Beneficial effects of cholesterol-lowering therapy on the coronary endothelium in patients with coronary artery disease

Emerging concepts: angiotensin-converting enzyme inhibition in coronary artery disease

Angiotensin-converting enzyme (ACE) inhibitors have played a highly beneficial role in the therapy of hypertension and congestive heart failure. Detailed analysis of some of the heart failure trials in patients with these diseases has uncovered unexpected benefits in the prevention of cardiovascular events. Paralleling these observations are the rapidly accruing basic studies describing important molecular and cellular effects of these agents. For example, ACE inhibition will prevent stimulation of smooth muscle cell angiotensin II receptors, thereby blocking both contractile and proliferative actions. In addition, ACE inhibition of kininase II inhibits the breakdown of bradykinin. Bradykinin is a direct stimulant of nitric oxide release from the intact endothelial cell. Thus, at the cellular level ACE inhibition shifts the balance of ongoing mechanisms in favor of those promoting vasodilatory, antiaggregatory, antithrombotic, and antiproliferative effects. These effects underlie the potential benefits of ACE inhibition in the therapy of coronary artery disease and atherosclerosis.

Pathogenic mechanisms of atherosclerosis: effect of lipid lowering on the biology of atherosclerosis

Numerous trials have demonstrated that cholesterol-lowering therapy leads to marked reductions in cardiovascular and overall mortality and in the need for coronary revascularization. Angiographic regression trials have shown that cholesterol lowering can reduce progression and, in some instances, achieve regression of coronary atherosclerotic lesions. However, recent studies have contradicted the traditional view that the clinical course of coronary artery disease is closely linked to the severity of coronary artery stenosis. It is now apparent that stenoses responsible for myocardial infarction or unstable angina are typically mild rather than severe. These observations suggest that regression may not be the principal mechanism by which cholesterol lowering affects cardiovascular risk. Two mechanisms---plaque stabilization and improved endothelial function-have been examined in this regard. Basic studies suggest that cholesterol lowering favorably alters those features of atherosclerosis that promote plaque stability. Recent clinical studies have clearly established that aggressive lipid-lowering therapy improves endothelial function and reduces myocardial ischemia in patients with hypercholesterolemia.

Review of cholesterol-lowering therapy: coronary angiographic and events trials

Coronary angiographic trials have demonstrated that the lowering of cholesterol slows the progression of atherosclerosis, enhances atherosclerotic regression, limits the formation of new lesions, and reduces the incidence of coronary events. Atherosclerotic progression has been shown to be associated with an increased risk of cardiac death, cardiac death plus nonfatal myocardial infarction (MI), and all coronary events. Most of the atherosclerotic regression trials were too small and of too short duration to demonstrate a significant difference in hard coronary events between patients receiving cholesterol-lowering intervention and controls. However, when data from these studies were pooled, total mortality was found to be reduced by 26% and the rate of nonfatal MI by 39% in actively treated patients. The first events trial to demonstrate clearly a reduction in overall mortality was the Scandinavian Simvastatin Survival Study (4S), in which lowering of serum cholesterol in patients with coronary artery disease (CAD) and hypercholesterolemia also reduced coronary mortality, fatal and nonfatal MI, sudden cardiac death, and the need for revascularization. Reductions in major coronary events were seen consistently in all subgroups of patients studied and regardless of concomitant therapy with aspirin, beta blockers, or calcium antagonists. Further evidence of the benefit of cholesterol-lowering therapy was provided by the West of Scotland Coronary Prevention Study (WOSCOPS), which evaluated men with hypercholesterolemia but no history of CAD. Those receiving active treatment had less overall mortality, lower risk of definite nonfatal MI or death from definite or suspected CAD, and less need for revascularization. The Cholesterol and Recurrent Events (CARE) Study recently showed that lipid-lowering therapy is also beneficial in CAD patients with less severe dyslipidemia.

Effects of short-term reduction in serum cholesterol with simvastatin in patients with stable angina pectoris and mild to moderate hypercholesterolemia

To evaluate the effects of short-term cholesterol-lowering treatment on myocardial effort ischemia, 22 patients with stable effort ischemia and mild to moderate hypercholesterolemia (low density lipoprotein [LDL] cholesterol 160 to 220 mg/dl) were randomly allocated at baseline (TO) in 2 groups. Group A included 12 patients treated with simvastatin 10 mg bid; group B included 10 patients treated with placebo. All patients underwent a treadmill electrocardiography (ECG) test; total cholesterol, HDL and LDL cholesterol, triglycerides, plasma, and blood viscosity were measured. All tests were repeated after 4 and 12 weeks. For 18 of the same patients (11 taking simvastatin, 7 receiving placebo), forearm strain-gouge plethysmography was performed at baseline and after 4 weeks, both at rest and during reactive hyperemia. At 4 and 12 weeks, group A showed a significant reduction in total cholesterol (p <0.05) and LDL (p <0.05), with unchanged HDL, triglycerides, blood, and plasma viscosity. Effort was unmodified, ST-segment depression at peak effort and ischemic threshold were significantly improved after 4 and 12 weeks (all p <0.05) with unchanged heart rate x systolic blood pressure product. A significant increase in the excess flow response to reactive hyperemia was detected in group A (p <0.03); group B showed no changes in hematochemical and ergometric parameters. These data suggest that cholesterol-lowering treatment is associated with an improvement in myocardial effort ischemia; this might be explained by a more pronounced increase of coronary blood flow and capacity of vasodilation in response to effort.

Reduction of transient myocardial ischemia with pravastatin in addition to the conventional treatment in patients with angina pectoris. REGRESS Study Group

BACKGROUND

Lipid-lowering therapy reduces cardiac morbidity and mortality. Less is known about its potential anti-ischemic effect.

