Donald Trump’s address to the nation on Wednesday left many viewers unsettled—not because of what he said, but how he said it. While reactions initially focused on the claims in his speech, a prominent medical expert raised concerns about Trump’s delivery and overall health.

Trump, who typically speaks in a measured tone, appeared unusually intense, speaking rapidly and forcefully during the roughly 20-minute address on the economy and immigration. Social media users quickly questioned whether something seemed off, prompting cardiologist and George Washington University professor Dr. Jonathan Reiner to weigh in.