Thromboembolism in peripartum cardiomyopathy: a systematic review

Introduction

Peripartum cardiomyopathy (PPCM) is an uncommon, idiopathic cardiomyopathy characterized by slowly progressing left ventricular (LV) dysfunction late in pregnancy, during delivery, or in the postpartum months of women with no known cardiovascular disease (1,2). Most women present after delivery with nonspecific symptoms of heart failure (HF), including shortness of breath or ankle swelling. Practitioners should have a high clinical suspicion for PPCM, and appropriate diagnostic testing should be ordered immediately.

Despite a better understanding of diagnostics, management, and treatment of PPCM, mainly as a result of registry-based work, uncertainties still exist about complications associated with PPCM, especially thromboembolic events. At the time of diagnosis of PPCM, there is an increased risk of arterial and venous thromboembolic events compared to those of the general female population of the same age (3). Understanding the underlying pathophysiology and risk factors for elevated thromboembolic risk is important because of the significant morbidity and mortality associated with these complications. An unselected approach e.g., antithrombotic treatment, is also unreasonable for women of reproductive age. Therefore, identifying women in need of closer monitoring during and after pregnancy when diagnosed with PPCM can help healthcare professionals optimize management of these patients.

Generally, studies have shown age (>40 and <20 years), antepartum diagnosis, non-Caucasian race, LV ejection fraction (LVEF) <30%, LV end-diastolic diameter of >60 mm, biventricular dysfunction, and delay of diagnosis are risk factors for adverse outcomes (4). One dangerous complication of PPCM is the increased risk of arterial and venous thromboembolic events, which can eventually lead to catastrophic maternal consequences [e.g., stroke, pulmonary embolism (PE)] and potentially fetal demise. Prophylactic anticoagulation can be considered in some high-risk women, and in the presence of LV thrombus, therapeutic anticoagulation should be started immediately. Long-term antithrombotic therapy for prophylaxis, however, is unlikely to be efficacious, due to the hazard of fetal toxicity and bleeding with subsequent pregnancies. Also, compliance would also be a problem because of these issues. Therefore, risk stratification for thromboembolism after a diagnosis of PPCM and patient selection for anticoagulation would be important.

In this review, we summarize the evidence regarding the incidence of thromboembolic complications in women with PPCM, diagnostic approaches, related outcomes, and effects of therapies that have been used. We present this article in accordance with the PRISMA reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-945/rc).

Methods

Data source/search strategy

The search strategy aimed to identify studies in patients with established or suspected PPCM (using the terms peripartum cardiomyopathy or postpartum cardiomyopathy) in the title or abstract. Patients may not have had an established diagnosis of PPCM, but they were in the process of being worked up. The search strategy also aimed to identify articles which referred to the outcome of thromboembolism, including both arterial and venous events.

Relevant articles in English language were retrieved from Web of Science and PubMed queries using the following search terms: (((((((peripartum) OR (period, peripartum [MeSH terms])) OR (postpartum)) OR (postpartum period [MeSH terms])) AND ((cardiomyopath*) OR (cardiomyopathies [MeSH terms]))) OR (peripartum cardiomyopathy)) OR (postpartum cardiomyopathy) AND (English [Filter])) AND ((stroke) OR (thromb*) AND (English [Filter])). This search was done from inception until August 2022. Covidence (https://www.covidence.org/) was used to collect, review, and select relevant articles.

Study selection and classification

A total of 327 total articles were retrieved from PubMed and 85 from Web of Science. Of those, duplicates were removed, and the remaining 327 articles were screened and then classified into 4 domains: epidemiology, risk factors, diagnosis, and therapy of thromboembolism in PPCM. Initially, 72 articles were retained as relevant to this review; however, 49 were excluded because of lack of original data (e.g., review articles, case reports, commentary, etc.). Of the excluded articles, references were scanned for any other articles that could be included; this yielded 8 additional articles in addition to the 22 original included articles. One article was excluded due to being clearly outdated, leaving a total of 30 articles for this review. The workflow of the article selection process is summarized in Figure 1.

Figure 1 PRISMA flow diagram of study selection.

Study quality/data synthesis

Studies that met inclusion/exclusion criteria were included in the systematic review. A summary table describing baseline features for each study (study design, inclusion criteria, definition of PPCM, mean age, number of subjects, and follow-up period) was created for study comparison purposes, summarized in Table 1. The findings for the four domains of interest (epidemiology, risk factors, diagnosis, and therapy of thromboembolism in PPCM) were summarized in corresponding tables. For thromboembolism, we also reported subsequent mortality and persistent or chronic thromboembolism. Risk was reported as hazard ratio (HR), odds ratio, or relative risk, depending on the study. Finally, therapy for thromboembolism was reported as % of therapy used in each study with corresponding outcomes of thromboembolic events.

