Bradycardia and apnea

I've been using Xpap for about 4 years now, currrently on auto bipap and doing reasonably well.
I scheduled a visit with a cardiologist to look into another matter... possible tia's. He put me on a holter monitor for 48 hours. Called me today to tell me that there were no arrythmias, however my pulse rate during sleep fell into the high 40's and low 50's. He suggested that I check with my primary care Dr to see if I have sleep apnea. (By the way, that was already in my chart that I was being treated for sleep apnea, so he should have known this already).
I asked him if apnea wouldn't cause my blood to desaturate, he agreed yes that would likely happen. Then I asked if the body's normal response to desaturation is increasing heart rate, not decreasing. His response was that sleep apnea causes heart rate to drop, not increase.
Has anyone heard of this????
I think that all my prior sleep studies showed increasing heart rate with lowered blood oxygen. Pulse ox studies, as I recall showed the same relationship.
So, the question is..... is bradycardia (or near 45 bpm) a clinical symptom of sleep apnea?

In my observation during a sleep study: The heart rate may drop during an apnea, then when you snort (for lack of a better word) your airway open, the heart rate may increase. This is called brady-tachy on a PSG. Now if you have snoring, apnea, and/or upper airway resistance and then get treated with cpap, it has been my observation that the heart rate will decrease. This can often be seen on the hypnogram or graphs of the PSG/CPAP titration.
I hope this helps explain the lower heart rate. Now, this is my observation, but, if you or your Doctor is concerned then seek more medical advice.
I believe you may be able to see this on the RESMED website located in clinicians, then click "Understanding Sleep Disordered Breathing". This is a computer generated sleep study with explanations.
Lisa

what makes you think you are having TIA's?

any tingling felt in the lips? on hypertension medication? Start taking your BP at home, take it several times during the day and write down the values, take it at different times during day/evening. When you get about 7 days worth take those to your GP.

TIA would be to one side (vs both), you may experience tingling to the lips, you may experience temporary loss of motor control to one side.

-drink plenty of water every day avoid dehydration
-ask your doctor about starting an aspirin regiment, use Ecotrin or enteric coated aspirin
-keep hypertension under control, make sure it is not spiking or dropping too low

One of the more common things seen with CPAP

- you have hypertension and are taking medication for controlling it (before cpap)
- you go on CPAP and continue taking that same medication, but now the CPAP lowers hypertension on its own and you continue with dosage or medication. The result can be: BP now drops to a hypotensive level and your start experiencing dizzyiness and even vertigo especially when going from a sitting to standing position.
-it is time to have your potassium levels checked and modification to hypertension medication.

Yes, what Snoredog just said
My BP went to normal after 11 months on cpap. I was experiencing dizziness when I would awaken and stand up. BP low...

Thanks Lisa, the Resmed demo was very useful. However it did not really identify if the bradycardia is the result of the loss of muscle tone or the result of hypoxia (the hypoxia being a consequence of apnea).
I did some additioanl research:

http://thorax.bmj.com/cgi/content/full/53/suppl_3/S20

One of the more interesting assertions in this article is:
It has therefore been clearly established that bradycardia is the expected rhythm during apnoeas. Short apnoeas without hypoxaemia or prolonged apnoeas during which time hypoxaemia is prevented by breathing enriched oxygen gases do not result in bradycardia. Accordingly, apnoea combined with hypoxaemia appears to be required to produce significant bradycardia.
For those of us who do not use supplemental 02, it would seem like pulse-ox monitor is a good tool to evaluate the effectiveness of cpap therapy.