What is my heart big but it beat quiet?

It sounds like you are using poetic language to describe your emotions or personality rather than a literal medical condition. When someone says they have a "big heart," it often means they are very kind, compassionate, or generous. Saying that it "beats quiet" might suggest that even though they have a lot of love or compassion, they don't express it loudly or overtly.

In a medical context, having a "big heart" could refer to a condition called cardiomegaly, which is an enlargement of the heart that can be caused by various factors such as high blood pressure, heart valve disease, or cardiomyopathy. However, this condition wouldn't typically be described as the heart "beating quiet" unless related to specific symptoms such as fatigue or shortness of breath.

If you are referring to any medical concern, it is important to consult with a healthcare professional for accurate diagnosis and advice. However, if this is a metaphorical expression, it might be helpful to reflect on how you express your emotions and how you can communicate your feelings effectively with others.