How do doctors evaluate treatments for heart disease?

Research on drugs, diets, and devices to treat or prevent cardiovascular disease includes clinical trials and observational studies. In clinical trials, volunteers are randomly assigned to receive either the new treatment or the comparison, which may be a placebo (an inactive therapy) or a treatment that’s already available. Observational studies follow a large group of people over a long period of time and gather information on diet, exercise, and medical and family history, for example. All studies have strengths and weaknesses, but the evidence from clinical trials is the most trustworthy.