Apparently it's somewhat common. According to this WIKI article on sudden cardiac deaths of athletes:

Sudden cardiac death occurs in approximately one per 200,000 young athletes per year, usually triggered during competition or practice.[6] The victim is usually male and associated with soccer, basketball, ice hockey, or American football, reflecting the large number of athletes participating in these sustained and strenuous sports.[3] For a normally healthy age group, the risk appears to be particularly magnified in competitive basketball, with sudden cardiac death rates as high as one per 3,000 annually for male basketball players in NCAA Division I.[19] This is still far below the rate for the general population, estimated as one per 1,300–1,600 and dominated by the elderly.[20] However, a population as large as the United States will experience the sudden cardiac death of a competitive athlete at the average rate of one every three days, often with significant local media coverage heightening public attention.[17]

In the United States approximately 8 to 10 deaths per year can be attributed to sudden cardiac death in NCAA with overall rate of 1 per 43,000.

That being said, a five fold increase is a noticeable jump! How are they going to try and explain it away? Perhaps they will blame it on the climate.