gms | German Medical Science

Objective: In shunt papers the causes for shunt revisions such as ventricular/distal catheter occlusion, migration, infection, were specified. These factors are selfevident or can be checked with simple methods (flushing, watercolumn). The same is true for visible valve lesions: body ruptures, in transparent bodies also debris and broken adjustment rotors; not-transparent valves remain enigmatous. Ca. 20–50 % of these lesions are iatrogeneously produced during explantation. Only a few use a rubric “lesion during explantation”, most classify ”insufficiency”.

Primary patent valves can suck air, blood or debris during OP, which change the hydraulic properties. After >1 h protein drys and transform to an sticking mass, insolvable by water or flushing. Ultrasound cleaning (cavitation 42,000 Hz) can remove some occludates. Ca. >98 % of “insufficient valves” goes without investigations into trash, a few to producers or independent valve labs (closed since 2010). The classification “defective valve” is arbitrary.

Method: Between 1987–2010 we tested 586 explanted valves, 62% of 942 test-specimen. Infected and totally obstructed probes were excluded. If possible, we made a test with valve in situ using water-column. After explantation of suspect valves and first inspection we cleaned the valve avoiding forced flushing. A desinfection with alcohol for some hours followed; storage under water.

We compared the documented comment of the explanteur with the test results, typically after a simplified ISO-test.

Results: We observed no infectious problems. The mean deviation of new valves was 57 mm H₂O (measured with flowrates of manufacturers), all testable spezimen displayed Ø 66 mm H₂O failure. Of new valves 35.1 % were accurat (±20 mm H₂O) compared to 35.6%. That means, that most explanted valves showed a similar accuracy and were not “defective”. Looking on valve design the ball-valves had the best results, followed by diaphragm, distal-, proximal slit and Orbis-Sigma-valves.

Conclusions: A high quote of “defective valves” are intact and the explantation an expensive error. The most common cause for “blockade” are air-bubbles in the valves, which can increase the resistance by 350 %.

Professional tests of explanted valves are comparable to investigations of crashed airplanes, which showed decisional informations for failure analyses and safer technologies.