Risks to the Fetus of Radiologic Procedures Used in the Diagnosis of Maternal Venous Thromboembolic Disease

Pulmonary Embolism in Pregnancy

Even though venous thromboembolism is a leading cause of maternal mortality in high-income countries, there are limited high-quality data to assist clinicians with the management of pulmonary embolism in this patient population. Diagnosis, prevention, and treatment of pregnancy-associated pulmonary embolism are complicated by the need to consider fetal, as well as maternal, well-being. Recent studies suggest that clinical prediction rules and D-dimer testing can reduce the need for diagnostic imaging in a subset of patients. Low-molecular-weight heparin is the preferred anticoagulant for both prophylaxis and treatment in this setting. Direct oral anticoagulants are contraindicated during pregnancy and in breastfeeding women. Thrombolysis or embolectomy should be considered for pregnant women with pulmonary embolism complicated by hemodynamic instability. Treatment of pregnancy-associated pulmonary embolism should be continued for at least 3 months, including 6 weeks postpartum. Management of anticoagulants at the time of delivery should involve a multidisciplinary individualized approach that uses shared decision making to take patient and caregiver values and preferences into account.

Current opinion and emerging trends on the treatment, diagnosis, and prevention of pregnancy-associated venous thromboembolic disease: a review

Pregnancy associated venous thromboembolism (PA-VTE) is a leading cause of maternal morbidity and mortality worldwide. Despite the availability of international guidance on the prevention, diagnosis and treatment, practice differs between countries and clinical institutions. The evidence base in this area is limited due to the vulnerable population who are affected, with the majority of guidelines deriving their recommendations from experience in surgical and medical venous thromboembolic disease. This review includes best evidence in PA-VTE management, highlighting specific literature which supports current diagnosis, prevention, and treatment strategies. Additionally, we hope to demonstrate emerging trends in the field through discussion of ongoing trials designed to progress towards evidence-based practice in the context of PA-VTE.

Ischemic stroke and cerebral venous sinus thrombosis in pregnancy

Maternal ischemic stroke and cerebral venous sinus thrombosis (CVST) are dreaded complications of pregnancy and major contributors to maternal disability and mortality. This chapter summarizes the incidence and risk factors for maternal arterial ischemic stroke (AIS) and CVST and discusses the pathophysiology of maternal AIS and CVST. The diagnosis, treatment, and secondary preventive strategies for maternal stroke are also reviewed. Special populations at high risk of maternal stroke, including women with moyamoya disease, sickle cell disease, HIV, thrombophilia, and genetic cerebrovascular disorders, are highlighted.

Massive Pulmonary Embolism in a Pregnant Woman with an Excellent Response to Early Thrombolytic Therapy

Thrombolytic agents have been used successfully to treat patients with massive pulmonary embolism and cardiorespiratory insufficiency. Experience with these drugs in pregnancy is limited, nevertheless. We report a 32-year-old pregnant female, who was at 16 weeks of gestation, presented with acute collapse and progressive dyspnea caused by massive pulmonary embolism. The diagnosis was rapidly made in the emergency department with two dimensional-doppler echocardiography that showed signs of right ventricular dysfunction and pulmonary hypertension, as well as direct visualisation of large thrombus at the bifurcation of the main pulmonary artery. Because of significant haemodynamic instability and no improvement after intravenous heparin, the patient was successfully treated with recombinant tissue plasminogen activator and low-molecular-weight heparin. The response to fibrinolytic therapy was excellent without haemorrhagic complications and a healthy child was born at term. We conclude that early thrombolytic therapy may be a reasonable treatment for pregnant patients with unstable pulmonary embolism. (Hong Kong j.emerg.med. 2014;21:260-265)

[Pulmonary embolism]

Pulmonary embolism is a potentially fatal disorder and frequently seen in critical care and emergency medicine. Due to a high mortality rate within the first few hours, the accurate initiation of rational diagnostic pathways in patients with suspected pulmonary embolism and timely consecutive treatment is essential. In this review, the current European guidelines on the diagnosis and therapy of acute pulmonary embolism are presented. Special focus is put on a structured patient management based on the individual risk of early mortality. In particular risk assessment and new risk-adjusted treatment recommendations are presented and discussed in this article.

