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                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                 SCHEDULE 13G/A


                    Under the Securities Exchange Act of 1934
                                (Amendment No 4)


                          CARDIOVASCULAR SYSTEMS, INC.
--------------------------------------------------------------------------------
                                (Name of Issuer)


                         Common Stock, $0.001 par value
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                         (Title of Class of Securities)


                                    141619106
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                                 (CUSIP Number)


                                December 31, 2011
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             (Date of Event Which Requires Filing of this Statement)


Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

    |X|    Rule 13d-1(b)
    |_|    Rule 13d-1(c)
    |_|    Rule 13d-1(d)

     *The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which would
alter disclosures provided in a prior cover page.

     The information required in the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 (the "Act") or otherwise subject to the liabilities of that section
of the Act but shall be subject to all other provisions of the Act (however, see
the Notes).

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-----------------------------                        ---------------------------
CUSIP No. 141619106              SCHEDULE 13G/A               Page 2 of 10 Pages
-----------------------------                        ---------------------------

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     1     Names of Reporting Persons


           Maverick Capital, Ltd. - 75-2482446
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     2     Check the Appropriate Box if a Member of a Group (See Instructions)
           (a)  |_|
           (b)  |_|
--------------------------------------------------------------------------------
     3     SEC Use Only

--------------------------------------------------------------------------------
     4     Citizenship or Place of Organization

           Texas
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                |   5   |  Sole Voting Power
                |       |  60,947
 Number of      ---------------------------------------------------------------
   Shares       |   6   |  Shared Voting Power
Beneficially    |       |  0
  Owned by      ----------------------------------------------------------------
    Each        |   7   |  Sole Dispositive Power
 Reporting      |       |  60,947
Person With     ----------------------------------------------------------------
                |   8   |  Shared Dispositive Power
                |       |  0
--------------------------------------------------------------------------------
     9     Aggregate Amount Beneficially Owned by Each Reporting Person

           60,947
--------------------------------------------------------------------------------
    10     Check Box if the Aggregate Amount in Row (9) Excludes
           Certain Shares (See Instructions)
                                                                        |_|
--------------------------------------------------------------------------------
    11     Percent of Class Represented by Amount in Row 9

           0.3%
--------------------------------------------------------------------------------
    12     Type of Reporting Person (See Instructions)

           IA
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-----------------------------                        ---------------------------
CUSIP No. 141619106              SCHEDULE 13G/A               Page 3 of 10 Pages
-----------------------------                        ---------------------------

--------------------------------------------------------------------------------
     1     Names of Reporting Persons


           Maverick Capital Management, LLC - 75-2686461
--------------------------------------------------------------------------------
     2     Check the Appropriate Box if a Member of a Group (See Instructions)
           (a)  |_|
           (b)  |_|
--------------------------------------------------------------------------------
     3     SEC Use Only

--------------------------------------------------------------------------------
     4     Citizenship or Place of Organization

           Texas
--------------------------------------------------------------------------------
                |   5   |  Sole Voting Power
                |       |  60,947
 Number of      ---------------------------------------------------------------
   Shares       |   6   |  Shared Voting Power
Beneficially    |       |  0
  Owned by      ----------------------------------------------------------------
    Each        |   7   |  Sole Dispositive Power
 Reporting      |       |  60,947
Person With     ----------------------------------------------------------------
                |   8   |  Shared Dispositive Power
                |       |  0
--------------------------------------------------------------------------------
     9     Aggregate Amount Beneficially Owned by Each Reporting Person

           60,947
--------------------------------------------------------------------------------
    10     Check Box if the Aggregate Amount in Row (9) Excludes
           Certain Shares (See Instructions)
                                                                        |_|
--------------------------------------------------------------------------------
    11     Percent of Class Represented by Amount in Row 9

           0.3%
--------------------------------------------------------------------------------
    12     Type of Reporting Person (See Instructions)

           HC
--------------------------------------------------------------------------------





-----------------------------                        ---------------------------
CUSIP No. 141619106              SCHEDULE 13G/A               Page 4 of 10 Pages
-----------------------------                        ---------------------------

--------------------------------------------------------------------------------
     1     Names of Reporting Persons


           Lee S. Ainslie III
--------------------------------------------------------------------------------
     2     Check the Appropriate Box if a Member of a Group (See Instructions)
           (a)  |_|
           (b)  |_|
--------------------------------------------------------------------------------
     3     SEC Use Only

