Hot sauna is often cautioned against for those with existing cardiac or vascular problems, with some reason.

Exercising or stressing damaged or degenerated tissues = bad

Sauna raises HR without increasing blood pressure though (modulo some possible initial short spike at the beginning), because your blood vessels dilate.

Cannabis causes dilation of blood vessels and elevated HR, it’s the same effect. If you take a big dab you can definitely feel your blood pressure drop and muscles relax even though your heart rate has increased.