I've noticed my resting heart rate has been a bit higher than usual, usually between 90 and 110. Sometimes it goes over 100, although not too often. I'm wondering if this is normal or if I should be concerned? I had an ECHO last month, and it was normal. At what point should I think about this as potentially dangerous arrhythmia?

An arrhythmia can be dangerous if it leads to symptoms such as chest pain, fainting, dizziness, or shortness of breath. The frequency of arrhythmia that could be considered dangerous varies depending on the type and underlying cause. In your case, with a resting heart rate consistently between 90-110 and occasionally above 100, it is advisable to monitor it closely. Since your ECHO was normal last month, it is reassuring that there are no structural abnormalities with your heart. However, given the increased resting heart rate, it would be prudent to consult a healthcare provider for further evaluation. In the meantime, you can consider taking a beta-blocker medication like Metoprolol at a low dose of 25mg once daily to help control your heart rate.