Leaflet embolisation from Duromedics valves: a report of two cases

Embolized mechanical aortic valve leaflet causing infrarenal aortic stenosis and claudication

Leaflet escape from mechanical heart valves is a rare but potentially fatal complication of prosthetic valve replacement. Historically, the incompetent valve is replaced emergently and the escaped leaflet is subsequently retrieved from its settlement in a distal vessel. If it is not retrieved, the fragment can increase the risk of infection, thrombosis, and migration. We report a case of a mechanical aortic valve leaflet that embolized during valve reoperation and caused occlusive aortic disease found 2 years later. This case emphasizes the importance of locating leaflet fragments after they are noticed missing.

Spontaneous leaflet fracture resulting in embolization from mechanical valve prostheses

Spontaneous leaflet fracture of mechanical heart valve prostheses is very rare. We describe a case of spontaneous leaflet embolization 31 years after aortic valve replacement with an Edwards-Duromedics prosthesis (Baxter Healthcare Corp., Edwards Division, Santa Ana, CA). We review the literature on this subject to increase awareness and recognition for this potentially life-threatening complication.

Mechanical heart valve cavitation

Cavitation was first directly related to mechanical heart valves in the mid 1980s after a series of valve failures observed with the Edwards-Duromedics valve. The damages observed indicated that cavitation could be responsible. Later, several in vitro studies visualized the bubble formation and collapse of cavitation at mechanical heart valves. It was suggested that cavitation could also cause damage to the formed elements of blood and thereby enhance the risk of thromboembolic complications seen in mechanical heart valve patients. Therefore, an applicable technique for in vivo detection of cavitation is required. This article reviews techniques developed for in vivo detection of cavitation and suggests focus for future studies.

Prosthetic mitral valve leaflet escape

Leaflet escape of prosthetic valve is rare but potentially life threatening. It is essential to make timely diagnosis in order to avoid mortality. Transesophageal echocardiography and cinefluoroscopy is usually diagnostic and the location of the missing leaflet can be identified by computed tomography (CT). Emergent surgical correction is mandatory. We report a case of fractured escape of Edward-Duromedics mitral valve 27 years after the surgery. The patient presented with symptoms of acute decompensated heart failure and cardiogenic shock. She was instantly intubated and mechanically ventilated. After prompt evaluation including transthoracic echocardiography and CT, the escape of the leaflet was confirmed. The patient underwent emergent surgery for replacement of the damaged prosthetic valves immediately. Eleven days after the surgery, the dislodged leaflet in iliac artery was removed safely and the patient recovered well.

Long-term event-free survival with an embolised prosthetic valve leaflet in the thoracic aorta

We report the case of a patient who underwent a redo surgery for a leaflet escape from a Bjork-Shiley tilting disc mitral prosthesis inserted 18 years previously. The escaped disc remained lodged in the thoracic aorta without any complication. She ultimately died of terminal heart failure 13 years after the second operation. We believe this to be the longest survival with a dislodged leaflet from a mechanical valve. Removal of dislodged disc is recommended in literature but there may be a place for watchful observation in exceptional cases with no haemodynamic compromise.

Intraoperative and postoperative evaluation of cavitation in mechanical heart valve patients

BACKGROUND

Cavitation has been claimed partly responsible for the increased risk of thromboembolic complications, hemolysis, and fatal valve failure seen in mechanical heart valve patients. In vivo studies have investigated cavitation using high-pass filtering of the high-frequency pressure fluctuations with the root mean square values as an assessment of intensities. In vitro studies have shown that this well-known method may not be ideal owing to loss of data as a consequence of filtering, and because it requires a priori knowledge of the valve resonance pattern. Therefore, a new method has been developed, which decomposes the signal into nondeterministic (cavitation) and deterministic (valve resonance) signal components, and hence decreases data loss. This study aimed to evaluate cavitation in patients with mechanical, biological, and native heart valves both intraoperatively and postoperatively using the new method.

METHODS

High-frequency pressure fluctuations were measured by a hydrophone intraoperatively and postoperatively in 14 patients with mechanical valves, 10 patients with normal aortic valves, and 5 patients with bioprosthesis. The total signal energy was evaluated as nondeterministic and deterministic energies.

RESULTS

Nondeterministic energies were verified both intraoperatively and postoperatively in all patients who had a mechanical valve; this finding confirms the cavitation potential of mechanical valves. None of the data recorded in patients with bioprosthetic or native valves contained nondeterministic energy.

CONCLUSIONS

The study confirms the presence of cavitation in mechanical heart valve patients using the nondeterministic energy of high-frequency pressure fluctuations as a quantitative measure of cavitation both intraoperatively and postoperatively.

Cavitation dynamics of medtronic hall mechanical heart valve prosthesis: fluid squeezing effect

The cause of cavitation in mechanical heart valves is investigated with Medtronic Hall tilting disk valves in an in vitro flow system simulating the closing event in the mitral position. Recordings of pressure wave forms and photographs in the vicinity of the inflow surface of the valve are attempted under controlled transvalvular loading rates averaged during valve closing period. The results revealed presence of a local flow field with a very high velocity around the seat stop of mechanical heart valves that could induce pressure reduction below liquid vapor pressure and a cloud of cavitation bubbles. The analysis of the results indicates that the "fluid squeezing" between the stop and occluder as the main cause of cavitation in Medtronic Hall valves. The threshold loading rate for cavitation initiation around the stop was found to be very low (300 and 400 mmHg/s; half the predicted normal human loading rate that was estimated to be 750 mmHg/s) because even a mild impact created a high speed local flow field on the occluder surface that could induce pressure reduction below vapor pressure. The present study suggests that mechanical heart valves with stops at the edge of major orifice region are more vulnerable to cavitation, and hence, have higher potential for damage on valve components and formed elements in blood.