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Ann Thorac Surg 2006;82:537-541
© 2006 The Society of Thoracic Surgeons

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Original article: Cardiovascular

Occasional Single Beat Regurgitation Observed with the Medtronic Advantage Bileaflet Heart Valve

^a Department of Cardiovascular Surgery, German Heart Center, Munich, Germany
^b Department of Anesthesiology, German Heart Center, Munich, Germany
^c Kardiologische Gemeinschaftspraxis, Munich, Germany

Accepted for publication March 10, 2006.

^_* Address correspondence to Dr Eichinger, Department of Cardiovascular Surgery, Lazarettstr 36, Munich 80636, Germany (Email: eichinger{at}dhm.mhn.de).

	Abstract

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
BACKGROUND: The purpose of this clinical study was to obtain further evidence of the underlying mechanism causing the echocardiographically detected phenomenon of single beat regurgitation in a new bileaflet heart valve. As part of a prospective multicenter trial at our institution, 63 patients received the Advantage bileaflet mechanical heart valve (Medtronic, Minneapolis, Minnesota) in aortic position. During routine follow-up performed at discharge and annually after the operation, intermittent moderate transvalvular regurgitation was detected by echocardiography in 5 patients.

METHODS: Fluoroscopy of leaflet motion (n = 4), invasive blood pressure measurements in the ascending aorta (n = 3) and digital phonocardiography (n = 5) was obtained in the patients showing an intermittent regurgitation during echocardiography.

RESULTS: Valve thrombosis, sutures, or pannus ingrowth impairing valve closure was not detected. Fluoroscopy of leaflet motion showed intermittent incomplete closure of either one of the two leaflets in the same prosthesis. This could be correlated with a distinct diastolic blood pressure drop in the same cardiac cycle. Digital phonocardiography showed pathologic closure sounds in those cycles in which echocardiographically the intermittent regurgitation was observed.

CONCLUSIONS: Some patients with the Medtronic Advantage prosthesis in the aortic position show an intermittent inability of complete valve closure that leads to a single beat transvalvular regurgitation. As thrombotic or other material that might cause a disturbance of leaflet motion could not be detected, and the patients seem not to be exposed to any risk except for some chronic regurgitant volume, we decided not to replace the prostheses.

	Introduction

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Bileaflet mechanical valves exhibit some minor regurgitation at the pivotal points. The pivotal region is designed to allow washing jets to reduce the risk of thrombus formation. This regurgitation is seen during color Doppler flow imaging as two small jets not exceeding the left ventricular outflow tract, homogeneous in color, reflecting its low momentum. The current report deals with five cases where we observed an intermittent, trivial to moderate, single beat transvalvular regurgitation which is clearly different from the expected trivial regurgitation. To obtain further evidence of the underlying mechanism causing this phenomenon, we performed additional testing.

	Material and Methods

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The Medtronic Advantage Prosthetic Heart Valve
The Medtronic Advantage prosthesis (Medtronic, Minneapolis, Minnesota) is a bileaflet mechanical heart valve. The design consists of two pyrolytic carbon leaflets constrained within a pyrolytic carbon housing. The leaflet tips and housing are radiolucent. A rotatable, fabric sewing ring is affixed to the valve by a titanium insert ring, which is located below the level of the carbon housing. A new asymmetric, multilevel butterfly hinge mechanism is realized in this prosthesis; the leaflet opening angle is 86 degrees, the closing angle is 22 degrees [1, 2].

Patients
As part of a prospective, multicenter clinical evaluation of the Medtronic Advantage bileaflet mechanical heart valve, we implanted 61 valves in the aortic position since March 2002 at our institution. The study was approved by the Institutional Review board on January 23, 2002 (project number 625/02), and all patients gave written informed consent. An additional 2 patients received an aortic Advantage valve without taking part in the multicenter trial. These patients were also routinely seen conforming to the study protocol. Patient enrollment was concluded for all European centers as of June 30, 2003.

Follow-Up
Clinical and echocardiographic examinations were performed early postoperatively, after 6 months and at annual intervals. Valve-related complications are documented at the time of appearance.