METHODS AND RESULTS

In a 2-year prospective randomized placebo-controlled study, the effect of pravastatin 40 mg on transient myocardial ischemia was assessed. Forty-eight-hour ambulatory ECGs with continuous ST-segment analysis were performed in 768 male patients with stable angina pectoris, documented coronary artery disease, and serum cholesterol between 4 and 8 mmol/L (155 and 310 mg/dL). During the trial, patients received routine antianginal treatment. In the patients randomized to pravastatin, transient myocardial ischemia was present at baseline in 28% and after treatment in 19%; in the placebo group, it was found in 20% and 23% of the patients, respectively (P = .021 for change in percentage between two treatment groups; odds ratio, 0.62; 95% CI, 0.41 to 0.93). Ischemic episodes decreased by 1.23 +/- 0.25 (SEM) episode with pravastatin and by 0.53 +/- 0.25 episode with placebo (P = .047). Under pravastatin, the duration of ischemia decreased from 80 +/- 12 minutes to 42 +/- 10 minutes (P = .017) and with placebo, from 60 +/- 13 minutes to 51 +/- 9 minutes (P = .56). The total ischemic burden decreased from 41 +/- 5 to 22 +/- 5 mm.min in the pravastatin group (P = .0058) and from 34 +/- 6 to 26 +/- 4 mm . min in the placebo group (P = .24). Adjusted for independent risk factors for the occurrence of ischemia, the effect of pravastatin on the reduction of risk for ischemia remained statistically significant (odds ratio, 0.45; 95% CI, 0.22 to 0.91; P = .026).

CONCLUSIONS

In men with documented coronary artery disease and optimal antianginal therapy, pravastatin reduces transient myocardial ischemia.

Effect of ACE inhibitors on endothelial dysfunction: unanswered questions and implications for further investigation and therapy

Experimental studies have suggested that angiotensin-converting enzyme (ACE) inhibitors may have an important role in blocking the progression of and/or reversing endothelial dysfunction. The extrapolation of these experimental studies to the clinical situation has, however, been disappointing. Studies of forearm-mediated endothelial vasodilatation in patients with hypertension with captopril, enalapril, and cilazapril have been negative. The finding of the Trial in Reversing Endothelial Dysfunction (TREND) that the administration of quinapril to normotensive patients with coronary artery disease in part restores endothelial-mediated coronary vasodilation, as assessed by intracoronary administration of acetylcholine, has important implications for future therapy and raises several important questions. The differences in the TREND and previous studies of ACE inhibitors on endothelial dysfunction in patients with coronary artery disease and hypertension. Although in general there has been a good correlation between endothelial dysfunction as assessed by forearm flow and coronary endothelial dysfunction as assessed by acetylcholine, these vascular beds may be affected differently by therapeutic interventions, especially with an ACE inhibitor, which may affect shear stress and angiotensin II formation in different vascular beds differently. Third, one needs to question whether the effect of quinapril on coronary endothelial dysfunction is a class effect or unique to quinapril. It will be necessary to test the effectiveness of other ACE inhibitors on coronary endothelial dysfunction in humans before concluding that the beneficial effects of quinapril are due to a class effect.

Pravastatin reduces restenosis after coronary angioplasty of high grade stenotic lesions: results of SHIPS (SHIga Pravastatin Study)

We conducted a multicenter prospective, randomized, double-blind, placebo-controlled trial to test whether pravastatin, a hydroxymethyl glutaryl coenzyme A reductase inhibitor, can decrease restenosis after percutaneous transluminal coronary angioplasty (PTCA). Pravastatin 10 mg twice daily was begun at least 10 days prior to elective PTCA in patients with total cholesterol less than 280 mg/dl. The end-point was a between-group comparison of the frequency of restenosis defined as a more than 50% loss of the initial gain in diameter stenosis at the PTCA site at 3 months during follow-up by automated quantitative coronary arteriography. Of 207 patients randomly assigned to study groups, 139 patients underwent PTCA; 133 procedures were successful, and 124 patients underwent follow-up angiography at 3 months, and 179 lesions (85 pravastatin, 94 placebo) in 124 patients (62 pravastatin, 62 placebo) were analyzed. The two groups were comparable for baseline characteristics. Total cholesterol decreased by 19.6% in the pravastatin group (p < 0.001) but not in the placebo group. Although the restenosis rate was not different in the two groups (29.4% in pravastatin vs. 39.4% in placebo, p = 0.215) as a whole, it was reduced to about one fifth (8.8%) in the pravastatin group compared with 44.8% in the placebo group (p = 0.0011) when the comparison was restricted to high grade lesions (> or = 75% diameter stenosis, 34 lesions in pravastatin, 29 lesions in placebo). Pravastatin thus reduces restenosis after PTCA of high grade lesions.

Monotherapy with HMG-CoA reductase inhibitors and secondary prevention in coronary artery disease

Although thrombolytic drugs, percutaneous transluminal coronary angioplasty, and coronary artery bypass grafting have provided major advances in the treatment of coronary artery disease, the use of lipid-lowering drugs for secondary prevention has significantly reduced cardiovascular events in the population with coronary artery disease. Secondary prevention trials using HMG-CoA reductase inhibitors include the Familial Atherosclerosis Treatment Study (FATS), the Monitored Atherosclerosis Regression Study (MARS), the Canadian Coronary Atherosclerosis Intervention Trial (CCAIT), the Asymptomatic Carotid Artery Progression Study (ACAPS), the Multi Anti-Atheroma Study (MAAS), the Scandinavian Simvastatin Survival Study (4S), the Pravastatin Limitation of Atherosclerosis in Coronary Arteries (PLAC I), the Regression Growth Evaluation Statin Study (REGRESS), the Pravastatin Multinational Study, and the Pravastatin, Lipids, and Atherosclerosis in Carotids (PLAC II). Mean changes from baseline of lipid fractions in these trials included: total cholesterol 18 to 35% reduction; low-density lipoprotein (LDL) cholesterol 26 to 46% reduction; high-density lipoprotein (HDL) cholesterol 5 to 15% increase; and triglyceride 7 to 22% reduction. Angiographic regression or lack of progression was statistically demonstrated in the FATS, MARS, CCAIT, MAAS, PLAC I, and REGRESS trials. Cardiovascular events decreased 25 to 92% in all trials, and there was a significant reduction in both cardiovascular and total mortality in the 4S. The greater reduction in cardiovascular events than in anatomic changes suggests that the HMG-CoA reductase inhibitors stabilized the surface of plaques. Monotherapy with HMG-CoA reductase inhibitors provides the clinical opportunity to modify the natural history of coronary artery disease.

