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Introduction

Mechanical heart valve prostheses have shown an outstanding long term stability. They are still the first choice for valve replacements and are implanted in large numbers throughout the world. The main disadvantage of this valve type for patients is the necessity of consistent and uninterrupted anticoagulation for the rest of their lives! The path between too much and too little anticoagulation is narrow. Any deviation from the therapeutic coagulation regime increases the risk of either thrombosis or bleeding. Every year 2 & 6 % of valve patients suffer events such as apoplectic stroke due to these complications.

Valve degradation is not usually discovered in time during regular inspections by the physician; thrombotic depositions may form within 72 hours. This period is far below the regular interval for detailed inspections.

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Valve Signals

The below figure shows a double click signal (left) and a single click signal (right) within one heartbeat, corresponding to an implanted valve with either two or one leaflets.

Click Click

In the frequency domain a typical peak structure is measured. Characteristic frequencies are within the ultrasonic range and cannot be perceived by the human ear. Examples for click spectra taken from patients with different valve types:

Spectrum Spectrum

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Animal Experiments and In Vitro Testing

Besides clinical studies with extensive patient groups, CARDIOSIGNAL also carries out serial experiments with pigs, sheep and cattle. Thrombotic heart valves are systematically generated in these animals and the changing clicking sounds recorded and analyzed:

Thrombs
Typical appearance of terminal heart valves from animal experiments. During the growth period of the thrombus the changing cklicking signal is recorded.
Measurement Slope of an inverted valve thrombosis in a sheep: The freshly thrombosed valve was implanted in a sheep heart and the thrombus dissolved by administration of urokinase. The characteristic signal according to ThromboCheck recovered significantly during thrombolysis, at #40 the thrombus was flushed out and the signal completely restored.

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Example #1 of a Real Life Valve Thrombosis

X-ray examination of a patient with AVR bi-leaflet heart valve prosthesis.
One leaflet is significantly limited in its movements, the second leaflet works normally.

This case is haemodynamically inconspicuous but could be detected using Ultrasonic-Cardiography.
This recording has been done in the Clinic for Heart and Thorax Surgery Bergmannsheil in Bochum, Germany. It has kindly been made available to us by Prof. Dr. med. A. Laczkovics.

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Example #2 of a Real Life Valve Thrombosis

Case 1
Here the level of fingerprint identity is shown, day by day. On the last day the level has strongly decreased, with thrombotic deposits on the implant.

In our clinical studies acoustic data are continuously evaluated from patients after valve replacement. This data is used to monitor the day-to-day fingerprint identity of the patients.

In our example a patient (AVR, St. Jude Medical) with irregular anticoagulation showed a very suspicious degradation in fingerprint identity after the ninth day. The patient was strongly advised to undergo further diagnostics. Heart flow measurements produced no positive finding but angiographic and echo-cardiographic diagnostics did indeed clearly show a thrombotic degradation of one leaflet of the prosthesis.

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Example #3 of a Real Life Valve Thrombosis

Case 2
View into the aorta with a strongly thrombosed mechanical valve. The deposit was carefully removed and flushed. The removed thrombus (little picture) was a massive risk factor for embolic stroke and caused a pronounced valve insufficiency.

Due to a fracture in the upper arm a 70-year old patient with a mechanical bi-leaflet valve in aortic position had to interrupt anticoagulation with marcumar. The correct change to heparin medication was not made.

Acoustic examinations of the patient with ThromboCheck revealed massive and suspicious changes in the sound structure of the valve. Further diagnosis with echocardiography revealed a significant insufficiency and stenosis of the valve. The patient was prescribed to re-operation. The valve could be preserved after removal of the deposited material.

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Publications

The following publications have been released during the development of ThromboCheck and Myotis:

D. Fritzsche, Th. Eitz, D. Horstkotte, R. Körfer: Home-Monitoring von Patienten nach künstlichem Herzklappenersatz
Herz, 32, Heft 6, 2007, S. 491

D. Fritzsche, Th. Eitz, A. Laczkovics. A. Liebold, M. Knaut, K. Matschke, A. Sagie, U. Mehlhorn, D. Horstkotte, R. Körfer: Early Detection of Mechanical Valve Dysfunction Using a New Home Monitoring Device
Annals of Thoracic Surgery, 83, 2007, S. 542-548

D. Reber, M. Fritz, C. Helm, A. Brensing, A. Laczkovics: Early detection of valve dysfunction by digital phonocardiography
Gazetta Medica Italiana, 164, Heft 3, 2005, S. 227-229

S. Ben Zekry, A. Sagie, I. Ben-Dor, D. A. Weisenberg, H. Nukrian, A. Battler, Y. Shapira: Initial Clinical Experience with a Hand-held Device (ThromboCheck) for the Detection of Bileaflet Prosthetic Valve Malfunction
Journal of Heart Valve Disease, 14, 2005, S. 476-480

D. Fritzsche, Th. Eitz, K. Minami, D. Reber, A. Laczkovics, U. Mehlhorn D. Horstkotte, R. Körfer: Digital Frequency Analysis of Valve Sound Phenomena in Patients after Prosthetic Valve Surgery: Its Capability as a True Home Monitoring of Valve Function
Journal of Heart Valve Disease, 14, 2005, S. 657-663

D. Fritzsche, Th. Eitz, O. Grimmig D. Horstkotte, R. Körfer: Postoperative Betreuung von Patienten nach alloprothetischem Herzklappenersatz
Zeitschrift für Kardiologie, 93, 2004, S. 664-670

Home Monitoring nach alloprothetischem Herzklappenersatz
Deutsches Ärzteblatt, Jg. 101, Heft 15, 9. April 2004

Home Monitoring of Patients after Prosthetic Valve Surgery
The Thoracic and Cardiovascular Surgeon, Volume 52, 2004

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