Decree affirmed. Costs of the appeal are to be determined by the single justice. The reviewing board adopted the findings of the single member in awarding compensation to the claimant widow. The single member relied upon the opinion of a specialist in internal medicine that the employee died from acute cardiac failure causally related to his occupation as a letter pressman in which he had been employed twenty to twenty-five hours a week overtime in the month preceding his death. Evidentiary support for the single member’s finding was not lacking. See General Motors Corp., petitioner, 344 Mass. 481. There was no prejudicial error in a lengthy hypothetical question addressed to and answered by the expert.