Eur J Cardiothorac Surg 1999;15:867-869
© 1999 Elsevier Science NL
Leaflet escape in Omnicarbon monoleaflet valve
A. Kornberg,
Stephen M. Wildhirt,
C. Schulze,
E. Kreuzer
Department of Cardiac Surgery Klinikum Großhadern, Ludwig-Maximilian-University, Marchioninistraße 15, 81377 Munich, Germany
Received 16 November 1998;
received in revised form 22 February 1999;
accepted 11 March 1999.
Corresponding author. Tel.: +49-89-70952433 or 2633; fax: +49-89-70958898
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Abstract
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In almost every type of artificial valve, mechanical disruption has been described. We present the first case of leaflet fracture with aortic embolization in an Omnicarbon monoleaflet valve 42 months after implantation. The 22-year-old male patient suffered of acute respiratory insufficiency and was referred to our hospital as an emergency case. Until a few days before presentation, he was in good condition without clinical complaints. By means of transesophageal echocardiography (TEE) and abdominal sonography the diagnosis of leaflet fracture with embolization to the abdominal aorta could be made. The patient underwent consecutive operative valve replacement and foreign body extraction that resulted in a complete recovery.
Key Words: Omnicarbon valve • Mechanical valve • Leaflet fracture • Embolization
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1. Introduction
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Mechanical malfunction of modern prosthetic heart valves is usually caused by extrinsic factors such as bacterial endocarditis, thrombosis or inadequate surgical techniques rather than by intrinsic factors like incorrect design [1]. Leaflet fracture with peripheral escape of the foreign body is a very rare event, usually happening in artificial mitral valves [2,3]. We report an unusual case of a young male patient with leaflet fracture of an Omnicarbon monoleaflet valve in aortic position and embolization to the abdominal aorta 42 months after implantation. Differentiated clinical examination and the primary use of non-invasive diagnostic tools led to the exact diagnosis and operative therapy.
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2. Case report
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A 19 year old Caucasian male patient underwent mitral valve replacement in May 1993 because of endocarditic valve failure as a consequence of chronic drug abuse. An Omnicarbon monoleaflet 33 mm valve was implanted in a foreign hospital with an uneventful postoperative course. In November 1996, the patient was admitted to our hospital intubated and ventilated because of acute pulmonal edema and septic temperatures up to 40°C. During stay in the intensive care unit (ICU), the patient became hemodynamically unstable and catecholamines had to be administered (suprarenin, 0.5 mg/kg, noradrenalin, 0.8 mg/kg). The pulse was irregular with 150 beats/min. On auscultation, the valve click was absent and a systolic murmur about the heart's apex could be noticed. Chest X-ray demonstrated an Omnicarbon valve prosthesis in aortic position and a pulmonary edema. Right heart catheterization showed a v-wave of 60 mmHg pulmonary wedge pressure. Because of increasing serum lactat levels an abdominal ultrasound examination was performed. It demonstrated a circular ‘tumor’ in the abdominal infrarenal aorta. For better visualization of the foreign body, an abdominal angiography was performed revealing the embolized leaflet just below the renal arteries. (Fig. 1)
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Fig. 1. Angiography of the Aorta abdominalis revealing the escaped occluder disk of the Omnicarbon monoleaflet valve just below the Aa. renales.
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At reoperation, the patient was placed on cardiopulmonary bypass after cannulation of aorta, right atrium, inferior and superior vena cava. When the left atrium was opened, the valve's leaflet was missing (Fig. 2)
. The remains of the prosthesis was excised and replaced by a 29 mm Carpentier-Edwards bioprosthesis. The patient was weaned from cardiopulmonary bypass and could be referred to the ICU in a stable condition. In a second operative intervention, the foreign body was removed 6 days later using a median laparotomy and a transverse abdominal aortotomy. The further postoperative course was uneventful and the patient could be discharged in good condition 20 days later.
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Fig. 2. The intraoperative situs shows the remains of the Omnicarbon monoleaflet valve in aortic position, missing the occluder disk.
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3. In vitro examination
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The valve was returned to the manufacturer and underwent a series of investigations in accordance with a standard protocol in order to evaluate the origin of its in vivo failure. Using optical and scanning electron microscopy, a region of severe chipping along the inflow seat of the valve housing at the major orifice between the two pivots could be found. In addition, the occluder disk had fractured along a chord, located at a distance of 10% of the diameter from the disk edge. Scanning electron microscopy of this large piece revealed that the fracture was caused by the initiation of multiple fatigue cracks along the concave edge of the disk; these cracks proceeded from the surface inward toward the graphite substrate before turning into a fast running cleavage crack which resulted in the final catastrophic fracture of the disk. The origin of the many fatigue cracks was found to be severe surface porosity on the concave side of the disk in the region of the fracture. It is believed that there are two possible reasons for the surface damage which caused the fatigue and fracture of the disk. Either the damage originated from the manufacture of the disk, i.e. from the deposition and/or polishing steps, or was produced during handling and primary implantation.
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4. Discussion
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There are several remarkable clinical aspects about this case.
To our knowledge, this is the first report of leaflet fracture with disk occluder escape to the abdominal aorta in the Omnicarbon monoleaflet valve (Medical Incorporated, Inver Grove Heights, MN) which has been in clinical use since 1984. It is an advanced version of the Omniscence valve using an all-carbon (Pyrolite, Carbomedics, Inc., Austin TX) construction for both valve occluder and body in order to reduce thrombogenicity and to improve biocombatibility [4,5]. Compared to other valve related problems, such as thromboemboly, endocarditis or anticoagulant related hemorrhage, leaflet fracture with consecutive embolization is a very rare and catastrophic complication. In contrast to disk escape in bileaflet valves, this event in monoleaflet or ball valves mostly results in sudden death, which did not happen in this case [6].
Unlike in our report, the largest number of documented cases of mechanical disruptions have been reported in mitral valves due to the strong mechanical forces influencing these valves [6,7].
Anyhow, the sudden deterioration in the condition of a previously healthy patient after valve replacement is highly suggestive of mechanical dysfunction, including leaflet fracture. Doppler echocardiography for evaluation of valve function and abdominal ultrasound imaging for the detection of the embolized disk are useful non-invasive diagnostic tools for repeated bedside use [8]. Before operative extirpation of the valve occluder, angiography provides exact visualization of the position of the foreign body. Computed tomography proved to be a further complementary diagnostic method for an accurate search of escaped parts.
As previously reported, the embolization of leaflets normally does not create severe problems [9]. That is the reason why the abdominal revision in our case was performed after 6 days of recovery for the patient. Similar as previously described in the pyrolytic carbon valve of Duromedics [9,10], fatigue fracture has been shown to be the origin of the mechanical disruption, the exact inducible factor however being unclear.
This case impressively demonstrates the need of careful manufacturing and conscious handling of all carbon pyrolytic valves. In addition, it points out the awareness of a rare potential catastrophic complication after valve replacement that requires rapid diagnosis and adequate therapy.
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References
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Abstract
1. Introduction
