Exhibit 10.52

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December 22, 2010

Board of Directors

Hansen Medical, Inc.

800 East Middlefield Road

Mountain View, CA 94043

Dear Sirs:

I hereby voluntarily relinquish any rights to a cash incentive bonus in respect
of Hansen Medical, Inc.’s 2011 fiscal year and agree that in lieu of a cash
incentive bonus opportunity in respect of the Company’s 2011 fiscal year I will
be eligible for a performance restricted stock unit covering 120,000 shares of
the Company’s common stock, which units will vest based on the Company’s
Corporate 2011 Critical Success Factors approved by the Board. I acknowledge and
agree that this change will not constitute “Good Reason,” nor will it be
considered to be a “Good Reason Event,” under the Retention Agreement, dated
May 26, 2010, between me and the Company.

Very truly yours,

/s/ Bruce J Barclay

Bruce J Barclay

800 East Middlefield Road, Mountain View, California 94043· T 650.404.5800
www.hansenmedical.com