hello, current bp medicine can cause low pulse rate but not high pulse rate. If you have episodic high heart rate then it can be a cardiac arrhythmia like psvt or atrial fibrillation, in which heart rate suddenly goes up and also suddenly decreases. Blood pressure falls during these episodes and one has dizziness, fainting, blackouts, sometimes syncope. Usually ecg is normal as it is usually done in between the episodes. ECG done during episodes will show abnormality. You will need 24 hour holter monitoring and event monitoring which you are having and we ll probably get answers out of it. Also, hemoglobin and thyroid test should be done. ln order to abort such episodes you should try to cough hard. Is there any stress or anxiety associated. You can discuss with your doctor regarding reduction in dose of metoprolol as pulse rate is low. If none of the above is successful then last option is of electrophysiological studies which is invasive test which can diagnose and treat the arrhythmia permanently in most of the cases.