Hello! Actually, I'm not sure if the medication would be used for the anxiety attacks themselves or for the acceleration of heart rate that accompanies them, as you described. Assuming it's anxiety attacks accompanied by tachycardia, which is palpitation or an increase in heart rate, the use of this medication has shown very good results. It acts through mechanisms that prevent a significant increase in heart rate during anxious episodes, consequently reducing the sensation of chest tightness, sweating, and tremors, typically.
Lorazepam is not recommended for prolonged use, as far as I know. Being a benzodiazepine, it has the potential for abuse due to tolerance, meaning there's a tendency to increase the dose to achieve the same effect after some time of using the medication. Additionally, in individuals with cognitive complaints like brain fog - I'm not sure if that applies to you - they may experience a slight additional decrease in concentration.
Of course, you and your doctor need to decide, but it seemed like a choice worth considering based on what you've described. I'm hopeful that the results will be very positive.