Many roller-coasters have signs warning people suffering from high blood pressure not to go on the ride. If this roller-coaster had such a sign and you went on the ride anyhow, the park’s liability may be somewhat lessened. However, the most likely cause of your seizure appears to have been the fact that the seat belt, provided by the park, came unlatched. Whether that was due to a malfunction of the strap or because the park’s employee did an inadequate job of fastening the strap is immaterial – the park is liable, at least to some extent, for your seizure and any additional ongoing injuries or conditions.
Furthermore, when you visit an amusement park, you realize there are certain risks inherent in riding on the rides and, when you go on those rides, you are assuming that risk. In some states, assumption of risk is sufficient to find the park not liable at all; in other states, it will affect the amount of your damages award, and in some, it will have no affect at all. Your case has some good facts to help get past the assumption of risk. While you may assume many of the risks, you also depend on the safety equipment provided by the park to function and help shield you from some of the risks. This may be enough to overcome the fact that if there were warning signs telling people with high blood pressure not to go on this particular ride, you probably should not have gone the ride anyhow.