From factcheck.org:

Michael Baden, a former chief medical examiner of New York City and a high-profile pathologist, told Fox News that it’s reasonable to include people with the virus, who also had other health issues, in the count.

“In the normal course, autopsies would then determine whether the person died of the effects of the COVID virus, whether the person had a brain tumor or brain hemorrhage for example that might be unrelated to it and what the relative significance of both the infection and the pre-existing disease is,” he said. Even if the number of autopsies being conducted are low because of concerns of infection, he said, “then you will include in those numbers some people who did have a pre-existing condition that would have caused death anyway, but that’s probably a small number.”

Likewise, Marc Lipsitch, a professor of epidemiology at Harvard University, told us in an email: “There are going to be some people who die of something else, happen to have COVID and get tested, and get counted as COVID deaths but would die anyway. It would be wrong to say that number is zero. However given current testing shortages and protocols, the number of such cases will be small.”

“[Guidance for Certifying Deaths Due to Coronavirus Disease 2019 (COVID–19)](.”https://www.cdc.gov/nchs/data/nvss/vsrg/vsrg03-508.pdf) Vital Statistics Reporting Guidance. National Center for Health Statistics, U.S. Centers for Disease Control and Prevention. 2 Apr 2020