Angiotensin-converting enzyme inhibition with quinapril improves endothelial vasomotor dysfunction in patients with coronary artery disease. The TREND (Trial on Reversing ENdothelial Dysfunction) Study

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors may exert some of their benefits in the therapy of hypertension, congestive heart failure, and acute myocardial infarction by their improvement of endothelial dysfunction. TREND (Trial on Reversing ENdothelial Dysfunction) investigated whether quinapril might improve endothelial dysfunction in normotensive patients with coronary artery disease and no heart failure, cardiomyopathy, or major lipid abnormalities so that confounding variables that affect endothelial dysfunction could be minimized.

METHODS AND RESULTS

Using a double-blind, randomized, placebo-controlled design, we measured the effects of quinapril (40 mg daily) on coronary artery diameter responses to acetylcholine using quantitative coronary angiography. The primary response variable was the net change in the acetylcholine-provoked constriction of target segments between the baseline (prerandomization) and 6-month follow-up angiograms. The constrictive responses to acetylcholine were comparable in the placebo (n = 54) and quinapril (n = 51) groups at baseline. After 6 months, only the quinapril group showed significant net improvement in response to incremental concentrations of acetylcholine (4.5 +/- 3.0% [mean +/- SEM] versus -0.1 +/- 2.8% at 10(-6) mol/L and 12.1 +/- 3.0% versus -0.8 +/- 2.9% at 10(-4) mol/L, quinapril versus placebo, respectively; overall P = .002).

CONCLUSIONS

TREND shows that ACE inhibition with quinapril improved endothelial dysfunction in patients who were normotensive and who did not have severe hyperlipidemia or evidence of heart failure. These benefits of ACE inhibition are likely due to attenuation of the contractile effects and superoxide-generating effects of angiotensin II and to enhancement of endothelial cell release of nitric oxide secondary to diminished breakdown of bradykinin.

Atherosclerosis and the vascular biology of aging

With advancing age, a series of structural, architectural and compositional modifications take place in the vasculature. The diameter of the vessels tends to increase, and thickening of intimal and medial layers is often observed. In the subendothelial space, blood-derived leukocytes and an increased amount of "activated" smooth muscle cells are present. Extracellular matrix accumulates and becomes particularly rich in glycosaminoglycans. Collagen content increases, while elastin fibers appear progressively disorganized, thinner, and frequently fragmented. These changes in the normal architecture of the vessel wall, that could be referred to as "the vasculopathy of aging", are likely to be the consequence of adaptive mechanisms to maintain normal conditions of flow, mechanical stress and/or wall tension. Although many of these features are similar to the histological findings of the atherosclerotic vessels, atherosclerosis and age-related "vasculopathy" are two distinct phenomena. Nonetheless, several experimental observations in animal models suggest a special link between "the vasculopathy of aging" and atherosclerotic disease, and suggest a particular predisposition of the old vessel to develop the atherosclerotic lesion. Compared to vessels from young animals, older ones show a greater reactivity to mechanical injury and to chronic insults. This may reflect changes in the biology of the vessels that are "intrinsic" to the aging process. Indeed, aging affects the function and responsiveness of the endothelium and vascular smooth muscle cells. Endothelial permeability is increased with age, while ability to produce vasoactive substances declines. Smooth muscle cells from old individuals show a growth advantage over the young ones, and display an increased ability to migrate toward chemoattractants. Moreover, the accumulation of advanced glycation end products (AGEs) occurring with aging can trigger a series of cellular events, such as cellular oxidative stress, expression of leukocyte adhesion molecules, endothelial transmigration of monocytes, and smooth muscle cell chemotaxis, all considered important prelesional events in the atherogenesis process. Taken together, the changes occurring with aging, while unproven to initiate lesion formation per se, are likely to accelerate the development of the atherosclerotic plaque and contribute to increased severity of this disease in the elderly.

Prognostic significance of transient ischemic episodes: response to treatment shows improved prognosis. Results of the Total Ischemic Burden Bisoprolol Study (TIBBs) follow-up

OBJECTIVES

The Total Ischemic Burden Bisoprolol Study (TIBBS) follow-up examined cardiac event rates in relation to transient ischemia and its treatment.

BACKGROUND

It is unclear whether transient ischemia on the ambulatory electrocardiogram has prognostic implications in stable angina and whether medical treatment can improve the prognosis.

METHODS

The TIBBS trial was an 8-week, randomized, controlled comparison of the effects of bisoprolol and nifedipine on transient ischemic episodes in patients with stable angina pectoris. Of the 545 patients screened, 520 (95.4%) could be followed up. Rates of cardiac and noncardiac death, nonfatal acute myocardial infarction, hospital admission for unstable angina and need for coronary artery bypass graft surgery or percutaneous transluminal coronary angioplasty were recorded.

RESULTS

A total of 145 events occurred in 120 (23.1%) of 520 patients. Patients with more than six episodes had an event rate of 32.5% compared with 25.0% for patients with two to six episodes and 13.2% for patients with less than two episodes (p < 0.001). Hard events (death, acute myocardial infarction, hospital admission for unstable angina pectoris) were more frequent in patients with two or more ischemic episodes (12.2% vs. 4.7%, p = 0.0049). Patients with a 100% response rate of transient ischemic episodes during the TIBBS trial had a 17.5% event rate at 1 year compared with 32.3% for non-100% responders (p = 0.008). Patients receiving bisoprolol during the TIBBS tria had a lower event rate (22.1%) at 1 year than patients randomized to nifedipine (33.1%, p = 0.033).

