1. The progression from CV risk factors to endothelial injury and clinical events
Content Points:
Well-recognized cardiovascular risk factors (hypertension, dyslipidemia, diabetes, smoking, etc) are associated with changes in the vessel wall that lead to cardiovascular disease.
One of the earliest changes associated with these risk factors is an increase in oxidative stress in the vessel wall. This causes endothelial cells to decrease production of some compounds and increase production of others.1
Production of nitric oxide (NO), a powerful vasodilator, is decreased. Production of vasoconstrictors, notably endothelin and angiotensin II (Ang II), is increased. Greater production of local mediators (eg, vascular cell adhesion molecule [VCAM], and plasminogen activator inhibitor 1 [PAI-1]) promotes inflammation, disrupts fibrinolysis, increases vascular remodeling and plaque rupture. The vascular endothelium secretes numerous other substances that modulate blood vessel tone and participate in the development and progression of atherosclerosis.
Thus, the presence of cardiovasular risk factors begins a progression that sets the stage for clinical events.

2. Physiology of NO in the human coronary and peripheral vasculature
Content points:
• NO is considered the most important endothelium-derived relaxing factor. It appears to play a pivotal role in the pathophysiology of endothelial dysfunction and atherosclerosis.2
• NO is produced from L-arginine by activity of nitric oxide synthase (NOS), an enzyme that is present in endothelial cells. Under resting conditions, NO is continually released from healthy endothelial cells. L-NMMA, an L-arginine analog, completely inhibits NOS and therefore prevents the release of NO.
• Calcium appears to be the primary stimulus required for short-term activation of endothelial NOS. Other substances that increase NO production include endothelium-dependent pharmacologic probes such as acetylcholine, as well as bradykinin, substance P, and adenosine diphosphate.
• Factors involved in long-term regulation of endothelial cell NOS regulation include shear stress, cytokines, growth, and possibly estrogens.
• NO seems to produce smooth muscle vasodilation, inhibit platelet aggregation and adhesion, and prevent or inhibit cell growth and plaque formation.
• As shown on this slide, diffusion of NO from the endothelium into smooth muscle cells activates guanylate cyclase and increases intracellular cyclic guanine monophosphate (cGMP), leading to relaxation.
• Luminal diffusion of NO and its uptake into circulating platelets inhibits platelet adhesion, and to a lesser extent, it suppresses platelet aggregation.

3. Atherosclerosis timeline
Content points:
• The pathological effects of atherosclerosis occur over decades. A subtle injury to the endothelium initiates the atherosclerotic process.3 Injury of the vascular wall and endothelium underlie many stages in atherosclerosis progression from onset through formation of advanced lesions and clinical events.4
• Foam cells infiltrate the vessel and progress to formation of a fatty streak. Small pools of extracellular lipid form within the smooth muscle cell layers, disrupting the intimal lining of the vessel. The formation of atheroma and fibrous plaque, a pearly white area within the artery, disturbs the arterial wall.
• The atheroma, or plaque, is composed of lipid, cell debris, smooth muscle cells and collagen (or calcium, in older persons). This type of advanced lesion can be found beginning in the fourth decade of life. Once the plaque becomes fibrous, the danger of rupture increases.
• The clinically important complication of atheroma usually involves thrombosis. Most coronary thromboses result from rupture of the protective fibrous cap, which permits contact between the blood and the highly thrombogenic material in the lipid core of the lesion.
• Stenoses seldom cause acute MI. Indeed, sizable atheromas may remain silent for decades or produce stable angina due to increased demand.

4. Therapeutic strategies to enhance vascular wall function
Content points:
• The vascular endothelium plays a key role in the control of vasomotor tone, local hemostasis, and vascular wall proliferation processes.
• Risk factors for coronary atherosclerosis impair NO bioactivity, mainly due to an oxidative stress by superoxide radicals (O2-), which are able to rapidly inactive endothelium-derived NO.5
• Thus, the aim of therapeutic interventions is to increase NO bioavailability by either increasing NO production or decreasing O2- production in the endothelium. The balance between NO and O2- determines not only vasoreactivity, but also processes which affect plaque progression and stability.
• This goal can be reached by angiotensin-converting enzyme (ACE) inhibitors, lipid-lowering drugs, increased shear stress by physical exercise, estrogens, and L-arginine.
• Physical activity increases intracoronary blood flow and therefore shear stress, which is an important factor causing endothelium-dependent vasodilation. In the long-term, physical exercise-induced flow leads to increased expression of NO synthase and an improvement in endothelium-dependent vasodilation.
• L-arginine, the precursor of NO, acutely improves flow-dependent dilation and endothelial vasodilation of the coronary microvasculature in patients with hypercholesterolemia, atherosclerosis, and advanced age, and in patients with advanced microvascular angina.
• ACE inhibitors improve endothelial function through effects on both the breakdown of bradykinin, which increase NO production and activity, and the inhibition of angiotensin II (Ang II), which decreases O2- production.
• Estrogen replacement in postmenopausal women improves endothelial vasodilator function in the cardiovasculature, an effect explained by increased NO.
• Endothelial function can be improved by lipid lowering drugs and by antioxidants, such as vitamin C and vitamin E.

5. Candidates for therapies to enhance vascular endothelial function
Content points:
• Patients with specific disorders including hypertension, dyslipidemia, diabetes, atherosclerosis, and heart failure have varying degrees of vascular dysfunction and would benefit from therapies known to improve vascular endothelial wall function.5
• Candidates for therapy targeted to the vascular endothelial wall include smokers, postmenopausal women, minorities, the elderly, those with a family history of premature heart disease, and patients with vascular disease. These patient groups have demonstrated a decline in vascular endothelial function.

