Note 15 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands							1 Months Ended		12 Months Ended
	Jul. 09, 2024	May 01, 2024	Apr. 24, 2024	Feb. 26, 2024	Jan. 08, 2024	Jan. 09, 2023	Jul. 31, 2023	Sep. 30, 2018	Dec. 31, 2024	Dec. 31, 2023	Mar. 31, 2020
Share-Based Payment Arrangement, Option [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number (in shares)									70,605	21,465
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)									66,000
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)									$ 4.08
Non-plan Options [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number (in shares)									25,000	0
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)									25,000
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)									$ 5.32
Non-plan Options [Member] | Chief Commercial Officer [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)		25,000
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)		$ 5.321
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Grant Date Fair Value		$ 131
Non-plan Options [Member] | Chief Commercial Officer [Member] | Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)		5 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage		20.00%
Restricted Stock [Member]
Share-Based Payment Arrangement, Expense									$ 54	$ 1,200
Old Catheter [Member]
Business Combination, Consideration Transferred						$ 72,544
Share-Based Payment Arrangement, Expense						$ 1,100
Old Catheter [Member] | Options to Purchase Common Stock [Member]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in shares)						75,367
Business Combination, Consideration Transferred						$ 3,400
2018 Equity Incentive Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)							0
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number (in shares)									7
Employee Stock Purchase Plan 2018 [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)									0	2
Employee Stock Purchase Plan, Maximum Employee Election Threshold, Percentage								15.00%
Employee Stock Purchase Plan, Percentage of Fair Value Common Stock Price								85.00%
Employee Stock Purchase Plan, Contingency, Maximum Shares to Increase Stock Reserved for Issuance (in shares)								23
Employee Stock Purchase Plan, Contingency, Percentage of Total Shares Outstanding								1.25%
Proceeds from Stock Plans									$ 0	$ 0
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)									95	95
Inducement Equity Incentive Plan 2020 [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)									0	54	64
Equity Incentive Plan 2023 [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)									926,882	50,186
Shares Available for Issuance, Quarterly Increase, Percentage of Common Shares Outstanding on Adjustment Date Less Fiscal Quarter Beginning Balance									10.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)					28,500
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Grant Date Fair Value									$ 262
Equity Incentive Plan 2023 [Member] | Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)					21,000
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)					$ 4
Equity Incentive Plan 2023 [Member] | Share-Based Payment Arrangement, Nonemployee [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)					7,500
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)					$ 4
Equity Incentive Plan 2023 [Member] | Share-Based Payment Arrangement, Nonemployee [Member] | Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)					3 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage					8.33%
Equity Incentive Plan 2023 [Member] | Share-Based Payment Arrangement, Employee [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross (in shares)	10,000		12,500	15,000
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)	$ 3.5		$ 4.6	$ 4.2
Equity Incentive Plan 2023 [Member] | Share-Based Payment Arrangement, Employee [Member] | Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)	5 years		5 years	5 years	5 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage	20.00%		20.00%	20.00%	20.00%
Equity Incentive Plan 2023 [Member] | Share-Based Payment Arrangement, Option [Member] | Employees and Consultants [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)							5 years
Equity Incentive Plan 2023 [Member] | Share-Based Payment Arrangement, Option [Member] | Non-employee Directors [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)							3 years