Can anxiety be fatal?

Eventually only: It's a very slow (usually many decades) and painful way to die. The acute anxiety/panic attacks may feel like you're dying, but almost never do kill anyone. It's the long-term damage wrecked on your body by excess exposure to stress hormones that eventually does us in. Also the hazardous risk-taking, abusive behaviors many do to react to anxiety. The death certificate will not say "Anxiety".