Hi,
I wouldn't worry about this at all.
It happens to me all the time because my heart rate goes up during measuring, or I have benign sinus arrhythmia (variable heart rate with breathing). That your heart rate is measured as "irregular" just means that your BP monitor detects different time between heart beats. The most common cause is as mentioned sinus arrhythmia or the fact that your heart rate may increase during measuring. Other common causes are PACs or PVCs.
If your heart rate is really irregular for long times, you should of course have it examined by your doctor, but I strongly assume that's not what happened here.
Your blood pressure and blood pressure response to the stress and panic is excellent.
All your numbers look good to me if you don't have any dizzy symptoms, for example.
I would not worry about a reading on a BP monitor about irregular. Check yourself, if you can't feel you pulse you may want to spend $25 and add a stethoscope to your at home heart tools. If your "ear" can't detect an irregularity, I'd conclude it isn't irregular.
I have an irregular HB, due to AFib, and that means I have to guard against clot formation, aspirin plus an anticoagulant. PVC/PAC do not increase the risk of clots even though they cause an irregular HB.... so I understand.
Try not to work up a worry, that by itself is unhealthy.