Risk of bias

No formal assessment for risk of bias was done, as each study had widely different types of effect estimates.

Results

Epidemiology of thromboembolism in PPCM

Although the incidence of PPCM is well documented, the incidence of thromboembolism is not. Through our literature search, we were able to find only a few articles with documentation of thromboembolism and their outcomes. In one of the earliest prospective cohort studies based in the United States, of 27 patients with PPCM, approximately 30% experienced PE and 4% experienced systemic emboli within a 20-year period (35). In a more recent United States-based retrospective cohort study of 34,219 patients with PPCM, in-hospital thromboembolism was a significant and frequent complication presenting in 6.6% of patients during late pregnancy and early postpartum along with cardiac arrest (2.1%), acute pulmonary edema (1.8%), cardiogenic shock (2.6%) (17). Globally, rates of thromboembolism were similar if not higher. In a prospective cohort study based on the European Society of Cardiology (ESC) EURObservational Research Programme (EROP) PPCM registry of 735 women, about 6% of overall patients presented with thromboembolism within 6 months of PPCM diagnosis (31). Using the EORP-PPCM registry approach, in 64 PPCM patients from Iraq, 4.1% presented with thromboembolism within 6 months. Interestingly, among participants from Pakistan, 16% of patients were administered anticoagulation prophylactically, significantly greater than that of the global registry, and may also explain Pakistan’s comparatively lower thromboembolic rate (29). In a retrospective cohort study conducted in India, among 36 patients with PPCM, 14% presented with thromboembolic events (three central and two peripheral) within 4–6 months of PPCM diagnosis. The study also reported a 14% mortality rate with a significant portion due to cerebrovascular accidents, despite all patients with thromboembolism receiving therapeutic anticoagulation (11). Similarly, a 10-year case series in Pakistan with 45 PPCM patients reported that 13% of patients had either LV clot or thromboembolism (16). Lastly, in China, a retrospective study of 71 PPCM patients reported a deep vein thrombosis (DVT) rate of 3% and acute PE rate of 3% with 0% mortality by at least 12-month follow-up (20). Findings are summarized in Table 2.

Risk factors for thromboembolism in PPCM

Increased levels of factor VII, VIII, X, fibrinogen, and von Willebrand; decreased protein C and S activity; and decreased fibrinolysis render PPCM patients more susceptible to thromboembolic events (27,31,36).

Additionally, a LVEF <35% has been associated with a high risk of thromboembolism (37). A retrospective review of 182 patients with PPCM showed that 46 patients (25%) presented with >1 major adverse event, including thromboembolic complications. All of them had LV thrombus, three had a cerebrovascular accident (plus PE in one), and two had leg ischemia requiring amputation. In these patients, significant predictors of major adverse events were LVEF fraction <25% [HR, 4.20; confidence interval (CI): 2.04–8.64] and non-Caucasian background (HR, 2.16; CI: 1.17–3.97), with the extent of initial myocardial insult as indicated by decreased LVEF at time of diagnosis being the most powerful one. In addition, 84% of major adverse events occurred during the first year after diagnosis of PPCM. The higher likelihood of major adverse events among non-Caucasian women aligns with previous studies that have highlighted a higher relative risk of unfavorable outcomes in African American women, compared to non-Hispanic white women (9). Indeed, a retrospective cohort study of all admissions with PPCM as the primary diagnosis from the Nationwide Inpatient Sample database over an 11-year-period showed a higher incidence of LV thrombus in African American patients with PPCM compared to Caucasian Americans (50.7% vs. 28.8%). The study also reported a higher prevalence of LV thrombus in patients with smoking, complicated diabetes, peripheral vascular disease, coagulopathy, and drug abuse with respect to patients without LV thrombus (34).

Cesarean delivery and post-operative status after cesarean section have also been correlated with a higher incidence of thromboembolic complications (DVT, stroke, and PE) in women with PPCM, with endothelial injury, immobility, and ventricular dilatation representing other potential contributors (4,38).

Furthermore, the expression of certain plasminogen activator inhibitor-1 (PAI-1) promoter variants has been reported to be higher and more prevalent in PPCM patients compared to healthy controls, and has been associated with a higher risk of thromboembolic complications, miscarriages, and mild pre-eclampsia (39).

Interestingly, 30 cases of stroke and 9 cases of myocardial infarction have been reported among postpartum women taking bromocriptine, most at higher dosages (40,41).

Finally, estrogen-containing preparations carry an increased risk of thrombosis, therefore they should be avoided in patients with PPCM (42). Findings are summarized in Table 3.

Diagnosis

Two-dimensional (2D) and three-dimensional (3D) echocardiography are valuable tools for evaluation of intraventricular thrombi (43). Considering the evidence linking thromboembolic complications to a LVEF of <0.30 at the time of PPCM diagnosis, recent studies suggest that earlier diagnosis, when cardiac function is more likely to be preserved, is important for preventing thromboembolism (44).