CONCLUSIONS

In patients with stable angina pectoris, frequent episodes of transient ischemia are a marker for an increased event rate. A 100% response to medical treatment reduces the event rate. The greater reduction of ischemia with bisoprolol than nifedipine during the TIBBS trial translated into an improved outcome at 1 year.

Direct measurement of serum low-density lipoprotein cholesterol in patients with acute myocardial infarction on admission to the emergency room

Measurement of low-density lipoprotein cholesterol during acute myocardial infarction in nonfasting patients on initial presentation to an emergency room by any of 3 methods (ultracentrifugation, immunoseparation, or the Friedewald estimate), identifies patients eligible for antilipemic interventions. Although slightly less sensitive, the conventional Friedewald estimate of low-density lipoprotein cholesterol levels provides clinicians good correlation with ultracentrifugation.

LDL-Apheresis Atherosclerosis Regression Study (LAARS). Effect of aggressive versus conventional lipid lowering treatment on coronary atherosclerosis

BACKGROUND

Intensive lipid lowering may retard the progression of coronary atherosclerosis. LDL-apheresis has the potential to decrease LDL cholesterol to very low levels. To assess the effect of more aggressive lipid lowering with LDL-apheresis, we set up a randomized study in men with hypercholesterolemia and severe coronary atherosclerosis.

METHODS AND RESULTS

For 2 years, 42 men were treated with either biweekly LDL-apheresis plus medication or medication alone. In both groups a dose of simvistatin of 40 mg per day was administered. Baseline (mean+/-SD) LDL cholesterol was 7.8+/-1.9 mmol x L(-1) and 7.9+/-2.3 mmol x L(-1) in the apheresis and medication groups, respectively. The mean reduction in LDL cholesterol was 63% (to 3.0 mmol x L(-1)) and 47% (to 4.1 mmol x L(-1)), respectively. Primary quantitative coronary angiographic end points were changes in average mean segment diameter and minimal obstruction diameter. No differences between the apheresis and medication groups were found in mean segment diameter (-0.01+/-0.16 mm versus 0.03+/-0.16 mm, respectively) or in minimal obstruction diameter (0.01+/-0.13 mm versus 0.01+/-0.11 mm, respectively), expressed as means per patient. On the basis of coronary segment, mean percent stenosis of all lesions showed a tendency to decrease; only in the apheresis group more minor lesions disappeared in comparison to the medication group. On bicycle exercise tests, the time to 0.1 mV ST-segment depression increased significantly by 39% and the maximum level of ST depression decreased significantly by 0.07 mV in the apheresis group versus no changes in the medication group.

CONCLUSIONS

Two years of lipid lowering both with medication alone or LDL-apheresis with medication showed angiographic arrest of the progression of coronary artery disease. However, more aggressive treatment induced functional improvement, which may precede anatomic changes.

Clinical pharmacologic concepts for the rational selection and use of drugs for the management of dyslipidemia

The long-term clinical benefits of lowering serum lipid levels have been demonstrated in multiple clinical trials in recent years. These include coronary artery disease regression and decreases in the incidence of adverse clinical events, such as myocardial infarction or refractory ischemia. Reductions in overall mortality have also been demonstrated. The health risk of dyslipidemia led the National Cholesterol Education Program expert panel to recommend intervention to bring low-density lipoprotein cholesterol values to within certain goal levels through a variety of interventions. This article reviews the available pharmacologic agents and compares their efficacy, safety, and cost-effectiveness.

Effect of short-term regression of atherosclerosis on reactivity of carotid and retinal arteries

BACKGROUND AND PURPOSE

This study tested the hypothesis that functional abnormalities of carotid and ocular arteries may improve after short-term regression of atherosclerosis, before regression of structural abnormalities.

METHODS

We examined effects of short-term dietary treatment of atherosclerosis on carotid and ocular vascular responses to serotonin and to platelet activation by collagen in vivo. Three groups of monkeys were studied: normal cynomolgus monkeys, monkeys fed an atherogenic diet for 34 months, and atherosclerotic monkeys that were fed a regression diet for 8.6 +/- 1.1 months (mean +/- SE). We measured changes in carotid blood flow (using a Doppler probe), retinal blood flow (using microspheres), and diameter of the internal carotid artery (using quantitative angiography). Endothelium-dependent relaxation to acetylcholine was studied in rings of internal carotid artery in vitro.

RESULTS

Carotid blood flow increased in response to both serotonin and collagen in normal monkeys, decreased in response to both agents in atherosclerotic monkeys, and was restored toward normal after regression. Serotonin had little effect on retinal blood flow in normal monkeys and produced a marked decrease in retinal blood flow in atherosclerotic monkeys; the vasoconstrictor response to serotonin was reduced after regression. Activation of platelets by collagen increased blood flow in normal monkeys, decreased blood flow in atherosclerotic monkeys, and had little effect after regression. Alterations in responses of the internal carotid artery were consistent with changes in carotid and ocular blood flow. Endothelium-dependent relaxation in vitro was impaired by atherosclerosis and was restored toward normal by regression. There was no reduction in intimal area of the atherosclerotic lesion in common carotid and ophthalmic arteries from regression monkeys, despite a marked reduction in cholesteryl ester.

CONCLUSIONS

Within a few months of regression of atherosclerosis, endothelial function and hyperresponsiveness of carotid and ocular arteries to serotonin and platelet activation return toward normal. Functional improvement is associated with resorption of lipid from atherosclerotic lesions, but with little reduction in size of intimal lesions.

Cholesterol-lowering therapy: is there really a controversy?