Venous Thromboembolism in Pregnancy

The risk of venous thromboembolism (VTE) is increased in pregnancy and puerperium. Thrombophilia has been identified in pregnancy-related VTE. Venous ultrasound and ventilation-perfusion lung scanning are the initial tests; pulmonary angiography should be performed if necessary for the definitive diagnosis. Anticoagulation is achieved with heparin antepartum and warfarin postpartum. Low molecular weight heparin has been effective and safe in pregnancy. Thrombolytic therapy has been administered to pregnant patients.

Experience with Greenfield Filters in Pregnant Women for Deep Venous Thrombosis and Pulmonary Embolism Case Reports

The indications for inferior vena caval filter placement in the gravid female are ill defined. During pregnancy, however, pulmonary embolism (PE) secondary to venous thrombosis is the most common cause of maternal mortality. Pregnant women are at risk for deep venous thrombosis (DVT) due to hypercoagulability caused by increased levels of coagulation factors and decreased fibrinolytic activity. In addition, decreased venous tone and velocity of blood flow in the lower extremities lead to venous stasis. Although heparin is the treatment of choice for DVT associated with pregnancy, propagation of thrombus or development of bleeding diathesis mandates discontinuation of anticoagulant therapy and consideration for caval interruption. In this review, two patients are presented who required vena caval filters during pregnancy, and indications for their usage in this patient population are defined. Filter placement is recommended during pregnancy in the presence of extensive iliofemoral thrombus, free-floating thrombus, bleeding complications, or pulmonary embolism despite adequate anticoagulation.

[Pulmonary embolism]

Pulmonary embolism is a potentially fatal disorder and frequently seen in critical care and emergency medicine. Due to a high mortality rate within the first few hours, the accurate initiation of rational diagnostic pathways in patients with suspected pulmonary embolism and timely consecutive treatment is essential. In this review, the current European guidelines on the diagnosis and therapy of acute pulmonary embolism are presented. Special focus is put on a structured patient management based on the individual risk of early mortality. In particular risk assessment and new risk-adjusted treatment recommendations are presented and discussed in this article.

Acute respiratory failure in pregnancy

Respiratory failure affects up to 0.2% of pregnancies, more commonly in the postpartum period. Altered maternal respiratory physiology affects the assessment and management of these patients. Respiratory failure may result from pregnancy-specific conditions such as preeclampsia, amniotic fluid embolism or peripartum cardiomyopathy. Pregnancy may increase the risk or severity of other conditions, including thromboembolism, asthma, viral pneumonitis, and gastric acid aspiration. Management during pregnancy is similar to the nonpregnant patient. Endotracheal intubation in pregnancy carries an increased risk, due to airway edema and rapid oxygen desaturation following apnea. Few data are available to direct prolonged mechanical ventilation in pregnancy. Chest wall compliance is reduced, perhaps permitting slightly higher airway pressures. Optimizing oxygenation is important, but data on the use of permissive hypercapnia are limited. Delivery of the fetus does not always improve maternal respiratory function, but should be considered if benefit to the fetus is anticipated.

Venous thromboembolism in pregnant woman — a challenge for the clinician

Deep vein thrombosis and pulmonary embolism are two clinical entities of a single disease called venous thromboembolism. Venous thromboembolism is an important cause of maternal morbidity and mortality. Diagnosis and treatment of venous thromboembolism in pregnant women are much more difficult than in non-pregnant women. Pregnant patients were excluded from all major clinical trials investigating therapeutic combinations for acute thromboembolism. Although, for many years, the standard anticoagulant during pregnancy and postpartum was unfractionated heparin, current guidelines recommend low molecular weight heparin. The advantages of low molecular weight heparin are lower risk of bleeding, predictable pharmacokinetics, lower risk of fracture because of thrombocytopenia and heparin-induced osteoporosis.

