CASE HISTORY
A 53-year old female patient was admitted in a peripheral hospital with severe, acute onset dyspnea and orthopnea. Her past medical history included bioprosthetic aortic valve replacement (AVR) and mitral valve replacement (MVR) 4 years ago. Two hours later, she required intubation and mechanical ventilation, and transthoracic ECHO showed significant MR. Two days later, she developed high grade fever (39C), accompanied by radiological changes compatible with right lower lobe pneumonia, and a sharp rise in serum inflammatory markers. Multiple blood cultures, skin and nasopharyngeal swabs were taken, and she was commenced on i.v. antibiotics (Tamiflu, Tazocin, Azithromycin). All cultures returned negative including those for MERS-COV and H1N1. Meanwhile, she grewMethicillin Resistant Staphylococcus Aureus in a nasopharyngeal swab and the antibiotic treatment was changed to i.v. Meropenem, Vancomycin and Levofloxacin. Transesophageal echo (TEE) showed severe MR and malfunction of the bioprosthetic MV and was referred to our center.
On admission to the intensive care unit, she was mechanically ventilated, highly pyrexial, on high doses of noradrenaline. Repeat TTE showed a flail mitral valve leaflet and severe MR (Figures 1,2, 2D TEE), (Figures 3, 3D TEE), dilated left atrium (LA), elevated systolic pulmonary artery pressure (75mmHg), moderate tricuspid regurgitation (TR), accelerated flow across the aortic bioprosthesis (mean gradient 32mmHg) and preserved bi-ventricular function. Computed tomography of the chest and abdomen showed right lower lobe consolidation consistent with pneumonia. She continued to run high fever and to require high doses of vasopressors and inotropes in order to maintain adequate blood pressure and urine output. Considering persisting fever, the unsatisfactory response to antibiotic therapy, severe haemodynamic compromise caused by the mechanical dysfunction of the prosthetic MV and the risk for irreversible multiorgan failure, a decision was taken to proceed with urgent surgical intervention seven days after her admission to our hospital.
A standard redo-MVR and De Vega TV annuloplasty were performed through a median re-sternotomy, utilizing cardiopulmonary bypass (aortic and bicaval cannulation), antegrade delivery of Del Nido cardioplegia and a right atrial-transeptal route to access LA and the MV. On inspection, one of the leaflets of the prosthetic MV was detached across its base from the frame of the valve, almost from commissure to commissure (Figure 4). The valve otherwise appeared normal without vegetations, thrombus or signs of valve dehiscence. The bioprosthesis was excised and after thorough tissue debridement and washing with normal saline, a mechanical valve (27mm On-XCryoLife, Inc. NW, U.S.A) was implanted. The LA appendage was obliterated with continuous suture, the interatrial septum closed, and the operation completed in the standard manner. Intraoperative TEE showed moderate biventricular dysfunction, well seating and normally functioning prosthetic MV without paravalvular leak, and mild TR.
Six days after surgery, the inotropes were stopped, the patient became afebrile and was extubated. Thereafter, she made steady progress becoming fully ambulant; Warfarin was commenced aiming for an INR of 2.5-3. Culture of the explanted valve was negative as were the tissues and fluids taken at operation. The patient was eventually transferred to the referring hospital three weeks after her operation for convalescence and completion of her antibiotic therapy. Pre-discharge ECHO showed well-functioning valves, mild TR, and mildly impaired bi-ventricular function.