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Heart Disease

Cardiovascular disease
Classification and external resources
10 9 DiseasesDB MeSH D002318

Cardiovascular disease (also called heart disease) is a class of diseases that involve the heart, the blood vessels (arteries, capillaries, and veins) or both.[1]

Cardiovascular disease refers to any disease that affects the cardiovascular system, principally cardiac disease, vascular diseases of the brain and kidney, and peripheral arterial disease.[2] The causes of cardiovascular disease are diverse but atherosclerosis and/or hypertension are the most common. Additionally, with aging come a number of physiological and morphological changes that alter cardiovascular function and lead to subsequently increased risk of cardiovascular disease, even in healthy asymptomatic individuals.[3]

Cardiovascular disease is the leading cause of deaths worldwide, though since the 1970s, cardiovascular mortality rates have declined in many high-income countries.[4][5] At the same time, cardiovascular deaths and disease have increased at a fast rate in low- and middle-income countries.[6] Although cardiovascular disease usually affects older adults, the antecedents of cardiovascular disease, notably atherosclerosis, begin in early life, making primary prevention efforts necessary from childhood.[7] There is therefore increased emphasis on preventing atherosclerosis by modifying risk factors, such as healthy eating, exercise, and avoidance of smoking tobacco.

Types

Risk factors

Evidence suggests a number of risk factors for heart disease: age, gender, high blood pressure, high serum cholesterol levels, tobacco smoking, excessive alcohol consumption, sugar consumption,[9][10] family history, obesity, lack of physical activity, psychosocial factors, diabetes mellitus, air pollution.[2] While the individual contribution of each risk factor varies between different communities or ethnic groups the consistency of the overall contribution of these risk factors to epidemiological studies is remarkably strong.[11] Some of these risk factors, such as age, gender or family history, are immutable; however, many important cardiovascular risk factors are modifiable by lifestyle change, drug treatment or social change.

Age


Age is by far the most important risk factor in developing cardiovascular diseases, with approximately a tripling of risk with each decade of life.[6] It is estimated that 87 percent of people who die of coronary heart disease are 60 and older.[12] At the same time, the risk of stroke doubles every decade after age 55.[13]

Multiple explanations have been proposed to explain why age increases the risk of cardiovascular diseases. One of them is related to serum cholesterol level.[14] In most populations, the serum total cholesterol level increases as age increases. In men, this increase levels off around age 45 to 50 years. In women, the increase continues sharply until age 60 to 65 years.[14]

Aging is also associated with changes in the mechanical and structural properties of the vascular wall, which leads to the loss of arterial elasticity and reduced arterial compliance and may subsequently lead to coronary artery disease.[15]

Sex

Men are at greater risk of heart disease than pre-menopausal women.[6][16] Once past menopause, it has been argued that a woman's risk is similar to a man's[16] although more recent data from the WHO and UN disputes this.[6]

Among middle-aged people, coronary heart disease is 2 to 5 times more common in men than in women.[14] In a study done by the World Health Organization, sex contributes to approximately 40% of the variation in the sex ratios of coronary heart disease mortality.[17] Another study reports similar results that gender difference explains nearly half of the risk associated with cardiovascular diseases[14] One of the proposed explanations for the gender difference in cardiovascular disease is hormonal difference.[14] Among women, estrogen is the predominant sex hormone. Estrogen may have protective effects through glucose metabolism and hemostatic system, and it may have a direct effect on improving endothelial cell function.[14] The production of estrogen decreases after menopause, and may change the female lipid metabolism toward a more atherogenic form by decreasing the HDL cholesterol level and by increasing LDL and total cholesterol levels.[14] Women who have experienced early menopause, either naturally or because they have had a hysterectomy, are twice as likely to develop heart disease as women of the same age group who have not yet gone through menopause.

Among men and women, there are differences in body weight, height, body fat distribution, heart rate, stroke volume, and arterial compliance.[15] In the very elderly, age related large artery pulsatility and stiffness is more pronounced in women.[15] This may be caused by the smaller body size and arterial dimensions independent of menopause.[15]