The coagulation system in humans

Complex, interrelated systems exist to maintain the fluidity of the blood in the vascular system while allowing for the rapid formation of a solid blood clot to prevent hemorrhaging subsequent to blood vessel injury. These interrelated systems are collectively referred to as haemostasis. The components involved in the haemostatic mechanism consist of vessel walls, platelets, coagulation factors, inhibitors, and the fibrinolytic system. In the broadest sense, a series of cascades involving coagulation proteins and enzymes, as well as cell surfaces (platelets and endothelial cells), work together to generate thrombin, the key enzyme in coagulation, subsequently leading to the formation of a fibrin clot. However, there also exist direct and indirect inhibitors of thrombin to ensure that clot formation does not go uncontrolled. Once the fibrin clot is formed, the fibrinolytic system ensures that the clot is lysed so that it does not become a pathological complication. Taken together, the systems exist to balance each other and maintain order. The balance of coagulation and fibrinolysis keeps the haemostatic system functioning efficiently.

Reducing ionizing radiation doses during cardiac interventions in pregnant women

BACKGROUND

There is concern over ionizing radiation exposure in women who are pregnant or of child-bearing age. Due to the increasing prevalence of congenital and acquired heart disease, the number of women who require cardiac interventions during pregnancy has increased. We have developed protocols for cardiac interventions in pregnant women and women of child-bearing age, aimed at substantially reducing both fluoroscopy duration and radiation doses.

METHODS

Over five years, we performed cardiac interventions on 15 pregnant women, nine postpartum women and four as part of prepregnancy assessment. Fluoroscopy times were minimized by simultaneous use of intracardiac echocardiography, and by using very low frame rates (2/second) during fluoroscopy.

RESULTS

The procedures most commonly undertaken were closure of atrial septal defect (ASD) or patent foramen ovale (PFO) in 16 women, coronary angiograms in seven, right and left heart catheters in three and two stent placements. The mean screening time for all patients was 2.38 minutes (range 0.48-13.7), the median radiation dose was 66 (8.9-1501) Gy/cm(2). The median radiation dose to uterus was 1.92 (0.59-5.47) μGy, and the patient estimated dose was 0.24 (0.095-0.80) mSv.

CONCLUSIONS

Ionizing radiation can be used safely in the management of severe cardiac structural disease in pregnancy, with very low ionizing radiation dose to the mother and extremely low exposure to the fetus. With experience, ionizing radiation doses at our institution have been reduced.

Diagnosis of DVT: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Objective testing for DVT is crucial because clinical assessment alone is unreliable and the consequences of misdiagnosis are serious. This guideline focuses on the identification of optimal strategies for the diagnosis of DVT in ambulatory adults.

METHODS

The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that clinical assessment of pretest probability of DVT, rather than performing the same tests in all patients, should guide the diagnostic process for a first lower extremity DVT (Grade 2B). In patients with a low pretest probability of first lower extremity DVT, we recommend initial testing with D-dimer or ultrasound (US) of the proximal veins over no diagnostic testing (Grade 1B), venography (Grade 1B), or whole-leg US (Grade 2B). In patients with moderate pretest probability, we recommend initial testing with a highly sensitive D-dimer, proximal compression US, or whole-leg US rather than no testing (Grade 1B) or venography (Grade 1B). In patients with a high pretest probability, we recommend proximal compression or whole-leg US over no testing (Grade 1B) or venography (Grade 1B).

CONCLUSIONS

Favored strategies for diagnosis of first DVT combine use of pretest probability assessment, D-dimer, and US. There is lower-quality evidence available to guide diagnosis of recurrent DVT, upper extremity DVT, and DVT during pregnancy.

