In afternoon trade, the S&P/ASX 200 Index (ASX: XJO) is on course to record a decent gain. At the time of writing, the benchmark index is up 0.6% to 7,803.9 points.

Four ASX shares that have failed to follow the market higher today are listed below. Here's why they are falling:

Imricor Medical Systems Inc (ASX: IMR)

The Imricor share price is down 3% to $1.41. This is despite the medical systems company releasing some good news this morning. Imricor revealed that its Advantage-MR EP Recorder/Stimulator has received CE mark certification under the European Union's new Medical Device Regulation (MDR). This follows the earlier CE mark approval of Imricor's 2nd generation Vision-MR Ablation Catheter under the MDR regime. Commercial launch of the 2nd generation Vision-MR Ablation Catheter and the new AdvantageMR system is planned to commence in June across the EU.

Nanosonics Ltd (ASX: NAN)

The Nanosonics share price is down 7.5% to $4.48. This may have been driven by a broker note out of Bell Potter this morning. According to the note, the broker has downgraded the medical device company's shares to a sell rating with a $4.05 price target. It said: "With FY26 almost upon us, we note consensus revenues are 5% above our forecast. Forecast revenues are generally highly transparent and we expect minimal contribution from the new CORIS device in FY26, hence our view that consensus revenues are cum downgrade at the August result. The note includes our sum of parts valuation assessment which yields a target price of $4.05, accordingly we downgrade to Sell from Hold."

Perpetual Ltd (ASX: PPT)

The Perpetual share price is down 1.5% to $15.39. This morning, analysts at Citi downgraded the fund manager's shares to a neutral rating (from buy) with a reduced price target of $18.25 (from $24.80). It made the move after running the rule over the company's quarterly update, which was released earlier this week.

Tourism Holdings Ltd (ASX: THL)

The Tourism Holdings share price is down 14% to $1.31. The catalyst for this has been the released of a trading update from the recreational vehicles company. The company warned: "Recent global geopolitical and tariff developments have significantly weakened the operating environment and lead to an additional decline in consumer confidence globally. This decline has resulted in further deterioration in vehicle sales demand, impacting both volumes and margins in all countries."