Pages

Tuesday, February 28, 2012

Heart disease

Cardiovascular disease


Cardiovascular disease
Classification and external resources

Micrograph of a heart with fibrosis (yellow) and amyloidosis (brown). Movat's stain.
ICD-10 I51.6
ICD-9 429.2
DiseasesDB 28808
MeSH D002318

Cardiovascular disease or heart disease is a class of diseases that involve the heart or blood vessels (arteries and veins).[1] While the term technically refers to any disease that affects the cardiovascular system (as used in MeSH C14), it is usually used to refer to those related to atherosclerosis (arterial disease). These conditions usually have similar causes, mechanisms, and treatments.

Cardiovascular diseases remain the biggest cause of deaths worldwide, though over the last two decades, cardiovascular mortality rates have declined in many high-income countries but have increased at an astonishingly fast rate in low- and middle-income countries. The percentage of premature deaths from cardiovascular disease range from 4% in high-income countries to 42% in low-income countries. More than 17 million people died from cardiovascular diseases in 2008.[2] Each year, heart disease kills more Americans than cancer. In recent years, cardiovascular risk in women has been increasing and has killed more women than breast cancer.[3] (PDAY) showed vascular injury accumulates from adolescence, making primary prevention efforts necessary from childhood.[4][5]

By the time that heart problems are detected, the underlying cause (atherosclerosis) is usually quite advanced, having progressed for decades. There is therefore increased emphasis on preventing atherosclerosis by modifying risk factors, such as healthy eating, exercise, and avoidance of smoking.

Contents

[hide]

[edit] Risk factors

[edit] Age

Age is an important risk factor in developing cardiovascular diseases. It is estimated that 82 percent of people who die of coronary heart disease are 65 and older[6]. At the same time, the risk of stroke doubles every decade after age 55.[7]

Multiple explanations have been proposed to explain why age increases the risk of cardiovascular diseases. One of them is related to serum cholesterol level.[8]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.[8]

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.[9]

[edit] Gender

Men are at greater risk of heart disease than pre-menopausal women.[10] However, once past menopause, a woman’s risk is similar to a man’s.[10]

Among middle-aged people, coronary heart disease is 2 to 5 times more common in men than in women.[8] In a study done by the World Health Organization, gender contributes to approximately 40% of the variation in the sex ratios of coronary heart disease mortality.[11]Another study reports similar results that gender difference explains nearly half of the risk associated with cardiovascular diseases[8] One of the proposed explanations for the gender difference in cardiovascular disease is hormonal difference.[8] 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.[8] 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.[8] 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.[12]

Among men and women, there are differences in body weight, height, body fat distribution, heart rate, stroke volume, and arterial compliance.[13] In the very elderly, age related large artery pulsatility and stiffness is more pronounced in women.[14]This may be caused by the smaller body size and arterial dimensions independent of menopause.[15]

[edit] Air pollution

Particulate matter have been studied for their 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.[16] Women had a higher relative risk (RR) (1.42) for PM2.5 induced coronary artery disease than men (0.90) did.[16] Overall, long-term PM exposure increased rate of atherosclerosis and inflammation. In regards to short-term exposure (2 hrs), every 25 μg/m3 of PM2.5 resulted in a 48% increase of CVD mortality risk.[17] 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.[18] 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.[21][22]

[edit] Types

[edit] Coronary heart disease

Main article: Coronary heart disease

Coronary heart disease refers to the failure of the coronary circulation to supply adequate circulation to cardiac muscle and surrounding tissue. Coronary heart disease is most commonly equated with Coronary artery disease although coronary heart disease can be due to other causes, such as coronary vasospasm.[23]

Coronary artery disease is a disease of the artery caused by the accumulation of atheromatous plaques within the walls of the arteries that supply the myocardium. Angina pectoris (chest pain) and myocardial infarction (heart attack) are symptoms of and conditions caused by coronary heart disease.

Over 459,000 Americans die of coronary heart disease every year.[24] In the United Kingdom, 101,000 deaths annually are due to coronary heart disease.[25]

[edit] Cardiomyopathy

Main article: Cardiomyopathy

Cardiomyopathy literally means "heart muscle disease" (cardio=heart, myo=muscle, pathy=disease) It is the deterioration of the function of the myocardium (i.e., the heart muscle) for any reason. People with cardiomyopathy are often at risk of arrhythmia and/or sudden cardiac death.

[edit] Cardiovascular disease

Cardiovascular disease is any of a number of specific diseases that affect the heart itself and/or the blood vessel system, especially the veins and arteries leading to and from the heart. Research on disease dimorphism suggests that women who suffer with cardiovascular disease usually suffer from forms that affect the blood vessels while men usually suffer from forms that affect the heart muscle itself. Known or associated causes of cardiovascular disease include unhealthy ratios of the two smallest lipoproteins (see LDL and HDL), hyperlipidemia (including hypercholesterolemia), elevated blood glucose levels, i.e. diabetes mellitus, upper normal and high blood pressure, i.e.hypertension, Lp-PLA2, lipoprotein(a) and hyperhomocysteinemia, among others.

Types of cardiovascular disease include:

  • Atherosclerosis – Ruptures of atherosclerotic plaque within the artery wall. This both showers clot inducing debris into the blood stream and induces clots within the blood flowing inside the artery and has been identified to be the most common mechanism producing ischemia.

