Medical science continues to make big strides in the war on heart disease—the leading cause of death in the U.S., according to the American Heart Association—by turning its attention to some culprits that are just now becoming known.
For years, doctors and the public at large have been well aware that smoking, high blood cholesterol, hypertension, obesity, physical inactivity, stress and diabetes are proven causes of coronary heart disease (CHD). These and various uncontrollable risk factors like age, gender, race and family history of heart disease contribute to atherosclerosis, narrowing of the arteries from plaque buildup. Left unchecked, atherosclerosis may result in angina, arrhythmia, congestive heart failure or heart attack.
And for years, doctors have known that the blood holds clues to a person’s cardiovascular health. Until recently, the main villain they sought out was cholesterol—particularly the type carried through the bloodstream in low-density lipoproteins (LDL). LDL cholesterol tends to adhere to artery walls, thereby earning its nickname as the “bad” cholesterol.
Today, however, researchers are finding mounting evidence that the blood holds many more clues to CHD beyond bad cholesterol. Among them:
- Homocysteine. In two large studies, people with very high levels of homocysteine, an amino acid in blood, carried a 70 percent greater risk of developing CHD. These patients typically ate high-fat, low-nutrition foods and tended to skip meals. Their blood also had low levels of folate and vitamins B6 and B12, key nutrients that keep homocysteine from harming artery walls and causing clots. For now, doctors say patients with poor eating habits should have a blood test and, if necessary, eat extra folic acid, which is added to cold cereals. These patients should also get vitamins B6 and B12 from foods like lean meat, poultry, tuna, green vegetables, eggs and low-fat dairy items.
- Triglycerides. A landmark study of family genetics found that high triglycerides, blood fats that store energy, are a major marker for cardiovascular disease. Researchers looked at two types of disorders in at-risk families: those with both high cholesterol and high triglycerides, and those with high triglycerides only. Both groups had significant increases in fatty deposits in the arteries. The report urged doctors to screen for both cholesterol and triglycerides when doing blood work. Ideally, your total cholesterol count should not exceed 200 milligrams per deciliter of blood, LDL should be no higher than 100 mg/dL and your triglyceride count should be less than 150 mg/dL. The report urged a healthier diet, less alcohol and adequate exercise for at-risk individuals.
- Germs. Researchers also have cast light on another possible CHD culprit: blood-borne bacteria and viruses. They think that infection by microorganisms like certain pneumonia bacteria or herpes viruses inflames the arteries, giving CHD a foothold. Scientists suspect patients with these infections have at least twice the risk of developing CHD as uninfected patients.
- Proteins. One confirmed marker for inflamed arterial walls is C-reactive protein. A major study determined that high blood levels of the protein translated into a 70 percent greater risk of CHD in patients. Elevated C-reactive protein could be caused by high LDL cholesterol. A blood test will show elevated C-reactive protein.
- Lipoprotein(a). Lp(a), a blood protein passed on from generation to generation, may raise a person’s risk for CHD anywhere from 10 percent to more than double the normal risk. This lipoprotein resembles LDL (“bad”) cholesterol and is suspected of slowing the removal of blood clots and aiding LDL’s ability to stick to artery walls. In families with a history of CHD before age 60, Lp(a) is especially worrisome—nearly one in every five CHD patients is found to have high Lp(a) levels in his or her blood. Unfortunately, doctors still don’t know how to treat high Lp(a).
- Oxidized LDL. Japanese researchers have recently pointed to this modified form of LDL cholesterol as a significant marker for heart attack. In the future, measuring blood levels of oxidized LDL cholesterol, which is more likely to stick to artery walls than garden-variety LDL cholesterol, may help identify people at greatest risk of heart attack, possibly allowing them to benefit from early intervention.
As scientists seek more answers to the heart disease puzzle, new risk factors will undoubtedly be discovered. However, doctors say nothing will outweigh the impact of following the “big three”—eating a diet low in saturated fat, exercising and not smoking—in lowering your personal risk for CHD.