hs-CRP stands for "high sensitivity C-reactive protein". It's a blood test that very precisely measures the level of inflammation in your bloodstream. Even though it's often called the "Cardio CRP", this test is not specific for the heart -- it's a nonspecific measure of inflammation. CRP is produced in at least three places: the liver, fat cells, and white blood cells. People with more fat or more white blood cells will have higher CRP. White blood cells may actually be the culprits in triggering heart attacks, as they've been shown to be involved in attacking the plaques in our coronary arteries, and that can sometimes cause plaque rupture and a heart attack. Elevated levels of CRP mean that your white blood cells are "on the attack" and higher levels mean a bigger response, and more risk. Studies show that for people over the age of 50, having a CRP level of 2.0 mg/L or greater increases the risk of heart attack by 54% over the next two years. The risk of stroke is also increased by 50% and the risk of death from all causes increased by 20% (Jupiter Study, published in the New England Journal of Medicine Nov 2008).
Lowering CRP also lowers risk, also shown in the Jupiter study. In that study, a "statin" medication (Crestor) was used to lower CRP, but there may be other effective ways to lower CRP including regular exercise, weight loss, and some supplements like vitamin D and fish oil (DHA).