"Irritable heart" is a term used to describe a condition formerly known as soldier's heart, shell shock, or post-traumatic stress disorder. It is characterized by symptoms such as heart palpitations, shortness of breath, and chest pain, which can be brought on by stress, anxiety, or physical exertion. Antonyms for "irritable heart" would be calm, composed, peaceful, and tranquil. These words describe a state of mind and body that is free from stress and tension, and where there is a sense of ease and relaxation. In contrast to the turbulence and unease of "irritable heart," these antonyms suggest a sense of balance and stability, both physically and emotionally.