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HOMOCYSTEINE – SOMETHING ELSE TO WORRY ABOUT??
August 11, 1997

Short-take: Homocysteine is an amino acid which can be found in high quantities in some people’s blood. It appears to be an important compound in causing injury to blood vessel walls, in addition to causing an increased tendency for the blood to clot, both important causes of heart attacks and strokes. Levels can be lowered, and risks reduced, by eating good quality foods and/or supplementing the diet with some common vitamins.

This isn’t just another scare tactic, or another story about the possible risks of coffee drinking. It is another in a series of studies discovering an important cause of injury to blood vessels. The information presented on HeartPoint is conservative by design, and seeks to avoid sensationalizing early findings: this is neither early nor sensational, but appears to be new and important.

Homocysteine is an amino acid, the building blocks of protein, which are in our body. Amino acids aren’t "bad" in general, but high levels of homocysteine have been correlated with damage to the walls of arteries and veins, and furthermore cause platelets to become unusually "sticky". Thus, while homocysteine is not deposited in the walls of blood vessels like cholesterol is, it can damage the inside lining of the vessels, and allow the cholesterol to be more easily deposited. Furthermore, it can give patient’s a "double whammy" by making the platelets more likely to adhere and form a clot, a situation which can lead to heart attacks and strokes. This may be particularly important in the young and in women who do not otherwise seem to have enough risk factors to explain their vascular disease.

Here’s some technical aspects of homocysteine metabolism if you’re interested (skip this paragraph if you’re not). Homocysteine is not generally found in high quantities in the food we eat, but is formed from another amino acid which is in our diets, methionine. Homocysteine can be further broken down to cystathionine, and then cysteine which can be broken down and excreted in the urine. In addition, homocysteine can be turned back into methionine. The original hints of homocysteine’s tendency toward causing vascular problems was noted in children who lacked the enzyme to convert homocysteine to cystathionine, and homocysteine eventually overflows into the urine (the name of the disease is therefore "homocystinuria"). This is a rare disease associated with mental retardation and other disorders, but there is also a 50% chance of having a clot involving the arterial or venous system by the age of 30. Some, and it appears this maybe "many", have inefficiencies in the metabolism of homocysteine. Variations in the gene that codes for the enzyme that converts homocysteine to cystathionine have been described, and were recently correlated with vascular risk (Schwartz et.al. Circulation 1997:96:412-417).

Back to the real stuff, this most recent study. Norwegian investigators studied a population of patients with known blockage of the heart vessels (coronary artery disease) and correlated the levels of homocysteine in the blood with mortality at 5 years. 6% of those with levels less than 9 micromoles per liter died, 19% with levels from 9-20 died, and about 32% with levels greater than 20 died. Impressive study. (Nygard, O et al. Plasma homocysteine levels and mortality in patients with coronary artery disease, N Engl J Med 1997;337:230-236).

Fortunately, the metabolism of homocysteine can be altered by the availability of vitamins that stimulate the pathways favoring its breakdown (vitamin B-6) or reconversion to methionine (B-12 and folic acid [or "folate"]). These vitamins are found in abundance in fish, and dairy products, cereals, and fruits – all of the stuff you were supposed to be eating anyhow! Relatively modest doses of these vitamins have been shown to reduce homocysteine levels significantly:

B-6 (or "pyridoxine") in a dosage of 50-100 mg daily
Folic acid (or "folate") in doses of 400 or more micrograms daily
B-12 probably is important only in those with frank deficiencies

These are comparable to the amounts of these common vitamins that are found in many multivitamin preparations. It is to be stressed that the proper doses of these vitamins has not been determined however, and these are "best estimates" only. It would appear that this may be a good estimate however – patients in a study from earlier this year published in the Journal of the American Medical Association again showed a marked increase in the risk of vascular disease in patients with high homocysteine levels, but that the risk appeared to be lower in those who took multivitamins (Graham et. al., Plasma homocysteine as a risk factor for vascular disease).

You may want to discuss having your homocysteine level determined, or undergoing a "methionine loading test" to see if your levels are high, or whether they are responding to therapy.

