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CVD risk factors

 The many guises of cardiovascular disease

The term cardiovascular disease is a catch-all for a number of conditions that affect the heart, the blood vessels that nourish the heart (the coronary arteries), and the arteries that distribute blood to the brain, legs, and everywhere in between. Two harmful processes underlie most forms of cardiovascular disease:

  •  Atherosclerosis: Atherosclerosis is the accumulation of cholesterol-filled plaque in the inner walls of an artery. It is usually accompanied by low-grade inflammation. Atherosclerosis is a slow-growing, generally silent condition that plays a key role in many types of cardiovascular disease. It can begin in the teen years, or even earlier. Atherosclerosis first appears as whitish streaks on the inner lining of artery walls. As more and more cholesterol enters the artery wall, these fatty streaks turn into plaques—pockets of cholesterol, white blood cells, and more. Plaque can bulge outward into the bloodstream, or inward away from the bloodstream. Large plaques can narrow the opening available for blood flow, causing the chest pain known as angina during physical exertion or stress. Large and small plaques can rupture, causing a heart attack or stroke.
  • Endothelial dysfunction: The endothelium is the layer of tissue that lines the inside of arteries. A healthy endothelium works to keep an artery free from plaque or blood clots. It also allows the artery to easily widen and narrow to regulate blood flow. Smoking, high blood pressure, and other “insults” can cause the endothelium to malfunction. Endothelial dysfunction harms health directly and also contributes to atherosclerosis.

Atherosclerosis and endothelial dysfunction can be prevented. Halting them once they’ve started, or reversing them, is possible, too, but is much harder to achieve. Atherosclerosis and endothelial dysfunction can lead to a variety of conditions:

  •  Coronary artery disease is essentially atherosclerosis in one or more arteries that nourish the heart muscle. Coronary artery disease underlies:

Angina: chest pain or discomfort with exertion or stress. Angina occurs when the heart’s demand for oxygen (because it is working harder) outstrips the coronary arteries’ abilities to supply part of the heart with enough oxygenated blood.
Heart attack: the complete blockage of blood flow through an artery, which prevents part of the heart muscle from receiving any oxygenated blood. Such blockages occur when a plaque ruptures and a clot forms to seal the break. If the clot is large enough, it can completely block the blood vessel. A clot can also break away and lodge in a smaller artery.

  • Stroke: essentially a brain attack. Most strokes occur when a clot blocks an artery feeding part of the brain (these are called ischemic strokes). Without a constant supply of oxygen, brain cells rapidly die. About 20% of strokes occur when a blood vessel bursts and bleeds into the brain (these are called hemorrhagic strokes).
  • Heart failure: the inability of the heart to pump blood through the body as efficiently as it should. This prevents other organs from getting as much oxygenated blood as they need to carry out their functions
  • Heart arrhythmias: potentially harmful changes in the rhythm of the heartbeat. They include ventricular fibrillation, which nearly always cause death, and atrial fibrillation, which causes fatigue and increases the risk of stroke.
  • Valve disorders: four valves inside the heart ensure a one-way flow of blood through the heart and around the body. Corrosion of a valve can cause it to leak, which makes the heart work harder. This can cause symptoms such as shortness of breath or lead to heart failure.
  • Peripheral artery disease: atherosclerosis-induced reductions in circulation to the arms, legs, kidneys, digestive system, and other parts of the body.
  • Cognitive decline: age-related memory loss and decline in thinking abilities. Although it is usually blamed on Alzheimer’s disease, the most common cause is poor blood flow to the brain through atherosclerosis-narrowed arteries.

The American Heart Association estimates that nearly 80 million Americans have some form of cardiovascular disease. (1) It is the leading cause of death in the United States (7) and most developed countries.

Risk Factors

Several factors influence your risk of having a heart attack or stroke, or developing another form of cardiovascular disease. Some of these you can’t change; some you can.

Non-modifiable risk factors – risk factors you can’t change – include:

  • Age
  • Gender
  • Genes
  • Ethnic origin
  • There’s also strong evidence that your early development in the womb and during childhood helps set the stage for heart health or heart disease.

Cardiovascular disease risk factors that can be modified include habits and choices such as:

  • Tobacco use
  • Physical activity
  • What you eat and drink

All of the above affect physiologic factors like:

  • Blood pressure
  • Cholesterol level
  • Blood sugar
  • Other potentially modifiable risk factors include air pollution, noise, stress, and infection, though these are not as easy to control directly.

Having a risk factor doesn’t automatically mean you will develop cardiovascular disease. But the more of them you have, the higher the odds—unless you take action.

 Calculating risk

Several models have been developed to help individuals predict their risk of having a heart attack or developing cardiovascular disease. The American Heart Association has endorsed the use of these models in the primary prevention setting. (8)

  • The most commonly used calculator was developed by Framingham Heart Study researchers. The National Heart, Lung, and Blood Institute has an online version of this risk calculator. It uses seven pieces of information (age, gender, total cholesterol, HDL cholesterol, smoking status, blood pressure, and the use of blood pressure medicine) to calculate the odds of having a heart attack in the next 10 years.
  • The newer Reynolds Risk Scores, one for men and one for women, include the Framingham variables plus family history of a heart attack, the level of C-reactive protein, a marker of inflammation and the level hemoglobin A1c, a marker of blood sugar control, among diabetic patients.
  • The most recent CVD risk calculator, developed as part of the 2013 American College of Cardiology and American Heart Association (ACC/AHA) Guideline on the Assessment of Cardiovascular Risk, includes sex- and race-specific estimates of both 10-year and lifetime risks for atherosclerotic cardiovascular disease, and is available through the American Heart Association’s website.

These calculators are useful for estimating the risk of developing cardiovascular disease among individuals who already have strong risk factors and who are at high risk for having a heart attack or stroke or other cardiovascular event. However, these calculators may underestimate the true lifetime burden of cardiovascular disease, especially in middle-aged adults, as more than half of all such cardiovascular events occur in individuals who aren’t classified as high risk. (9) In addition, while most American adults have low short-term risk of cardiovascular disease, two-thirds of them have a high lifetime risk. (10)

  • The Healthy Heart Score was created by a team from the Department of Nutrition at Harvard School of Public Health to fill this gap. It estimates cardiovascular disease risk in seemingly healthy individuals. The Healthy Heart Score is a simple tool that can be used to identify individuals at high risk for cardiovascular disease due to unhealthy lifestyle habits. Its use is intended to complement, not replace, existing primary prevention risk scores, since different calculators may be most appropriate for different populations.

References

1.   Go, A.S., et al., Heart disease and stroke statistics–2013 update: a report from the American Heart Association. Circulation, 2013. 127(1): p. e6-e245.

7. Hoyert, D. and J. Xu, Deaths: Preliminary data for 2011, in National vital statistics reports. 2012, National Center for Health Statistics: Hyattsville, MD.

8.  Greenland, P., et al., 2010 ACCF/AHA guideline for assessment of cardiovascular risk in asymptomatic adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation, 2010. 122(25): p. e584-636.

9. Polonsky TS, Greenland P. CVD screening in low-risk, asymptomatic adults: clinical trials needed. Nat Rev Cardiol., 2012. 2012;9:599-604.

10. Marma AK, Berry JD, Ning H, Persell SD, Lloyd-Jones DM. Distribution of 10-year and lifetime predicted risks for cardiovascular disease in US adults: findings from the National Health and Nutrition Examination Survey 2003 to 2006. Circ Cardiovasc Qual Outcomes., 2010. 2012;3:8-14.

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