It's obviously not a topic a lot of people like to talk about, but heart disease is serious. Cardiovascular diseases as a whole are still the number one killer of Americans, which is terrible, because it can easily be prevented, in most cases. Other than genetics, one of the top risk factors for heart disease is obesity. Genetics are out of control, but every single person can control their weight. Cutting things like trans fats and sugar from your diet will help that, but about 70% of weight control comes from exercise. According to the Mayo Clinic, to prevent heart disease due to obesity, you need to exercise most (5-6) days every week, for between thirty and sixty minutes. That seems like a lot, but the Mayo Clinic also says “...even shorter amounts of exercise offer heart benefits, so if you can't meet those guidelines, don't give up. You can even break up your workout time into 10-minute sessions. Now, any cardio workouts (something that gets your heart rate up) are going to improve your heart (cardiovascular) health. Most people think that to get a cardiovascular workout, they need to go to the gym. And while you can walk into any gym, and there will be cardio machines all around, you don't need a gym membership to get in 30 minutes a day.
If you have a bicycle, you can take a thirty minute bike ride through your neighborhood, or you can simply take a walk. Obviously when it comes to walking, leisurely walking while shopping, while it burns calories, doesn't count. You need to be walking around three miles per hour for your heartbeat to noticeably raise.
When it comes to the gym, there are many things you can do. Any machine that isn't related to weight lifting is going to be good for cardio. There are treadmills, which are better for walking because they can tell you how many calories you're burning. But there are also recumbent bikes, elliptical, and stair machines that are incredibly good for heart health.