title: Patient self-monitoring of prosthetic heart valve function.
abstract: OBJECTIVE
  Prosthetic heart valve dysfunction impacts on morbidity and quality of life. Although the diagnosis can be made by imaging studies, clinical symptoms commonly precede the diagnostic work-up. The ThromboCheck device analyzes the sound frequency spectra of valve motion, and alterations due to valve dysfunction are observed before overt clinical symptoms develop. The study aim was to determine if the ThromboCheck can be used to monitor the prosthetic valve function of patients at home.
  
  
  METHODS
  Between 2003 and 2007, a total of 541 prosthetic heart valve recipients was prospectively enrolled into a double-blind, multi-center study. ThromboCheck devices were used to evaluate the sound frequency phenomena of valve motion. If the sound frequency spectra deviated from baseline, alarm signals were returned to the medical center via telephone, and these prompted evaluation by fluoroscopy and echocardiography. The clinical follow up included questionnaires at regular intervals.
  
  
  RESULTS
  The cumulative observation period exceeded 748 patient-years, with a median follow up of 25.2 months per patient (range: 1 to 36 months). Almost all patients used the device at least two to three times per week to evaluate valve function, and the vast majority found it easy to operate. About 135,000 codes were returned to the study centers for further analysis; of these codes, 30 (0.0002%) were alarm signals. On 29 of the 30 occasions, prosthetic valve dysfunction was confirmed by fluoroscopy and echocardiography, yielding positive predictive values and specificities of 97% and 100%, respectively. There was no clinical event in the absence of a ThromboCheck alarm signal. Thrombolysis or increased warfarin-based anticoagulation quickly restored the initial sound frequency spectrum of the prosthetic valve in 16 patients. Another 13 patients were surgically revised; their prosthetic valves revealed significant thrombi upon replacement. By using the ThromboCheck device as part of a surveillance system, 79% of the patients felt safer with regards to prosthetic valve dysfunction.
  
  
  CONCLUSIONS
  Analysis of sound frequency spectra by the ThromboCheck identified prosthetic heart valve dysfunction before clinical symptoms developed, and promoted early therapy. The restoration of valve function normalized the frequency spectra, which may be utilized to guide treatment. These results justify further efforts to introduce the analysis of sound phenomena into routine clinical care after prosthetic valve implantation.
authors.affiliation: Heart and Diabetes Center North-Rhine Westphalia, Thoracic and Cardiovascular Surgery, Bad Oeynhausen, Germany. dfritzsche@hdz-nrw.de
authors.forename: Dirk
authors.initials: D
authors.lastname: Fritzsche
authors.forename: Soren
authors.initials: S
authors.lastname: Schenk
authors.forename: Thomas
authors.initials: T
authors.lastname: Eitz
authors.forename: John
authors.initials: J
authors.lastname: Mantas
authors.forename: Dieter
authors.initials: D
authors.lastname: Horstkotte
authors.forename: Reiner
authors.initials: R
authors.lastname: Koerfer
mesh_terms: D000465:Algorithms; D001021:Aortic Valve / Q000502:physiology* / Q000601:surgery; D004311:Double-Blind Method; D005500:Follow-Up Studies; D006347:Heart Sounds / Q000502:physiology; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation; D006801:Humans; D008943:Mitral Valve / Q000502:physiology* / Q000601:surgery; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods; D011446:Prospective Studies; D012648:Self Care; D013927:Thrombosis / Q000175:diagnosis / Q000503:physiopathology