Implantation Technique
Valves were placed intra-annularly using noneverting mattress sutures. The orientation of each implanted valve was documented immediately after the operation (Fig 1).

View larger version (20K): [in this window] [in a new window]   Fig 1. (A) Distribution of orientation of the valve leaflets in all patients. (B) Valve orientation in patients with intermittent regurgitation. (L.C. = left coronary; N.C. = noncoronary; R.C. = right coronary.)

Echocardiograms were performed using a Hewlett-Packard Sonos 5500 (Boeblingen, Germany) ultrasound system and a sample of them was over-read by a central core echocardiography laboratory for quality assurance purposes.

Prosthetic regurgitation was assessed by color Doppler imaging of the left ventricular outflow tract from parasternal and apical transducer positions. Severity of regurgitation was categorized as none, trivial, mild, moderate, or severe based on visual estimates.

Digital Phonocardiography
The Myotis digital phonocardiogram (Cardiosignal GmbH, Hamburg, Germany) was used for the detection of pathologic valve sounds in addition to echocardiography in 5 patients [4].

Fluoroscopy and Pressure Measurement
Fluoroscopy was carried out in 4 patients through GE Digital Mobile Imaging System (GE OEC Series 9800; General Electric, Fairfield, CT) using the mobile workstation with C-arm. The examination was considered successful when the "tilting disk" projection (with the x-ray beam parallel to both the valve ring plane and the tilting axis of the disks) was obtained. For pressure measurements, a 6F Cordis pigtail catheter (Johnson & Johnson, La Jolla, CA) inserted from the left brachial artery was placed 3 cm above the prosthesis. Pressure and electrocardiographic recordings were taken simultaneously to fluoroscopy (EPMed Systems Inc, Berlin, Germany) in 3 patients.

Statistical Analysis
Categorical variables are presented as absolute numbers and compared using a ² test (SPSS 12.0 for Windows; SPSS, Chicago, Illinois).

	Results

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Regurgitation
Depending on imaging conditions, washing jets could be visualized in most of the patients. The typical shape and localization of these jets is shown in Figure 2A. Five patients—all in regular sinus rhythm—additionally showed an intermittent, single beat trivial to moderate regurgitant jet during diastole that was different in extension and grade of insufficiency compared with the expected leakage volume (Fig 2B, C). This appeared in irregular intervals with a frequency between 1 to 30 times per minute and was reproducible in most of the consecutive echocardiography investigation. The mean follow-up time of the patients with an intermittent regurgitation was 26.2 months (range, 24 to 31).

View larger version (104K): [in this window] [in a new window]   Fig 2. (A) The expected leakage volume through the hinge region of an Advantage prosthesis is depicted as it can be seen in color flow imaging. (B) An intermittent trivial to moderate valve insufficiency is shown as it was detected in 5 patients during routine transthoracic echocardiography. (C) An M-mode recording of the left ventricular outflow tract and anterior mitral leaflet. The arrow indicates the intermittent regurgitation during diastole. (LV = left ventricle; LA = left atrium.)

View larger version (15K): [in this window] [in a new window]   Fig 3. Digital phonocardiogram of 1 patient with an intermittent regurgitation. Beats 1, 2, and 4 show the normal closure sound of a bileaflet prosthesis. The two peaks represent the closure sound of the two leaflets. After beat 3, an intermittent regurgitation was echocardiographically detected. The closure sound of one leaflet is missing in beat 3.

View larger version (87K): [in this window] [in a new window]   Fig 4. (A) While one leaflet is completely closed, the second leaflet stays in a slightly open position during the whole diastole (white arrow, top). The housing and leaflet edges are radiolucent and cannot be visualized with this technique. It should be noted that the housing extends above and below the titanium insert ring. (B) Injection of contrast fluid into the aortic root shows the regurgitant jet (white arrow, bottom) (same patient as in Fig 4A.) This time the other leaflet did not close completely. Angiographically, the severity of the regurgitation was graded as II+ to III+.

View larger version (31K): [in this window] [in a new window]   Fig 5. Invasive blood pressure measurement in a patient with intermittent regurgitation. The arrow indicates the diastolic pressure drop that clearly could be associated with each pathologic leaflet motion of the prosthesis.

