"Meet the Press" moderator Tim Russert's fatal heart attack in June tragically reminded middle-aged Americans that cardiovascular disease is the nation's leading cause of death. One in every six heart attacks has sudden death as its first, last and only symptom. Overall, about 40 percent of both women and men die of a heart-related ailment. On the plus side, U.S. cardiovascular-disease deaths have dropped dramatically in recent years. But public health officials warn that the downward trend is about to reverse itself as two large waves of cardiovascular disease wash over the U.S. health-care system in the next several decades — one caused by the aging of the nation's 76 million baby boomers and the other by Americans' sedentary lifestyles and poor diet. "The lid is going to blow off vascular diseases, and it could bankrupt society," according to one cardiovascular expert.