Coronary heart disease: Difference between revisions

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| European Coronary Surgery Study<br>1988<br>767 patients<ref name="pmid3260659">{{cite journal |author=Varnauskas E |title=Twelve-year follow-up of survival in the randomized European Coronary Surgery Study |journal=N. Engl. J. Med. |volume=319 |issue=6 |pages=332–7 |year=1988 |month=August |pmid=3260659 |doi= |url= |issn=}}</ref> || Greater survival with surgery - especially during first 5 years.
| European Coronary Surgery Study<br>1988<br>767 patients<ref name="pmid3260659">{{cite journal |author=Varnauskas E |title=Twelve-year follow-up of survival in the randomized European Coronary Surgery Study |journal=N. Engl. J. Med. |volume=319 |issue=6 |pages=332–7 |year=1988 |month=August |pmid=3260659 |doi= |url= |issn=}}</ref> || Greater survival with surgery - especially during first 5 years.
|-
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! Pooled results<ref name="pmid7914958">{{cite journal |author=Yusuf S, Zucker D, Peduzzi P, ''et al'' |title=Effect of coronary artery bypass graft surgery on survival: overview of 10-year results from randomised trials by the Coronary Artery Bypass Graft Surgery Trialists Collaboration |journal=Lancet |volume=344 |issue=8922 |pages=563–70 |year=1994 |month=August |pmid=7914958 |doi= |url= |issn=}}</ref> || Surgery fared better except for patients with one or two vessel disease with neither vessel being te LAD or left main.
! Pooled results<ref name="pmid7914958">{{cite journal |author=Yusuf S, Zucker D, Peduzzi P, ''et al'' |title=Effect of coronary artery bypass graft surgery on survival: overview of 10-year results from randomised trials by the Coronary Artery Bypass Graft Surgery Trialists Collaboration |journal=Lancet |volume=344 |issue=8922 |pages=563–70 |year=1994 |month=August |pmid=7914958 |doi= |url= |issn=}}</ref> || Surgery fared better except for patients with one or two vessel disease with neither vessel being the LAD or left main.
|}
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Coronary heart disease (CHD), or called coronary artery disease (CAD), is caused by abnormalities the arteries that supply the heart with blood. Those arteries are called the coronary arteries and the usual cause of coronary artery disease is athersosclerosis. Atherosclerosis is a degenerative disease of the arterial walls, in which the normal elastic walls of the arteries become thickened and replaced with deposits of fatty material, including cholesterol. As the walls of the affected arteries thicken, the hollow lumen at the center of each, that conduit through which oxygen enriched blood normally pulses, becomes narrower and, eventually, the flow of blood within it is decreased. With narrowing of the artery's lumen and reduced flow comes the risk of sudden occlusion of the artery, especially if the lining is abnormally roughened by deposits of irregular plaques of minerals and fats.

Etiology/cause

The cause and manifestation of coronary heart disease is multifactorial. One factor, emotional stress was supported in a study of the incidence of coronary events in the Munich area during the 2006 World Cup Football (soccer) championship.[1] The incidence of coronary events was higher during the match, especially for people who had pre-existing coronary disease.

Regarding which coronary arteries become blocked, about 10% of patients with chronic angina have left main disease.[2][3] IN males over age 70 with definite angina, almost 50% have obstruction of the left main coronary artery.[3]

Diagnosis

History, physical examination, and risk factors

Angina pectoris, or simply angina, is the chest pain due to coronary heart disease; however, most patients do not report angina.[4] The nature of the chest pain affects the probability of underlying coronary disease.[5]

The Pryor nomogram, a clinical prediction rule, can help diagnose patients with suspected chest pain in a non emergent setting.[6][7]

Exercise treadmill test

The exercise treadmill test (ETT) can help diagnose and prognose patients with suspected CHD. Clinical prediction rules are available to help interpret the results of the ETT. These rules are the Duke Treadmill score[8] and the newer Cleveland Clinic model[9]. The Duke score has been more extensively studied; however, in a direct comparison by the authors of the Cleveland Clinic model, the latter performed better.[9]

The likelihood of a positive treadmill test depends on the severity of the underlying coronary disease.[2] For example, 87% of patients with obstruction of the left main coronary artery will have a positive treatmill test, whereas only 57% of patients with obstructions of one or two of the other coronaries will have a positive treadmill test.

X-ray computed tomography

There are two types of computed tomography used for noninvasive coronary arteriography.

Electron beam computed tomography

Electron beam computed tomography (EBCT) is also called ultrafast CT.

Cardiac computed tomography angiography

Cardiac computed tomography angiography (CCTA) uses multidetector spiral computed tomography.[10][11] The physiologic significance of obstructions estimated to be 60% to 80% is difficult to predict.[12]

Treatment

Medications

Invasive treatments

Major randomized controlled trials of surgery for chronic stable angina
Trial results
Veterans Administration cooperative study
1977
686 patients[13]
No difference overall
Coronary Artery Surgery Study
(CASS)
1984
780 patients[14]
No difference overall
European Coronary Surgery Study
1988
767 patients[15]
Greater survival with surgery - especially during first 5 years.
Pooled results[16] Surgery fared better except for patients with one or two vessel disease with neither vessel being the LAD or left main.

Patient who have a left ventricular ejection fraction above 50%, no angina or their angina is controlled with medicines, do not benefit from either percutaneous transluminal coronary angioplasty (PCI)[17] or from coronary artery bypass surgery[14].

Patient who have a left ventricular ejection fraction between 35 and 49 percent benefit from coronary artery bypass surgery if they have disease of three coronary arteries.[14].