How I treat pregnancy-related venous thromboembolism

Venous thromboembolism (VTE) complicates ∼ 1 to 2 of 1000 pregnancies, with pulmonary embolism being a leading cause of maternal mortality and deep vein thrombosis an important cause of maternal morbidity, also on the long term. However, a strong evidence base for the management of pregnancy-related VTE is missing. Management is not standardized between physicians, centers, and countries. The management of pregnancy-related VTE is based on extrapolation from the nonpregnant population, and clinical trial data for the optimal treatment are not available. Low-molecular-weight heparin (LMWH) in therapeutic doses is the treatment of choice during pregnancy, and anticoagulation (LMWH or vitamin K antagonists postpartum) should be continued until 6 weeks after delivery with a minimum total duration of 3 months. Use of LMWH or vitamin K antagonists does not preclude breastfeeding. Whether dosing should be based on weight or anti-Xa levels is unknown, and practices differ between centers. Management of delivery, including the type of anesthesia if deemed necessary, requires a multidisciplinary approach, and several options are possible, depending on local preferences and patient-specific conditions.

Evidence base for the management of venous thromboembolism in pregnancy

Venous thromboembolism (VTE), comprising deep vein thrombosis (DVT) and pulmonary embolism (PE), is a leading cause of maternal mortality during pregnancy. DVT and PE are commonly suspected due to many mimicking signs and symptoms that are normal in pregnancy. However, validated diagnostic approaches are lacking, and a fear of teratogenic/oncogenic exposure from imaging procedures affects the acceptability of diagnostic approaches used for VTE during pregnancy. DVT and PE treatment in pregnancy is also challenging due to this lack of validated diagnostic approaches, changes in maternal physiology, and the need for intact hemostasis at the time of delivery/epidural analgesia. Prevention requires an optimal balancing of absolute increased bleeding risk from pharmacologic thromboprophylaxis and the absolute benefit of reduced DVT and PE, which, while serious, are relatively uncommon.

Guidelines for computed tomography and magnetic resonance imaging use during pregnancy and lactation

There has been a substantial increase in the use of computed tomography (CT) and magnetic resonance imaging (MRI) in pregnancy and lactation. Among some physicians and patients, however, there are misperceptions regarding risks, safety, and appropriate use of these modalities in pregnancy. We have developed a set of evidence-based guidelines for the use of CT, MRI, and contrast media during pregnancy for selected indications including suspected acute appendicitis, pulmonary embolism, renal colic, trauma, and cephalopelvic disproportion. Ultrasonography is the initial modality of choice for suspected appendicitis, but if the ultrasound examination is negative, MRI or CT can be obtained. Computed tomography should be the initial diagnostic imaging modality for suspected pulmonary embolism. Ultrasonography should be the initial study of choice for suspected renal colic. Ultrasonography can be the initial imaging evaluation for trauma, but CT should be performed if serious injury is suspected. Pelvimetry now is used rarely for suspected cephalopelvic disproportion, but when required, low-dose CT pelvimetry can be performed with minimal risk. Although iodinated contrast seems safe to use in pregnancy, intravenous gadolinium is contraindicated and should be used only when absolutely essential. It seems to be safe to continue breast-feeding immediately after receiving iodinated contrast or gadolinium. Although teratogenesis is not a major concern after exposure to prenatal diagnostic radiation, carcinogenesis is a potential risk. When used appropriately, CT and MRI can be valuable tools in imaging pregnant and lactating women; risks and benefits always should be considered and discussed with patients.

Guidelines on the diagnosis and management of acute pulmonary embolism: the Task Force for the Diagnosis and Management of Acute Pulmonary Embolism of the European Society of Cardiology (ESC)

Non-thrombotic PE does not represent a distinct clinical syndrome. It may be due to a variety of embolic materials and result in a wide spectrum of clinical presentations, making the diagnosis difficult. With the exception of severe air and fat embolism, the haemodynamic consequences of non-thrombotic emboli are usually mild. Treatment is mostly supportive but may differ according to the type of embolic material and clinical severity.

