Postpartum hemorrhage in the setting of a mechanical heart valve

Introduction

Due to advances in cardiothoracic surgery, there are an increasing number of women with a history of reparative surgery for congenital heart disease reaching reproductive age [1]. Therefore, identifying appropriate management strategies for these patients during the antepartum, intrapartum and postpartum period is extremely relevant for obstetricians. Patients with mechanical mitral valves, in particular, require anticoagulation at therapeutic levels [2]. For non-pregnant patients, the anticoagulation medication of choice is warfarin [2]. Warfarin, however, is considered relatively contraindicated in early pregnancy due to its teratogenic effects on the fetus, which are dose dependent. Warfarin embryopathy has been noted to cause defects in fetal cartilage and bone, especially in doses higher than 5 mg daily [3], [4], [5]. In this report, we evaluate the best available evidence to manage pregnant patients with a mechanical heart valve. In addition, we review the challenges surrounding anticoagulation and the risk for massive hemorrhage in the peripartum period.

Case

A 28-year-old gravida 2, para 1 woman at 36 weeks’ 3 days’ gestation presented to labor and delivery in early labor. Her antenatal course was complicated by a history of congenital mitral regurgitation for which she had undergone five mitral valve replacements; the most recent being an On-X mechanical mitral valve placed 5 years prior to this pregnancy. Her cardiac history was further complicated by an anomalous origin of the left coronary artery arising from the left pulmonary artery for which she had undergone surgery when she was 3 months of age. She had also recently underwent coronary artery bypass graft at the time of her last mitral valve replacement 5 years prior. In addition, the patient had a history of supraventricular tachycardia for which she was on metoprolol XL 25 mg daily, anemia, and a remote history of an atrial thrombus. The patient’s obstetrical history was significant for one previous spontaneous preterm vaginal delivery at 35 weeks 10 years prior to this current pregnancy.

At the time of her unplanned conception, the patient was under the care of her cardiology team and therapeutically anticoagulated on warfarin to prevent valve thrombosis. At her initial prenatal visit at 8 weeks’ gestation she was transitioned to low molecular weight heparin (LMWH) to mitigate the teratogenic effects of warfarin on the fetus during the first trimester. Due to the paucity of data on the effectiveness of low molecular weight heparin in the setting of a mechanical mitral valve, the risk of valve thrombosis was felt to outweigh the risk of malformation in the fetus in the second trimester, the patient was extensively counseled and therefore she was restarted on warfarin at 13 weeks’ gestation. She continued warfarin until 35 weeks’ gestation, at which time she was transitioned to LMWH 80 mg twice daily. The patient was followed closely by her cardiologist and her maternal fetal medicine specialist throughout the pregnancy and had frequent echocardiograms showing stable cardiac and valvular function.

At 36 weeks’ 3 days’ gestation, the patient experienced spontaneous onset of labor and presented to labor and delivery. Her cervical exam was 2.5 cm dilated, 50% effaced, cephalic presentation at –3 station, and membranes were intact. Tocodynamometry indicated contractions every 2–3 min. The patient had taken her last dose of LMWH approximately 12 h prior to presentation and further doses were held until delivery. Her admission hemoglobin (Hgb) was 13.6, platelets 147,000 and INR 0.9. Her labor was augmented with oxytocin to shorten the interval of time without anticoagulation to minimize risk of valve thrombosis during labor. In consultation with cardiology, the decision was made for an assisted second stage to avoid stasis of blood over the mechanical valve with valsalva and resumption of full anticoagulation was planned for 6–8 h postpartum. The patient received endocarditis prophylaxis with clindamycin 600 mg intravenous 1 h prior to delivery. She had a vacuum assisted vaginal delivery approximately 20 h after presentation.

