Multiple Strokes Secondary to an Early Thrombosis of Aortic Bioprosthesis on Aspirin Therapy.

We describe here a rare case of a 74-year-old man with essential thrombocythemia who presented an early nonobstructive thrombosis of aortic porcine bioprosthesis complicated by multiple ischemic strokes 14 days after the primary operation. Transesophageal echocardiography on the postoperative day (POD) 17 revealed a mobile, nonobstructive thrombosis inserted on the anterior cusp right of the bioprosthesis. Anticoagulation by intravenous unfractionated heparin was effective with disappearance of the thrombus with good aortic prosthesis function on the POD 20 without requiring reoperation. The patient had a complete recovery of neurological disorders and was discharged on POD 26.

INTRODUCTION

Thrombosis of aortic bioprosthesis early after cardiac surgery is a rare but serious complication not really known and documented. This report is about a 74-year-old man with early nonobstructive thrombosis treated by a St. Jude Epic (St. Jude Medical, Inc., St. Paul, Minn) aortic porcine bioprosthesis 14 days after the primary operation.

CASE REPORT

A 74-year-old-man with severe aortic stenosis without coronary artery disease underwent aortic valve replacement (AVR) with a 23-mm St. Jude Medical Epic heart valve at the supra-annular position.

The only medical history is essential thrombocythemia treated with clopidogrel, without any background of bleeding or previous thromboembolism.

There was no complication during the surgery, but the patient presented an important bleeding in the early postoperative suites with requiring 3 red blood cell units and 1250 cc of fresh frozen plasma on the postoperative day (POD) 0.

During the hospitalization, transthoracic echocardiography (TTE) performed on POD 5 showed mean transvalvular pressure gradient (PG) of 12 mmHg, effective orifice area of 1.1 cm2, and normal prosthetic valve function without thrombosis.

For these reasons, the patient was discharged from the hospital on POD 11, with a bitherapy by aspirin 100 mg/day and enoxaparin 0.4 ml/day.

On POD 14, the patient suddenly developed severe left-sided weakness and speech difficulty revealing multiple ischemic strokes (left and right middle and posterior cerebral arteries), splenic infarction, and lateral myocardial infarction of embolic origin.

Transesophageal echocardiography (TEE) on POD 17 revealed a good aortic prosthesis function (mean PG, 16 mm Hg; effective orifice area, 1.03 cm2; and permeability index at 0.3) with good cusps mobility and no structural valve deterioration, but visualization of a mobile isoechoic mass bell clapper inserted on the anterior cusp right of the bioprosthesis suggestive of a nonobstructive thrombosis [Figure 1].

Figure 1

Transesophageal echocardiography on the postoperative day 17 showing a mobile isoechoic mass bell clapper inserted on the anterior cusp right of the aortic bioprosthesis (“white arrow”)

According to guidelines,[12] anticoagulation by intravenous unfractionated heparin was started with continuation of aspirin therapy. On POD 20, TEE control showed the disappearance of the thrombus with good aortic prosthesis function [Figure 2].

Figure 2

Transesophageal echocardiography on the postoperative day 20 showing disappearance of the mass, with good aortic prosthesis function

Thrombophilia testing confirmed essential thrombocythemia with JAK2 mutation and showed hyperhomocysteinemia with MTHFR gene mutation.

After multidisciplinary meeting, it was decided to introduce a treatment by hydroxyurea and pursue long-term fluindione and aspirin therapy.

The patient had a complete recovery of neurological disorders and was discharged on POD 26.

After this episode, the patient presented none disturbs neurological or cardiovascular complications and is still alive after 9 years with a good functioning of the bioprosthesis.

DISCUSSION

While thrombosis of porcine bioprosthesis early after mitral valve replacement has been often described, thrombosis of aortic bioprosthesis is more anecdotic.

Because of the possible catastrophic consequences of unrecognized left ventricular outflow obstruction in conjunction with early thrombosis, some investigators have recommended anticoagulant therapy for all patients for 3 months after they have undergone AVR with a porcine bioprosthesis.

However, because many patients who undergo AVR are elderly and frail, complete anticoagulant therapy in some such patients may be inappropriate in consideration of the possible risk of anticoagulant-related hemorrhage. Therefore, antithrombotic therapy during the early postoperative period after bioprosthetic AVR is controversial and needs evaluation of the patient's age and the adequacy of supervision.

ACC/AHA and ESC guidelines[1] recommended a low-dose aspirin for the first 3 months after implantation of an aortic bioprosthesis rather than an oral anticoagulation because the thromboembolic risk for epic valves and other types of bioprosthetic valves in the aortic position are reportedly low.[2]

In a study by Jamieson et al.,[2] no patient showed valve thrombosis after AVR with epic valves. The incidence of thrombosis associated with bioprosthesis is estimated to be only 0.03–0.7% per patient-year.[3]

However, several studies have reported early thrombosis of bioprosthesis in the aortic position.

By comparing the incidence of thrombosis among valve types, there is a significant difference between stented porcine valves, pericardial valves, and stentless porcine valves with increased risk in stented porcine valve.

Indeed, Brown et al. showed that all patients with aortic valve thrombosis received a stented porcine valve, with greater risk in epic valves (calculated incidence was 1.26% [confidence interval, 0.56–1.96]).[3]

However, overall incidence of aortic bioprosthesis thrombosis is low except in any hypercoagulable state as in our case report.

Hence, previous studies found risk factors for thrombus formation depending of the type of bioprosthetic valves and risk factor of thromboembolic complications such as left ventricular dysfunction, endocarditis, use of steroids or hormones or thrombophilia.[3]

In bioprosthetic valves in the aortic position, the incidence of thromboembolic episodes is probably greatest during the first 3 months after operation, but literature review found that approximately half of the cases occurred after 13 months.[4]

Recent studies showed that thrombosis are often hemodynamically subclinical with reduced leaflet motion and normal aortic-valve gradients on echocardiography.[5]

Hence, diagnosis was frequently performed on computerized tomography (CT) or TEE but was missed on TTE.

Only five cases of subclinical leaflet thrombosis in transcatheter aortic valves have been reported, but reduced leaflet motion was found in 40% of patients in a recent trial, suggesting that this phenomenon is not uncommon.[5]

CONCLUSION

So far, in case of hypercoagulable state, thrombosis of aortic bioprosthetic valve may occur on aspirin therapy. Even if leaflet thrombosis is often subclinical, incidence of nonobstructive thrombosis in porcine bioprosthetic valves within 3 months after implantation is probably underestimated, and this raises the interest of a systematic CT after surgery and curative anticoagulation, especially in patients, with high risk of thromboembolic complication.

Therefore, we need others studies to determine which patient must be treated by anticoagulation during 3 months after aortic bioprosthetic valve implantation.

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Nil.

Conflicts of interest

There are no conflicts of interest.