Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Operating activities:
Net income (loss)	$ 1,495	$ (11,755)	$ (19,024)
Adjustments required to reconcile net income (loss) to net cash provided by (used for) operating activities:
Depreciation and amortization	4,336	3,948	4,898
Bad debt expense	117	139	22
Stock-based compensation	7,773	5,421	5,365
Write-down of inventory	1,833	2,781	3,536
Loss on disposal of fixed assets	53	29	54
Deferred tax provision	789	970	954
Change in unrealized loss on marketable securities			(342)
Gain on sale of WorldHeart common stock		(456)	(6,389)
Gain on settlement of investment	(1,017)
Changes in assets and liabilities:
Accounts receivable	(5,284)	(1,923)	2,210
Inventories	(6,229)	(1,508)	927
Prepaid expenses and other assets	(239)	161	(560)
Accounts payable	287	2,480	(1,387)
Accrued expenses and other long-term liabilities	(1,330)	605	2,299
Deferred revenue	1,050	682	75
Net cash provided by (used for) operating activities	3,634	1,574	(7,362)
Investing activities:
Purchases of short-term marketable securities	(24,502)	(8,004)	(11,869)
Proceeds from the sale and maturity of short-term marketable securities	7,750	7,000	17,848
Proceeds from the sale of WorldHeart common stock		456	6,389
Proceeds from settlement of investment	1,017
Contingent milestone payment on acquisition			(1,750)
Expenditures for property and equipment	(1,745)	(1,804)	(1,800)
Net cash (used for) provided by investing activities	(17,480)	(2,352)	8,818
Financing activities:
Proceeds from the exercise of stock options	14,257	1,061	639
Proceeds from the issuance of stock under employee stock purchase plan	423	313	340
Net cash provided by financing activities	14,680	1,374	979
Effect of exchange rate changes on cash	(675)	447	568
Net increase in cash and cash equivalents	159	1,043	3,003
Cash and cash equivalents at beginning of year	5,831	4,788	1,785
Cash and cash equivalents at end of year	5,990	5,831	4,788
Supplemental disclosures:
Fixed asset additions included in accounts payable	535	48	107
Common shares issued for business acquisition			3,827
Taxes paid, net of refunds			$ 300