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Ann Thorac Surg 2000;69:507-512
© 2000 The Society of Thoracic Surgeons

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Original Articles

Evaluation of valve sound and its effects on ATS prosthetic valves in patients’ quality of life

^a Second Department of Surgery, Nihon University School of Medicine, Tokyo, Japan

Address reprint requests to Dr Akira Sezai, Second Department of Surgery, Nihon University School of Medicine, 30-1 Oyaguchi-kamimachi, Itabashi-ku, Tokyo, 173-8610, Japan

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
Background. We interviewed patients and carried out frequency analyses to compare the closing sounds of ATS and St. Jude Medical (SJM) prosthetic valves.

Methods. Forty-five patients undergoing valve replacements using ATS valves were investigated. We interviewed patients at 1 month and 1 year after the operation, and carried out frequency analysis to investigate the prosthetic valve’s closing sound.

Results. According to the results of the interviews, 84.4% of patients with ATS valves were not aware of the valve sounds. ATS valves scored significantly lower than SJM valves on audibility of the valve sound, disturbance during daytime, sleep disturbance, request for replacement with a soundless prosthetic valve, audibility to others, and noise index. According to the frequency analysis on the prosthetic valve’s closing sound, the sound peak of the ATS valves was around 1.2 kHz, and the sound pressure of the ATS valves was significantly lower than that of the SJM valves.

Conclusions. Though a further long-term observation on thromboembolism and hemolysis is needed for evaluation of prosthetic valves, the ATS valve is presently considered to impart a better quality of life.

	Introduction

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Since Hufnagel and associates implanted a plastic ball valve into the descending aorta in 1952 [1] and Starr and associates performed a mitral valve replacement using a ball valve in 1960 [2], valve replacements with prosthetic valves have rapidly spread all over the world. Various valves with improved features necessary for a prosthetic valve in terms of hemodynamics, durability, antithrombogenesis, and hemolysis have been. The ATS valve (ATS Medical Inc, Minneapolis, MN) we studied has an enlarged orifice area and improved durability as a consequence of the pyrolytic carbon materials used to construct its orifice. The ATS valve was developed as a bileaflet valve with superior functions to traditional prosthetic valves in antithrombogenesis and hemolysis because of the convex structure of its pivot against the blood flow (open pivot). This valve was first implanted into a patient in May 1992; the first replacement with this valve in Japan was performed in September 1993 in our institute. Though the literature on this valve is scant, the few reports there are vouch for its efficiency [3–6]. According to the patients themselves, the valve sound of the ATS valve is quieter than that of traditional mechanical valves.

In this study, we interviewed patients and carried out frequency analyses to compare the closing sound of the ATS prosthetic valve with that of the St. Jude Medical valve (SJM valve; St. Jude Medical Inc, St. Paul, MN), another type of bileaflet valve. We also evaluated the effects of the ATS valve on patients’ quality of life.

	Material and methods

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The subjects were 45 patients who underwent valve replacements using ATS valves in our institute (the Second Department of Surgery, Itabashi Hospital, Nihon University School of Medicine), between September 1993 and May 1998, excluding those who died early or had hearing impairments. Fifty-seven patients who underwent valve replacements using SJM valves were compared as a control. In addition, consecutive patients were implanted with ATS valves between March 1993 and June 1994, during a clinical investigation of this valve, and then with SJM valves between July 1994 and October 1996, and then once more with ATS valves from November 1996 until the end of the present study, May 1998, at which time the clinical use of the ATS valve was approved by the Japanese Ministry of Health and Welfare.

The patients receiving the ATS valves were 27 males and 18 females ranging in age from 14 to 75 years (average 56.9 ± 13.8 years), including 22, 15, and 8 cases of aortic valve replacement (AVR), mitral valve replacement (MVR), and AVR+MVR, respectively. The mean body surface area of patients was 1.6 ± 0.2 m². The patients receiving the SJM valves were 31 males and 26 females ranging in age from 24 to 71 years (average 53.0 ± 12.3 years), including 23, 23, and 11 cases of AVR, MVR, and AVR + MVR, respectively. The mean body surface area of patients was 1.6 ± 0.2 m². Among the cases receiving AVR + MVR, ATS valves were used more in males and SJM valves were used more in females. In other cases, there was no difference in the frequency of usage between ATS and SJM valves (Table 1).

