Malfunction of a disc mitral valve prosthesis: detection by phonocardiography

An in vitro study of prosthetic heart valve sound

Patients with an implanted mechanical heart valve sometimes experience the closing sounds of the valve as disturbing. To study the generation of valve sounds in general, a pulse duplicator study was carried out, testing eight commonly used types of prosthetic valves in the aortic position. Pulse rate was set at 70 beats/min, stroke volume at 70 ml and mean 'aortic' pressure at 100 mmHg. Despite the controlled conditions, there was great variability of the closing sound, in both intensity and spectral composition, making noise comparisons and spectral characterization ('sonoprint') difficult. In general, bileaflet mechanical valves produced less noise than did tilting disc valves, particularly those with large opening angles. One small-size (23 mm) tilting disc valve produced 50% less noise than large types. The plastic ball valve, the porcine and the polyurethane trileaflet valve all were very quiet.

Cineradiographic assessment of Björk-Shiley aortic and mitral prosthetic heart valves

A non-invasive method for assessment of Björk-Shiley mitral and aortic heart valve movements has been developed. The Björk-Shiley tilting disc valve is described and its placement within the heart is explained. Twenty patients have been studied post-operatively with 23 valves, 10 mitral valves and 13 aortic valves, three patients having both. The method of assessment is described and consists of projecting the valve with its opaque disc marker in true profile and en face using the C arm screening system of a C.G.R. Angiorama coronary angiography unit. A cineradiograph is taken and the maximum opening angle of the valve is measured from the projected image directly or calculated from measurements taken from the image. Movement of the valve ring can also be assessed when paraprosthetic leak is suspected. The results of the study show that: (1) This method is simple, non-invasive, requires no preparation and is reproducible. (2) The valve discs open to a smaller angle than expected in most cases, and in only a few cases to 60 degrees or more. (3) It is valuable to record valve function post-operatively so that a comparison can be made later should valve malfunction be suspected. (4) In only one case was it found impossible to assess valve movement because of orientation of the valve within the patient.

Mitral regurgitation due to intermittent prosthetic valvular dysfunction

A second case of malfunction of a Harken disk valve due to undue disk wear is reported. Two and one-half years after aortic and mitral valvular replacement, the patient had paraprosthetic aortic insufficiency and physical findings suggesting intermittent dysfunction of his prosthetic mitral valve. Catheterization showed intermittent hemodynamic abnormalities; fluoroscopic and cineangiographic findings indicated intermittent mitral regurgitation secondary to undue mitral disk wear. At operation, the excised valve showed normal struts and sewing ring but severe disk wear. There was loss of disk substance and rim notching.

Choosing a substitute cardiac valve: type, size, surgeon

Certain ideal characteristics of substitute cardiac valves are analyzed for each of the four basic types of available substitute cardiac valves. Of the four, the caged disc prosthesis is the least desirable: it obstructs, it clots and it degenerates. Each of the other three types of substitute cardiac valves has more favorable characteristics. Ideally, the caged ball prosthesis might be limited to patients with predominantly regurgitant lesions because of the problem of prosthetic disproportion. The tilting disc has favorable hemodynamic and wear characteristics, but long-term anticoagulant therapy is essential, as with the caged ball and caged disc types of prosthesis. The porcine xenograft appears to be desirable, but patients with sufficient implantation time (more than 5 years) for proper evaluation are just beginning to be studied and, therefore, final judgment must be reserved. Assuming that valve replacement is to be carried out in a large medical center by a surgical team experienced in this procedure, the results of this operation today are dependent more on the type and size of substitute valve inserted than on the surgeon who inserts the valve. It is therefore important for the cardiologist to become more informed about the various types of prosthetic cardiac valves and to become a member of the team deciding which type and size of cardiac valve are most suitable for his (or her) patient.

Cardiac pathology after valve replacement by disc prosthesis. A study of 61 necropsy patients

Clinical and necropsy observations are described in 61 patients who had one or more cardiac valves replaced with a discoid prosthesis of the Hufnagel type. The most common (31 percent) cause of death among the 45 patients who died early (less than 65 days after operation) appeared to be prosthetic disproportion; that is, the prothesis was too big for the aorta or ventricular cavity into which it was inserted so that inadequate space was present between the margins of the disc and the endocardium of ventricle or intima of aorta. Prosthetic thrombosis occurred in only 3 of the 45 patients who died early, but poppet movement appeared considerably altered in each. In contrast, thrombi were observed on a prosthesis in 14 of the 16 patients who died late (4 to 47 months [average 21] postoperatively), but in none did the thrombi appear of sufficient size to alter poppet function. Escessive bleeding occurred in 11 (24 percent) of the 45 early deaths and was primarily related to the insertion of a patch in the root of the aorta. Uncorrected valvular disease either by itself or by its ability to alter function of the prosthesis appeared responsible for death in 6 (13 percent) of the 45 patients who died early and in 2 (6 percent) of the 16 who died late. Insertion of a mitral poppet disc in a patient with uncorrected aortic regurgitation, even of mild degree, may be hazardous because the aortic regurgitant jet stream may interfere with proper function of the mitral disc. Likewise, insertion of a poppet disc only in the aortic valve position in a patient with combined aortic and mitral regurgitation may considerably increase the degree of mitral incompetence because the aortic prosthesis is intrinsically obstructive. Disc wear or variance was observed in all but one prosthesis in place for more than 1 year. Although hemolytic anemia of significant degree was not observed in any of the 16 patients who died late, the occurrence of renal hemosiderosis in 13 of the 16 patients indicates that the poppet disc prosthesis is considerably traumatic to erythrocytes. Thus, this type of prosthesis is not an ideal substitute cardiac valve. It clots, despite anticoagulant therapy, it is intrinsically stenotic, portions of it, that is, the disc, degenerate, and it causes hemolysis to erythrocytes.