Additional Manufacturer Narrative · 1
EXAMINATION OF THE RETURNED MOTOR REVEALED THAT IT WAS FREE OF DAMAGE OR DEFECTS. THE RETURNED PUMP, HOWEVER, WAS ASSOCIATED WITH THE FOLLOWING FINDINGS: THE PRESENCE OF THROMBUS IN THE WELL OF THE LOWER HOUSING AND ON THE BASE OF THE IMPELLER, AND SURFACE DEFECTS ON THE BLADES OF THE IMPELLER AND FLANGE OF THE PUMP HOUSING CONSISTENT WITH CONTACT BETWEEN THE IMPELLER AND PUMP HOUSING. THIS LATER OBSERVATION WAS CONSISTENT WITH THE PUMP NOT BEING INSERTED AND SECURED PROPERLY IN THE MOTOR MOUNT. IMPROPER SEATING AND SECURING OF THE PUMP COULD EXPLAIN THE FORMATION OF THE THROMBUS AND TRIGGERING THE MOTOR FAIL ALARM. IMPROPER SEATING OF THE PUMP CAN RESULT IN CONTACT OF AN IMPELLER WITH A HOUSING CAUSING TURBULENT FLOW, HEMOLYSIS AND THROMBUS FORMATION IN A BLOOD PUMP. THE ROTATION OF THE IMPELLER WAS LIKELY RESTRICTED DUE TO THE PRESENCE OF THE THROMBUS AND CONTACT OF THE IMMPELLER WITH THE PUMP HOUSING, AND USERS WERE CORRECTLY ALERTED TO THIS CONDITION BY THE CONSOLE ALARMS. IN THE ABSENCE OF ANY DEFECTS ON THE SURFACE OF THE PUMP HOUSING, THE POTENTIAL FOR THROMBUS FORMATION IN THE PUMP COULD HAVE BEEN ELEVATED DUE TO THE LOW LEVEL OF ANTICOAGULATION AT THE TIME OF THE REPORTED EVENT. THE PT HAD A HISTORY OF BLEEDING, AND THE ACT LEVELS USED TO MONITOR THE LEVEL OF HEPARIN ANTICOAGULATION WERE REPORTED TO BE LESS THAN THE RECOMMENDED MINIMUM 160 SEC. REDUCED ANTICOAGULATION PRESENTS AN INCREASED RISK FOR THROMBUS FORMATION. THE COMBINATION OF CONTACT OF THE IMPELLER WITH THE HOUSING AND REDUCED LEVEL OF ANTICOAGULATION CAN EXPLAIN THE FORMATION OF THROMBUS IN THE PUMP, THE HEMOLYSIS OBSERVED, AND THE CORRESPONDING ALARMS. ENGINEERING EVAL CONCLUSION: AN EVAL OF THE RETURNED CENTRIMAG BLOOD PUMP AND MOTOR WAS PERFORMED. THE INVESTIGATION FAILED TO IDENTIFY ANY MFG OR PRE-EXISTING DEFECTS IN THE PUMP OR MOTOR. THE PUMP EVAL IDENTIFIED PRESENCE OF A LARGE THROMBUS ON THE BOTTOM OF THE PUMP HOUSING AND IMPELLER. AFTER REMOVING THE THROMBUS FROM THE TWO AREAS, INSPECTION REVEALED THAT THERE WERE NO SURFACE IRREGULARITIES IN THE AREA OR REGIONS WHERE THE THROMBUS WAS OBSERVED. FURTHER INSPECTION REVEALED THERE WAS A LOCKING SCREW INDENTATION ON THE LOWER FLANGE OF THE PUMP HOUSING INDICATING THAT THE PUMP MAY NOT HAVE BEEN SEATED PROPERLY DURING USE. IN CONJUNCTION WITH THIS OBSERVATION, THERE WERE PLASTIC ICICLES OBSERVED ON THE UNDERSIDE OF THE IMPELLER BLADES AND SCUFF MARKS ON THE SHOULDER OF THE LOWER PUMP HOUSING. THIS INDICATES THAT THE IMPELLER BLADES MAY HAVE BEEN RUBBING ON THE PUMP HOUSING SHOULDER DURING OPERATION. SUCH CONTACT CAN OCCUR IF THE PUMP WAS NOT SEATED OR SECURED PROPERLY IN THE MOTOR MOUNT. A SEPARATE ANALYSIS WAS PERFORMED ON THE MOTOR. INSPECTION REVEALED THAT THE MOTOR DID NOT APPEAR DAMAGED, AND WHEN TESTED, PERFORMED AS DESIGNED. A SIMULATION OF THE OPERATIONAL CONDITIONS WITH A SIMULATED THROMBUS WAS PERFORMED WITH A MATERIAL OF SIMILAR THICKNESS TO THE OBSERVED THROMBUS BETWEEN THE IMPELLER AND LOWER HOUSING. THIS SIMULATION DEMONSTRATED THE EFFECT OF AN ADD'L MECHANICAL LOAD ON THE IMPELLER. THE MOTOR WAS NOT ABLE TO MAINTAIN THE RPM OF THE IMPELLER IN ALL CASES, AND WHEN THE IMPELLER SPEED WAS NOT MET, THE PRIMARY CONSOLE TRIGGERED THE "MOTOR FAIL" ALARM. THE ALARM REPORTED BY THE HOSP WAS "MOTOR DRIVE FAIL" OR "MOTOR FAIL" TYPE ALARM. THE BEHAVIOR SIMULATED VIA BENCH TEST IS CONSISTENT WITH WHAT WAS REPORTED BY THE HOSP, BUT THE RESULTING ALARM TRIGGERED BY THE CONSOLE IS "MOTOR FAIL" ALARM NOT A "MOTOR DRIVE FAIL" ALARM. NOTE: ACTIVATION OF THE "MOTOR FAIL" ALARM IS THE NORMAL BEHAVIOR EXPECTED OF THE CENTRIMAG SYS, AND CAN BE EXPECTED UNDER SOME CIRCUMSTANCES WHEN THE IMPELLER OPERATES OUTSIDE OF PRESCRIBED DESIGN OPERATION CONDITIONS. THE GROSS OBSERVATIONS FROM THE EXAMINATION OF THE RETURNED PUMP SUGGEST THAT THE PUMP MAY NOT HAVE BEEN INSERTED AND SEATED PROPERLY IN THE MOTOR MOUNT DURING USE. ROTATION OF THE IMPELLER MAY HAVE BEEN HINDERED DUE TO THE PRESENCE OF THE THROMBUS AS WELL AS FROM FRICTION DUE TO CONTACT OF THE IMPELLER WITH THE LOWER HOUSING. RESISTANCE TO ROTATION OF THE IMPELLER WOULD POTENTIALLY EXPLAIN WHY THE IMPELLER MAY NOT HAVE BEEN ABLE TO ACHIEVE SET SPEED, WHICH WOULD HAVE TRIGGERED THE "MOTOR FAIL" ALARM AS AN APPROPRIATE RESPONSE. THE BEHAVIOR OF THE SYS, UNDER THESE CIRCUMSTANCES, IS CONSISTENT WITH THE SYS PERFORMING WITHIN DESIGN SPECS.