Immediately postpartum in the delivery room, significant vaginal bleeding was noted. This bleeding initially resolved with bimanual massage and no vaginal or cervical lacerations were visualized on speculum exam. The estimated blood loss (EBL) from delivery was 600 mL and 1000 μg of misoprostol were administered to the patient rectally. Several minutes later in the delivery room, heavy vaginal bleeding was again noted; an additional 800 mL of blood loss was estimated. The patient received a bolus of intravenous fluids (IVF) and intramuscular methergine. Due to suspected uterine atony, a Bakri balloon was placed, which initially resulted in good hemostasis with minimal output from the catheter. A transfusion of two units packed red blood cells (pRBC), hemabate and albumin were given in the delivery room and a CBC resulted with a Hgb of 7.7, platelets 162,000, INR 1.2, and PTT 30.3. The patient required phenylephrine administration for hypotension and the total EBL was 2000 mL. Therefore, given her persistent tachycardia and hypotension unresponsive to resuscitation as well as the continued vaginal bleeding despite Bakri balloon placement, the decision was made to perform a hysterectomy. A massive transfusion protocol was initiated, however, the two units of fresh frozen plasma (FFP) that were requested were not given at the request of the cardiology team due to concern for valve thrombosis. In the operating room an enlarged 24-week sized uterus with a hematoma in the left broad ligament was noted. A total abdominal hysterectomy was performed and hemostasis was achieved. The EBL from the hysterectomy was an additional 2000 mL and the total EBL from delivery and postpartum was 5000 mL. The patient received an additional four units of pRBC, 5 L of IVF, one unit cryoprecipitate and two units platelets intraoperatively.

Post-operatively, the patient was transferred directly to the cardiac ICU, where she was restarted on therapeutic anticoagulation 4 h later with an IV heparin infusion given her high risk for valve thrombus. Her immediate post-operative hemoglobin was 10.5; she received an additional unit of pRBC post-operatively and by post-operative day 3, her Hgb was stable at 9.9. She was transitioned to LMWH and warfarin on post-operative day 1 and transferred to the general post-partum floor. She was stable and discharged home on post-operative day 3. Pathology report was notable for placenta accreta at the posterior insertion site.

Comment

Congenital cardiac malformations are now the most common cause of maternal morbidity and mortality from heart disease in North America [1], [6]. The American Heart Association, the American College of Cardiologists and the European Society of Cardiology recommend that any woman desiring pregnancy with congenital heart disease should seek preconception counseling from a cardiologist and maternal fetal medicine specialist with expertise in the area [2], [7], [8]. Furthermore, a thorough cardiac evaluation should be performed prior to attempting pregnancy, as the increased blood volume of pregnancy can be dangerous to a patient with an already compromised left ventricular function or valvular dysfunction [1], [2], [6]. In fact, a recent study by van Hagen et al., reported that women with mechanical heart valves only have a 58% chance of experiencing an uncomplicated pregnancy with live birth [9]. Given this high morbidity and mortality risk, preconception and contraception counseling is imperative [6]. Patients with mechanical valves in the mitral or aortic position are considered WHO 3 Risk Classification for the use of combined hormonal contraceptives. Therefore, these should be avoided and all other alternatives considered first. Progesterone only methods of contraception, while considered safe and useable with an arterial or venous thrombotic risk, can interact with warfarin and alter the international normalized ratio. Furthermore, in patients on chronic anticoagulation with warfarin, warfarin’s known teratogenicity, is an added risk to the pregnancy. However, preconception counseling is not always sought and unplanned pregnancy is common, with most patients presenting for initial prenatal care on warfarin late in the first trimester or later in gestation. The patient described in this case chose to continue her pregnancy after being extensively counseled on the risks of valve thrombus and possible death, anticoagulation complications during pregnancy, and the risks of warfarin, including 14.6–56% risk of miscarriage, 5–33% risk of stillbirth, and the risks of congenital abnormalities and warfarin embryopathy [10].

