Intermittent Entrapment of a Prosthetic Mitral Valve Disc
What You See Is Not What You Get
A 42-year-old man had undergone mitral valve (MV) replacement 12 years earlier with the use of a CarboMedics bileaflet mechanical prosthesis (Sorin Biomedica). On a routine visit, he was asymptomatic, and cardiac auscultation revealed closing and opening MV clicks. A transthoracic echocardiogram with the use of a 2-beat acquisition protocol showed normal excursion of both MV discs (Figure 1; Movie I in the online-only Data Supplement). Spectral Doppler of transmitral flow indicated normal peak gradients; however, abnormalities in the Doppler signal were intermittently noted. Whereas some cardiac cycles showed normal disc motion with near-simultaneous opening clicks, other cycles demonstrated a delay in 1 opening click or a single rather than dual opening clicks (Figure 2). The beats with a single opening click were associated with significant prolongation of the transmitral pressure half-time suggestive of obstruction to flow. The abnormalities on spectral Doppler prompted us to reimage the MV over several cardiac cycles. Intermittent delay in the opening of 1 disc with periodic disc entrapment in a closed position was noted (Figure 3;Movie II in the online-only Data Supplement). Interrogation with color Doppler showed intermittent lack of blood flow across the orifice corresponding to the periodically entrapped disc (Figure 4; Movie III in the online-only Data Supplement). These findings were confirmed by cine fluoroscopy (Figure 5; Movie IV in the online-only Data Supplement). Transesophageal echocardiography did not show any MV thrombi or vegetations. At surgery, a circumferential pannus was identified on the ventricular aspect of the mitral prosthesis impinging on the free margin of the periodically entrapped disc.
Intermittent dysfunction of a prosthetic valve results from periodic interference with disc motion by a pannus, thrombus, or subvalvular tissue.1–3 Entrapment leads to delayed disc motion or immobilization in closed or open position resulting in the obstruction to flow or regurgitation, respectively. It is likely that marginal contact between the disc and pannus led to random interference with disc opening and accounts for the intermittent nature of MV dysfunction in our patient. Further pannus growth would likely result in permanent disc entrapment.
Establishing a diagnosis of intermittent prosthetic valve malfunction can be challenging. To reduce memory usage many laboratories acquire and store echocardiography cine loops spanning 1 to 2 cardiac cycles. Abnormal events that occur intermittently can thus be missed.
In our patient, MV malfunction was initially detected by spectral Doppler. This fact underlines the importance of careful analysis of the Doppler signal. Assessment of the presence and timing of valve clicks provides valuable information regarding prosthesis function.4 A normal transprosthetic gradient does not exclude the presence of MV obstruction especially if this is intermittent; however, prolongation of the pressure half-time is usually evident (Figure 2).1
Intermittent prosthetic valve dysfunction can have catastrophic consequences and thus requires prompt diagnosis and treatment.2,3 Physicians caring for patients with prosthetic valves should be aware of this condition. Sonographers should be encouraged to visualize individual disc motion over several beats before image acquisition.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/lookup/suppl/doi:10.1161/CIRCULATIONAHA.113.003918/-/DC1.
- © 2014 American Heart Association, Inc.