I didn't catch it.

Well it's not really mentioned until the latest chapters, anyway if you don't mind the spoiler(is it tho?) you can continue reading below.



He suffers from coronary sindrome,
arrhythmia and panic attacks. In his case, stress is not really well received, especially when suffering from heart diseases, so it all adds up to his pain. If I didn't misunderstand he also had surgery in the past, also heart related.