Piper Jaffray analyst Matt O'Brien lowered his price target for Abiomed to $320 from $480 following the company's "surprising" Q4 miss and reduced outlook. The analyst, still believes in the company and is a buyer of the stock with an unchanged Overweight rating. Abiomed in early trading is down 7%, or $20.47, to $256.60. The primary cause of the shortfall was weakness in the company's protected PCI business, which was negatively impacted by the FDA's cautionary letter to clinicians on Impella RP, O'Brien tells investors in a research note. The analyst, however, believes the totality of "compelling" clinical data will improve utilization of this patient population going forward. He encourages investors to buy the stock on today's weakness.