Is a heart rate of 45 dangerous?

Slow heart beat: If you don't have any symptoms like dizziness, pre-syncope, syncope or fatigue or chest pain or shortness of breath, then you are ok. But you complained of chest pain. Hence it should be treated. Its etiology should be elicited. Thyroid problems and blocks in heart arteries should be ruled out. Consult your physician.

Depends. : Low heart rate (bradycardia) is dangerous when the patient is symptomatic. I.E., light -headed, or becomes unable to respond to stress or exercise. Many athletes have low resting hr because their hearts are fit. At night, most of us have somewhat lower hrs as the demands of our bodies are low. Generally, i don't like to see a hr in a patient less than 50 as it tends not to be well tolerated.