The FDA today updated data from a post-approval study of Abiomed‘s (NSDQ:ABMD) Impella RP heart pump system, reporting a new 30-day survival rate of 28.6% for patients post-explant, hospital discharge or the start of longer term therapy.

A total of 12 of the 42 patients enrolled in the post-market trial of the Danvers, Mass.-based medtech company’s Impella RP have survived to 30 days, significantly lower than the 73.3% survival rate reported in the premarket clinical study of the device.

The percentage is up from earlier data, which the FDA released in February, indicating a 17.4% survival rate with only four of the 23 individuals enrolled at the time surviving to 30 days post-explant, hospital discharge or start of longer term therapy.

Patient selection was deemed the cause for the strikingly lower survival rate, as the majority of the patients in the trial would not have met enrollment criteria for the premarket studies of the device.

The survival rate for patients in the post-approval study that met the enrollment criteria was reported to be 64.3%, or nine of 14, the FDA said. For the subgroup of patients who would not have qualified for the preclinical study, the survival rate is only 10.7%, or three of 28 patients.

The federal watchdog said that when the device is used based on its current indication in “appropriately selected patients”, it still believes the benefits of the device outweigh the risks.

The FDA recommended that healthcare providers read and follow revised labeling, released earlier this year, which includes a patient selection checklist to identify patients that could benefit from treatment with the system, and to “carefully consider these interim survival results from the ongoing PAS when making treatment decisions.”