Obstetric risks for women with epilepsy during pregnancy

Women with epilepsy (WWE) face particular challenges during their pregnancy. Among the several obstetric issues for which there is some concern and the need for further investigation are: the effects of seizures, epilepsy, and antiepileptic drugs on pregnancy outcome and, conversely, the effects of pregnancy and hormonal neurotransmitters on seizure control and antiepileptic drug metabolism. Obstetric concerns include preclampsia/eclampsia, preterm delivery, placental abruption, spontaneous abortion, stillbirth, and small-for-date babies in WWE whether or not they are taking antiepileptic drugs. The role of nutritional health elements, including body mass index, caloric and protein intake, vitamins and iron, and phytoestrogens, warrants further study. During the course of obstetric management, there is a need for a fuller understanding by neurologists of the risk-benefit calculations for various types and frequencies of fetal imaging, including CT, MRI, and ultrasound, as well as for the screening standards of care. As part of the Health Outcomes in Pregnancy and Epilepsy (HOPE) project, this expert panel provides a brief overview of these concerns, offers some approaches to management, and outlines potential areas for further investigation. More detailed information and guidelines are available elsewhere.

Perfusion scintigraphy: diagnostic utility in pregnant women with suspected pulmonary embolic disease

Pulmonary embolism (PE) is a major preventable cause of maternal mortality during pregnancy and accurate diagnosis is essential. Computed tomography pulmonary angiography (CTPA) is a robust diagnostic test in non-pregnant patients with suspected PE. The potential latent carcinogenic effects of CTPA-related breast irradiation mandates careful use of this technique in young women. The aim of this study was to determine the efficacy of perfusion scintigraphy as the first line investigation in pregnant women with suspected PE. All pregnant women referred for radiological investigation of suspected PE in a 5-year period from January 2001 to December 2005 were included. Demographic data and imaging studies were reviewed. Subsequent pregnancy outcome was determined by case note review. One hundred and five consecutive patients had either perfusion scintigraphy (Q scan) (n = 94), CTPA (n = 9) or both (n = 2), one patient presented twice. Q scans were the first line investigation in 96 (91%) patients. Eighty-nine (92%) scans were normal, seven (7%) were non-diagnostic and one (1%) was high probability. One patient had a thromboembolic event 3 weeks post partum. No adverse events were reported during the follow-up period. Pulmonary embolic disease is uncommon in pregnancy. Perfusion scintigraphy in pregnant patients has an excellent diagnostic yield. The percentage of non-diagnostic scans is much lower than in other patient groups. Scintigraphy imparts a significantly lower breast dose than CTPA and should be used as the first-line investigation in most pregnant patients with suspected PE.

The obstetrical patient with a prosthetic heart valve

Definitive recommendations on anticoagulation strategy in pregnant women who have prosthetic heart valves are lacking because of the paucity of prospectively collected data. The use of warfarin, UFH, LMWH, or any combination of these choices has potentially adverse outcomes for the mother and fetus. Although there is no treatment option that has proven to be completely satisfactory, there is agreement that failures are most often due to underdosing and the lack of intensive monitoring of anticoagulation. A careful discussion with the patient must be undertaken so that she and the clinician can come to a decision about the most appropriate protocol.

Internal Barium Shielding to Minimize Fetal Irradiation in Spiral Chest CT: A Phantom Simulation Experiment

PURPOSE

To use a phantom to prospectively examine the attenuating effect of barium sulfate as an internal shield to protect the fetus.

MATERIALS AND METHODS

In an adult-size phantom, 1- and 2-cm-thick acrylic slabs containing 315 or 630 mL of water, 2% or 40% barium sulfate suspension, and a 1-mm lead sheet were placed under the diaphragm. In 17 experiments, fetal dose was measured by using thermoluminescent dosimeters that were placed immediately under (near field) and 10 cm below (far field) the water slab (eight experiments), barium sulfate slab (eight experiments), and lead sheet (one experiment). In a pulmonary embolism protocol, the phantom was scanned with single-detector spiral computed tomography (CT) at 130 kVp and 230 mAs.

