Assessment of the opening angle of implanted Björk-Shiley prosthetic valves

The role of ECG-gated MDCT in the evaluation of aortic and mitral mechanical valves: initial experience

OBJECTIVE

The objective of our study was to evaluate the role of ECG-gated MDCT in the functional evaluation of mechanical prosthetic aortic and mitral valves.

MATERIALS AND METHODS

Twenty sequential patients with 23 mechanical prosthetic valves were evaluated with an ECG-gated 40- or 64-MDCT scanner. Multiplanar reformation, maximal-intensity-projection, volume-rendering, and volume-averaging techniques were used for visualization of valve leaflets in systole and diastole. The visibility of each mechanical valve was evaluated by consensus of a radiologist and a cardiologist using a subjective 5-point scale (0-4). MDCT findings were correlated with fluoroscopic opening and closing angle measurements and echocardiographic pressure gradient measurements in 11 and 19 valves, respectively.

RESULTS

The series included 18 bileaflet and five single-leaflet mechanical valves. The visibility score for the bileaflet mechanical valves was excellent (score of 4) in all 18 cases, but it was lower for single-leaflet valves (mean score, 2.8; range, 1-4) (p = 0.04). Bland-Altman plots showed high agreement between MDCT and fluoroscopy for measurements of opening and closing angles of bileaflet mechanical valves. In four patients, a stuck valve was seen on MDCT and was confirmed by fluoroscopy. Doppler echocardiography showed increased transvalvular pressure in two of the four patients with a stuck mitral valve and increased transaortic pressure in four patients with normal prosthetic aortic valve motion.

CONCLUSION

Our preliminary results suggest that MDCT is a promising technique for functional evaluation of bileaflet mechanical valves, allowing reliable measurements of opening and closing leaflet angles. However, the role of MDCT in the evaluation of single-leaflet valves might be limited.

Doppler sonographic evaluation of mechanical and bioprosthetic mitral valve prostheses during exercise with a rate corrected pressure half time

OBJECTIVE

To compare the effect of exercise on pressure half time in patients with mechanical or bioprosthetic mitral valves. A relative pressure half time (pressure half time as a percentage of RR interval) was used in an attempt to correct for the shortening of the diastolic time interval caused by the increase in heart rate during exercise and thus to uncover the effects of valve design on pressure half time during exercise.

PATIENTS

Twenty clinically stable (New York Heart Association grade I-II) patients with mechanical (n = 12) or bioprosthetic (n = 8) mitral valves (median age 51) years. The median time since valve replacement was 42 months.

METHODS

Continuous wave Doppler echocardiography from the apical view at rest and during moderate supine bicycle exercise (50 W).

RESULTS

During exercise the mean (SD) heart rate increased from 79 (12) to 101 (12) beats per minute (95% confidence interval (95% CI) of difference, 15 to 29/min) and the peak pressure gradient from 11 (5) to 18 (6) mm Hg (95% CI of difference 5 to 9 mm Hg). The pressure half time decreased from 114 (30) to 78 (26) ms (95% CI of difference (30-42 ms). There was no difference between the valve types. The relative pressure half time remained unchanged in patients with mechanical valves during exercise (13 (4) rest and 13 (5)% exercise, respectively) and decreased in patients with bioprostheses (17 (3) and 12 (3)%, respectively (95% CI of difference 2 to 8%, p = 0.025).

CONCLUSIONS

In patients with mechanical mitral valves the decrease in the pressure half time during exercise is probably mostly the result of the shortening of the diastolic time interval with increasing heart rate whereas in patients with bioprosthetic valves an increase in functional valve area may contribute to the shortening of pressure half time during exercise.

Development of motion analyzing system for implanted tilting disk valves

A motion-analyzing system was developed to quantitatively evaluate functions of the implanted tilting disk valve, e.g., an open angle and a duration of valve open and/or shut. In this system a picture of the valve on an x-ray cinefilm is displayed on the CRT screen by the TV camera for extraction of valve position. Data extracted are stored in the computer and are used to calculate parameters for motion analysis of the valve. The reliability of this system was confirmed within 3 degrees of error using the valve model prior to the evaluation of cinefilms clinically procured. With the aid of this motion analyzing system, complicated motions of the tilting disk valve were easily quantified and the useful information as given for clinical diagnosis and further valve development.

