But it's not clear if the performance lapses seen in the study would be meaningful in real-world operating rooms, says surgeon Emily Boyle, the lead author of the study and a researcher at the Royal College of Surgeons, in Dublin, Ireland.

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It's not exactly clear which real-world factors might account for the broad trends identified in the study.

CNN: More Americans drinking (alcohol)

Registry studies such as the current one enable researchers to use accumulated data on the real-world experience of thousands of patients, but as the current study suggests, that doesn't necessarily resolve uncertainty over which treatment approach is better.

WSJ: Heart Bypass Surgery May Offer Lower Death Risk Than Angioplasty

Manchester United is one of the world's most valuable clubs -- second only to Spanish giants Real Madrid -- according to a study by financial experts, Forbes.

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