All health problems impedes the heart to alleviate quickly and properly. This includes obesity, respiration problems, high blood pressure (as well as low blood pressure), contamination of the air, etc…

more blood does not mean more healing – in case of the heart it is probably fatal because with poor diet,injury or illness blood clots and will damage the heart.
No human organ can “heal itself” – it always needs the whole organism to compensate for damage – if a vital organ as the heart is involved the time to do so is often too short