In a retrospective study using surgical confirmation as the gold standard, contrast-enhanced magnetic resonance imaging (MRI) demonstrated higher sensitivity and specificity in diagnosing such thrombi compared to transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE). However, its adoption in clinical practice is limited due to the time required for the study and high cost (37,43).

When there is suspicion of lower extremity DVT, manifesting as extremity pain or swelling, the recommended initial diagnostic test is compression ultrasonography of the proximal veins. If there is still a suspicion of iliac vein thrombosis despite negative results, further evaluation with non-gadolinium-enhanced magnetic resonance venography is advised (45).

The initial evaluation of PE should include electrocardiogram, chest X-ray, and blood tests, while D-dimer testing for the exclusion of PE remains controversial. To establish a conclusive diagnosis, imaging techniques such as lung scintigraphy (ventilation/perfusion scan) or coronary tomographic angiography are necessary. Recently, pregnancy-adapted decision algorithms have shown promising preliminary data, but their effectiveness needs to be validated in larger-scale studies (46). Findings are summarized in Table 4.

Therapy

In an American Heart Association (AHA) scientific statement for the diagnosis and treatment of specific dilated cardiomyopathies, anticoagulation is recommended for patients with PPCM who present with a LVEF <30% (47). In a guidance for the care of acute PPCM, the ESC recommends anticoagulation with heparin to avoid cardio-embolic complications in patients with LVEF ≤35% or treated with bromocriptine (if no contraindication exists) (48). The level of evidence for these recommendations is C (i.e., expert consensus), as higher quality evidence is scarce. Some experts suggest starting anticoagulation and continue until 8 weeks postpartum in all women with PPCM (27,41). In contrast, in some healthcare systems anticoagulation is administered only to PPCM patients with a definite indication for anticoagulation, such as atrial fibrillation or LV thrombus (49). Therapeutic anticoagulation should be administered to patients with intracardiac thrombus identified through imaging or those presenting with systemic embolism, as well as to those experiencing paroxysmal or persistent atrial fibrillation (40).

Some experts suggest continuing anticoagulation therapy until full recovery of LV function. Therefore, regular assessments of LVEF should be conducted over a period of 6 to 12 months (41). Although a full recovery is usually achieved within 2 to 6 months from diagnosis, a potential delay up to 5 years has been reported (50). A cohort study of 36 patients with PPCM [100% with ejection fraction (EF) <45% and 75% with EF <35%] not on prophylactic anticoagulation, showed that, during the 2-year follow-up period, 5 (14%) thromboembolic complications occurred and 2 patients with stroke died. The authors concluded that prophylactic anticoagulation should be given at least for the first 6 months after delivery (41).

Both unfractionated heparin and low molecular weight heparin (LMWH) represent safe choices in pregnancy since they do not cross the placenta (49). Some evidence suggests subcutaneous heparin (5,000 IU twice daily), especially in patients presenting with a LVEF <35% (51). Although warfarin is contraindicated during pregnancy because of its teratogenic potential, it is recommended in the postpartum period (especially in the first several months) in patients with LVEF <30% or in the presence of other indications, such as atrial fibrillation, DVT or PE, or LV thrombus. Anticoagulation for other conditions is based on clinical experience. Data on use of novel oral anticoagulants (NOACs) in PPCM are scarce (52).

Finally, bromocriptine, a dopamine agonist that inhibits the release of prolactin, has demonstrated a high rate of full LV recovery in PPCM (50). Although some case reports suggested that bromocriptine is associated with thromboembolic complications, two prospective cohort studies in ESC and non-ESC countries reported no difference in thromboembolic events with bromocriptine compared [5 events in 84 patients (6%) on bromocriptine vs. 26 events in 463 patients (6%) not on bromocriptine; P=0.802] (2,28). Most experts recommend anticoagulation with heparin (LMWH or unfractionated heparin), at least in prophylactic dosages, in PPCM patients receiving bromocriptine (53). Findings are summarized in Table 5.

Discussion

Thromboembolic complications in women with PPCM pose a significant clinical challenge, with potential life-threatening consequences. In this systematic review, we summarized the epidemiology, risk factors, diagnosis, and therapy of thromboembolic complications in PPCM patients, shedding light on the current understanding of this important clinical issue.

The epidemiology of thromboembolism in PPCM is not extensively studied, and the available literature provides limited information. Our review identified several studies reporting on the incidence of thromboembolic events in PPCM patients across different geographical regions. Although the incidence varied, ranging from 3% to 16%, it was consistently higher than that observed in the general population. These findings highlight the need for heightened awareness and monitoring for thromboembolic complications in women with PPCM.