Our frequency analysis on the prosthetic valve’s closing sound was performed only in cases of single valve replacement at 1 year after the operation. These subjects included 11 patients receiving ATS valves (5 at the aortic valve position and 6 at the mitral valve position) and 14 receiving SJM valves (5 at the aortic valve position and 9 at the mitral valve position). The measurement was carried out in a sound-proof room. A supersensitive microphone (TS-32235; Nihon Koden Inc, Tokyo, Japan) was placed on the second intercostal space at the right margin of the sternum for prosthetic valves implanted in the aortic valve position and on the sixth intercostal space on the middle line of the left clavicle for prosthetic valves implanted in the mitral valve position. Attempts were made to achieve as close contact with the body as possible in order to eliminate any space between the microphone and body. A cardiac sound amplifier (PC-X1; Nihon Koden Inc) and AD converter (ADC488/16A; Iotech Inc, Cleveland, OH) were used in addition to the microphone. For frequency analysis, a Super Scope II (GW Instruments Inc, Boston, MA) was used. Controlling the procedure by a Macintosh computer (PowerBook 520; Apple Computer Inc, Cupertino, CA), we determined the frequency and sound pressure at peak, observed the characteristics of the wave pattern, and examined the correlation between the sound pressure and noise index. Frequency and sound pressure were shown as means during 10 consecutive heart rates.

Measurements were expressed as means ± standard deviations. Fisher’s exact probability test was used to assess differences in the interview responses, excluding noise index, and Mann-Whitney U test was applied among investigation periods, techniques, and between peak frequency and sound pressure, with p less than 0.05 considered to indicate a significant difference. Spearman’s correlation coefficient by rank was used for the correlation between sound pressure at peak and noise index.

	Results

Top Abstract Introduction Material and methods Results Comment References

 
Interview
One month after operation (Table 2), 7 (15.6%) patients with ATS valves and 41 (71.9%) with SJM valves could hear the prosthetic valve sound. Among patients with ATS and SJM valves, 0 and 26 (45.6%) of the patients sometimes felt uneasy about the valve sound, 0 and 11 (19.3%) were disturbed by the sound during daytime, 0 and 12 (21.1%) were disturbed by the sound during their sleep, and 0 and 5 (8.8%) wanted to replace their prosthetic valves with a soundless type, respectively. While some of the patients with ATS valves could hear the valve sound, none of them felt uneasy about it. On the other hand, only 4 patients with SJM valves who could hear their valves were undisturbed. Three (6.7%) and 17 (29.8%) patients with ATS and SJM valves indicated that their valves were audible to others, respectively. Noise indices were 0.2 ± 0.6 points (0 to 2 points) and 4.2 ± 3.2 points (0 to 9 points) in the cases with ATS and SJM valves, respectively. In all of the interview items, the results in the cases with ATS valves were significant lower than in those with SJM valves. Therefore, at 1 month after the operation, the ATS valve was excellent in terms of quality of life. A comparison of all the interview items between surgical procedures showed that there were no differences in the cases with ATS valve in any of the items, while there were significant differences between AVR and AVR + MVR (DVR) in sleep disturbance and disturbance during daytime (p = 0.048).

View larger version (43K): [in this window] [in a new window]   Fig 1. Sound pressure of ATS and SJM valves.

View larger version (29K): [in this window] [in a new window]   Fig 2. Characteristics of frequency pattern in the ATS aortic valve cases.

View larger version (29K): [in this window] [in a new window]   Fig 3. Characteristics of frequency pattern in the SJM mitral valve cases (1).

View larger version (29K): [in this window] [in a new window]   Fig 4. Characteristics of frequency pattern in the SJM aortic valve cases (2).

	Comment

Top Abstract Introduction Material and methods Results Comment References

While the valve sound can be scientifically measured with good accuracy, the response of a patient to the valve sound depends on various physiological and psychological factors, which make it difficult to assess. In an examination of the CarboMedics (CM) valve, Bjork-Shiley (BS) valve, Duromedicus-Edwards (DE) valve, and SJM valve at a point 1 m from the chest wall, Moritz and associates reported that sound pressures of the BS valve (31 dB) and DE valve (33.4 dB) were significantly higher than those of the DE valve (25 dB) and SJM valve (24 dB), and that there were significantly more complaints about the valve sounds with BS and DE valves. Youths and patients with sinus rhythm tended to hear the valve sound, suggesting that the valve size and the patient body weight influence the sound emission [7]. Blome-Eberwein and associates examined six kinds of prosthetic valves (DE valve, BS valve, SJM valve, Medtronic valve, CM valve, and Omicarbon valve) at a point 10 cm from the chest wall. They reported that the valve sounds of the DE valve (84.2 dB) and SJM valve (73.5 dB) were the highest and lowest among them, respectively, and that the complaints about the valve sound were not related to age, gender, type of valve, position, or heart rhythm, and that audition of the patient was a determination factor [8]. In an examination of the CM valve, BS valve, and SJM valve at a point 1 cm from the chest wall, Laurens and associates reported that the BS valve (55.4 dB) had a significantly higher pressure than the CM valve (46.0 dB) and SJM valve (44.1 dB), and that significantly more patients complained about the valve sound of the BS valve. They also reported that complaints about the valve sound were not related to gender, height, weight, or body surface area, and that the young patients with MVR complained more than the older patients with AVR [9]. The causes influencing the valve sounds have not been known because the above studies employed various measuring methods and their interviews were carried out at different times. However, no one can refute the finding that SJM valve cases seldom complain about the valve sound. In this study, we interviewed patients at 1 month and 1 year after operation and compared the results. Also, for the first time, we used a noise index as "an index indicating patients’ complaints about the valve sound." It seems that this index is available as one indication of patients’ quality of life. Both at 1 month and 1 year after the operation, the interview responses and sound pressure data showed that the ATS valves were significantly quieter than the SJM valves. Even in the patients who could hear the valve sound, the valve sound of the ATS valve was not disturbing during the daytime or sleep, suggesting its excellence for the patients’ quality of life. On the other hand, only 4 (7.0%) of the patients with the SJM valve who could hear the valve sound were not disturbed at postoperative 1 month, and this number increased to 27 (47.4%) patients at postoperative 1 year, suggesting that patients accustomed themselves to the valve sound with passing time.