--------------------------------------------------------------------------------
     4     Citizenship or Place of Organization

           United States
--------------------------------------------------------------------------------
                |   5   |  Sole Voting Power
                |       |  60,947
 Number of      ---------------------------------------------------------------
   Shares       |   6   |  Shared Voting Power
Beneficially    |       |  0
  Owned by      ----------------------------------------------------------------
    Each        |   7   |  Sole Dispositive Power
 Reporting      |       |  60,947
Person With     ----------------------------------------------------------------
                |   8   |  Shared Dispositive Power
                |       |  0
--------------------------------------------------------------------------------
     9     Aggregate Amount Beneficially Owned by Each Reporting Person

           60,947
--------------------------------------------------------------------------------
    10     Check Box if the Aggregate Amount in Row (9) Excludes
           Certain Shares (See Instructions)
                                                                        |_|
--------------------------------------------------------------------------------
    11     Percent of Class Represented by Amount in Row 9

           0.3%
--------------------------------------------------------------------------------
    12     Type of Reporting Person (See Instructions)

           HC
--------------------------------------------------------------------------------




Item 1(a)     Name of Issuer:

              Cardiovascular Systems, Inc.

Item 1(b)     Address of Issuer's Principal Executive Offices:

              651 Campus Drive
              St. Paul, Minnesota 55112-3495

Item 2(a)     Name of Person Filing:

              This Schedule 13G (the "Schedule 13G") is being filed on behalf of
              each of the following persons (each, a "Reporting Person"):

              (i)   Maverick Capital, Ltd.;
              (ii)  Maverick Capital Management, LLC; and
              (iii) Lee S. Ainslie III ("Mr. Ainslie").

              The Schedule 13G relates to Shares (as defined herein) held
              for the accounts of Maverick Capital, Ltd.'s clients.


Item 2(b)     Address of Principal Business Office, or, if none, Residence:

              The address of the principal business office of (i) Maverick
              Capital, Ltd. and Maverick Capital Management, LLC is 300 Crescent
              Court, 18th Floor, Dallas, Texas 75201, and (ii) Mr. Ainslie is
              767 Fifth Avenue, 11th Floor, New York, New York 10153.


Item 2(c)     Citizenship:

              (i)   Maverick Capital, Ltd. is a Texas limited partnership;
              (ii)  Maverick Capital Management, LLC is a Texas limited
                    liability company; and
              (iii) Mr. Ainslie is a citizen of the United States.

Item 2(d)     Title of Class of Securities:

              Common Stock, $0.001 par value (the "Shares").

Item 2(e)     CUSIP Number:

              141619106

                               Page 5 of 10 Pages



Item 3.       If this statement is filed pursuant to ss.ss.240.13d-1(b) or
              240.13d-2(b) or (c), check whether the person filing is a:

   (a)   |_|  Broker or dealer registered under section 15 of the Act (15
              U.S.C. 78o).

   (b)   |_|  Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

   (c)   |_|  Insurance company as defined in section 3(a)(19) of the Act
              (15 U.S.C. 78c).

   (d)   |_|  Investment company registered under section 8 of the
              Investment Company Act of 1940 (15 U.S.C. 80a-8).

   (e)   |X|  An investment advisor in accordance with
              ss.240.13d-1(b)(1)(ii)(E).

   (f)   |_|  An employee benefit plan or endowment fund in accordance with
              ss.240.13d-1(b)(1)(ii)(F).

   (g)   |X|  A parent holding company or control person in accordance with
              ss.240.13d-1(b)(1)(ii)(G).

   (h)   |_|  A savings association as defined in Section 3(b) of the
              Federal Deposit Insurance Act (12 U.S.C. 1813).

   (i)   |_|  A church plan that is excluded from the definition of an
              investment company under Section 3(c)(14) of the Investment
              Company Act of 1940 (15 U.S.C. 80a-3).

   (j)   |_|  A non-U.S. institution in accordance with
              ss.240.13d-1(b)(1)(ii)(J).

   (k)   |_|  Group, in accordance with ss.240.13d-1(b)(1)(ii)(K).

   If filing as a non-U.S. institution in accordance with
ss.240.13d-1(b)(1)(ii)(J), please specify the type of institution:______________



Item 4        Ownership

              Ownership as of December 31, 2011 is incorporated by reference to
              items (5) - (9) and (11) of the cover page of the Reporting
              Person.

