Cineradiographic evaluation of prosthetic cardiac valves

Mechanical valve obstruction: Review of diagnostic and treatment strategies

Prosthetic valve obstruction (PVO) is a rare but feared complication of mechanical valve replacement. Diagnostic evaluation should focus on differentiating prosthetic valve thrombosis (PVT) from pannus formation, as their treatment options differ. History of sub-optimal anti-coagulation and post-op time course to development of PVO are useful clinical characteristics in differentiating thrombus from pannus formation. Treatment of PVT is influenced by the patient’s symptoms, valve location, degree of obstruction and thrombus size and may include thrombolysis or surgical intervention. Alternatively, pannus formation requires surgical intervention. The purpose of this article is to review the pathophysiology, epidemiology, diagnostic approach and treatment options for aortic and mitral valve PVO.

Evaluation of prosthetic valve function and associated complications

Significant advances in imaging modalities have occurred to evaluate prosthetic valve function and associated complications. These developments involve predominantly the introduction of Doppler technology for the non-invasive determination of gradients and valve areas and TEE for an improved assessment of valve structure, function, and associated complications. The current role of cinefluoroscopy is mostly to complement TEE in the evaluation of motion of mechanical prosthetic valves in the aortic position. Cardiac catheterization is now rarely needed to assess valve function. Diagnosis of prosthetic valve obstruction can be performed in the majority of cases with transthoracic Doppler echocardiography. Differentiation of valve obstruction from normal valve function in small valves with high flow conditions, however, may be difficult. Because of this and the variability in normal valves among different prostheses, knowledge of the type and size of the implanted valve is essential. Patients and ultrasound laboratories are encouraged to seek and provide this information on a routine basis. Although transthoracic echocardiography is the main diagnostic modality for the serial evaluation of prosthetic valve function, it is important to recognize its limitations in assessing prosthetic mitral regurgitation and evaluating structural abnormalities of prosthetic valves. These are the situations in which TEE has the most impact. A summary of general indications of TEE in prosthetic valves is provided in Table 6. Finally, a baseline transthoracic Doppler study is essential in the overall follow-up and serial evaluation of valve function. For future comparisons, the best indices of valve functions are those obtained for patients as their own control, from a baseline Doppler echocardiographic study performed early after the operation.

Assessment of mitral Björk-Shiley prosthetic dysfunction using digitised M mode echocardiography

Digitised M mode echocardiograms were analysed in 22 patients with possible Björk-Shiley mitral prosthetic dysfunction. Patients with paraprosthetic mitral regurgitation had a significantly greater shortening fraction, an increased peak rate of dimension change during systole, and an increased peak velocity of circumferential fibre shortening than those with poor left ventricular function. Patients with a clotted prosthesis had lower values for shortening fraction and peak rate of dimension change during systole than patients with paraprosthetic regurgitation. In this latter group, the peak rate of dimension change during diastole and peak lengthening rate were greater than in either those patients with poor left ventricular function or those with a clotted prosthesis. In addition, the peak lengthening rate was greater in those with a clotted prosthesis than in those with poor left ventricular function. Thus M mode echocardiography is a useful method of assessing mitral prosthetic dysfunction and allows patients with paraprosthetic regurgitation to be distinguished from those with either poor left ventricular function or a clotted prosthesis.

Noninvasive evaluation of normal and abnormal prosthetic valve function

Noninvasive techniques are helpful in evaluating the function of mechanical prostheses and tissue valves. Combined phonocardiography and M-mode echocardiography together with cinefluoroscopy are the most useful noninvasive techniques in differentiating normal from abnormal metallic prosthetic valve function. The intensity of the opening and closing clicks and associated murmurs will depend on the type of prosthetic valve, the heart rate and rhythm and the underlying hemodynamic status. Arrhythmias or conduction disturbances, or both, may produce motion patterns that mimic some of the echocardiographic signs of malfunctioning prosthetic valves. Differentiation of thrombus formation or tissue ingrowth from paravalvular regurgitation or dehiscence is possible by noninvasive techniques. Disc variance, a potentially serious and lethal problem with the older Beall valves, can be readily detected by cinefluoroscopy and echophonocardiography. With regard to bioprosthetic valves, two-dimensional echocardiography is superior to M-mode echocardiography in detecting primary valve failure. In addition, detection of vegetations, valve alignment and ring and individual leaflet motion can be best accomplished by two-dimensional echocardiography. Of greater importance is the patient serving as his or her own control in the follow-up assessment of prosthetic valve function by noninvasive techniques.