Geurian concludes that recommendations for the management of hypercholesterolemia are difficult to make because a previously black and white issue is becoming "increasingly gray." Actually, it appears that the opposite is occurring. Our knowledge of atherogenesis, as well as the mechanisms by which thromboembolic events occur, continues to expand. We are gaining new insights into the mechanisms by which cholesterol-lowering therapy can prevent the development of coronary events. Newer cholesterol-lowering agents are more potent than those previously available and make substantial reductions more readily achievable. Finally, we are gaining a better understanding of the relative benefits of cholesterol-lowering therapy in various patient populations, although more work is needed, particularly in women and older patients. Cholesterol-lowering therapy has had an important positive impact on CHD, particularly in preventing recurrent events and reducing mortality when used as secondary prevention. Clearly, there are substantial numbers of patients who will benefit greatly from cholesterol-lowering drugs, and clinicans should not be dissuaded from providing this valuable form of drug therapy.

The 4S study. Implications for prescribing

This article discusses various aspects of cholesterol-lowering therapy using the HMG-CoA reductase inhibitor simvastatin in the light of the large Scandinavian Simvastatin Survival Study (4S). In 4S, patients with proven coronary heart disease (CHD) and plasma total cholesterol > 5.5 mmol/L (212 mg/dl) despite dietary measures received statin therapy or placebo for > or = 5 years. A significant mortality reduction was accomplished in those receiving the statin. Moreover, a significant decrease of nonfatal myocardial infarction and requirement for coronary bypass surgery or angioplasty was demonstrated, which will contribute to the cost-effectiveness of this well tolerated therapy. Plaque stabilisation and improvement of endothelial function are thought to be mediators of this therapeutic success. Responsible drug prescription in the post-4S era may result in the recognition and treatment of more patients with CHD. This is likely to be more beneficial than exhaustive efforts to completely achieve the goals of the most strict guidelines in the individual patient. In patients who carry the highest absolute risk for a recurrent event, aggressive drug therapy may be most justified. Reluctance to initiate lipid lowering drug therapy in patients with proven CHD should now be disputed.

Low-density lipoprotein apheresis versus lipid lowering drugs in the treatment of severe hypercholesterolemia: four years' experience

Elevated lipoprotein concentrations seem to be linked strongly in a dose dependent manner to an increased incidence of atherosclerosis. A total of 47 patients suffering from severe hyperlipidemia were matched to treatment with LDL apheresis (Baxter, Kaneka, Lipopak; 24 patients, aged 50.2 + or - 11.5 years), diet, and/or lipid-lowering drugs or with diet and lipid-lowering drugs only (23 patients, aged 48.8 + or - 11.8 years). After treatment periods of 49.8 + or - 13.4 months (apheresis group, 2,396 treatment sessions) and 38.6 + or - 15.1 months (drug group), the ensuing results revealed significant differences (p < 0.0001): -47.3% versus -12.1% for total cholesterol, -46.9% versus -21.8% for LDL, +8.4% versus +0.9% for HDL, -52.0% versus -13.1% for the LDL/HDL ratio, -36.4% versus - 16.2% for triglycerides, and -25.9% versus + 1.5% for lipoprotein (a). In the apheresis group, one patient died of myocardial infarction; in the drug group, there was one nonfatal myocardial infarction and the manifestation of coronary heart disease in 3 cases. There were no severe side effects in either group. All patients in the apheresis group responded to therapy. The present trial suggests that a continuing reduction in serum lipid concentrations may lower, in a dose dependent manner, the risk for development and progression of coronary heart disease. Regarding clinical and laboratory results, LDL apheresis seems to be safe, effective therapy for treatment of severe hyperlipidemia.

Drug therapy of severe hypercholesterolemia in patients with coronary artery disease

The beneficial effect of cholesterol-lowering therapy for secondary prevention in patients with coronary artery disease (CAD) is well established. The therapeutic goal in this situation is a low-density lipoprotein (LDL) cholesterol level of 100 mg/dl. Cholesterol-lowering therapy will not only lead to a reduction in the progression of lesions but also and probably more importantly will reduce lesion activation and rupture and improve endothelial vasomotor function. Depending on the underlying hyperlipoproteinemia, the first choice for single drug therapy is a bile acid-binding resin or a hepatic hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitor in isolated LDL hypercholesterolemia, and nicotinic acid, a fibric acid, or a HMG-CoA reductase inhibitor in combined hyperlipidemia. Combination therapy usually consists of a bile acid-binding resin with either an HMG-CoA reductase inhibitor, a fibric acid, or nicotinic acid in LDL hypercholesterolemia and nicotinic acid with a fibric acid in combined hyperlipidemia.

Levels of soluble cell adhesion molecules in patients with dyslipidemia

BACKGROUND

Increased expression of cell adhesion molecules (CAMs) on the vascular endothelium has been postulated to play an important role in atherogenesis. Both in vitro and in vivo studies have suggested that dyslipidemia may increase expression of CAMs.

METHODS AND RESULTS

To determine whether dyslipidemia is associated with increased expression of CAMs, we examined the levels of soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1 (sVCAM-1), and soluble E-selectin (sE-selectin) in individuals with either hypercholesterolemia or hypertriglyceridemia and in control subjects matched for age and sex. Patients with hypertriglyceridemia had significantly higher levels of sVCAM-1 (739 +/- 69 ng/mL) compared with patients with hypercholesterolemia (552 +/- 63 ng/mL) and control subjects (480 +/- 56 ng/mL). Levels of sICAM-1 were significantly increased in both the hypercholesterolemic and hypertriglyceridemic groups (298 +/- 29 and 342 +/- 31 ng/mL, respectively) compared with the control group (198 +/- 14 ng/mL). Levels of sE-selectin were significantly increased in hypercholesterolemic patients (74 +/- 9 ng/mL) compared with control subjects (48 +/- 5 ng/mL). Ten hypercholesterolemic patients were treated aggressively with atorvastatin alone or a combination of colestipol and either atorvastatin or simvastatin for a mean of 42 weeks and had an average LDL cholesterol reduction of 51%. Comparison of soluble CAMs before and after treatment showed a significant reduction only in sE-selectin (77 +/- 11 versus 56 +/- 6 ng/mL, P < or = .03) but not for sVCAM-1 or sICAM-1.

