Consider a SERM or Aromatase Inhibitor?

I have been going through treatments for IDC (age 47,pre-menopausal,stage IIB, grade 3, 2/17 nodes +, ER+/PR+ and Her2+++) since Dec '06--mastectomy, AC chemo (12 weeks), followed by Taxol(12 weeks), and am just finishing up 25 radiation sessions.
I will be seeing my medical oncologist to discuss the next course of treatment, Tamoxifen and Herceptin.
I have been reading that Her2 overexpression often predicts resistence or a poorer response to Tamoxifen therapy, but can be more receptive to Anastrazole. Would it be prudent to consider ovarian shutdown, either by ovarian ablation or Zoladex, and then use an Aromatase Inhibitor instead of a SERM?
Also, my LVEF on MUGA was 55%, which seems low. Could this be a predictor that I would be more likely to develop cardiotoxicity while on Herceptin?
The MUGA was not done before chemo, so I don't know if the lower value may be due to Adriamycin.
Thank you for your thoughts.

[CCF-RN,MSN-rf]

Dear chirok17:  There is controversy in terms of whether Her2 overexpression leads to reduced efficacy of tamoxifen. There are generally insufficient data to make that determination.  Nonetheless, it is a worthy topic to discuss with your oncologist as it relates to your specific situation.  

A MUGA scan is considered "normal" when the LVEF is anything above 0.5 (or 50%).  It is not a predictor of the heart's response to therapy.  It is a baseline for evaluation that can be repeated to indicate if there has been any cardiotoxicity during from treatment.   If there was no baseline MUGA before the adriamycin, it is unknown whether there was any effect on your heart from this medication.