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.