In 1970, nearly 40% of older heart attack victims who made it to the hospital never left, dying there from the attack or its complications. Today, that number is well below 10%. Younger victims fare even better. Moreover, instead of lingering in the hospital for a week, some people are now home the next day. The question is "what accounts for this remarkable improvement in heart attack survival?" Using linear and non-linear mixed-effects models (lme4 and the nlme packages in R), we purpose to examine how the risk factors have a bearing on the amount of time a person who suffered a heart attack will live.