology Alert. It was peer reviewed by Rakesh Mishra, MD, FACC. Dr. Mishra is Assistant Professor of Medicine, Weill Medical College, Cornell University; Assistant Attending Physician, NewYork-Presbyterian Hospital. Dr. Crawford serves on the speaker's bureau for Pfizer; he reports no financial relationships relevant to this field of study.
Source: Pitt B, et al. Lipid levels after acute coronary syndromes. J Am Coll Cardiol. 2008;51:1440-1445.
It has long been taught that lipid levels measured during hospitalization for an acute illness will be artificially low because of an acute-phase metabolic reaction. Consequently, many physicians wait weeks after hospitalization to measure lipids when they have returned to baseline levels and then start appropriate lipid lowering therapy. On the other hand, acute coronary syndrome (ACS) studies have suggested that the early administration of statins may improve outcomes in ACS. Thus, the investigators from the Limiting UNdertreatment of lipids in ACS with Rosuvastatin (LUNAR) study accessed lipid levels on days 1, 2, and 4 after the onset of ACS without statin therapy in 828 patients with ACS. The day 2 and 4 samples were taken after a 12-hour overnight fast. Patients were excluded for conditions that would obscure the results, such as lipid-lowering therapy within the previous four weeks. After considering excluded patients and those who did not get all three blood samples, 507 patients were included (212 STEMI, 176 non-STEMI, 119 UA). LDL-cholesterol decreased from 136 to 134 mg/dL, followed by an increase over the next two days to 142 mg/dL. Although these changes were statistically significant, their biologic significance is small. Similar changes were observed for total cholesterol and HDL-C, but triglyceride levels did not change significantly. An analysis of time-from-symptom onset to the blood samples in 12-hour increments showed the second day decrease persisted for up to 36 hours post-symptom onset, suggesting that the decrease was associated with hospital admission. The authors concluded that lipid levels change very little in the four days after admission for ACS and can be used to select appropriate lipid lowering therapy.
Another myth bites the dust. Or does it? Older studies of acute myocardial infarction patients showed drops in total cholesterol of 50%. The decreases observed in this study were in the 2%-5% range. More recent studies have suggested decreases of 7%-10%. So, it would appear that the decrease in lipid values is progressively less over the last 50 years. This may be due to newer therapies that reduce myocardial injury and lessen the acute phase response, or it may be due to new treatments that effect lipid levels, such as heparin and beta blockers. However, the values observed in this study may not have decreased much because the drug trial from which the data was derived excluded sicker patients who might have experienced greater drops. Also, it is possible that the biggest drop occurs between the onset of symptoms and hospital admission and we are only seeing the tail end of the drop after hospital admission. Unfortunately, there were no pre-event values and the post-event measurements stopped at day 4 when the patients were randomized to drug therapy, so we have no late baseline values.
The time-from-symptom onset to the first blood draw data suggest that hospital admission itself causes the small decrease in lipid values observed. This could be because of changes in diet, withholding food for tests, and IV fluids. Since these changes are biologically meaningless, it makes sense to take a blood sample soon after admission and then start empiric statin therapy. Some believe high-dose statins should be used early in the course of ACS regardless of the cholesterol levels, but knowledge of the pre-drug levels will be of value later when dosing adjustments can be made without stopping therapy. I have had several patients on high dose statins in the hospital without baseline values and, when they arrive in clinic six weeks later, their LDL-C is < 20 md/dL. This is probably too low, and such extremes can be avoided if the admission levels are taken into account and the statin dose is adjusted prior to or early after discharge.It has long been taught that lipid levels measured during hospitalization for an acute illness will be artificially low because of an acute-phase metabolic reaction. Consequently, many physicians wait weeks after hospitalization to measure lipids when they have returned to baseline levels and then start appropriate lipid lowering therapy. On the other hand, acute coronary syndrome (ACS) studies have suggested that the early administration of statins may improve outcomes in ACS.
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