FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * Tyska Paul A   2. Issuer Name and Ticker or Trading Symbol Cardiovascular Systems Inc [CSII] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) VP of Business Dev (Last) (First) (Middle) 651 CAMPUS DRIVE 3. Date of Earliest Transaction (Month/Day/Year) 04/21/2010 (Street) ST. PAUL, MN 55112 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock               1,294 I Held as custodian for minor children. Common Stock               125 D (1)

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Stock Option (right to buy)

$ 8.83

04/21/2010

D(2)

90,580

(2)

10/02/2011

Common Stock

90,580

$ 0

0

D

Stock Option (right to buy)

$ 7.9

(3)

08/06/2017

Common Stock

22,645

22,645

D

Stock Option (right to buy)

$ 12.15

(4)

12/11/2017

Common Stock

32,350

32,350

D

Stock Option (right to buy)

$ 8.75

(5)

03/01/2019

Common Stock

7,764

7,764

D

Stock Option (right to buy)

$ 8.83

04/21/2010

A(2)

90,580

(2)

10/02/2016

Common Stock

90,580

$ 0

90,580

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Tyska Paul A 651 CAMPUS DRIVE ST. PAUL, MN 55112			VP of Business Dev

Signatures

/s/ John R. Remakel as Attorney-in-Fact for Paul A. Tyska pursuant to Power of Attorney previously filed.		04/23/2010
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Shares acquired through the Issuer's Employee Stock Purchase Plan on December 31, 2009.
(2)	The two reported transactions involved an amendment of an outstanding option, resulting in the deemed cancellation of the "old" option and the grant of a replacement option. The option was originally granted on October 3, 2006 and is fully exercisable.
(3)	Exercisable: 7,549 on 8/7/08 and 7,548 on 8/7/09 and 8/7/10.
(4)	Exercisable: 16,175 on 2/25/10 and 2/25/11.
(5)	Exercisable: 3,882 on 3/2/10 and 3/2/11.

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