Coronary heart disease primary prevention

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Risk calculators and risk factors for Coronary heart disease primary prevention

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

The LDL target in primary prevention depends upon the patient's risk factors. If the patient has CHD or its equivalent, then the LDL goal is under 100 mg/dl. If the patient has 2 risk factors, the LDL goal is 130 mg/dl. If the patient has < 2 risk factors, the LDL goal is < 160 mg/dl.

Risk Equivalents in Primary Prevention

If CHD or a risk equivalent is present, the LDL goal is < 100 mg/dl. You are essentially considered to have the equivalent of coronary heart disease if you have any of the following "risk equivalents":

• Aortic aneurysm
• Diabetes
• Framingham Risk Score (FRS) of > 20% (A 20% risk of death or MI over 10 years)
• Peripheral vascular disease (PVD) (defined as claudication, an Ankle Brachial Index (ABI) of < 0.9)
• Symptomatic carotid artery disease (defined as prior stroke or TIA)

CV Risk Factors in the Setting of Primary Prevention

If you have two or more of the following risk factors, the LDL goal is < 130 mg/dl:

• Cigarette smoking
• Family history of premature coronary artery disease (CAD)
• High LDL (defined as LDL > 130 mg /dl)
• Hypertension ( defined as a BP ≥140/90 mm Hg or if the patient is on antihypertensive drugs)
• Low HDL (defined as HDL < 40 mg/dL males, < 50 mg/dL in females)
• Older Age (men ≥45 years old; women ≥55 years old)

If you have < two risk factors, the goal is an LDL < 160 mg/dl.

Primary Prevention: LDL Goals for Various Categories of Risk

Risk Category	LDL-C Goal	Consider Drug Therapy
CHD or CHD risk equivalent	<100 mg/dl	>130 mg/dl*
> 2 Risk Factors
10 yr risk 10-20%	<130 mg/dl	>130 mg/dl
10 yr risk < 10%	<130 mg/dl	> 160 mg/dl
< 2 Risk Factors	<160 mg/dl	>190 mg/dl

• after lifestyle modification, if LDL is 100-129, consider a statin, niacin, or fibrate therapy.

Lifestyle Modification Goals

• Reduce obesity
• Treat hypertension
• Smoking cessation
• Exercise

Treat Underlying Causes of Hyperlipidemia

• Hypothyroidism can increase LDL and triglycerides.
• Obstructive liver disease can increase LDL and increase HDL.
• Uncontrolled diabetes may increase triglycerides and reduce HDL.
• Nephrotic syndrome markedly increases LDL.
• Renal failure increases LDL, increases triglycerides and decreases HDL.

Drugs that Cause Dyslipidemia

• Androgenic steroids (↑LDL ↓HDL)
• Progestogens/estrogens (↑HDL/TG)
• Retinoic acid (Accutane) (↑TG)
• Corticosteroids (↑LDL/TG)
• Protease inhibitors (↑TG ↓HDL ↑LDL)
• Thiazide diuretics (↑LDL/TG)
• Beta-blockers (↑LDL/TG)

Modification of Risk Factors that do not have a Robust Evidence Base

Just because something has been identified as a risk factor, that does not mean that lowering the risk factor improves outcomes. This is because the risk factor may not lie in the causal pathway for CHD. Risk factors that when modified may not improve outcomes include the following:

• There is little evidence that aggressive blood sugar control actually improves cardiac risk.
• Lowering uric acid and homocysteine levels
• Omega-3 fatty acids. The benefit of fish oil is controversial with conflicting conclusions reached by a negative meta-analysis of randomized controlled trials by the international Cochrane Collaboration and a partially positive systematic review by the Agency for Healthcare Research and Quality. Since these two reviews, a randomized controlled trial reported a reduction on coronary events in Japanese hypercholesterolemic patients. Omega-3 fatty acids are also found in some plant sources including flax seed oil, hemp seed oil, and walnuts. Plant sources may be safer as fish products have been shown to contain heavy metals and other fat soluble pollutants.
• Vitamin C
• The World Health Organization (WHO) recommends "low to moderate alcohol intake" to reduce risk of coronary heart disease.
• Avoidance of fats that are readily oxidized (e.g., saturated fats and trans-fats),
• Limit carbohydrates and processed sugars to reduce production of Low density lipoproteins while increasing High density lipoproteins.

Preventive diets

Main article: Diet and Heart Disease

It has been suggested that coronary heart disease is partially reversible using an intense dietary regimen coupled with regular cardio exercise.

• Vegetarian diet: Vegetarians have been shown to have a 24% reduced risk of dying of heart disease.

• Cretan Mediterranean diet: The Seven Country Study found that Cretan men had exceptionally low death rates from heart disease, despite moderate to high intake of fat. The Cretan diet is similar to other traditional Mediterranean diets: consisting mostly of olive oil, bread, abundant fruit and vegetables, a moderate amount of wine and fat-rich animal products such as lamb, sausage and goat cheese. However, the Cretan diet consisted of less fish and wine consumption than some other Mediterranean-style diets, such as the diet in Corfu, another region of Greece, which had higher death rates.

The consumption of trans fat (commonly found in hydrogenated products such as margarine) has been shown to cause the development of endothelial dysfunction, a precursor to atherosclerosis.

Aspirin

Aspirin, in doses of less than 75 to 81 mg/d, can reduce the incidence of cardiovascular events. The U.S. Preventive Services Task Force 'strongly recommends that clinicians discuss aspirin chemoprevention with adults who are at increased risk for coronary heart disease'. The Task Force defines increased risk as 'Men older than 40 years of age, postmenopausal women, and younger persons with risk factors for coronary heart disease (for example, hypertension, diabetes, or smoking) are at increased risk for heart disease and may wish to consider aspirin therapy'. More specifically, high-risk persons are 'those with a 5-year risk ≥ 3%'. A risk calculator is available.

Regarding healthy women, the more recent Women's Health Study randomized controlled trial found insignficant benefit from aspirin in the reduction of cardiac events; however there was a signficant reduction in stroke. Subgroup analysis showed that all benefit was confined to women over 65 years old. In spite of the insignficant benefit for women < 65 years old, recent practice guidelines by the American Heart Association recommend to 'consider' aspirin in 'healthy women' <65 years of age 'when benefit for ischemic stroke prevention is likely to outweigh adverse effects of therapy'.