Air pollution

Particulate matter has been studied for its short- and long-term exposure effects on cardiovascular disease. Currently, PM2.5 is the major focus, in which gradients are used to determine CVD risk. For every 10 μg/m3 of PM2.5 long-term exposure, there was an estimated 8-18% CVD mortality risk.[18] Women had a higher relative risk (RR) (1.42) for PM2.5 induced coronary artery disease than men (0.90) did.[18] Overall, long-term PM exposure increased rate of atherosclerosis and inflammation. In regards to short-term exposure (2 hours), every 25 μg/m3 of PM2.5 resulted in a 48% increase of CVD mortality risk.[19] Additionally, after only 5 days of exposure, a rise in systolic (2.8 mmHg) and diastolic (2.7 mmHg) blood pressure occurred for every 10.5 μg/m3 of PM2.5.[19] Other research has implicated PM2.5 in irregular heart rhythm, reduced heart rate variability (decreased vagal tone), and most notably heart failure.[19][20] PM2.5 is also linked to carotid artery thickening and increased risk of acute myocardial infarction.[19][20]

Pathophysiology

Population based studies show that atherosclerosis the major precursor of cardiovascular disease begins in childhood. The Pathobiological Determinants of Atherosclerosis in Youth Study demonstrated that intimal lesions appear in all the aortas and more than half of the right coronary arteries of youths aged 7–9 years.[21]

This is extremely important considering that 1 in 3 people will die from complications attributable to atherosclerosis. In order to stem the tide education and awareness that cardiovascular disease poses the greatest threat and measures to prevent or reverse this disease must be taken.

Obesity and diabetes mellitus are often linked to cardiovascular disease,[22] as are a history of chronic kidney disease and hypercholesterolaemia.[23] In fact, cardiovascular disease is the most life threatening of the diabetic complications and diabetics are two- to four-fold more likely to die of cardiovascular-related causes than nondiabetics.[24][25][26]

Screening

Screening ECGs (either at rest or with exercise) are not recommended in those without symptoms who are at low risk.[27] In those at higher risk the evidence for screening with ECGs is inconclusive.[27]

Some biomarkers may add to conventional cardiovascular risk factors in predicting the risk of future cardiovascular disease; however, the clinical value of some biomarkers is still questionable.[28][29] Currently, biomarkers which may reflect a higher risk of cardiovascular disease include:

Prevention

Currently practiced measures to prevent cardiovascular disease include:

  • A low-fat, high-fiber diet including whole grains and plenty of fresh fruit and vegetables (at least five portions a day)[34][35]
  • Tobacco cessation and avoidance of second-hand smoke;[34]
  • Limit alcohol consumption to the recommended daily limits;[34] consumption of 1-2 standard alcoholic drinks per day may reduce risk by 30%[36][37] However excessive alcohol intake increases the risk of cardiovascular disease.[38]
  • Lower blood pressures, if elevated;
  • Decrease body fat (BMI) if overweight or obese;[39]
  • Increase daily activity to 30 minutes of vigorous exercise per day at least five times per week;[34]
  • Reduce sugar consumptions;
  • Decrease psychosocial stress.[40] Stress however plays a relatively minor role in hypertension.[41] Specific relaxation therapies are not supported by the evidence.[42]

For adults without a known diagnosis of hypertension, diabetes, hyperlipidemia, or cardiovascular disease, routine counseling to advise them to improve their diet and increase their physical activity has not been found to significantly alter behavior, and thus is not recommended.[43]

Diet

Evidence suggests that the Mediterranean diet improves cardiovascular outcomes.[44] This may be by "about 30 percent" in those at high risk.[45] There is also evidence that a Mediterranean diet may be more effective than a low-fat diet in bringing about long-term changes to cardiovascular risk factors (e.g., lower cholesterol level and blood pressure).[46] In clinical trials the DASH diet (high in nuts, fish, fruits and vegetables, and low in sweets, red meat and fat) has been shown to reduce blood pressure,[47] lower total and low density lipoprotein cholesterol [48] and improve metabolic syndrome;[49] but the long term benefits outside the context of a clinical trial have been questioned.[50]

Total fat intake does not appear to be an important risk factor.[51] A diet high in trans fatty acids however does appear to increase rates of cardiovascular disease.[51][52]

Worldwide, dietary guidelines recommend a reduction in saturated fat.[53] There however are some questions around the effect of saturated fat on cardiovascular disease in the medical literature.[54][55] A 2012 Cochrane review found suggestive evidence of a small benefit from replacing dietary saturated fat by unsaturated fat.[56] A 2013 meta analysis concludes that substitution with omega 6 linoleic acid (a type of unsaturated fat) may increase cardiovascular risk.[53] Replacement of saturated fats with carbohydrates does not change or may increase risk.[57][58] Benefits from replacement with polyunsaturated fat appears greatest[51][59] however supplementation with omega-3 fatty acids (a type of polysaturated fat) does not appear have an effect.[60]

