Prosthetic Mitral Valve Thrombosis During Pregnancy Treated Successfully With Thrombolysis

Keywords

Echocardiography
pregnancy
prosthetic heart valves
thrombosis

A 32-year-old primigravida, in the 14th gestational week, with a mechanical prosthetic mitral valve, implanted 10 years ago (no further details available), was referred to our department due to acute pulmonary edema. Of note, her anticoagulation therapy had been switched in the 3rd gestational week from warfarin 2.5 mg daily to enoxaparin 4000 IU/d.

On admission, the patient was anxious and diaphoretic with tachypnea and severe orthopnea. The arterial blood pressure was 130/70 mmHg. She was in sinus tachycardia at 120-130 bpm. The saturation of oxygen was 85% on room air, her respiratory rate at 35 breaths per minute and crackles heard bilaterally at the lower and middle lung fields on pulmonary auscultation while chest X-ray showed pulmonary congestion. The patient was initially supported with non-invasive mechanical ventilation and intravenously administration of furosemide.

The bedside transthoracic echocardiogram (TTE) showed an increased transmitral mean pressure gradient at 18mmHg. The subsequent transoesophageal echocardiogram (TEE) revealed a large semilunar thrombus occupying >50% of the prosthetic valve surface (Figure A, B, Video 1,2).

Figure 1. A. Real-time 3-dimensional transesophageal echocardiography (TEE) reveals a large obstructive thrombus (red arrow) occupying at least the half of the prosthetic mitral valve surface. B. 2D TEE showing the edges (red arrows) of the thrombus with its mobile components. C. Seven days after thrombolytic treatment to the repeated TEE a small remnant of clot is seen (red arrow). D. A serial TEE, 7 days after thrombolysis, depicts thrombus’ remnants (red arrow) on the posterior side of the mitral ring. MV= Mitral valve, AO= Aortic valve, LAA= Left atrial appendage.

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Video S1. . Real-time 3-dimensional transesophageal echocardiography (TEE) reveals a large obstructive thrombus (blue arrow) occupying at least the half of the prosthetic mitral valve surface.

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Video S2. 2D TEE showing the edges of the thrombus with its mobile components

Taking into consideration the high risk of the prosthetic valve thrombosis management in the context of pregnancy, a low-dose, slow-infusion tissue plasminogen activator (tPA) was administered (25 mg over 6 hours, without bolus dose), followed by intravenous Unfractionated Heparin 70 IU/kg bolus and 16 IU/kg/h infusion (target aPTT >2 times control levels).

Thrombolysis was considered successful as a significant improvement in symptoms was achieved in the acute phase and a reduction by ≥75% of the thrombus area with a concomitant decrease of the transmitral mean PG to 10mmHg noted in the serial TEE, 7 days later (Figures C, D, Video 3,4). Consequently, the intravenous unfractionated Heparin was switched to enoxarapin 10000 IU/bid with an anti- Xa activity of 1 IU/ml plus ASA 100 mg daily as the patient denied the re-initiation of warfarin.

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Video S3. Seven days after thrombolytic treatment to the repeated TEE a small remnant of clot is seen

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Video S4. A serial TEE, 7 days after thrombolysis, depicts thrombus’ remnants on the posterior side of the mitral ring.

The patient was self-discharged, 10 days after thrombolysis, while thrombus’ remnants were still obvious in the TTE (Video 4).

In the 30th gestational week, she was re-admitted with preeclampsia and underwent an urgent caesarian section that was uneventful for her and the neonatal. On the transthoracic echocardiogram, no obvious thrombus was illustrated.

Pregnancy is associated with changes in haemostasis, including an increase in the majority of clotting factors, a decrease in the quantity of natural anticoagulants and a reduction in fibrinolytic activity (1).

Prosthetic heart valve thrombosis (PVT) is a rare complication, with an estimated incidence of only 0.3% to 1.3% per patient-year in developed countries. (2) However, during pregnancy, changes in the hemostatic system lead to a procoagulant state that increases the risk of PVT up to 10 %.(3).

So PVT during pregnancy is an urgent and difficult to manage complication (4). To date, there is lack of specific guidelines.

According to the European guidelines for the management of patients with valvular heart disease, in women requiring <_5 mg warfarin (before pregnancy), oral anticoagulants throughout pregnancy and a change to UFH before delivery is favored while in patients requiring higher doses prior to pregnancy, switching to LMWH during the first trimester with strict anti-Xa control (therapeutic range 0.8–1.2 IU/mL) and oral anticoagulants afterwards is favored (2,5,6). The AHA/ACC guidelines also suggest the addition of ASA 75-100 mg during the 2nd and 3rd trimester.(2).

Emergency valve replacement is recommended for obstructive prosthetic valve thrombosis in critically ill patients without a contraindication to surgery (2,5). However, cardiac surgery in pregnancy is associated with high maternal and fetal mortality (6% and 30%, respectively) and morbidity (24% and 9%, respectively).(7).

On the other hand, low-dose, slow-infusion tPA thrombolysis seems to be safer (8).

Six-hour infusion of 25 mg tPA without a bolus dose, repeated once after 24 hours, up to 6 times if needed, for a maximum total dose of 150 mg followed by intravenous administration of UFH is suggested. The tPA was preferred as it is a highly fibrin-specific drug not causing systemic thrombolytic effects. Its placental passage is minimal and it has a short biological half-life not inducing any antigenic reactions.

This case illustrates the effective use of a specific thrombolytic therapy as an alternative to surgery in a pregnant woman with mechanical valve thrombosis.

References

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