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The Authors Respond
Submit responseWe appreciate Dr. Nichols’ comments and agree that the agents studied in the Armed Forces Regression Study (AFREGS), particularly niacin, have not traditionally been well tolerated. With newer formulations of niacin and proper patient instruction, much improved compliance has been achieved(1). Until newer agents have undergone more rigorous study and review, niacin remains the single most effective agent to raise high density lipoprotein cholesterol (HDL). Whether its well established clinical benefits are derived from changes in quantity or quality of HDL or low density lipoprotein cholesterol remains controversial, and unfortunately lipoprotein subtyping was not performed in the AFREGS population.
Though fibrinogen levels did not change with therapy, modulation of inflammation by study drugs cannot be excluded by such a small study. We examined fibrinogen and white blood cell count (WBC) in several subsets of patients in AFREGS and could not find evidence of any greater benefit in patients with increased inflammation, or evidence that levels of fibrinogen or WBC were significantly altered by therapy.
In terms of assessing atherosclerotic burden, we agree with Dr. Nichols that intravascular ultrasound (IVUS) is a tremendous advance and provides significantly better plaque characterization than angiography(2). It unfortunately remains slightly more invasive, is time consuming, and is not widely available. It is also important to note that despite the limits of angiography, the AFREGS results and the results of other quantitative coronary angiography studies do not dramatically differ in magnitude from recent studies using IVUS(3). In particular, in the REVERSAL study, a 1.4% difference in % obstructive volume was seen in comparing high and moderate dose statins(4). Using the suggested 2% progression of atherosclerosis in those patients not receiving final angiography in AFREGS, the difference in progression between treatment groups remains ~2% (0.6% reduction with combination therapy compared with a 1.5% progression in patients receiving placebo), with even stronger statistical significance.
The use of combination therapy without a statin, despite our favorable results, cannot be generally recommended for the secondary prevention of cardiovascular disease. The proven benefit for statins in the reduction of clinical events, including myocardial infarction, stroke, and death is too significant to totally disregard. Guidelines mainly recommend targeted HDL treatment if goal levels are not achieved with diet, lifestyle, and statins(5). For primary prevention, however, the data are less clear and further studies will be necessary to establish the most effective treatment strategy.
Richard A. Krasuski, M.D. Wilford Hall Medical Center San Antonio, TX
Edwin J. Whitney, M.D. Heart and Vascular Institute of Texas San Antonio, TX
1. Knopp RH. Evaluating niacin in its various forms. Am J Cardiol. 2000;86(12A):51L-56L. 2. Schoenhagen P, Nissen SE. Coronary atherosclerotic disease burden: an emerging endpoint in progression/regression studies using intravascular ultrasound. Curr Drug Targets Cardiovasc Haematol Disord. 2003;3(3):218- 26. 3. Thompson GR. Angiographic trials of lipid-lowering therapy: end of an era? Br Heart J. 1995;74(4):343-7. 4. Nissen SE, Tuzcu EM, Schoenhagen P, et al. Effect of intensive compared with moderate lipid-lowering therapy on progression of coronary atherosclerosis: a randomized controlled trial. JAMA. 2004;291(9):1071-80. 5. Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation. 2002;106(25):3143-421.
