Obesity seems to impact long-term cardiovascular health only through the other numbers--i.e., raising your blood pressure and lipids. In the Framingham 30-year risk study (http://www.ncbi.nlm.nih.gov/pubmed/19506114), they tried adding BMI to the risk model, but it didn't add any predictive value. But they used it to create a very approximate risk model for people who don't know their biomarkers.

Also note that you can appear perfectly thin, but have high blood pressure and cholesterol, and thus be at risk! So know your numbers. A lot of health is only revealed by what's going on within your body.