But now scientists think they have found a link between some common infections and more serious conditions.
And that could mean it's possible to predict if an individual is likely to have a cardiac arrest allowing time for preventive action.
She will be joined in the studio by Dr Liam Smeeth who led the research for the London School of Hygiene and Tropical Medicine
Scientists say the research which links three infections to heart attacks and strokes is a major breakthrough and will give a greater understanding.
Heart and Circulatory Disease Facts
Heart attacks and circulatory disease are Britain's biggest killer
270'000 people suffer a heart attack every year - that's one person every two minutes
Coronary Heart Disease kills 117'000 people a year year
CHD claims more lives in the winter months
The respiratory infections which cause pneumonia and bronchitis have been connected to heart attacks along with cystitis which is an infection of the urinary tract.
All three are said to increase the chance of suffering a cardiac arrest by five times and triple the risk of having a stroke for the first week after falling ill.
However the risk is only short lived and drops away after a few weeks.
Scientists funded by the British Heart Foundation, the Medical Research Council and the Wellcome Trust looked at the medical records of 40'000 patients.
The lead researcher was Dr Liam Smeeth who is an epidemiologist at the London School of Hygiene and Tropical Medicine.
You can find links to all the above organisations from the top right hand side of this page
Another of the project's researchers, Professor Patrick Vallance at the BHF laboratory at University College Hospital in London said:
'The work shows the timing of a heart attack is not random. The question "why today?" is now answered in part and the research provides an insight into what eventually triggers a heart attack or stroke."
Scientists say there is no increased risk from vaccines for flu and tetanus.
The reason for the link is thought to be due to inflammation caused by infection which leads to cardio vascular problems - even a minor or brief infection can trigger an attack.
Dr Smeeth says that people shouldn't be too scared about the research but he thinks it is an interesting scientific breakthrough.
If you have any concerns about your health, consult your doctor or NHS Direct