6. Correlation between vascular function and hypertension
Content points:
• The endothelium plays a pivotal role in maintaining hemostasis and tone in blood vessels. The impact of hypertension on endothelial function is seen in these two studies.
• Panza and colleagues, on the left, showed that hypertensive patients have reduced endothelium-mediated forearm blood flow during cholinergic vasodilation, which was induced by infusion of acetylcholine, as compared with subjects with normal blood pressure.6
• Taddei and colleagues showed that endothelium-mediated vasodilation in the forearm is reduced in subjects with a family history of hypertension compared with those who do not have a family history of hypertension.7
• Both studies show that hypertension is associated with changes in the endothelium that lead to endothelial dysfunction.

7. Impaired vascular function in diabetes patients
Content points:
• Diabetes is associated with impaired vascular wall function that has been observed in studies of forearm blood flow.8
• This study compared vascular wall function in 15 diabetic subjects and normal subjects by measuring their response to the administration of methacholine, which causes endothelium-dependent arterial vasodilation.
• As shown in the graph, compared with normal subjects, the diabetic subjects had significantly less of an increase in forearm blood flow in response to increasing doses of methacholine, which indicates the presence of impaired vascular wall function.

8. Correlation between vascular function and atherosclerosis
Content points:
• Hashimoto and colleagues examined whether vascular dysfunction in the brachial artery is related to the intima media thickness of the carotid artery in 34 men with atherosclerosis and 33 age-matched men without atherosclerosis.9
• Flow-mediated dilation (FMD) in the brachial artery is widely accepted as a means to evaluate endothelial function. Intima-media thickness of the common carotid artery is used as a surrogate end-point to assess the progression and regression of atherosclerosis.
• As shown in the slide, the group with atherosclerosis had significantly greater intima-media thickness of the common carotid artery than the control group (P < 0.05). During reactive hyperemia, the group with atherosclerosis also had a significantly smaller increase in FMD (P < 0.01). There was a significant negative correlation between carotid artery intima-media thickness and increases in FMD.
• These findings support the concept that vascular endothelial dysfunction is significantly related to atherogenesis.
• The next few slides will show recent findings regarding the correlation between endothelial function and cardiovascular risk.

9. Severe vascular dysfunction predicts increased CV risk in patients
with mild CAD
Content points:
• This study extends previous observations that early coronary atherosclerosis is associated with vascular wall dysfunction.10
• The association between impaired vascular wall function and future cardiac events was studied in 157 patients with mildly diseased coronary arteries. Patients were divided into three groups on the basis of changes in coronary artery blood flow in response to acetylcholine infusion.
• Group 1 (n = 83) included patients with normal coronary vascular wall function, defined as an increase of >50% in coronary blood flow in response to acetylcholine.
• Group 2 (n = 32) included patients with mild vascular wall dysfunction, defined as an increase of 0% to 50% in coronary blood flow in response to acetylcholine.
• Group 3 (n = 42) was composed of patients with severe dysfunction. These patients had decreased coronary blood flow in response to acetylcholine.
• Over an average 28-month follow-up, none of the patients with normal or mild vascular wall dysfunction had cardiac events. In contrast, 6 patients (14%) with severe dysfunction had 10 cardiac events (P < .05 vs groups 1 and 2) including myocardial infarction (MI), percutaneous or surgical coronary revascularization, and/or cardiac death.
• These findings demonstrate that severe vascular wall dysfunction in patients with nonobstructive coronary artery disease (CAD) is associated with increased cardiac events.

10. Vascular dysfunction predicts CV events: 5-year follow-up
in patients with angina
Content points:
• Neunteufl and colleagues attempted to assess whether endothelium-dependent FMD was correlated with prognosis in patients with chest pain who underwent coronary angiography.11 Following angiography, they used ultrasound to study changes in FMD in the brachial artery in response to acetylcholine infusions.
• Patients were grouped according to whether FMD was >10% or <10% (normal vs impaired), respectively. There were 27 patients with FMD of >10% and 46 patients with FMD of <10%. There were no significant differences between the 2 groups with respect to age, body mass index, smoking, diabetes, and the degree of angina pectoris, gender, or cholesterol levels.
• Patients were followed up for 5 years. Cardiovascular events occurred more often in patients with impaired FMD than in those with preserved FMD. Patients with FMD <10% were more likely to undergo coronary angioplasty and coronary bypass, but they did not show an increased incidence of myocardial infarction, as seen in the figure. None of the patients died during follow-up. No patient who underwent bypass had showed FMD of >10%.
• Events after the first month were only observed in patients with FMD <10%.
• The data demonstrate that FMD is correlated with prognosis in patients with chest pain and also predicts which patients are at low risk of short- and long-term cardiac events.

11. Effects of ACEI vs other antihypertensive agents on vascular
function in hypertensive patients
Content points:
• Impairment in functioning of the vascular wall is observed in patients with essential hypertension. This study compared the effect of different antihypertensive agents, including calcium antagonists, ACE inhibitors, b-blockers, and diuretic agents on vascular wall function.12
• Forearm blood flow (FBF) was measured in 296 patients with essential hypertension at baseline and during reactive hyperemia, which is an index of endothelial function. The forearm blood flow during reactive hyperemia in hypertensive patients was significantly less than in the control subjects who had normal blood pressure.
• The maximal FBF response from reactive hyperemia was significantly greater in the ACE inhibitor-treated group than in the group treated with calcium antagonists, b-blockers, diuretic agents, or nothing.
• Higashi and coworkers infused patients with NG-monomethyl-L-arginine, a NO synthase inhibitor, and this abolished the enhancement of reactive hyperemia in hypertensive patients treated with ACE inhibitors.
• These findings suggest that ACE inhibitors augment reactive hyperemia, an index of endothelium-dependent vasorelaxation, in patients with essential hypertension. This augmentation may be due to increases in NO.