Analysis of Doppler-obtained velocity curves in functional evaluation of mechanical prosthetic valves in the mitral and aortic positions

A total of 145 patients with 160 mechanical prostheses of the Björk-Shiley or Starr-Edwards type (15 with double mitral plus aortic valves) underwent clinical and Doppler echocardiography analysis. In the mitral position (85 valves) 10 patients with valve-related symptoms, calculated prosthetic area less than or equal to 1 cm2, or mean transprosthetic gradient greater than 10 mm Hg by Doppler echocardiography were predefined as abnormal. Seven patients had operations, and prosthetic obstruction was confirmed in all. All patients had higher pulmonary pressures (p less than 0.001) before valve replacement. Clinical presentation was variable; however, all those with proved prosthetic thrombosis had a fulminant course and distinctive velocity curves on Doppler. In the 75 patients predefined as normal, calculated valve area (2.3 +/- 0.6 cm2, mean +/- SD, range 1.3 to 3.7 cm2) and mean gradient (4.9 +/- 1.7 mm Hg, range 1.5 to 9.5 mm Hg) were widely spread and were independent of prosthetic size greater than or equal to 27 mm. Clinically 37 of 75 patients were moderately to severely limited. Mean gradient above 5 mm Hg was associated with a higher incidence of chronic atrial fibrillation (p less than 0.05), significant tricuspid regurgitation, failure of the right side of the heart, and significant functional limitation (p less than 0.02 for all). In the aortic position (75 valves) peak gradients were 28.2 +/- 15 mm Hg (8 to 80 mm Hg). Mean gradients were 18 +/- 9.6 mm Hg (6.5 to 46.5 mm Hg). Averaged gradients derived from the average of peak and late systolic gradients were 22.4 +/- 12.7 mm Hg (6 to 62 mm Hg). In all five abnormal patients (two with endocarditis and three with hemodynamic decompensation) but also in 18 of 70 clinically normal valves, peak gradients were greater than or equal to 36 mm Hg (ranges 36 to 65 mm Hg in both). Gradients were unrelated to symptoms or to the duration of the valve in situ (3 weeks to 20 years). Gradients correlated with prosthetic size (r = 0.57) and were higher (p less than 0.001) across small (19 to 23 mm) versus large (25 to 31 mm) valves. Regurgitation was present in 40% of the mitral prostheses. It was detected in 32% of the mitral prostheses defined as normal and was estimated as mild in most. Aortic regurgitation was present in all five abnormal aortic prostheses, significant in four, and in 26 of the valves (37%) defined as normal, significant in two.(ABSTRACT TRUNCATED AT 400 WORDS)

Cineradiographic functional evaluation of the Björk-Shiley monostrut prosthesis. A follow-up study of 46 consecutive patients

In 46 patients, 51 Björk-Shiley monostrut valves were studied with high-speed cineradiography 9 months after implantation. Each valve was viewed in lateral, frontal and oblique projections for 10-12 heart beats. In the aortic valves the opening time was 0.04-0.067 (mean 0.052) and closing time 0.04-0.067 (mean 0.046) sec. In all these valves the maximum opening angle was 70 degrees. Disc rotation could be monitored in 29/31 valves, and during 10 heart beats averaged 20 degrees. Disc slide of 2.0-2.5 mm was seen in 27/31 valves. It occurred during the last 40-50 degrees of opening and the first 20-40 degrees of closing. In mitral valves with sinus rhythm (12/20), the opening time was 0.053-0.106 (mean 0.073) and closing time 0.040-0.106 (mean 0.061) sec. Mean disc rotation (recorded in 17/20 valves) during 10 heart beats was 25 degrees, and disc slide of 2.0-2.5 mm was found in all but one case, mainly during the last 50 degrees of opening and the first 30 degrees of closing. The valve opened to 70 degrees in all but one patient, in whom the disc clearly impinged against the left ventricular wall and opened only to 35-50 degrees at rest. At reexamination a year later the patient was asymptomatic, in sinus rhythm, and the disc had regained full movement with 70 degrees opening.

