BOSTON — Massachusetts medical malpractice lawsuit filings continued their downward trajectory last year, with cases falling below the 500 mark for the first time this decade, according to Massachusetts state court data.

According to the data recently released by Barbara J. Rouse, the chief justice of the Superior Court, and first reported by Massachusetts Lawyers Weekly, 485 cases were filed last year, down by about 4% from 504 new cases filed in 2007. New case filings slid by 32% from 708 in 2000.

Lawyers attribute the decrease in filings in most years since 2000 to the low percentage of plaintiffs’ verdicts, hospitals’ efforts to communicate more effectively with patients and families after an adverse medical outcome and a 2004 Massachusetts law change that decreased interest payments on legal judgments.

Andrew C. Meyer Jr., a founding partner of Boston-based medical practice boutique plaintiffs’ firm Lubin & Meyer, said a low percentage of plaintiffs’ verdicts is increasingly discouraging lawyers who don’t specialize in medical malpractice from taking new cases.

“Other attorneys [outside the specialty] have become very selective,” Meyer said. “These cases are very difficult, time-consuming and expensive.”

Defense lawyer Alan Rindler, who is also president and managing director of Boston’s Rindler Morgan, agreed that “plaintiffs’ lawyers are being more particular about the cases they take.”

Rindler also said hospitals are doing a better job explaining adverse outcomes to patients and their families.

“It may well be that patients are more forgiving if the way that it’s handled is kinder,” Rindler said.

Rindler also credits a 2004 Massachusetts state law change, which altered the prejudgment interest rate attached to medical malpractice awards.

“The amount of interest that might accrue on a potential judgment is [now] substantially lower if the plaintiffs win at trial,” Rindler said. “The total award will be lower.”

Under the prior system, medical malpractice awards were assessed 12% interest starting with the date the claim was filed. Now, the prejudgment interest rate is prime plus 4%, said Massachusetts Medical Society spokesman Richard P. Gulla.