CONCLUSIONS

Although severe hyperlipidemia is associated with increased levels of soluble CAMs, aggressive lipid-lowering treatment had only limited effects on the levels. Increased levels of soluble CAMs in patients with hyperlipidemia may be a marker for atherosclerosis.

Pathophysiology of plaque rupture and the concept of plaque stabilization

Atherosclerosis complicated by plaque rupture or disruption and thrombosis is primarily responsible for the potentially lethal acute coronary syndromes. Plaques with a large extracellular lipid-rich core, thin fibrous cap with reduced collagen content and smooth muscle density, and increased numbers of activated macrophages and mast cells appear to be most vulnerable to rupture. Plaque disruption tends to occur at points at which the plaque surface is weakest and most vulnerable, which coincide with points at which stresses, resulting from biomechanical and hemodynamic forces acting on plaques, are concentrated. Reduced matrix synthesis as well as increased matrix degradation may predispose fibrous caps to rupture spontaneously or in response to extrinsic mechanical or hemodynamic stresses. Modification of endothelial dysfunction and reduction of vulnerability to plaque rupture and thrombosis may lead to plaque stabilization resulting in reduction of the frequency of acute coronary syndromes. This putative concept of plaque stabilization, although attractive, has not yet been rigorously validated in humans. Indirect data from clinical trials involving lipid lowering/modification and lifestyle/risk factor modification, however, provide strong support for this new paradigm. Thus, plaque stabilization may prove to be an important modality for reduction of lethal consequences of coronary atherosclerosis.

Preservation of endothelium-dependent vascular relaxation in cholesterol-fed mice by the chronic administration of prazosin or pravastatin

The relaxation of aortic rings in response to acetylcholine (ACh) was significantly decreased in cholesterol-fed mice. The attenuated relaxation in cholesterol-fed mice was preserved by the chronic administration of prazosin (20 mg/kg/day) or pravastatin (12.5 mg/kg/day). Serum low-density lipoprotein (LDL) levels were significantly increased in mice given cholesterol. The increased serum LDL levels in cholesterol-fed mice were returned to normal by the chronic administration of prazosin and pravastatin. A prior incubation of aortic rings with lysophosphatidylcholine (LPC) significantly attenuated ACh- and A23187-induced endothelium-dependent relaxation. The inhibitory effects of LPC on endothelium-dependent relaxation were not affected by indomethacin or superoxide dismutase. The sodium nitroprusside-induced relaxation of aortic rings was not changed by LPC. The inhibitory effects on ACh-induced relaxation by NG-monomethyl-L-arginine were restored by a prior exposure to L-arginine, whereas the inhibition of endothelium-dependent relaxation by LPC was not affected by L-arginine. These results suggest that cholesterol-fed mice are useful animal models of hypercholesterolemia, and chronic administration of prazosin or pravastatin can preserve endothelium-dependent relaxation by lowering serum LDL in these animals. It is further suggested that LPC derived from oxidized LDL may be involved in the reduced endothelium-dependent relaxation in hyperlipidemia.

Barriers to lifestyle change, and the need to develop an integrated approach to prevention

Many barriers exist to the delivery of preventive services by both cardiologists and other physicians. These barriers can be overcome by appropriate training and the development of supportive infrastructures. In addition, institutional priorities must change in a direction that encourages such efforts. Cardiologists must recognize the importance of risk-factor modification, and training programs in cardiology should teach appropriate counseling techniques, the use of risk factor-lowering pharmacologic agents, and the manner in which cardiologists should interface with dietitians and other ancillary personnel. In addition, we need to recognize and teach, both by didactics and by example, that counseling patients and carrying out long-term preventive interventions can be as gratifying and interesting as performing dramatic procedures that although valuable and rewarding take place at a very late point in the patient's clinical course and perhaps could have been averted by greater attention to risk-factor modification. Increasingly, the public and governmental agencies are becoming involved in encouraging these endeavors, and cardiologists should be in the vanguard of such efforts, not reluctantly bringing up the rear.

Genetic and biochemical factors associated with variation in blood pressure in a genetic isolate

We previously found an association between blood pressure and genetic variation of angiotensinogen in Canadian Hutterites. We hypothesized that variation in other candidate genes would also be associated with variation in blood pressure. We included genotypes of 12 candidate genes, along with clinical features and biochemical variables as covariates in an association analysis. We found that sex and body mass were significantly associated with variation in both systolic and diastolic blood pressures. We found that genotypes of APOB codon 4154 and AGT codon 174 were significantly associated with variation in systolic blood pressure. We found that genotypes of APOB codon 4154, AGT codon 174, and F7 codon 353 were significantly associated with variation in diastolic blood pressure. We found a significant association between age and variation in systolic but not diastolic blood pressure. We found a significant association between plasma apo B concentration and variation in diastolic but not systolic blood pressure. The association of genomic variation with resting blood pressure is consistent with the existence of important structural elements within or proximal to some genes in lipoprotein metabolism, the renin-angiotensin system, and the coagulation cascade. The association between plasma apo B concentration and diastolic blood pressure suggests that these traits may share some determinants.

Lipid lowering: the case for identifying and treating the high-risk patient

The rationale for the identification and aggressive treatment of lipid disorders in the patient with established vascular disease is thoroughly convincing. Elevated LDL cholesterol level is one of the few risk factors for which there is evidence of involvement in endothelial dysfunction, smooth-muscle proliferation, plaque destabilization, and thrombosis. Longitudinal studies have identified the role of elevated LDL cholesterol and low HDL cholesterol levels in the natural history of coronary artery disease. Clinical trials have successfully tested the feasibility of preventing coronary events using diet therapy or cholesterol-lowering drugs. These experiments have used a variety of end points, including myocardial infarction, cardiac death, total mortality rate, progression and regression of coronary artery stenoses, and progression of extracardiac atherosclerotic disease. The results are strikingly consistent. Economic analyses of the cost-benefit ratios also support these interventions in high-risk patients. These analyses also suggest that patients at high risk for coronary disease prior to its symptomatic presentation may be identified and treated to provide additional avenues for cost-effective primary prevention of this disease. The cardiologic community cannot ignore these results while embracing interventions such as angioplasty, coronary artery disease, antiarrhythmic therapy, and so forth. The scientific basis of cardiology demands the integration of techniques to control the atherosclerotic disease process itself, rather than merely the symptoms that it produces. Cardiology practices must reorganize to allow these proven interventions to become an integral part of comprehensive cardiologic care.

