REYNOLDS, J.
Appeal by the employer and its insurance carrier from a decision of the Workmen's Compensation Board on the ground that there is no substantial evidence to support the board's finding of accidental injury and causal relationship. The board found that claimant experienced aggravation of an underlying rheumatic endocarditis which in turn was a factor in the development of cardiac failure culminating in surgery as a result of his work activities inside the unventilated drum of a cement mixer. Clearly the board could find that the welding and lifting activities performed inside the confines of the air depleted drum met the test of Matter of Masse v. Robinson ( 301 N.Y. 34) and that the injury due to the usual effort, although spread over a period of some days or more, was accidental ( Matter of Murphy v. Howard Schaffer, 17 A.D.2d 882). The issue of causal relationship presents no more than the usual conflict of medical testimony, and since we find advanced no valid reason why the board could not accept the testimony that casual relationship existed, the board's determination must be upheld ( Matter of Palermo v. Gallucci Sons, 5 N.Y.2d 529). Decision affirmed, with costs to the Workmen's Compensation Board. Gibson, P.J., Herlihy, Reynolds, Staley, Jr., and Cooke, JJ., concur in memorandum by Reynolds, J.