Leaflet arrest in St Jude Medical and CarboMedics valves: an experimental study

Objective: Two patients who suffered acute failure of their St Jude Medical Masters aortic valve prostheses due to leaflet arrest that were unrelated to suture material are presented. It was hypothesized that the valves failed because force applied to bear upon the valve annulus caused the hinge mechanism to become restricted or to arrest. Methods: A study was designed to measure the force that would cause leaflet arrest in three sizes of St Jude Medical Masters valves and CarboMedics mechanical valves. A specially manufactured pushrod device was used to apply a variable force to the sewing cuff, low annulus level, or to the pivot guards of all the valves. Results: For every valve size tested, the St Jude Medical Masters valves required significantly less force applied than did the CarboMedics valves to cause one or both leaflets to arrest (P<0.0004). Conclusions: A force applied on the valve ring of mechanical valves can cause leaflet arrest. The force required to arrest the leaflets is within an order of magnitude of that measured in other in vivo animal studies. We conclude that force on the valve rings in patients after aortic valve surgery could cause leaflet malfunction and even arrest in some patients.