Well, is homocysteine something else to worry about? No, worrying won’t do a thing about it . . . but I think it is something to take care of. While the authors of the NEJM article recommend further studies, I think there is enough data to act, particularly since the treatment has little in the way of side effects. Eat those green vegetables and fish. If you can’t, or this is insufficient, take vitamins as noted above.

STRESS AND THE HEART
July 15, 1997

There is a great deal of "common wisdom" that associates stress with heart disease. While this is difficult to measure, several studies have recently shed light on the subject.

A very well designed study reported in the Journal of the American Medical Association on the occurrence of episodes of inadequate blood supply to the heart muscle ("ischemia") following various types of activities and emotional states. Using techniques to measure episodes of ischemia which the patient was not even aware of, they found that episodes of tension, frustration and sadness were followed by a doubling of the risk of experiencing an ischemic event in the next hour. (Gullette et al, Effects of mental stress on myocardial ischemia during daily life, JAMA 1997;277:1521-1526). Other studies have recently clearly shown a relationship between episodes of anger and heart attacks (this occurs less frequently however if the person was taking aspirin at the time). A link with extreme stress was shown by the increase in the rate of cardiac deaths following the recent Northridge, California earthquake. An interesting study of persons in a recent Japanese earthquake showed an increase in blood pressure and the tendency of the blood to clot in patients with high blood pressure (Kario K et al. Earthquake-induced potentiation of acute risk factors in hypertensive elderly patients: Possible triggering of cardiovascular events after a major earthquake. Journal of the American College of Cardiology, 1997;29:926-33).

Most of us tend to believe that hot-tempered people have an increased risk of heart disease, but this is an extremely difficult area to study due to the difficulty of measuring things like "anger", "stress" and "hostility". All of these have been novel and well-designed studies of such areas. They add substantially to the evidence that there is indeed a relationship between these emotions and heart disease. Two of the studies implicate "thickening" of the blood as the mechanism, and one suggests that the regular use of aspirin may help.

The Point: "Negative" emotions including loneliness, depression and now anger continue to be linked to poor outcomes with heart disease. Patients who spend time and effort in reducing these are probably investing wisely, although it is unrealistic to think that a "blissful serene" existence is either possible or curative. And again, in light of the link to clotting: Take your aspirin!

 

PACEMAKERS AND CELLULAR PHONES
July 15, 1997

Cardiac pacemakers are electrical devices, and as such are subject to a variety of electromagnetic fields in the environment. The sensing circuits of a pacemaker can mistakenly identify electrical activity in the area surrounding a patient as coming from the patient's heart. Whatever patients may have heard about pacemakers, they are generally aware that patients who have pacemakers were at one time told to stay away from microwave ovens. This is no longer the case, since microwave energy is no longer used to communicate with the devices. However, there are always new threats to the pacemaker's sophisticated circuitry.

Cellular telephones are common in our environment now and they do create an electromagnetic field which may be harmful to patients with pacemakers. A recent study systematically studied a number of different phones with a number of different pacemakers. (Hayes et al. Interference with cardiac pacemakers by cellular telephones. New England Journal of Medicine, 1997;336:1473-9). There indeed is a definite risk of interference of the pacemaker by cellular phones, but it appears to be uncommon, and produces generally mild if any symptoms.

Physicians can minimize these risks by using particular models of pacemakers with appropriate filters, the correct leads, and optimal programming of the pacemaker.

Patients should:

• Tell their physicians of their desire to use cellular phones so that determinations of the best approach can be made. Advice must be tailored to individual patients, since their underlying rhythm is a very important determinant of whether a significant event might occur. Reprogramming the pacemaker or other strategies may be necessary.
• Turn the cellular phone off if possible when carried in clothes, etc.
• When the cellular phone is on, it shouldn't be carried near the pacemaker (particularly in a pocket near the pacemaker).
• Hold the device away from the body while dialing.
• Use the ear on the side away from the pacemaker.
• If an inadequate filtering system is present, use an analogue (as opposed to digital) cellular system.
• There should be minimal risk to patients who are in the vicinity of a cellular phone. Most studies have found that the phone must be within 3-4 inches of the pacemaker itself.

©COPY 1997 HeartPoint  

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