For patients with congenital cardiac malformations, close antepartum follow-up with a cardiologist and active communication in a collaborative, interdisciplinary team approach is imperative [2]. In patients with a mechanical mitral valve, therapeutic anticoagulation is critical and a monthly echocardiogram should be performed to follow mitral valve function [1], [11]. The ideal antepartum anticoagulation plan for patients with prosthetic heart valves has long been a debated topic in the cardiology literature. Warfarin has been reported to be 4–5 times more effective than heparin in patients with prosthetic heart valves, especially if they are mechanical instead of bioprosthetic [12]. However, if warfarin is continued beyond 6 weeks’ gestation, the risk of miscarriage and congenital anomalies is reported to be as high as 10–28% [8], [9]. While heparin does not cross the placenta and has no fetal effects [11], the risk of valve thrombosis can be as high as 33% [8], [13]. Furthermore, LMWH carries a 9% greater risk of thrombosis than warfarin in these patients [3]. In fact, van Hagen et al. noted that 5% of patients with mechanical heart valves had valve thrombosis during pregnancy and that half of those patients were on heparin in the first trimester [9]. By utilizing LMWH in the first trimester, the risk of teratogenicity and fetal loss is decreased. By using warfarin in the second trimester, maternal morbidity from thrombosis is decreased [2]. As the time for delivery approaches, switching to therapeutic LMWH or unfractioned heparin is beneficial to decrease the risk of maternal hemorrhage given the long half-life of warfarin, as well as decreasing the risk of fetal intracranial hemorrhage during a vaginal delivery. Full anticoagulation with warfarin is a contraindication to vaginal delivery due to the risk of fetal intracranial hemorrhage.

If a vaginal delivery is not contraindicated, it is preferable to have a set scheduled date for induction to allow all teams to coordinate the care of the patient [7]. Moreover, anticoagulation timing is imperative so that hemorrhage risk is reduced. Anticoagulation for prosthetic valves carries a significant risk for postpartum hemorrhage. A recent study by Lawley et al. reported that 15% (17/115) of patients with prosthetic valves suffered from a postpartum hemorrhage compared to <1% of patients without prosthetic valves [14]. In our case, anticoagulation had been held for a period >24 h prior to delivery, thus significantly reducing the patient’s risk of postpartum hemorrhage. However, secondary to an unsuspected placenta accreta, the patient experienced a significant postpartum hemorrhage. Given the delicate and critical balance between continued uterine hemorrhage and valvular thrombosis, the use of clotting factors in the resuscitation was discussed between the obstetric and cardiology teams. In a hemorrhage setting, the American College of Cardiology and American Heart Association guidelines recommend the avoidance of vitamin K if the patient is still on warfarin and prefer the administration of FFP if used appropriately [1]. Literature on hemorrhage transfusion protocols in patients with prosthetic heart valves who are not on warfarin at the time of hemorrhage is scarce, and there is a lack of information in pregnancy. However, in reviewing the neurosurgical literature, cryoprecipitate is preferred over FFP in patients with intracranial hemorrhage and a prosthetic heart valve [4]. Based on our own case, early surgical intervention and the limited use of cryoprecipitate may be a reasonable approach to correct coagulopathy while being cautious to prevent thrombosis.

To date, there have been no specific publications evaluating the incidence of abnormal placentation without any prior risk factors, as was seen with this patient. Placenta accreta is typically associated with specific risk factors such as prior uterine surgery, advanced maternal age, or placenta previa [15]. The incidence of placenta accreta reported in the literature varies between 1.7 in 10,000 deliveries and 90 per 10,000 deliveries [16], [17]. Thus, this case was a rare occurrence in which a patient had a placenta accreta with no known prior risk factors while having to be therapeutically anticoagulated due to a prosthetic mechanical mitral valve. The quick decision-making to take her to the operating room for a hysterectomy was instrumental in managing this patient’s life-threatening hemorrhage. Even if abnormal placentation had not been an issue, given the recommendation from cardiology to avoid clotting factors, the decision to perform a postpartum hysterectomy in this patient was the only viable option.

Teaching points

1. Warfarin is the best anticoagulant in patients with mechanical mitral valves, however, its effects on the fetus need to be taken into account when being used in pregnancy.

2. Heparin and LMWH are poorer alternatives in terms of thrombosis risk, but useful in the first trimester to decrease fetal morbidity and mortality and then again at the end of the third trimester to decrease hemorrhage risk associated with delivery.

3. Anticoagulation during labor, delivery, and the postpartum period must be well coordinated in order to balance both the risks of valvular thrombosis and postpartum hemorrhage.