A heart attack starts with blockages in the blood vessels, so where better to look for predictors of heart trouble than in the blood? At the moment, the most reliable way to check the status of the heart's vessels is by angiogram, an invasive procedure that involves snaking a thin tube into the vessels from an artery in the leg. But researchers have now identified a preliminary panel of 23 genes that code for blood proteins, which was 83% accurate in detecting blood-vessel obstructions typical of heart disease. When doctors added this blood test to existing measures of heart attack risk — including symptoms of chest pain and family history of health problems — it improved by 16% their ability to classify patients as being at high or low risk, compared with traditional methods alone. It's too much to expect that the blood test by itself can predict heart attack, at least for now, but it could serve as an early warning call for patients who register as high risk. Perhaps by prompting changes in diet and lifestyle habits in these patients, it can help prevent them from ever having a heart attack at all.