Endothelial control of vasomotion and nitric oxide production: a potential target for risk factor management

During the past 15 years, new concepts have arisen regarding regulation of vasomotor control. It is now clear that the vascular endothelium modulates vascular tone via the release of a variety of substances. Of these, nitric oxide is predominant in modulating vasodilation. Nitric oxide also has a number of other roles that are clearly antiatherogenic. Importantly, a number of disease processes alter the release of nitric oxide and in fact may serve as risk factors in part via this mechanism. In this review, the mechanisms through which hypercholesterolemia alters vasomotion are discussed, and interventions that may improve endothelial function are considered.

Lessons from coronary atherosclerosis "regression" trials

This article describes the background and methodology of the published studies assessing the effects of cholesterol-lowering therapy and of treatment of multiple risk factors on the progression of coronary atherosclerosis. The results are then presented, followed by a discussion of the lessons that can be learned from this large series of similar trials.

Atherosclerosis: risk factors and the vascular endothelium

The endothelium can respond to a local environment by releasing a variety of substances that regulate the level of vascular tone. One of the most important of these vasoregulatory substances is EDRF. The function of the endothelium is altered in a variety of pathologic and physiologic conditions. This review focused on the role of risk factors for atherosclerosis as it relates to EDRF. Atherosclerotic blood vessels respond abnormally on exposure to stimuli that release EDRF. It is now also apparent that this abnormal vascular response may precede the development of significant atherosclerosis and that normalization of the EDRF response with treatment is possible. Thus abnormal endothelium-dependent relaxation has been demonstrated in hypercholesterolemic patients with little or no evidence of coronary angiographic disease and in patients with hypertension before the development of atherosclerosis. The interaction between risk factors and the function of the vascular endothelium with development of atherosclerosis may become a useful focus for therapies that benefit patient outcomes.

The vascular biology of nitric oxide and its role in atherogenesis

Nitric oxide (NO), the biologically active component of endothelium-derived relaxing factor, has critical roles in the maintenance of vascular homeostasis. Decreased endothelial NO production, as a result of endothelial dysfunction, occurs in the early phases of atherosclerosis. NO appears to inhibit atherogenesis by inhibiting leukocyte and platelet activation and by inhibiting smooth muscle cell proliferation. Endothelial denudation is a prominent feature of vascular injury associated with percutaneous angioplasty, and decreased NO production appears to contribute to the restenosis process. Manipulation of the NO/cGMP signal transduction system may provide novel therapeutic approaches for limiting atherogenesis and neointimal proliferation in the future.

Is the presence of hyperlipidemia associated with impairment of endothelium-dependent neointimal relaxation after percutaneous transluminal coronary angioplasty?

To determine whether hyperlipidemia affects the endothelium-dependent vasomotor response along the dilated vessel after percutaneous transluminal coronary angioplasty (PTCA), we evaluated 32 patients with one-vessel disease, 3-6 months after successful PTCA without restenosis. Fourteen patients had mild stenotic lesions not subjected to PTCA (non-PTCA sites) in addition to the PTCA sites. Vessel diameter changes at 32 PTCA and 36 non-PTCA sites were assessed by quantitative angiography, before and after intracoronary injection of acetylcholine (20 micrograms to the right and 50 micrograms to the left coronary artery) and of nitroglycerin (0.1-0.3 mg). The acetylcholine response ranged from 46% (dilation) to -100% (constriction). All coronary arteries were dilated in response to nitroglycerin, which suggested preservation of the function of vascular smooth muscle, and the presence of an abnormality in endothelial function in those patients with a constrictor response to acetylcholine. There was a negative correlation between the acetylcholine response and the serum total cholesterol level at PTCA sites (r = -0.37; P = 0.038) and at non-PTCA sites (r = -0.46; P = 0.005). These findings indicate that hyperlipidemia is associated with a loss of endothelium-dependent vasodilation, not only at non-PTCA but also at PTCA sites, at which restoration of endothelial function might have occurred. They also suggest that hyperlipidemia may be related to the functional state of the regenerated endothelium at sites where PTCA had been previously performed.

Benefits and risks of HMG-CoA reductase inhibitors in the prevention of coronary heart disease: a reappraisal

Although several cholesterol-lowering interventions have reduced coronary heart disease (CHD) events in clinical trials, drug therapy for hypercholesterolaemia has not been as widely used as the US and European guidelines recommend, mainly because until recently there was insufficient clinical trial evidence for improved survival. The Scandinavian Simvastatin Survival Study (4S) is the first trial of lipid-lowering therapy to demonstrate an unequivocal reduction in total mortality. Largely as a result of this study, there is now little disagreement on the necessity to reduce low density lipoprotein (LDL) cholesterol effectively in hypercholesterolaemic patients with CHD. Many physicians believe it is also important to reduce elevated levels of LDL cholesterol in patients without overt coronary disease, but more clinical trial evidence will be required before this is universally accepted. Inhibitors of HMG-CoA reductase are the most effective class of agents for this purpose, and have become widely used. It is likely that the magnitude of risk reduction produced by lipid-lowering therapy is proportional to the degree of cholesterol lowering achieved, which is an important consideration when selecting an agent and deciding the dosage to use. The results of several multicentre comparative trials have clearly established that the 4 members of the class are not all equipotent on a mg basis in terms of their effects on lowering LDL cholesterol. They have shown that the hypolipidaemic effect of simvastatin 5 mg approximately equals that of pravastatin 15 mg and lovastatin 15 mg and that of fluvastatin 40 mg, all given once daily. The tolerability profiles of HMG-CoA reductase inhibitors are excellent. Five-year data are available for simvastatin and lovastatin, and to date there is no good evidence for important differences in safety or tolerability among the class.