Björk-Shiley mitral valvular dehiscence. Documented by radiography, echocardiography, fluoroscopy, and cineangiography

This case report presents combined radiographic, echocardiographic, fluoroscopic, and cineangiographic findings of the dehiscence of a Bjork-Shiley mitral prosthetic valve. The valvular dehiscence was confirmed at surgery. A distinct rounding of the opening phase of the valve was recorded on the echocardiogram. Other clinical evidence, documenting the severe valvular dehiscence, is reported in detail. Non-invasive procedures are therefore invaluable in recording prosthetic valvular dysfunction.

Hemodynamic evaluation of patients with combined mitral and aortic prostheses

Complete hemodynamic evaluation of patients with combined aortic and mitral mechanical valve prostheses presents a difficult technical problem. Yet such patients with cardiac symptoms postoperatively often require this evaluation to determine the diagnosis and the advisability of reoperation. A 4 year experience with 22 patients requiring such evaluation is reviewed. Eight patients (36 percent) required reoperation for malfunction of the prosthesis. Four (18 percent) had major complications of the cardiac catheterization study, but no fatalities or residual permanent defects resulted. In 17 cases transthoracic left ventricular needle entry was used. A standardized procedure of this type for both pressure measurement and angiographic studies has evolved, providing reasonable efficiency and a relative degree of safety. The patient is positioned in the right anterior oblique position for optimal needle entry into the left ventricular apex and angiographic visualization of mitral prosthetic incompetence and the myocardial contractile pattern. A 16 gauge needle with side holes but no end hole allows ventriculography to be performed after chamber entry using the prostheses as reference points under fluoroscopic guidance. Retrograde catheterization of the aortic prosthesis, transseptal left atrial catheterization with anterograde crossing of the mitral prosthesis and transapical pressure measurement with a similar needle, combined with quantitative left atrial angiography, are alternative choices for study.

Idiopathic perforation of a porcine aortic bioprosthesis in the aortic position

The report of a failure of glutaraldehyde-preserved porcine aortic xenograft bioprosthesis in the aortic position after 13 months is presented. Severe aortic regurgitation resulted from three "idiopathic" perforations in one of the cusps, and a linear tear in another cusp. Light and electron microscopy showed generalized degeneration of collagen thoughout the faulty valve. The absence of a platelet-fibrin coat on edges of the tear suggested a recent origin, compatible with cardiac catheter manipulation during unsuccessful attempts to cross the valve. The histopathologic data from this valve correlate with previously reported failures with formaldehyde preserved xenograft valves.

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.

Echocardiogram of the porcine aortic bioprosthesis in the mitral position

Echocardiography was performed in 10 consecutive patients who had a clinically normally functioning porcine aortic bioprosthesis in the mitral position. Strong well defined echoes were recorded from the anterior and posterior aspects of the xenograft stent. The maximal separation of the anterior and posterior stent echoes approximated the diameter of the stent at its base. The maximal excursion of the anterior stent was 5 to 10 mm (mean 7.5) with a mean systolic slope of 15 to 35 mm/sec (mean 22.2) and diastolic slope of 11 to 59 mm/sec (mean 21.5). In all 10 patients it was possible to record an anterior xenograft leaflet with anterior movement at the onset of diastole and posterior movement at the onset of systole and with appropriately steep (more than 200 mm/sec) slopes. The diastolic (E-F) slope of the anterior leaflet in 9 of the 10 patients ranged from 9 to 38 mm/sec (mean 19). In 6 of the 10 patients a posterior xenograft leaflet with a movement pattern symmetric with that of the anterior leaflet was recorded. In two patients, the central aortic leaflet was recorded with little diastolic displacement. These two patients also had mild aortic regurgitation, which was associated with diastolic shudder of the xenograft leaflets. Echocardiography was also performed in one patient who was later shown to have a 10 cm3 thrombus on the ventricular surface of a xenograft valve. The echocardiogram in this patient revealed the following abnormalities: (1) excessive anterior stent movement and systolic slope suggesting paravalvular leak in the presence of abnormal cinefluoroscopic valve tilt, and (2) multiple dense nonhomogeneous echoes between the anterior and posterior aspects of the valve stent, with an early diastolic clear space behind the anterior stent and abnormal echoes behind the posterior stent during systole. Echocardiography therefore appears to be useful in evaluating the porcine aortic bioprosthesis in the mitral position.