RESULTS

The control radiation dose was 3.60 mSv+/-0.54 (standard deviation) with the water slab at near field, where the uterus dome is at near term, and 0.507 mSv+/-0.07 with the water slab at far field, the uterus position during early gestation. Scattered radiation was attenuated 13% and 21% with 2% barium sulfate and 87% and 96% with 40% barium sulfate, as calculated in the near and far fields, respectively, and 99% with the 1-mm lead sheet. The extrapolated attenuations for 5%-40% barium sulfate suspensions indicated that beyond a 30% suspension, attenuation increased further only slightly.

CONCLUSION

Study results in the phantom experiment suggest that fetal irradiation during maternal chest CT can be reduced substantially with barium shielding.

Diagnosis of deep vein thrombosis and pulmonary embolism in pregnancy: a systematic review

INTRODUCTION

Diagnosing deep vein thrombosis (DVT) and pulmonary embolism (PE) in pregnancy is challenging. Many of the common diagnostic tests, including compression ultrasonography (CUS), ventilation-perfusion scintigraphy (VQ scan) and helical computed tomography (hCT) that have been extensively investigated in non-pregnant patients, have not been appropriately validated in pregnancy. Extrapolating results of diagnostic studies of DVT and PE in non-pregnant patients to those who are pregnant may not be correct because during pregnancy, physiologic and anatomic changes may affect diagnostic test results, presentation and natural history of VTE.

METHODS

We performed a systematic analysis of published studies addressing accurate diagnostic testing for DVT and PE in pregnancy to determine the accuracy of these tests in pregnancy.

RESULTS

Our initial search yielded 530 articles of which four remained for inclusion, three studies investigating diagnostic testing in patients with a clinical suspicion of DVT or PE and one study in patients with a clinical suspicion of PE.

CONCLUSIONS

From our systematic analysis of published studies investigating diagnostic testing for a clinical suspicion of DVT in pregnancy we conclude that; (i) two studies support withholding anticoagulant therapy in pregnant women with a clinical suspicion of DVT and normal results on serial IPG (impedance plethysmography), however, IPG is no longer used; (ii) one study demonstrated that a normal CUS at presentation combined with a normal D-dimer test or an abnormal D-dimer test combined with normal serial CUS appears promising for safely excluding DVT in pregnant patients, but too few patients were included in this pilot-study to draw firm conclusions; and (iii) one study investigated pregnant patients with a clinical suspicion of PE and this study concluded that in patients with normal or non-diagnostic VQ scans, withholding anticoagulant therapy might be safe, but this needs confirmation in larger studies. Recommendations on diagnostic testing of pregnant patients with a clinically suspected DVT or PE are provided.

Diagnosis of suspected venous thromboembolic disease in pregnancy

Venous thromboembolic disease is a leading cause of maternal mortality during pregnancy. Early and accurate radiological diagnosis is essential as anticoagulation is not without risk and clinical diagnosis is unreliable. Although the disorder is potentially treatable, unnecessary treatment should be avoided. Most of the diagnostic imaging techniques involve ionizing radiation which exposes both the mother and fetus to finite radiation risks. There is a relative lack of evidence in the literature to guide clinicians and radiologists on the most appropriate method of assessing this group of patients. This article will review the role of imaging of suspected venous thromboembolic disease in pregnant patients, highlight contentious issues such as radiation risk, intravenous contrast use in pregnancy and discuss the published guidelines, as well as suggesting an appropriate imaging algorithm based on the available evidence.

Pulmonary embolism during and after pregnancy

BACKGROUND

Venous thromboembolic disease is among the most common causes of morbidity and mortality during pregnancy. The clinical evaluation alone is insufficient for the diagnosis of venous thromboembolic disease, and the normal pregnant state makes this evaluation even more challenging.

DIAGNOSIS

Objective testing is the mainstay of diagnosis, including compression ultrasound, impedance plethysmography, ventilation-perfusion scanning, computed tomography scanning, and pulmonary angiography. All of these tests can be safety performed during pregnancy.

