In any claim for compensation for injury or death from cardiovascular or cerebrovascular causes, the claimant shall prove by a preponderance of the credible evidence that the injury or death was produced by effort or strain related to the performance of duty involving a substantial condition, event or happening in excess of the wear and tear of the claimant's daily living and in reasonable medical probability caused in a material degree the cardiovascular or cerebrovascular injury or death resulting therefrom.
Material degree means an appreciable degree or a degree substantially greater than de minimis.