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Sound analysis of a left ventricular assist device: A technical evaluation of iOS devices
Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Höglandssjukhuset, Sweden.ORCID iD: 0000-0001-5485-1052
Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Thoracic and Vascular Surgery. Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine.
Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
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2018 (English)In: International Journal of Artificial Organs, ISSN 0391-3988, E-ISSN 1724-6040, Vol. 41, no 5, p. 254-260Article in journal (Refereed) Published
Abstract [en]

Introduction: The use of left ventricular assist device (LVAD) has grown rapidly. Adverse events do continue to occur. In recent years, analysis of LVAD sound recordings emerged as a means to monitor pump function and detect pump thrombosis. The aim of this study was to characterize the sounds from HeartMate II and to evaluate the use of handheld iOS devices for sound recordings. Method: Signal analysis of LVAD sound recordings, with dedicated recording equipment and iOS devices, was performed. Two LVADs running in mock loop circuits were compared to an implanted LVAD. Spectral analysis and parametric signal models were explored to quantify the sound and potentially detect changes in it. Results: The sound recordings of two LVADs in individual mock loop circuits and a third one implanted in a patient appeared to be similar. Qualitatively, sound characteristics were preserved following changes in pump speed. Recordings using dedicated equipment showed that HeartMate II sound comprises low-frequency components corresponding to pump impeller rotation, as well as high-frequency components due to a pulse width modulation of the electric power to the pump. These different signal components interact and result in a complicated frequency spectrum. The iPhone and iPod recordings could not reproduce the sounds as well as the dedicated equipment. In particular, lower frequencies were affected by outside disturbances. Discussion: This article outlines a systematic approach to LVAD sound analysis using signal processing methods to quantify and potentially detect changes, and describes some of the challenges, for example, with the use of inexpensive recording devices.

Place, publisher, year, edition, pages
SAGE PUBLICATIONS LTD , 2018. Vol. 41, no 5, p. 254-260
Keywords [en]
HeartMate II; left ventricular assist device; sound; spectral analysis
National Category
Biomedical Laboratory Science/Technology
Identifiers
URN: urn:nbn:se:liu:diva-148111DOI: 10.1177/0391398818762352ISI: 000432135400004PubMedID: 29519192OAI: oai:DiVA.org:liu-148111DiVA, id: diva2:1211298
Available from: 2018-05-30 Created: 2018-05-30 Last updated: 2020-06-01
In thesis
1. Acoustic and afterload evaluation of left ventricular assist devices
Open this publication in new window or tab >>Acoustic and afterload evaluation of left ventricular assist devices
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Heart Failure is a serious condition with consequences not only for the individual patient but also for the society with a 5-year mortality rate of 45-60%, and a substantial economic burden. The estimated prevalence in Sweden is 2.2% and the age adjusted prevalence increases with higher age. The fundamental treatment for heart failure is pharmaceutical in combination with life-style changes, and physiotherapy. For patients with advanced heart failure, the use of long-term circulatory support can be an option as a bridge to transplantation, or as destination therapy. However, this treatment entails a risk of multiple adverse events. The incidence of pump thrombosis increased as a clinical problem in 2012 and the need for diagnostic methods were desired. The aim of this thesis was to develop and to evaluate the use of a mock loop circuit to study the acoustics of left ventricular assist devices, to evaluate different recording devices and to study the effect of afterload on pump function.

Methods: Two different mock loops, with the possibility to insert artificial thrombus and to adjust preload and afterload were created to facilitate recording of the left ventricular assist devices. An iPhone/iPodTM was used as recording device since remote monitoring is desirable. The sounds from HeartMate IITM during different conditions were studied. The iPhone/iPod was evaluated in comparison to dedicated recording equipment, and the mock loop recordings to clinical situation. The sound from HeartMate 3TM was studied, compared between in vivo and in vitro recordings, and the use of an electronic stethoscope was evaluated. The impact of afterload on left ventricular assist devices was studied in a mock loop circuit with different changes in preload and afterload.

Results: Mock loop circuit is a promising method to safely change the surrounding conditions as the pump is working. The sound from both HeartMate IITM and HeartMate 3TM can be recorded and analyzed in frequency and time domain. When inserting artificial thrombus in a HeartMate IITM the frequency spectrum is altered. The use of dedicated recording devices is superior to both electronic stethoscope and iPhone/iPodTM, but these handheld devices can be used in clinical settings. The recordings from mock loop circuit and patients appear similar for both HeartMate IITM and HeartMate 3TM. The flow of the devices is affected by the afterload. The HeartMate 3TM is more resistant to increased clot analogs within the pump. For both pumps, best efficacy is seen for clean circuits. The flow rate from the monitor might be misleading since the measured flow rate and the flow rate from monitor can differ due to surrounding conditions. The estimated flow might be adjusted by fitting a parabolic curve.

Conclusion: The use of mock loop circuit to study both flow and sound under different conditions is valid. It is possible to record and study the sound from both HeartMate IITM and HeartMate 3TM. The sound holds information of pump function and appears similar in vivo and in vitro. All recording devices can be used, but dedicated equipment is superior to the more handheld devices, although these might have a function as a screening device. The flow measurement on the monitor might not be valid and optimization of fluid status and afterload can further increase pump efficiency.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. p. 86
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1707
Keywords
Afterload, Electronic stethoscope, Flow, HeartMate II, HeartMate 3, iOS-devices, Sound Analysis
National Category
Medical Instrumentation
Identifiers
urn:nbn:se:liu:diva-161902 (URN)10.3384/diss.diva-161902 (DOI)9789179299880 (ISBN)
Public defence
2019-12-11, Granitsalen, Hus 448, Campus US, Linköping, 13:00 (Swedish)
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Available from: 2019-11-12 Created: 2019-11-12 Last updated: 2025-02-10Bibliographically approved

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Granfeldt, Hans

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Sundbom, PerRoth, MichaelGranfeldt, HansKarlsson, DanielAhn, Henrik CasimirGustafsson, FredrikHübbert, Laila
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Division of Cardiovascular MedicineFaculty of Medicine and Health SciencesAutomatic ControlFaculty of Science & EngineeringDepartment of Thoracic and Vascular SurgeryDivision of Biomedical EngineeringDepartment of Cardiology in Linköping
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