Changes in flow-mediated brachial artery vasoactivity with lowering of desirable cholesterol levels in healthy middle-aged men

Current National Cholesterol Education Program guidelines consider desirable total and low-density lipoprotein cholesterol levels to be < 200 and < 160 mg/dl, respectively, for healthy individuals without multiple coronary risk factors. To determine the extent to which these levels affect vascular function, we assessed flow-mediated (endothelium-dependent) brachial artery vasoactivity noninvasively before, during, and after cholesterol lowering (simvastatin 10 mg/day) in 7 healthy middle-aged men with cholesterol levels meeting current recommendations. Flow-mediated brachial artery vasoactivity was measured using 7.5 MHz ultrasound and expressed as percent diameter change from baseline to hyperemic conditions (1 minute following 5 minutes of blood pressure cuff arterial occlusion). Flow-mediated vasoactivity rose from 5.0 +/- 3.6% at baseline to 10.5 +/- 5.6%, 13.3 +/- 4.3%, and 15.7 +/- 4.9% (all p < 0.05) as cholesterol fell from 200 +/- 12 to 161 +/- 18, 169 +/- 16, and 153 +/- 11 mg/dl after 2, 4, and 12 weeks, respectively, of cholesterol-lowering therapy. Vasoactivity and cholesterol returned to baseline levels 12 weeks after simvastatin discontinuation. Overall, vasoactivity was found to correlate inversely with cholesterol levels (r = -0.47, p = 0.004). These data suggest that flow-mediated brachial artery vasoactivity responds rapidly to changes in cholesterol levels and that endothelial function improves by lowering cholesterol levels below recommendations of current guidelines.

Neuroimmunologic implications in coronary artery disease

In this review, the role of the macrophage in the pathophysiology of coronary artery disease (CAD) is examined. The central interaction of macrophage, endothelial cell and smooth muscle cell in the context of hyperlipidemia is considered. The macrophage appears to be at the beginning of a chain of events that starts with elevated low density lipoprotein (LDL). Stress, particularly in those with a core hostility, may be associated not only with higher catecholamine levels but also with higher serum lipid levels. These lipids will in turn be processed to oxidized LDL by macrophage and endothelial cells. Oxidized LDL molecules will contribute to atherosclerotic plaquing. A side effect of such plaque formation may be a diminished vasodilatory response to the nitric oxide (NO) produced by macrophages and endothelium. Indeed, paradoxical vasoconstriction occurs in atherosclerosis in response to neurotransmitters such as serotonin and acetylcholine, which under normal circumstances cause vasodilation. There also is evidence that both macrophages and endothelial cells can regulate NO production through a specific mu 3 morphine receptor, an effect that can be blocked by naloxone. The clinical effectiveness of morphine and nitroglycerin in CAD patients may relate to these mechanisms. More research will be needed to elucidate the neuroimmunologic basis for atherosclerosis with prospects for better treatment and management in future.

Exercise-induced vasomotion of angiographically normal and stenotic coronary arteries improves after cholesterol-lowering drug therapy with bezafibrate

OBJECTIVES

We attempted to determine whether the coronary vasomotor response to exercise improves after cholesterol-lowering drug therapy with bezafibrate.

BACKGROUND

Hypercholesterolemia and other coronary risk factors are associated with impaired endothelium-dependent coronary vasomotor response to physiologic or pharmacologic stimuli, even in the absence of overt coronary atherosclerosis. It is still unknown whether the coronary artery vasomotor response to dynamic exercise improves under cholesterol-lowering drug therapy.

METHODS

Of 15 male patients (age 51 +/- 7 years [mean +/- SD]) included in the study, 7 had markedly elevated cholesterol levels (> or = 6.5 mmol/liter, therapy group), and 8 had normal or slightly elevated cholesterol levels (< 6.5 mmol/liter, control group). At baseline and after 7 months of cholesterol-lowering therapy with bezafibrate (400 mg/day) in the therapy group, coronary vasomotor response to dynamic exercise (percent change in cross-sectional vascular area at maximal exercise vs. rest [100%]) in normal and stenotic, previously dilated vessels was assessed by quantitative coronary angiography.

RESULTS

During follow-up, total serum cholesterol levels in the therapy group decreased from 7.8 +/- 1.1 to 5.8 +/- 1.1 mmol/liter (p = 0.0001) and did not change significantly in the control group (from 5.4 +/- 0.9 to 6.0 +/- 1.2 mmol/liter, p = NS). Exercise-induced vasomotor response (at similar work loads in the therapy and control groups) in both normal and dilated stenotic coronary arteries improved significantly in the therapy group, from 100 +/- 9% to 109 +/- 7% (p = 0.0001, cross-sectional area at rest 100%) and from 80 +/- 11% to 106 +/- 7% (p = 0.0002), respectively, but did not improve during follow-up in the control group.

CONCLUSIONS

The present study indicates that cholesterol-lowering drug therapy with bezafibrate for 7 months improves exercise-induced vasomotion of angiographically normal coronary arteries. Seven months after coronary angioplasty, the reduction in serum cholesterol levels is, at least in part, associated with a restoration of the initially disturbed vasomotor response of stenotic vessel segments to exercise.

Effects of vitamin E on endothelial function in men after myocardial infarction

This study showed that endothelial dysfunction is present in men 3 to 6 months after myocardial infarction, but was unable to show any improvement in endothelial function after 3 months of therapy with vitamin E 800 IU/day. Further studies are necessary to determine whether higher doses or a longer course of vitamin E, or whether other antioxidant agents with or without lipid-modifying activity, would improve endothelial function.