TREATMENT

If deep vein thrombosis or pulmonary embolism is diagnosed, anticoagulation should be initiated. Either (unfractionated) heparin or low molecular weight heparin is an acceptable treatment for acute venous thromboembolic disease. Both have risks and benefits, but both can be used safely during pregnancy. Intravenous heparin is the treatment of choice surrounding delivery due to its short half life. Because of the risk of adverse effects on the fetus, warfarin is not generally used during pregnancy. Unstable pulmonary embolism is difficult to treat during pregnancy, as there are minimal data regarding the safety and efficacy of thrombolytic therapy, inferior vena cava filters, and embolectomy during pregnancy. Case reports and case series suggest that thrombolytic therapy may be associated with lower risks of fetal loss than embolectomy.

CONCLUSIONS

Venous thromboembolic disease is a significant cause of morbidity and mortality during pregnancy and the puerperal period. Objective testing is critical to establish the diagnosis and can be safely performed during pregnancy. Anticoagulation with heparin is the mainstay of therapy during the pregnancy, but patients may be transitioned to warfarin after delivery.

Deep vein thrombosis

Deep vein thrombosis and its sequelae pulmonary embolism and post-thrombotic syndrome are some of the most common disorders. A thrombus either arises spontaneously or is caused by clinical conditions including surgery, trauma, or prolonged bed rest. In these instances, prophylaxis with low-dose anticoagulation is effective. Diagnosis of deep vein thrombosis relies on imaging techniques such as ultrasonography or venography. Only about 25% of symptomatic patients have a thrombus. Thus, clinical risk assessment and D-dimer measurement are used to rule out deep vein thrombosis. Thrombus progression and embolisation can be prevented by low-molecular-weight heparin followed by vitamin K antagonists. Use of these antagonists for 3-6 months is sufficient for many patients. Those with antithrombin deficiency, the lupus anticoagulant, homozygous or combined defects, or with previous deep vein thrombosis can benefit from indefinite anticoagulation. In cancer patients, low-molecular-weight heparin is more effective than and is at least as safe as vitamin K antagonists. Women seem to have a lower thrombosis risk than men, but pregnancy or use of oral contraceptives or hormone replacement therapy represent important risk factors.

Diagnostic radiography in pregnancy: risks and reality

BACKGROUND

The use of X-rays, computed tomography scanning and nuclear medicine imaging in the pregnant woman is a source of great anxiety for the patient, her family and the treating doctor.

METHODS

A literature review of appropriate databases, articles and relevant institutional protocols was performed. Data was sought regarding any adverse effects of diagnostic radiation in pregnancy, fetal absorbed dose of diagnostic radiation and how the timing of exposure and form of administration might influence these effects.

RESULTS

The estimated radiation dose for a fetus from background sources as well as medical imaging was identified. Most diagnostic radiation procedures will lead to a fetal absorbed dose of less than 1 mGy for imaging beyond the abdomen/pelvis and less than 10 mGy for direct or nuclear medicine imaging. Potential adverse outcomes related to radiation exposure during pregnancy include teratogenicity, genetic damage, intrauterine death and increased risk of malignancy. The only adverse effect statistically proven at the dose levels associated with diagnostic radiation procedures is a very small increase in childhood malignancy, with an estimated increase of one additional cancer death per 1700 10 mGy exposures. The important exception was the risk to the fetal thyroid from radioiodine exposure after 12 weeks' gestation.

CONCLUSION

In practice, diagnostic radiography during pregnancy not involving direct abdominal/pelvic high dosage, is not associated with any significant adverse events. Counselling of pregnant women who require diagnostic radiographic procedures as well as those inadvertently exposed should be based on the available human data with an emphasis on the minimal impact of such procedures.

Pulmonary embolism and pregnancy

Pulmonary embolism is a significant cause of morbidity and mortality during pregnancy and the puerperium. The spectrum of venous thromboembolism is difficult to diagnose. Objective diagnostic testing is crucial and should not be delayed. Anticoagulation is the mainstay of therapy for deep vein thrombosis and pulmonary embolism. Most of the literature and practice protocols for the treatment of pregnant women are based on data extrapolated from the nonpregnant population, and more research is needed to improve the understanding of the efficacy and safety of testing and therapy in the pregnant population.