              Maverick Capital, Ltd. is an investment adviser registered under
              Section 203 of the Investment Advisers Act of 1940 and, as such,
              may be deemed to have beneficial ownership of the Shares which are
              the subject of this filing through the investment discretion it
              exercises over its clients' accounts. Maverick Capital Management,
              LLC is the General Partner of Maverick Capital, Ltd. Mr. Ainslie
              is the manager of Maverick Capital Management, LLC and is granted
              sole investment discretion pursuant to Maverick Capital
              Management, LLC's Regulations.

Item 5        Ownership of Five Percent or Less of a Class

              If this statement is being filed to report the fact that as of the
              date hereof the reporting person has ceased to be the beneficial
              owner of more than 5 percent of the class of securities, check the
              following |X|.

Item 6        Ownership of More than Five Percent on Behalf of Another Person.

              Not applicable.

                               Page 6 of 10 Pages




Item 7        Identification and Classification of the Subsidiary Which Acquired
              the Security Being Reported on By the Parent Holding Company or
              Control Person

              Not applicable.

Item8         Identification and Classification of Members of the Group

              Not applicable.

Item9         Notice of Dissolution of Group

              Not applicable.

Item10        Certifications

              By signing below each of the Reporting Persons certifies that, to
              the best of such person's knowledge and belief, the securities
              referred to above were acquired and are held in the ordinary
              course of business and were not acquired and are not held for the
              purpose of or with the effect of changing or influencing the
              control of the issuer of the securities and were not acquired and
              are not held in connection with or as a participant in any
              transaction having that purpose or effect.






                               Page 7 of 10 Pages




                                    SIGNATURE

         After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Date:  February 14, 2012          MAVERICK CAPITAL, LTD.

                                  By:     Maverick Capital Management, LLC,
                                          Its General Partner

                                          By:   Lee S. Ainslie III, Manager

                                                By: /s/ John T. McCafferty
                                                    ----------------------
                                                    John T. McCafferty
                                                    Under Power of Attorney
                                                    dated February 13, 2003

Date:  February 14, 2012          MAVERICK CAPITAL MANAGEMENT, LLC

                                  By:     Lee S. Ainslie III, Manager

                                          By: /s/ John T. McCafferty
                                              ----------------------
                                              John T. McCafferty
                                              Under Power of Attorney
                                              dated February 13, 2003


Date:  February 14, 2012          LEE S. AINSLIE III


                                  By: /s/ John T. McCafferty
                                      ----------------------
                                      John T. McCafferty
                                      Under Power of Attorney
                                      dated February 13, 2003


                               Page 8 of 10 Pages




                                  EXHIBIT INDEX

A.    Joint Filing Agreement, dated March 10, 2009, by and among Maverick
      Capital, Ltd., Maverick Capital Management, LLC, and Lee S. Ainslie III.




                               Page 9 of 10 Pages



                                                                       Exhibit A

                             Joint Filing Agreement

         The undersigned hereby agree that the statement on Schedule 13G with
respect to the Common Stock, $0.001 par value of Cardiovascular Systems, Inc.,
dated as of March 10, 2009, is, and any amendments thereto (including amendments
on Schedule 13D) signed by each of the undersigned shall be, filed on behalf of
each of us pursuant to and in accordance with the provisions of Rule 13d-1(k)
under the Securities Exchange Act of 1934.

Date:    March 10, 2009


                                  MAVERICK CAPITAL, LTD.

                                  By:  Maverick Capital Management, LLC
                                       Its General Partner

                                       By: Lee S. Ainslie III, Manager



                                           By: /s/ John T. McCafferty
                                               ---------------------------------
                                               John T. McCafferty
                                               Under Power of Attorney dated
                                               February 13, 2003


                                  MAVERICK CAPITAL MANAGEMENT, LLC

                                  By:   Lee S. Ainslie III, Manager



                                        By: /s/ John T. McCafferty
                                            ------------------------------------
                                            John T. McCafferty
                                            Under Power of Attorney dated
                                            February 13, 2003


                                  LEE S. AINSLIE III



                                  By: /s/ John T. McCafferty
                                      ------------------------------------------
                                      John T. McCafferty
                                      Under Power of Attorney dated
                                      February 13, 2003


                              Page 10 of 10 Pages