Regarding patients who must undergo invasive treatment, a systematic review comparing percutaneous coronary interventions and coronary artery bypass surgery (CABG) found that CABG was more effective but was more likely to be complicated by stroke.[18]

Prevention

Coronary heart disease is the most common form of heart disease in the Western world. Prevention centers on the modifiable risk factors, which include decreasing cholesterol levels, addressing obesity and hypertension, avoiding a sedentary lifestyle, making healthy dietary choices, and stopping smoking. There is some evidence that lowering uric acid and homocysteine levels may contribute. In diabetes mellitus, there is little evidence that blood sugar control actually improves cardiac risk. Some recommend a diet rich in omega-3 fatty acids and vitamin C. The World Health Organization (WHO) recommends "low to moderate alcohol intake" to reduce risk of coronary heart disease.[19]

An increasingly growing number of other physiological markers and homeostatic mechanisms are currently under scientific investigation. Among these markers are low density lipoprotein and asymmetric dimethylarginine. Patients with CHD and those trying to prevent CHD are advised to avoid 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, keeping blood pressure normal, exercise and stop smoking. These measures limit the progression of the disease. Recent studies have shown that dramatic reduction in LDL levels can cause mild regression of coronary heart disease.

Exercise

Separate to the question of the benefits of exercise; it is unclear whether doctors should spend time counseling patients to exercise. The U.S. Preventive Services Task Force (USPSTF), based on a systematic review of randomized controlled trials, found 'insufficient evidence' to recommend that doctors counsel patients on exercise.[20] However, the American Heart Association, based on a non-systematic review, recommends that doctors counsel patients on exercise [21]

Preventive diets

Dietary changes can potentially lead to large changes in the cholesterol.[22]

Aspirin

Aspirin, in doses of less than 75 to 81 mg/d[23], can reduce the incidence of cardiovascular events.[24] 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'.[25] 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.[26]

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.[27] Subgroup analysis showed that all benefit was confined to women over 65 years old.[27] 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'.[28]

Antilipemic drugs

The U.S. Preventive Services Task Force (USPSTF) estimated that after 5 to 7 years of treatment with statins, the relative risk reduction of coronary heart disease events is decreased by approximately 30%[29][30]. More recently, a meta-analysis reported an almost identical relative risk reduction of 29.2% in low risk patients treated for 4.3 years [31]. A relative risk reduction of 19% in coronary mortality was found in a meta-analysis of patients at all levels of risk.[32]

Various clinical practice guidelines have addressed the treatment of hypercholesterolemia. The American College of Physicians has addressed hypercholesterolemia in patients with diabetes [33]. Their recommendations are:

  • Recommendation 1: Lipid-lowering therapy should be used for secondary prevention of cardiovascular mortality and morbidity for all patients (both men and women) with known coronary artery disease and type 2 diabetes.
  • Recommendation 2: Statins should be used for primary prevention against macrovascular complications in patients (both men and women) with type 2 diabetes and other cardiovascular risk factors.
  • Recommendation 3: Once lipid-lowering therapy is initiated, patients with type 2 diabetes mellitus should be taking at least moderate doses of a statin (the accompanying evidence report states "simvastatin, 40 mg/d; pravastatin, 40 mg/d; lovastatin, 40 mg/d; atorvastatin, 20 mg/d; or an equivalent dose of another statin")[34].
  • Recommendation 4: For those patients with type 2 diabetes who are taking statins, routine monitoring of liver function tests or muscle enzymes is not recommended except in specific circumstances.

The National Cholesterol Education Program revised their guidelines[35]; however, their 2004 revisions have been criticized for use of nonrandomized, observational data.[36]

Omega-3 fatty acids (fish oil)

Biochemistry

(PD) Image: National Library of Medicine (NLM)
Polyunsaturated fatty acids (PUFAs) metabolic pathways in humans.[37]

Dietary fatty acids can be divided into saturated fatty acids and unsaturated fatty acids.[37] Unsaturated fatty acids can be further divided into monounsaturated and polyunsaturated fatty acids (PUFAs).

PUFAs are divided into two groups: omega-3 fatty acids and omega-6 fatty acids. Whereas omega-3 fatty acid have health benefits due to several mechanisms; omega-6 fatty acids are precursors to arachidonic acid (AA) which leads to thrombaxanes which promote platelet aggregation and vasoconstriction.

Two PUFAs, alpha-linolenic acid (ALA) and linoleic acid (LA) are called essential fatty acids because human function requires them, yet humans cannot synthesize then in vivo.[37] ALA is a omega-3 fatty acid while AL is a omega-6 fatty acid. In North America, LA comprises 89% of the total PUFAs consumed, while ALA comprises 9%.[37] LA is in many commonly used oils, including safflower, sunflower, soy, and corn oil. ALA is in leafy green vegetables and in canola and soybean oil.

Dietary fish oils are converted to eicosapentaenoic acid (EPA) which is further converted to docosahexaenoic acid (DHA). Both EPA and HHA are omega-3 fatty acids.

Studies of benefit

The benefit of fish oil is controversial with conflicting conclusions reached by a negative meta-analysis[38][39] of randomized controlled trials by the international Cochrane Collaboration and a partially positive systematic review[37] 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.[40]

Subsequent randomized controlled trials have also had conflicting results finding both benefit[40] and harm[41].

Homocysteine lowering

A meta-analysis concluded that lowering homocysteine with folic acid and other supplements may reduce stroke.[42] However, the two largest randomized controlled trials included in the meta-analysis had conflicting results. Lonn reported positive results[43]; whereas the trial by Toole was negative.[44]

Since the meta-analysis, two additional trials have shown no reduction in cardiovascular endpoint despite successfully lowering the plasma homocysteine level.[45][46]

References

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  45. ""[e]
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