Well, it depends. An average HR close to 45 may be the norm for someone like Usain Bolt but for the vast majority of us who are not professional long-distance runners (or athletes of any sort) it may be a tad low.
Therefore you need a one-to-one consult to look at individual factors such as your age, other medications or coexisting conditions, family history and fitness levels.
Though the vast majority of causes for "fainting"is benign, certainly low heartrate combined with low BP and symptoms will need to be looked at further.
Treatment will have to follow the cause and if you browse through some of the earlier Q&As on "fainting" here you may note that ECG, echocardiography, 24hr ambulatory ECG and Tilt-table test are usually required along with some blood tests (to ensure you are not anemic etc)
Hope this is somewhat helpful. Unfortunately I cannot be anymore specific as causes are manyfold. Rgrds.
