dizziness can be caused by many causes it can be due to anxiety the roses depression dehydration electrolyte imbalance high or very low blood pressure and these things should be checked before hand If you have a regular heartbeat or fast heartbeat it could be some specific arrhythmia or it could be due to poor conditioning this can only be determined by looking at your EKG when the heartrate was about 140 If there is no specific irregular heartbeat but just a sinus tachycardia than it can be improved by doing regular exercise doing biofeedback for your anxiety or depression and keeping yourself hydrated and to check for and to remove any underlying medical condition if you have any thank you very much please let me know if you want to send me copy of your EKG I will be glad to look at it