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
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                      	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	                      	

1. Name and Address of Reporting Person *

Koehn 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)
SVP Manufacturing & Operations	
(Last)          (First)          (Middle)

1225 OLD HIGHWAY 8 NW	3. Date of Earliest Transaction (MM/DD/YYYY)

2/28/2017		
(Street)

ST. PAUL, MN 55112
(City)        (State)        (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)

 	6. Individual or Joint/Group Filing (Check Applicable Line)

_ X _ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person	

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned	
1.Title of Security
(Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. 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  	2/28/2017  	 	M	  	8087  	A	$7.90  	91474  	D  	
 	
Common Stock  	2/28/2017  	 	S	  	8087  	D	$28.3331   (1)	83387  	D  	

Table II - Derivative Securities Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities)	
1. Title of Derivate Security
(Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. 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	7. Title and Amount of Securities Underlying Derivative Security
(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)  	$7.90  	2/28/2017  	 	M  	  	  	8087   	  (2)	6/11/2017  	Common Stock  	8087  	$0  	0  	D  	
 	
Stock Option (right to buy)  	$7.90  	 	 	   	  	  	  	  (2)	10/8/2017  	Common Stock  	12940  	 	12940  	D  	
 	
Stock Option (right to buy)  	$12.15  	 	 	   	  	  	  	  (2)	12/11/2017  	Common Stock  	24120  	 	24120  	D  	
 	
Stock Option (right to buy)  	$8.75  	 	 	   	  	  	  	  (2)	3/1/2019  	Common Stock  	8087  	 	8087  	D  	

Explanation of Responses:	
(  1) 	The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $28.28 to $28.41 inclusive. The reporting person undertakes to provide Cardiovascular Systems, Inc., any security holder of Cardiovascular Systems, Inc., or the staff of the Securities and Exchange Commission upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.	
(  2) 	Fully exercisable.	

Reporting Owners	
Reporting Owner Name / Address	Relationships	
	Director	10% Owner	Officer	Other	
Koehn Paul A.
1225 OLD HIGHWAY 8 NW
ST. PAUL, MN 55112			SVP Manufacturing & Operations		

Signatures		
/s/ Amanda Lorentz as Attorney-in-Fact for Paul Koehn pursuant to Power of Attorney filed herewith.		3/2/2017	
** Signature of Reporting Person		Date

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.	
*	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).	
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.	
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.	

POWER OF ATTORNEY

 The undersigned hereby constitutes and appoints Laurence Betterley,

Alexander Rosenstein, Jeffrey Points, Anne Meyer, Amanda Lorentz and

Ashley Brosius, or any one of them acting alone, the undersigned's true and

lawful attorney-in-fact and agent with full power of substitution and

resubstitution, for the undersigned and in the undersigned's name, place and

stead, in any and all capacities, to sign any or all Forms 3, 4 or 5

relating to beneficial ownership of securities of Cardiovascular Systems,

Inc. (the "Issuer"), to file the same, with all exhibits thereto and other

documents in connection therewith, with the Securities and Exchange

Commission and to deliver a copy of the same to the Issuer, granting unto

said attorney-in-fact and agent full power and authority to do and perform

each and every act and thing requisite and necessary to be done in and about

the premises, as fully to all intents and purposes as the undersigned might

or could do in person, hereby ratifying and confirming all said attorney-in-

fact and agent, or his substitute or substitutes, may lawfully do or cause

to be done by virtue thereof.  The undersigned acknowledges that the

foregoing attorney-in-fact, in serving in such capacity at the request of

the undersigned, is not assuming any of the undersigned's responsibilities

to comply with Section 16 of the Securities Exchange Act of 1934.

 This Power of Attorney shall remain in effect until such time as the

undersigned is no longer subject to the provisions of Section 16 of the

Securities Exchange Act of 1934 with respect to securities of the Issuer.

 The undersigned hereby indemnifies the attorneys-in-fact for all

losses and costs the attorneys-in-fact may incur in connection with or

arising from the attorneys-in-fact's execution of their authorities granted

hereunder.

 IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney

to be executed as of this 20th day of February, 2017.

     /s/ Paul A. Koehn