i have sinus tacycardia and have had it for 18 years. i usually had problems with it when i got excited,scared,etc. my rate got up to around 129. i take inderal and verapamil. i never had problems with light headedness,but my heart skips beats and flutters.,the doctors said not to worry unless i passed out or had chest pains. i have had catherizations,and echos and ekgs,and stress tests,holter monitors.
i guess it depends on how high your rate goes,and how bad it is,but remember most problems they can fix.