REVIEW ARTICLE
Cardiothoracic Imaging in the Pregnant Patient Diana E. Litmanovich, MD,* Dennis Tack, MD, PhD,w Karen S. Lee, MD,* Maryam Shahrzad, MD,* and Alexander A. Bankier, MD, PhD*
Abstract: Cardiovascular imaging during pregnancy poses a unique challenge to clinicians in differentiating between physiological changes mimicking pathology and true pathologic conditions, as well as for radiologists in terms of image quality. This review article will focus on 3 goals: first, to familiarize radiologists with safety issues related to imaging pregnant women using computed tomography and magnetic resonance imaging; second, to review the current, evidence-based recommendations for radiology topics unique and common to pregnant and lactating patients; and third, to provide practical algorithms to minimize risk and increase safety for both the pregnant woman and the fetus. Key Words: pregnancy, cardiovascular, multidetector computed tomography, magnetic resonance imaging, radiation dose
(J Thorac Imaging 2014;29:38–49)
C
ardiopulmonary disorders can compromise up to 4% of all pregnancies in the industrialized world due to preexisting conditions or conditions acquired during pregnancy.1 In part, this is related to increased age at pregnancy and an increased proportion of women of child-bearing age with congenital heart defects.2 In western countries, maternal heart disease is now the major cause of maternal death during pregnancy.2 Overall, the most frequent cardiopulmonary disorders complicating pregnancy are: pulmonary embolism (PE), aortic dissection, acute coronary syndrome, hypertension, and pneumonia, with the incidence of these disorders varying according to patient age and demographics.3 Pregnancy causes profound effects on the circulatory system, with most of them starting in the first trimester, peaking during the second, and reaching a plateau during the third trimester. The main parameters affected are plasma volume, cardiac output, heart rate, blood pressure, hematocrit level, and coagulability.4,5 During the first and second trimesters, cardiac output can increase between 30% and 50% secondary to increase in blood volume (plasma) and heart rate (commonly up to 10 to 15 bpm). Decrease in systemic vascular resistance caused by the low-resistance circuit of the placenta and vasodilatation contributes to decreases in blood pressure by 10 to 15 mm Hg.5 Decrease in the hematocrit level is due to an increase in plasma From the *Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA; and wDepartment of Radiology, Epicura Hospital, Baudour, Belgium. Diana E. Litmanovich is currently receiving grants from Radiological Society of North America and Society of Thoracic Radiology. Alexander A. Bankier is currently receiving a consult fee from Spiration/Olympus and has received royalties from Harvard Medical School-American Thoracic Society, Elsevier, and Amirsys. The remaining authors declare no conflicts of interest. Reprints: Diana E. Litmanovich, MD, Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave-Shapiro 4, Boston, MA 02215 (e-mail: [email protected]). Copyright r 2013 by Lippincott Williams & Wilkins
38 | www.thoracicimaging.com
volume (40% at 24 wk gestation, disproportional to increase in red cell mass). Finally, heart size increases by 30% by the end of the second trimester.4,5 In the third trimester, the supine position causes caval compression by the gravid uterus that may lead to a decrease in venous return, that is, decreased cardiac output with subsequent supine hypotension syndrome.5 Stroke volume decreases in the third trimester due to partial vena cava obstruction. In addition, the Virchow triad (hypercoagulability, venous stasis, and vascular damage) contributes to altered hemodynamics.6 For radiologists, cardiothoracic imaging of pregnant patients poses particular problems in terms of image quality. First, the physiological changes affect the quality of tissue/ vessel enhancement. Another challenge for imaging during pregnancy is the “2 in 1” setting, that is, the simultaneous imaging of the patient and the fetus, as imaging techniques optimal for the patient may be harmful for the fetus and vice versa. The “2 in 1” imaging implies unavoidable simultaneous exposure of the patient and the fetus to radiation, ultrasonographic (US) waves, or magnetic field, with all currently available techniques for cardiovascular and pulmonary imaging—US, computed tomography (CT) and magnetic resonance imaging (MRI)—having advantages and disadvantages when imaging pregnant women. The role of vascular US and echocardiography in cardiovascular imaging during pregnancy has been extensively discussed previously,7–9 and it is beyond the scope of this review. This manuscript will focus on 4 aspects of “2 in 1” imaging: CT safety, MRI safety, medico-legal issues, and practical algorithms.
