Medical Matters: With the welcome increase in public health education about the risk factors for heart disease, most of us are pretty up to date on the dos and don'ts of maintaining a healthy heart.
Smoking, high blood pressure, obesity, physical inactivity and poor diet are the principal risk factors; diabetes, a family history of heart attack at an early age and recent menopause are more specific risks for certain people.
Interestingly, however, over half of those who develop cardiovascular disease do so without having even one of these conventional risk factors. So I was especially interested in an article in the current issue of Heartwise (the official magazine of the Irish Heart Foundation) examining newer risk factors for heart disease.
Many readers will be familiar with the key role played by aspirin in preventing a second or subsequent heart attack, stroke or mini stroke. However, extensive research has shown that aspirin offers only a 19 per cent reduction for further cardiovascular events - failing to offer protection for one in eight people taking the drug.
The reason for this (and indeed the explanation as to why many drugs work better in some people and not so well in others) is because humans differ greatly. Aspirin works by preventing platelets in the blood sticking together; however, about one in 20 people have what is termed aspirin resistance, in which the platelets carry on as if there was no aspirin circulating in the body.
While there is clearly a role for identifying patients with this phenomenon, there is, as yet, no standard laboratory measurement for aspirin resistance. Nor is there a specific treatment for it, notwithstanding the availability of more potent anti-platelet drugs.
High levels of both homocysteine and fibrinogen have been linked with an increased risk of heart attack and stroke. Homocysteine is an amino acid that occurs naturally in the body. Normal levels in the blood vary between five and 15 micro moles/litre. High levels affect the ability of blood vessels to relax as well as causing inflammation of their lining.
While folic acid lowers homocysteine levels, there are no results as yet from medical trials in which folic acid is given to people with high blood levels of homocysteine. But there is evidence that folic acid improves blood vessel function in people with coronary artery disease and elevated homocysteine.
Fibrinogen is a substance, manufactured by the liver, which plays a key role in blood clotting. It binds to platelets as well as itself forming the basis for clot formation. As well as being an independent risk factor for heart disease, elevated levels of fibrinogen interact with other risk factors. In one study, patients with chronic but stable angina who had high levels of fibrinogen were shown to have three times the risk of an acute coronary event compared to those with normal fibrinogen levels.
The measurement of fibrinogen is usually confined to those people who have no other determinable risk factors for heart attack or stroke. While there is currently no drug treatment for the condition, fibrinogen levels can be reduced with exercise and a moderate intake of alcohol.
Inflammatory factors are now recognised as playing an important role in the development of cardiovascular disease. A substance called C reactive protein (CRP) has been found within the plaques of atherosclerosis in people with coronary artery disease. CRP levels have been shown to be an independent predictor of heart attack, stroke and peripheral vascular disease in healthy people. There is a suggestion that high levels of the inflammatory marker be a better predictor of heart disease risk in women than men. Current thinking is to include the measurement of CRP levels in the assessment of people with cardiovascular disease and in the absence of overt infection elsewhere in the body, patients with high levels of CRP must have other risk factors more aggressively treated.
Finally, readers may be interested in the latest guidelines on the management of high blood pressure from the British Hypertension Society. The most significant part of its statement is: "The main determinant of benefit from blood pressure lowering drugs is the achieved blood pressure rather than the choice of therapy." In other words, the lower the blood pressure the better, advice that is especially important for patients at high cardiovascular risk.
But the really key message comes from the European Society of Cardiology: it is far better for us to address the range of risk factors that can cause heart disease and stroke rather than becoming fixated with getting blood pressure or cholesterol levels absolutely right while neglecting to exercise or continuing to smoke. There is a range of risk factors out there, both old and new. A broad approach to prevention is the way forward.
• Dr Muiris Houston is pleased to hear from readers at mhouston@irish-times.ie. He regrets that he cannot answer individual medical queries.