Several risk factors have been associated with thromboembolic complications in PPCM patients. Hormonal changes during pregnancy contribute to a hypercoagulable state, which can persist for several weeks after delivery, rendering these patients more susceptible to thromboembolic events (27,36). LV systolic dysfunction, which characterizes PPCM, further contributes to blood stasis and the formation of intracardiac thrombi and subsequent systemic embolism, potentially leading to cerebrovascular events and other arterial embolic events, and venous thromboembolic events and PE.

Our review identified LVEF <35% as a significant risk factor for thromboembolism in PPCM patients. Non-Caucasian background and the extent of initial myocardial insult were also identified as predictors of major adverse events, emphasizing the importance of considering individual patient characteristics when assessing thromboembolic risk in PPCM and, therefore, highlighting the need for targeted risk factor modification in these high-risk groups (34).

Cesarean delivery and the post-operative period have been associated with a higher incidence of thromboembolic complications in women with PPCM. Endothelial injury, immobility, and ventricular dilatation likely contribute to the increased risk observed in these patients. Furthermore, elevated circulating levels of PAI-1 in some PPCM patients, due to genetic variability, may play a role in increased thrombotic susceptibility. However, further studies are needed to establish the precise relationship between PAI-1 levels and thromboembolic complications in PPCM (39).

Despite its current indication for treatment of PPCM, it has been postulated that the use of bromocriptine has been associated with high risk of thromboembolic complications, most at higher dosages. Whether concomitant anticoagulation should be given remains an open question.

Timely diagnosis of thromboembolic events is crucial for appropriate management. However, there is limited evidence regarding the diagnostic methods used to assess thromboembolic events in PPCM. MRI has shown higher sensitivity and specificity compared to echocardiography for intracardiac thrombi, but its use is limited due to cost and time requirements. Compression ultrasonography and non-gadolinium-enhanced MRI are recommended for diagnosing DVT. Diagnosis of PE remains challenging and requires a high index of suspicion, since one-third of patients do not present symptoms, with imaging techniques such as lung scintigraphy or coronary tomographic angiography being necessary for definitive diagnosis.

Despite the high rate of thromboembolic events in women with PPCM, the decision of anticoagulant therapy remains a subject of ongoing debate and there is limited evidence to guide management options as well as duration of therapy in these patients. Also, practice varies substantially across healthcare systems. The debate also concerns the decision of therapeutic vs. prophylactic anticoagulation in these patients, as evidence is limited (4). Current guideline statements address the use of anticoagulation in patients with PPCM. However, they primarily rely on expert opinions rather than conclusive empirical evidence. Therefore, which women with PPCM necessitate anticoagulation remains controversial.

The decision to initiate anticoagulation is often based on LVEF thresholds, ranging from <30% to <35%. Prophylactic anticoagulation may be considered for all PPCM patients, especially during the first 6 months after delivery, while therapeutic anticoagulation is recommended for patients with intracardiac thrombus or systemic embolism. There is no consensus on the duration of anticoagulation therapy, with some experts suggesting continuation until clinical and echocardiographic recovery (41). Factors such as patient compliance, the severity of HF, and other clinical considerations should be taken into account when determining need for anticoagulant treatment (50).

Bromocriptine, a dopamine agonist which inhibits the release of prolactin, continues to be studied for the treatment of PPCM and results about whether it is associated with an increased risk of thromboembolic events is controversial. Therefore, the question remains whether anticoagulation should be administered in women with PPCM treated with bromocriptine (41,50).

Conclusions

In conclusion, thromboembolic complications in women with PPCM represent a significant clinical challenge. Thromboembolism in PPCM is consistently higher than in the general population of pregnant women, emphasizing the need for increased awareness. Risk factors include LV systolic dysfunction and individual patient characteristics such as non-Caucasian background. Cesarean delivery and the post-operative period are associated with a higher risk of thromboembolism in PPCM, along with other factors like endothelial injury, immobility, ventricular dilatation, and genetic variability affecting PAI-1 levels. Diagnosis of thromboembolic events in PPCM remains challenging, with limited evidence for specific diagnostic methods. The decision regarding anticoagulant therapy in PPCM is subject to ongoing debate and lacks conclusive empirical evidence. Guidelines primarily rely on expert opinions, and the decision to initiate anticoagulation is often based on LVEF thresholds, presence of intracardiac thrombus or systemic embolism. The duration of therapy and the use of anticoagulation in PPCM patients treated with bromocriptine remain controversial. Overall, further research is needed to better understand the epidemiology, risk factors, diagnosis, and optimal management of thromboembolic complications in women with PPCM.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the PRISMA reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-945/rc

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-945/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-23-945/coif). A.P.K. serves as an unpaid editorial board member of Journal of Thoracic Disease from April 2022 to March 2024. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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