Auscultatory characteristics of normally functioning Lillehei-Kaster, Björk-Shiley, and St Jude heart valve prostheses

Auscultatory and echocardiographic and phonocardiographic studies were performed on 26 patients who had a total of 11 Lillehei-Kaster, 16 Björk-Shiley, and 18 St Jude heart valve prostheses functioning normally in the aortic or mitral positions or both. With all types and positions of prostheses a distinct closing sound was always detected. It was frequently heard in two parts which, according to echocardiographic and phonocardiographic studies, resulted from the onset and completion of the valve closure. An opening sound could be heard from all Björk-Shiley and St Jude valves but from only four of the 11 Lillehei-Kaster valves. The opening sounds due to mitral prostheses consisted of two to three closely spaced clicks detected as a faint early diastolic crackle on auscultation. Echocardiography with phonocardiography indicated that they were related to the onset and termination of the disc opening excursion. In the aortic position the valves always produced early to mid-systolic murmurs, and a soft early diastolic murmur was also heard in seven of 23 patients. A mid-diastolic rumble was heard in 12 of 22 patients with mitral prostheses. Normally functioning tilting disc valve prostheses produce characteristic auscultatory findings, and familiarity with these findings will be useful in clinical evaluation of patients with these prostheses.

Doppler hemodynamic evaluation of prosthetic (Starr-Edwards and Björk-Shiley) and bioprosthetic (Hancock and Carpentier-Edwards) cardiac valves

One hundred thirty-four patients with prosthetic or bioprosthetic heart valves were investigated with Doppler echocardiography to determine normal values for commonly used prosthetic valves and to test the specificity of abnormal Doppler findings. In 70 patients the aortic valves had been replaced and in 64 the mitral valves had been replaced. Gradients across prostheses in the aortic position were calculated from maximal velocity. Peak calculated aortic transvalvular gradients in normal subjects were 22 +/- 10 mm Hg in 33 Björk-Shiley valves, 23 +/- 10 mm Hg in 27 porcine valves and 29 +/- 13 mm Hg in 6 Starr-Edwards valves. Mild aortic regurgitation was seen in 42% of Björk-Shiley valves, 26% of porcine valves and 2 of 6 Starr-Edwards valves. Mitral valve orifice was calculated by the pressure half-time method. In clinically normal patients with mitral valve prostheses, the effective mitral valve orifice was 2.5 +/- 0.8 cm2 in 35 Björk-Shiley valves, 2.1 +/- 0.7 cm2 in 17 porcine valves, and 2.0 +/- 0.3 cm2 in 10 Starr-Edwards valves. Mitral regurgitation was found in 11% of Björk-Shiley valves, 19% of porcine valves and 30% of Starr-Edwards valves. Repeat studies at 2 weeks to 14 months revealed no difference in 8 aortic and 14 mitral prostheses. Seven aortic and 4 mitral valves functioned abnormally as determined by Doppler, and the abnormal function was confirmed in each at surgery or at cardiac catheterization.(ABSTRACT TRUNCATED AT 250 WORDS)

A computer-aided method to evaluate the function of implanted Björk-Shiley prosthetic heart valves

Evaluation of the function of implanted prosthetic valves is important in early diagnosis of valve dysfunction. Björk-Shiley valves contain two radiopaque rings, which are projected as ellipses in cineradiography. From these ellipses the actual valve opening angle can be calculated. A computer-aided method was developed that enables measurement of ellipse characteristics reliably, independent of projection angle and valve opening. It is demonstrated that calculated and real opening angles differ less than 2 degrees with this method. Using the same technique the tilting angle of the valve ring during the cardiac cycle is computed for evaluation of progression of valve dehiscense in case of a paravalvular leak. Application of the method to patient data is illustrated by three cases. The method is suitable for use by technicians. It can be implemented on a small microprocessor system. The method proved to be a powerful tool in the evaluation of patients with implanted Björk-Shiley valves.