Conflict of Interest:
Consultant,Honoraria, and Grants received (Krasuski)
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Biochemical sequelae when increasing HDL levels
Submit responseWhitney et al (1) report on a treatment regimen utilizing gemfibrozil, with staged introduction of niacin and cholestyramine, which was targeted to increase the HDL cholesterol in their study population, which had relatively normal LDL cholesterol levels (3.3 mmol/L on average). Their results show an improvement in the global angiographic stenosis in the study group, and they emphasize the association with a 36% increase in HDL cholesterol. However, the treatment regime had an effect on the overall plasma lipid profile. Concomitant with the rise in the HDL cholesterol there was also a decrease in total cholesterol (20%), LDL cholesterol (26%) and triglycerides (50%) which was to be expected from the known effects of these drugs. Whitney et al further indicate that there was a significantly greater increase in fasting glucose in their treatment arm – an average increase of 17.6%. This increase in the fasting glucose level leads us to believe that perhaps one in seven of the patients in the treatment arm might have developed pre-diabetes (fasting glucose 6.1-7.0 mmol/L), a condition which leads to an increased risk of Type 2 diabetes, heart attack and stroke. Indicating the number of patients (if any) who became pre-diabetic in the treatment group would facilitate a better understanding of the risk benefit ratio of their treatment. The article also reports incorrect fasting blood glucose concentrations in Table 1, when the concentration is reported in SI units (81 and 82 mg/dL is 4.5 mmol/L, not 2.1 mmol/L as reported). The biochemical profile at the 50-week follow-up showed a 36% increase in the HDL cholesterol level in the treatment arm. Since the lipid levels were measured at monthly intervals, it would be useful to report the time course of HDL improvements in the treatment group. Brousseau et al (2) recently reported a similar 46% increase in HDL cholesterol after only one month of treatment with torcetrapib (an inhibitor of cholesteryl ester transfer protein). Reporting the biochemical changes at earlier times in the Whitney et al study would facilitate the comparison of these two treatment strategies.
References:
1. Whitney EJ, Krasuski RA, Personius BE, Michalek JE, Maranian AM, Kolasa MW, et al. A randomized trial of a strategy for increasing high- density lipoprotein cholesterol levels: Effects on progression of coronary heart disease and clinical events. Ann Intern Med. 2005; 142: 95-104.
2. Brousseau ME, Schaefer EJ, Wolfe ML, Bloedon LT, Digenio AG, Clark RW, et al. Effects of an inhibitor of cholesteryl ester transfer protein on HDL cholesterol. N Engl J Med. 2004; 350: 1505-15.
Conflict of Interest:
None declared
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HDL Elevation and Plaque Burden
Submit responseWhitney and colleagues (1) provide an interesting glimpse into the agents that elevate high-density lipoprotein (HDL) cholesterol levels in the pre- statin era. The combination of a fibrate, niacin and a bile-acid sequestrant increased plasma HDL levels by 37%. This was associated with a beneficial impact on atherosclerotic burden and a combination of clinical end points. Careful follow-up resulted in effective compliance with both dietary modification and consumption of pharmacologic agents that have traditionally been associated with high intolerability rates.
The reported effect on plaque burden should be interpreted with caution. Atherosclerotic extent was measured by coronary angiography, using a global estimate of severity and qualitative assessment. This result should be viewed in the context of previous reports that infusion of reconstituted HDL promoted rapid atherosclerotic regression, as assessed by intravascular ultrasound, a more accurate measure of plaque burden. (2) Further, when patients who did not proceed to follow-up angiography were included in the analysis it was assumed that there was no change in their plaque burden. This is in contrast to the stated assumption that standard medical care during this period would be associated with a 2% progression in angiographic stenosis. This assumption should be applied to the analysis.
It is premature to dismiss the concept that these agents had no impact on inflammation. While fibrinogen levels were not altered, CRP was not reported. It is likely that the beneficial effects of fibrate therapy results, in part, from the anti-inflammatory sequelae of their interaction with the PPAR-alpha receptor. (3)
Strategies to raise plasma HDL are of immense interest. It remains unclear whether its quantity or quality is more important. Ultimately, we need to consider that whatever therapeutic options are developed to promote HDL, they will need to be tested in the setting of statin therapy.
References
1. Whitney EJ, Krasuski RA, Personius BE, Michalek JE, Maranian AM, Kolasa MW, et al. A randomised trial of a strategy for increasing high-density lipoprotein cholesterol levels: Effects on progression of coronary heart disease and clinical events. Ann Intern Med. 2005;142:95-104.
2. Nissen SE, Tsunoda T, Tuzcu EM, Schoenhagen P, Cooper CJ, Yasin M, et al. Effect of recombinant ApoA-I Milano on coronary atherosclerosis in patients with acute coronary syndromes: a randomised controlled trial. JAMA. 2003;290:2292-300.
3. Pineda Torra I, Gervois P and Staels B. Peroxisome proliferator- activated receptor alpha in metabolic disease, inflammation, atherosclerosis and aging. Curr Opin Lipidol. 1999;10:151-9.
Conflict of Interest:
None declared