	Comment

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The clinical results obtained at our institution of the Medtronic Advantage bileaflet mechanical heart valve revealed low overall complication rates based on the guidelines for reporting morbidity and mortality after cardiac valvular operations [5]. The Advantage aortic valve obtained CE Marking in January 2003. (A CE Marking is an European marking of conformity that indicates that a product complies with the essential requirements of the applicable European laws or directives with respect to safety, health, environment, and consumer protection.)

In bileaflet valves, a certain amount of transvalvular regurgitation is normal, as the hinge region has to be washed during diastole to avoid thrombus formation [6, 7]. This phenomenon usually can be visualized echocardiographically as two small jets in color flow imaging directed toward the left ventricular outflow tract. This is a common finding in other bileaflet valves as well [8, 9]. During routine follow-up examinations, 5 patients were detected in whom an intermittent trivial to moderate regurgitation was seen, different concerning grade of insufficiency and localization of the regurgitant jet compared with the expected leakage volume.

The first hypothesis to explain the regurgitation was thrombus formation or pannus ingrowth that may have led to impaired leaflet mobility. No evidence for this was detected, and anticoagulation levels were within the recommended margins or even higher except for three single measurements with INR values below 2.0. Therefore, patients who presented with this phenomenon were further evaluated by digital phonocardiography, fluoroscopy, and direct pressure measurements in the ascending aorta. Color flow echocardiography and digital phonocardiography as well as fluoroscopy and invasive pressure measurements were recorded in addition, so that the phenomenon could be evidenced by two independent methods when it occurred. In 1 patient presenting with a high frequency of intermittent regurgitation, contrast media was injected in the ascending aorta to grade the severity of the prosthetic regurgitation. The regurgitant jet could be visualized, reaching through the lateral region between the sewing ring cuff and the leaflet (Fig 4B). When intermittent, single beat regurgitation occurs, it appears that one of the two leaflets does not close completely. The fluoroscopy shows that an incidental asymmetric closure of the two leaflets tends to end up in incomplete closure of the leaflet that closes later (see Fig 4A). We found that either one of the two leaflets could be affected by incomplete closure in the same prosthesis. In the 3 patients who underwent direct pressure measurement we could show that a diastolic pressure drop was associated with each incomplete closure. Thus, the hemodynamic relevance of the regurgitation was documented. The findings of the digital phonocardiography with the closure sound of one leaflet completely missing also underlines the hypothesis of this mechanism.

The orientation of all prostheses was carefully documented. We could not find any correlation between the orientation and the occurrence of the phenomenon, as it occurred in different orientations of the prosthesis. Furthermore, this phenomenon was not related to only one specific valve size, as it was found in four size 23 valves and one size 27 valve.

As at the moment all patients in whom an intermittent regurgitation due to incomplete asymmetric valve closure was found are in good clinical condition and show no signs of hemolysis, we decided to strictly monitor their further outcome and the valve function.

In conclusion, in our series, 5 of 63 patients with the Advantage prosthesis in aortic position show an intermittent asymmetric incomplete valve closure that leads to a single beat transvalvular regurgitation. Thrombotic or other material that might cause a disturbance of leaflet motion could not be detected. Further investigation is required to determine whether this is an intrinsic phenomenon of the Advantage aortic valve. As the patients are clinically normal and not exposed to any risk except for some intermittent single beat regurgitant volume, we currently do not reoperate on these patients but choose to follow them closely.

	Acknowledgments

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Echocardiographic investigations were financially supported by Medtronic, Inc, Minneapolis, Minnesota. Recording of phonocardiograms was technically assisted by Cardiosignal (Cardiosignal GmbH, Hamburg, Germany).

	References

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

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7. Yoganathan A. Laser doppler velocimetry studies within the hinge region of a clear Medtronic bileaflet mechanical heart valve. Georgia Institute of Technology; 19998.
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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Walter B. Eichinger Sabine Bleiziffer Robert Bauernschmitt Ruediger Lange Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Eichinger, W. B. Articles by Lange, R. Search for Related Content PubMed PubMed Citation Articles by Eichinger, W. B. Articles by Lange, R. Related Collections Valve disease