The effect of a low salt diet is unclear. A Cochrane review concluded that any benefit in either hypertensive or normal tensive people is small if present.[61] Additionally, the review suggested a low salt diet may be harmful in those with congestive heart failure.[61] However, the review was criticized particularly for not excluding a trial in heart failure where people had low salt and water levels due to diuretics.[62] When this study is left out the rest of the trials show a trend to benefit.[62][63]

Another review of dietary salt[64] concluded that there is strong evidence that high dietary salt intake increases blood pressure and worsens hypertension, and that it increases the number of cardiovascular disease events; the latter happens both through the increased blood pressure and, quite likely, through other mechanisms.[64][65] Moderate evidence was found that high salt intake increased cardiovascular mortality; and some evidence was found for an increase in overall mortality, strokes and left-ventricular hypertrophy.[64]

Supplements

While a healthy diet is beneficial, the effect of antioxidant supplementation (vitamin E, vitamin C, etc.) or vitamins generally has not been shown to improve protection against cardiovascular disease and in some cases may possibly result in harm.[66][67] Niacin, a type of vitamin B3, may be an exception with a modest decrease in the risk of cardiovascular events in those at high risk.[68][69] Magnesium supplementation lowers high blood pressure in a dose dependent manner.[70] Magnesium therapy is recommended for patients with ventricular arrhythmia associated with torsade de pointes who present with long QT syndrome as well as for the treatment of patients with digoxin intoxication-induced arrhythmias.[71] Results from an observational study conducted in the general Japanese population demonstrated that lower serum magnesium levels were associated with a greater average intima-media thickness and the risk of at least two carotid plaques.[72] Evidence to support omega-3 fatty acid supplementation is lacking.[73]

Medication

Aspirin has not been found to be of benefit overall in those at low risk of heart disease as the risk of serious bleeding is equal to the benefit with respect to cardiovascular problems.[74]

Statins are effective in preventing further cardiovascular disease in those with a history of cardiovascular disease.[75] As the event rate is higher in men than in women, the decrease in events is more easily seen in men than women.[75] In those without cardiovascular disease but risk factors statins appear to also be beneficial with a decrease in mortality and further heart disease.[76] The time course over which statins provide preventation against death appears to be long, of the order of one year, which is much longer than the duration of their effect on lipids.[77]

Management

Cardiovascular disease is treatable with initial treatment primarily focused on diet and lifestyle interventions.[78][79][80]

Epidemiology


Cardiovascular diseases are the leading cause of death. In 2008, 30% of all global death is attributed to cardiovascular diseases. Death caused by cardiovascular diseases are also higher in low and middle-income countries as over 80% of all global death caused by cardiovascular diseases occurred in those countries. It is also estimated that by 2030, over 23 million people will die from cardiovascular diseases annually.

Research

The first studies on cardiovascular health were performed in 1949 by Jerry Morris using occupational health data and were published in 1958.[82] The causes, prevention, and/or treatment of all forms of cardiovascular disease remain active fields of biomedical research, with hundreds of scientific studies being published on a weekly basis.

A fairly recent emphasis is on the link between low-grade inflammation that hallmarks atherosclerosis and its possible interventions. C-reactive protein (CRP) is a common inflammatory marker that has been found to be present in increased levels in patients at risk for cardiovascular disease.[83] Also osteoprotegerin which involved with regulation of a key inflammatory transcription factor called NF-κB has been found to be a risk factor of cardiovascular disease and mortality.[84][85]

Some areas currently being researched include possible links between infection with Chlamydophila pneumoniae (a major cause of pneumonia) and coronary artery disease. The Chlamydia link has become less plausible with the absence of improvement after antibiotic use.[86]

Several research also investigated the benefits of melatonin on cardiovascular diseases prevention and cure. Melatonin is a pineal gland secretion and it is shown to be able to lower total cholesterol, very low density and low density lipoprotein cholesterol levels in the blood plasma of rats. Reduction of blood pressure is also observed when pharmacological doses are applied. Thus, it is deemed to be a plausible treatment for hypertension. However, further research needs to be conducted to investigate the side effects, optimal dosage and etc. before it can be licensed for use.[87]


References

External links

  • DMOZ
  • European Guidelines on cardiovascular disease prevention in clinical practice (version 2012)

Template:Certain conditions originating in the perinatal period

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