Patients Perception of Mechanical Heart Valve Sounds: Psychoacoustics and Quality of Life

Patient's perception of mechanical heart valve sounds: psychoacoustics and quality of life

Background: Approximately 90.000 mechanical prosthetic heart valves are implanted every year all over the world. They generate a clicking sound at closure, which can be a major problem for some patients. About 12% of them all experience annoyance, concentration disturbance, sleeping disorders and social embarrassment. All those factors could affect patients' quality of life.

Aim: to compare the sound pressure levels (SPLs) from three of the most frequently implanted mechanical heart valve prostheses, in order to determine whether there was any significant difference between the intensities of the valve sounds.

Material and Methods: We intended to include 150 patients with an implanted mechanical heart valve (ATS Medical, Medtronic-Hall or St. Jude Medical) in the aortic position between 3 months and 4 years before the analysis. For logistical reasons, the actual number of the patients included was 84. The total conducted valve sound was measured (by a method designed by the authors) for each patient. The measures took place in a bioacoustical laboratory built with a sound-insulated chamber with a very low background noise, designed for the purposes of the study. The measures were performed in German patients followed by "The Heart Centre" in Bad Oeynhausen (Herz- und Diabeteszentrum Nordrhein Westfalen, University of Bochum), where the mentioned laboratory is constructed. The sound analysis of the present study was conducted in a specially designed soundproof bioacoustic laboratory, which isolates the outside sound and vibration from the environment indoors. Inside the laboratory, heavy soundinsulated curtains were placed between the patient and the investigator chambers. The total background noise inside the patient chamber was 19 dB(A), and this was reduced further to 9 dB(A) by using a 250 Hz high-pass filter. The sounds were recorded with the patient in the supine position, and without clothes covering the chest. The valve closing sounds were recorded using a microphone (Brüel and Kjær 4179) placed 5 cm above the patient's chest. This sound was then preamplified (Brüel and Kjær 2660), amplified (Brüel and Kjær 2610) and 250 Hz high-pass filtered (Krohn-Hite 3944) (see Fig. 1). All valve sounds were recorded by the same experienced investigator and stored on an instrumentation recorder (TEAC 510) for later off-line analysis. The data acquisition time for each patient was approximately 10 min.

The patients were asked to fuldill a quality of life questionnaire (SF-36), which will be assessed in a future study regarding psychoacoustics for mechanical heart valve sounds.

Perspectives: The results obtained from this analysis will contribute to expand knowledge concerning the sound produced by these three different types of mechanical heart valve prosthesis. The study can add one important parameter in the choice of the implanted valve: patient's pleasantness. It will assess some of the most sold mechanical heart valve worldwide and the final results can contribute to elucidate which type, among those valves, that should be chosen to a specific patient.