According to criteria of International Standards and Recommendations (ISR), human auditory threshold ranges from 20 to 20 kHz, and sound pressure ranges from 0 to 130 dB. Our sensitivity to sound is not constant, but usually we are most sensitive to 2 to 5 kHz. In looking at the patterns of frequency among our subjects, the sound peak in the ATS valve cases was around 1.2 kHz and the power of the sound decreased as frequency increased. In the SJM valve cases, the sound peak was around 1.2 kHz, the power of the sound decreased conversely as the frequency increased albeit to a lesser extent than in the ATS valve cases, and a second peak at around 2 to 5 kHz, a point sensitive to us, was also shown. This pattern in the SJM cases seemed to influence the self-awareness of the valve sound. Because the same wave patterns were found in both the ATS and SJM valve cases, further cases need to be examined in the future. The sound pressure of the ATS valve was significantly lower than that of the SJM valve, and this may have had a strong influence on the self-audibility of the valve sound. Frequency analysis of prosthetic valves is useful for the diagnosis of thrombotic valves, and the characteristics of frequency have been examined in detail in several studies [10, 11]. The results from these earlier studies were consistent with own in that they showed a sound peak of around 1 kHz and a decrease in the power of the sound as frequency increased to 5 to 7 kHz in SJM valve cases [10]. Involvement of auditory sense, physical status, age, size of the replacing valve, blood pressure, and pulse rate in the noiselessness of the valve cannot be excluded. However, we did not statistically analyze those parameters in the present study because of the small number of cases used for frequency analysis. In the future, we will seek the reasons for the noiselessness of the valve from these aspects using larger numbers of cases. Villafana, the father of the ATS valve, compared the mechanisms of his invention and conventional mechanical valves with respect to noise. While in the former, the two leaflets first close and then the orifice side closes, in the latter, leaflets close from the orifices side. Thus, he inferred that the structural characteristics of the ATS valve contributed to the its superior noiselessness. However, there is still no in vitro report on its structure, so it is impossible to conclude that its noiselessness is caused by its structure. Alternative explanations are that its materials or less stress on the collision with leaflets help to improve the noiselessness. Further in vitro and in vivo studies will be needed to clarify the reason, and we will continue to examine this theme.

Though a long-term further observation on thromboembolism and hemolysis is needed for evaluation of prosthetic valves, the ATS valve at present is considered to offer a superior quality of life and a potential for wide use in the future.

Conclusion
In this study, we interviewed patients and carried out frequency analyses to compare the closing sounds of ATS and SJM prosthetic valves. The results of interviews with patients showed that more than 80% of patients with ATS valves could not hear the valves sounds. According to the frequency analysis of the closing sounds of the valves, peak sound pressure in the ATS valve cases was significantly low and the peak sound was around 1.2 kHz, while in most of the SJM valve cases, two peals were observed at around 2 to 7 kHz and around 1.2 kHz. Thus, a pattern in the SJM cases might have influenced the audibility of the valve sound. From these results, the ATS valve is considered as an excellent prosthetic valve in terms of the quality of life it offers patients.

	References

Top Abstract Introduction Material and methods Results Comment References

 

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7. Moritz A., Steinseifer U., Kobinia G., et al. Closing sounds and related complaints after heart valve replacement with St Jude Medical, Duromedics Edwards, Björk-Shiley Monostrut, and Carbomedics protheses. Br Heart J 1992;67:460-465.[Abstract/Free Full Text]
8. Blome-Eberwein S.A., Morwinski D., Hofmeister J., Hetzer R. Impact of mechanical heart valve prosthesis sound on patients’ quality of life. Ann Thorac Surg 1996;61:594-602.[Abstract/Free Full Text]
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11. Gomi A., Takeuchi Y., Okumura Y., et al. The improving method for the wave and frequency analysis of the various prosthetic heart valves sound. Jpn J Artif Organs 1989;18:698-701.

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