Heart attack patients are more likely to survive when top cardiologists are not in the hospital, a new study suggests.

Researchers at Harvard Medical School found that when heart specialists are away at academic conferences, the survival rate at their hospitals actually improves.

They believe that specialists who attend the meetings are more prone to using intensive interventions for their patients which may do more harm than good, rather than taking a more holistic approach.

"Many medical interventions deliver no mortality benefit, and the fact that mortality actually falls for heart attack patients during these conference dates raises important questions about how care might differ during these periods," said lead author Dr Anupam Jena, who described the findings as 'an unfortunate paradox.'

Dr Jena and his team looked at 3,153 heart attack patients who were admitted to hospitals in the US during the world's largest interventional cardiology meeting Transcatheter Cardiovascular Therapeutics. They then compared them to 31,156 heart attack patients who hospitalized when top cardiologists were present.

They found that 19.5 per cent of patients who did not need stents to widen blood vessels died within 30 days of admission when cardiologists were in the hospital, but only 16.9 when they were away.