Sex and gender issues and venous thromboembolism

At least 250,000 episodes of VTE leading to hospitalization or death are estimated to occur in the United States each year. A number of clinical and demographic risk factors for VTE are recognized,with the latter including both age and race. Overall,the incidence of VTE does not appear to vary significantly by sex, as evidenced by a lack of consistency in the magnitude and even direction of effect of sex in a variety of epidemiologic studies of varying design. Several studies have shown a higher incidence among women than men during childbearing age. The issue of a gender effect on the natural history of VTE has not been well studied. The main influence of gender on VTE is the relationship between female gender and several well-recognized clinical risk factors for VTE:oral contraceptive use, hormone replacement therapy, estrogen receptor modulator therapy, and pregnancy. Hormonal therapies are associated with a twofold to threefold increase in VTE incidence. Risk is higher with some formulations than others, during initial use, and among women who are obese, smoke, or have one of several forms of heritable thrombophilia. The pregnant state is associated with a threefold to fivefold increase in VTE risk, and thromboembolism is a major cause of peripartum death. Heritable thrombophilias are also important co-determinants of VTE risk in pregnancy. The mechanisms through which pregnancy and hormonal therapies increase VTE risk have not been definitively established, but hormonal effects on levels of coagulation and anticoagulation factors likely play a role. Venous compression and venous injury also contribute to increased risk during pregnancy and the puerperium. Approaches to diagnosis of VTE in the pregnant woman are largely the same as in the nonpregnant patient, but special treatment considerations do apply. Warfarin is embryopathic, particularly between the 6th and 12th weeks of pregnancy, and should be avoided in favor or heparin or low-molecular weight heparin when treatment of the pregnant woman is necessary. Guidelines have been published to assist the clinician in decision making about prophylaxis of pregnant women at increased risk or pregnancy-related or post-partum VTE.

Pulmonary Embolism in Pregnant Patients:A Survey of Practices and Policies for CT Pulmonary Angiography

OBJECTIVE

We surveyed the practices and policies of the radiology departments of the Society of Thoracic Radiology members regarding the use of CT pulmonary angiography in pregnant patients suspected of having pulmonary embolism.

MATERIALS AND METHODS

Surveys were mailed electronically to the 403 members of the Society of Thoracic Radiology (403 addresses). Respondents were asked to send one response from each institution or department. Information gathered included use of CT angiography in relation to ventilation-perfusion imaging in pregnant patients, written policies, informed consent procedures, and modifications of standard protocols for dose reduction.

RESULTS

Fifty-seven members responded; 43 (75%) reported that they perform CT angiography in pregnant patients suspected of having pulmonary embolism. Of the 43 respondents who perform CT angiography in pregnant patients, 23 (53%) generally perform CT angiography as the initial study rather than ventilation-perfusion scanning, 26 (60%) require informed consent from the patient, seven (16%) have a written policy concerning CT angiography in pregnant patients, and 17 (40%) modify standard imaging protocols for pregnant patients. The most common modification for dose reduction is decreasing the scanning area along the z-axis.

CONCLUSION

Most respondents perform CT angiography in pregnant patients suspected of having pulmonary embolism, but their policies and practices vary considerably.

Imaging modalities in obstetrics and gynecology

The practicing emergency physician often encounters diagnostic dilemmas involving the choice of the most appropriate radiologic study to evaluate patients in the emergency department. In addition, the uncertainty of potentially harmful fetal effects of radiation in the pregnant patient may add unnecessary delay and concern in the workup of obstetric emergencies. An emergency physician's in-depth understanding of the strengths, limitations, and potentially harmful effects of radiologic studies allows the safest and most appropriate studies to be ordered for the gynecologic and obstetric population. With the explosion of interest and growing level of expertise in focused emergency department ultrasonography during the last decade, the practicing emergency physician should add this skill to his or her armamentarium in the future. Many emergency physicians are already comfortable in using radiologic technologies in their daily practice and have discovered how quickly vital and specific information can be obtained.