Intermittent, Noncyclic Dysfunction of a Mechanical Aortic Prosthesis by Pannus Formation




Mechanical aortic prosthesis dysfunction can result from thrombosis or pannus formation. Pannus formation usually restricts systolic excursion of the occluding disk, resulting in progressive stenosis of the aortic prosthesis. Intermittent dysfunction of a mechanical aortic prosthesis is usually ascribed to thrombus formation. We describe an unusual case of intermittent, noncyclic dysfunction of a mechanical aortic prosthesis due to pannus formation in the absence of systolic restriction of disk excursion that presented with intermittent massive aortic regurgitation, severe ischemia, and shock. Pannus formation should be considered as a potential cause of acute intermittent severe aortic regurgitation in a patient with a mechanical aortic prosthesis.


Mechanical prosthetic valve dysfunction may result from thrombosis or pannus formation and has a spectrum of clinical presentations that range from an insidious illness with nonspecific symptoms to acute hemodynamic compromise leading to shock and death. Intermittent dysfunction of a mechanical prosthesis is usually attributed to thrombus formation. However, pannus formation on a mechanical mitral prosthesis can lead to intermittent, cyclic restriction of disk opening. Pannus formation rarely has been reported to cause intermittent, cyclic dysfunction of a mechanical aortic prosthesis. We describe the unusual case of intermittent, noncyclic dysfunction of a mechanical aortic prosthesis due to pannus formation presenting with intermittent massive aortic regurgitation, severe ischemia, and shock.


Case Report


A 78-year-old woman with a single-disc Medtronic Hall (Medtronic Inc, Minneapolis, MN) aortic prosthesis implanted 18 years earlier for aortic stenosis presented to a regional hospital after an episode of substernal chest pain and syncope. The chest pain began while she was at rest and resolved after 1 hour. She had experienced a syncopal episode while walking during the episode of chest pain. Her medical history was remarkable for chronic persistent atrial fibrillation and hypertension. A transthoracic echocardiogram (TTE) had been performed 6 months earlier and demonstrated normal function of the aortic prosthesis. Her international normalized ratio had been monitored closely and was therapeutic during the previous 6 months.


On presentation, her heart rate was 70 beats/min, and her blood pressure was 145/67 mm Hg. She had a grade 1/6 systolic ejection murmur, but no diastolic murmur. Troponin T level was mildly elevated at 1.2 μg/L. An acute coronary syndrome was diagnosed, and she was treated with heparin, aspirin, and clopidogrel. Coronary angiography demonstrated no obstructive coronary stenosis. However, during angiography, she had a recurrence of her chest pain associated with hypotension requiring inotropic support. Aortography was performed to rule out aortic dissection and identified severe aortic regurgitation with incomplete closure of the occluding disk ( Figure 1 ; Videos 1 and 2 ). After 20 minutes, the patient’s hemodynamics improved and inotropic therapy was discontinued. She was transferred to our center for further management.




Figure 1


Aortogram (left anterior oblique 46 degrees) demonstrating severe aortic regurgitation (A) . The occluding disk ( arrow ) of the mechanical aortic prosthesis can be seen above the prosthesis ring in systole (B) and diastole (C) during selective injection of the left coronary artery (right anterior oblique 15 degrees, caudal 25 degrees). The occluding disk has an upward tilt with normal excursion during systole (B) , but incomplete closure during diastole (C) .


On arrival, the patient was clinically and hemodynamically stable with no evidence of aortic regurgitation. A TTE and transesophageal echocardiogram (TEE) demonstrated normal function of the aortic prosthesis with normal systolic excursion of the occluding disk, a mean transprosthetic gradient of 10 mm Hg, and trivial transvalvular regurgitation ( Figure 2 A , B; Videos 3 and 4 ). A small nonmobile echogenic mass was seen in the outflow tract immediately below the prosthesis consistent with pannus formation ( Figure 2 A; Video 3 ). No thrombus was visualized on the prosthesis. The transient episodes of hemodynamic compromise were attributed to possible thrombus superimposed on the pannus formation, despite the absence of any visualized thrombus on TEE. Cardiac surgery was consulted, and arrangements were made for urgent in-house surgery. While awaiting surgery, the patient had the sudden onset of her previous chest pain associated with hypotension and a new diastolic murmur along the left sternal border. A TTE demonstrated severe aortic regurgitation ( Figure 2 C, Video 5 ). She was stabilized with inotropic therapy and transferred to the operating room for emergency surgical treatment.




Figure 2


TEE demonstrating pannus ( closed arrow ) on the outflow tract aspect of the mechanical aortic prosthesis (A) . There is normal systolic excursion of the disk ( open arrow ) (A) and trivial regurgitation (B) . Subsequent TTE demonstrating severe aortic regurgitation (C) . Ao , Aorta; AR , aortic regurgitation; LA , left atrium; LV , left ventricle.


At the time of surgery, circular pannus formation without thrombus was identified ( Figure 3 ). The mechanical aortic prosthesis and pannus were excised, and an aortic bioprosthesis was implanted. The patient’s postoperative course was uncomplicated.


Jun 16, 2018 | Posted by in CARDIOLOGY | Comments Off on Intermittent, Noncyclic Dysfunction of a Mechanical Aortic Prosthesis by Pannus Formation
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