[edit] Ischaemic heart disease

  • Ischaemic heart disease – disease of the heart muscle itself, characterized by reduced blood supply to the cardiac muscles i.e. myocardium.

[edit] Heart failure

Main article: Heart failure

Heart failure, also called congestive heart failure (or CHF), and congestive cardiac failure (CCF), is a condition that can result from any structural or functional cardiacdisorder that impairs the ability of the heart to fill with or pump a sufficient amount of blood throughout the body. Therefore leading to the heart and body's failure.

[edit] Hypertensive heart disease

Main article: Hypertensive heart disease

Hypertensive heart disease is heart disease caused by high blood pressure, especially localised high blood pressure. Conditions that can be caused by hypertensive heart disease include:

[edit] Inflammatory heart disease

Disability-adjusted life year for inflammatory heart diseases per 100,000 inhabitants in 2004.[26]
no data
less than 70
70-140
140-210
210-280
280-350
350-420
420-490
490-560
560-630
630-700
700-770
more than 770

Inflammatory heart disease involves inflammation of the heart muscle and/or the tissue surrounding it.

[edit] Valvular heart disease

Main article: Valvular heart disease

Valvular heart disease is disease process that affects one or more valves of the heart. There are four major heart valve which may be affected by valvular heart disease, including the tricuspid and aortic valves in the right side of the heart, as well as the mitral and aortic valves in the left side of the heart.

[edit] Pathophysiology

Population based studies show that the precursors of heart disease start in adolescence. The process of atherosclerosis evolves over decades, and begins as early as 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. However, most adolescents are more concerned about other risks such as HIV, accidents, and cancer than cardiovascular disease.[27]

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,[28] as are a history of chronic kidney disease and hypercholesterolaemia .[29] 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.[30][31][32]

[edit] Screening

Some biomarkers are thought to offer a more detailed risk of cardiovascular disease. However, the clinical value of these biomarkers is questionable.[33] Currently, biomarkers which may reflect a higher risk of cardiovascular disease include:

[edit] Prevention

See also: Saturated fat and cardiovascular disease controversy

Measures to prevent cardiovascular disease may include:

  • a low fat high fiber diet including whole grains and plenty of fresh fruit and vegetables (at least five portions a day)[35]
  • a diet high in vegetables and fruit[36]
  • tobacco cessation and avoidance of second-hand smoke;[35]
  • limit alcohol consumption to the recommended daily limits;[35]
  • lower blood pressures, if elevated, through the use of antihypertensive medications[citation needed];
  • decrease body fat (BMI) if overweight or obese[citation needed];
  • increase daily activity to 30 minutes of vigorous exercise per day at least five times per week;[35]
  • decrease emotional stress[citation needed].
  • Consumption of 1-2 standard alcoholic drinks per day may reduce risk by 30%[37][38]

The generally accepted viewpoint is that dietary saturated fat and cholesterol intake is associated with cardiovascular disease. However, this viewpoint has been disputed.[39] While many studies have affirmed the link between consumption of saturated fats and heart disease, some studies have not found a statistically significant link or have been inconclusive. A study of rats suggests that the links between a diet high in sugar and saturated fat compared with a sugar-free, low fat diet lead to cardiac dysfunction despite modest levels of obesity, and a diet for humans that is low in sugar and rapidly absorbed starches and high in polyunsaturated fatty acids are associated with a reduced risk of coronary heart disease.[40] Some experts suggest that the focus should reassess the recommendations to switch away from saturated fats and instead focus on carbohydrates, particularly switching refined carbohydrates (especially refined grains and sugar) to unsaturated fats and/or healthy sources of protein, a moved to whole grains and limiting sugar-sweetened beverage consumption. Though diets high in saturated fats or refined carbohydrates are not suitable for ischemic heart disease prevention, refined carbohydrates are likely to cause even greater metabolic damage than saturated fat in a predominantly sedentary and overweight population[41] Another study agrees with the approach and suggests this may be linked to the macronutrients associated with refined carbohydrates.[42]

Evidence shows that the Mediterranean diet improves cardiovascular outcomes.[43] As of 2010 however vitamins have not been found to be effective at preventing cardiovascular disease.[44]

[edit] Management

Cardiovascular disease is treatable with initial treatment primarily focused on diet and lifestyle interventions.[45][46][47] Medication may also be useful for prevention.

[edit] Epidemiology

Disability-adjusted life year for cardiovascular diseases per 100,000 inhabitants in 2004.[48]
no data
<900
900-1650
1650-2300
2300-3000
3000-3700
3700-4400
4400-5100
5100-5800
5800-6500
6500-7200
7200-7900
>7900

According to the World Health Organization, chronic diseases are responsible for 63% of all deaths in the world, with cardiovascular disease as the leading cause of death.[49]

Research

The first studies on cardiovascular health were performed in 1949 by Jerry Morris using occupational health data and were published in 1958.[50] 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 trend has emerged, particularly in the early 2000s, in which numerous studies have revealed a link between fast food and an increase in heart disease. These studies include those conducted by the Ryan Mackey Memorial Research Institute, Harvard University and the Sydney Center for Cardiovascular Health. Many major fast food chains, particularly McDonald's, have protested the methods used in these studies and have responded with healthier menu options.

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.[51] 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.[52][53]

Some areas currently being researched include possible links between infection with Chlamydophila pneumoniae and coronary artery disease. The Chlamydia link has become less plausible with the absence of improvement after antibiotic use.[54]


Posted by at
Labels: ,

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)