Scientists said that having a cat helped to relieve stress and anxiety, which is known to help protect against heart disease by lowering blood pressure and reducing the heart rate.
The 10-year study looked at 4,435 adults aged between 30 and 75, about half of whom owned a cat.
The findings, presented at a stroke conference in America, showed that 3.4 per cent of the cat owners died from a heart attack over 10 years. Among the group who had never owned a cat the rate was 5.8 per cent.
Cat owners still had a much reduced chance of developing strokes or heart attacks when researchers took account of other factors known to trigger heart disease, including high cholesterol levels, smoking and diabetes.
Prof Adnan Qureshi, from the Minnesota University, who carried out the study, said he was surprised by the strength of the effect that owning a cat appeared to have.
"The logical explanation may be that cat ownership relieves stress and anxiety and subsequently reduces the risk of heart disease."
He believes one reason could be that stroking the pet could cut the level of stress-related hormones in the blood. Reducing stress is known to help protect against heart disease by lowering blood pressure and reducing the heart rate.
But Prof Qureshi added that the type of person who owned a cat was usually already fairly stress-free and at low risk of heart disease.