SAFETY ASPECTS OF CT IMAGING General concerns of radiation exposure in diagnostic imaging (caused by substantial increase in CT utilization in the last decade) mainly focus on the relationship between radiation exposure and the associated lifetime attributable risk for cancer in the general population.10,11 In the context of female individuals of child-bearing age, several publications have addressed specific concerns, citing an increase in cancer risk of up to 0.8% for a 20-year-old woman undergoing chest CT angiography (CTA) and potential increase in relative risk for breast cancer of up to 4.2% per single cardiothoracic CTA.11,12 Relatively sparse and random scientific data in humans assessing radiation risks associated with imaging during pregnancy in both the radiology and nonradiology communities cause hesitation and apprehension.13–16 However, given the increase in imaging of pregnant patients for nonobstetric cardiopulmonary conditions, familiarity with the following topics is important: risk of CT radiation exposure to the patient, risk of direct and indirect CT radiation exposure to the fetus, fetal and maternal dosimetry, approach to CT imaging of pregnant J Thorac Imaging
Volume 29, Number 1, January 2014
J Thorac Imaging
Volume 29, Number 1, January 2014
Cardiovascular Imaging
patients in typical clinical scenarios, and the currently available options for CT radiation dose reduction. Safety of iodinated contrast administration during pregnancy and lactation must also be addressed. It is critical to understand that during pregnancy 2 individuals are exposed simultaneously, the woman and the fetus, and that the intensity of the exposure and potential consequences vary substantially between the 2. American College of Radiology (ACR) and American Congress of Obstetricians and Gynecologists agree that the necessary imaging examination should be performed after clinical workup, and the radiation level should be kept as low as reasonably achievable.17,18
Radiation Exposure to the Patient In pregnant women, all the organs exposed to diagnostic radiation as part of cardiopulmonary assessment are at risk for carcinogenesis: lung, heart, bone marrow, thyroid, and breast. For example, during most common cardiothoracic CT examinations, the radiation exposure to the lung approaches 18 to 25 mGy, even with modern scanners.19 Justifiably, radiation exposure of a pregnant woman is of higher concern than an age-matched nonpregnant female because of increased sensitivity of glandular breast tissue.11,12 Although minimal, radiation exposure to breasts exists even with a chest radiograph, at a range of 150 mGy (15 rad) such that, if reached, might require termination of pregnancy.24 Exposure to 100 to 500 mGy can induce spontaneous abortion, particularly at early stages of pregnancy. At exposures 1) can be used in the vast majority of CT examinations while maintaining diagnostic accuracy when GE and Toshiba scanners are used. With Siemens and Phillips scanners, careful selection of mAs is also recommended to decrease the effective tube current time product.32 (d) Appropriately limited length of the examination (z-axis) is important for both the patient and the fetus. Additional measures such as incorporation of novel reconstruction algorithms to reduce imaging noise and allow reduction in milliamperage and increasing the noise index when appropriate can substantially affect radiation dose.33,34 Imaging in multiple phases (such as noncontrast enhanced examination before contrast administration in patients with suspected aortic dissection) should be avoided. Appropriateness criteria, CT protocols, and radiation dose should be established and monitored on each clinical practice basis.
Intravenous Iodine Contrast Administration During Pregnancy and Lactation Iodine contrast agents are hydrophilic and of moderate molecular weight, thus they can cross the placenta by passive diffusion to be eventually excreted by fetal kidneys.35,36 No teratogenic effects have been reported with iodinated contrast agents.22 Although there is a potential to induce neonatal hypothyroidism by direct instillation into the amniotic sac37 or by maternal use of iodine-containing medications, no evidence exists of neonatal hypothyroidism induced by clinical doses of iodinated contrast media.38 Bourjeily et al39 have shown no clinical effect of in utero exposure to a single high dose of water-soluble iodinated contrast material on neonatal thyroid function. Owing to the lack of sufficient evidence that iodinated contrast material poses no risk to the fetus, the 2013 ACR Manual on Contrast Media states that iodinated contrast media may be given to the pregnant patient only if absolutely necessary.18 However, because of the theoretic concern that fetal thyroid function may be affected, neonates of all women exposed to iodinated contrast media during pregnancy should be screened for hypothyroidism.36 In many countries, including the United States and other industrialized countries, newborns routinely undergo this test. In cases in which a nursing patient was to undergo CT examination with an intravenous (IV) iodinated contrast agent, interruption of nursing was often suggested, usually for 12 to 24 hours. The theoretic risks are allergic sensitivity or reaction, neither of which has been reported.22 The estimated amount of iodinated contrast agent absorbed through the infant’s bowel is approximately 0.01% of the contrast agent administered to the patient, which is
Cardiothoracic Imaging in the Pregnant Patient Diana E. Litmanovich, MD,* Dennis Tack, MD, PhD,w Karen S. Lee, MD,* Maryam Shahrzad, MD,* and Alexander A. Bankier, MD, PhD*
Abstract: Cardiovascular imaging during pregnancy poses a unique challenge to clinicians in differentiating between physiological changes mimicking pathology and true pathologic conditions, as well as for radiologists in terms of image quality. This review article will focus on 3 goals: first, to familiarize radiologists with safety issues related to imaging pregnant women using computed tomography and magnetic resonance imaging; second, to review the current, evidence-based recommendations for radiology topics unique and common to pregnant and lactating patients; and third, to provide practical algorithms to minimize risk and increase safety for both the pregnant woman and the fetus. Key Words: pregnancy, cardiovascular, multidetector computed tomography, magnetic resonance imaging, radiation dose
(J Thorac Imaging 2014;29:38–49)
C
ardiopulmonary disorders can compromise up to 4% of all pregnancies in the industrialized world due to preexisting conditions or conditions acquired during pregnancy.1 In part, this is related to increased age at pregnancy and an increased proportion of women of child-bearing age with congenital heart defects.2 In western countries, maternal heart disease is now the major cause of maternal death during pregnancy.2 Overall, the most frequent cardiopulmonary disorders complicating pregnancy are: pulmonary embolism (PE), aortic dissection, acute coronary syndrome, hypertension, and pneumonia, with the incidence of these disorders varying according to patient age and demographics.3 Pregnancy causes profound effects on the circulatory system, with most of them starting in the first trimester, peaking during the second, and reaching a plateau during the third trimester. The main parameters affected are plasma volume, cardiac output, heart rate, blood pressure, hematocrit level, and coagulability.4,5 During the first and second trimesters, cardiac output can increase between 30% and 50% secondary to increase in blood volume (plasma) and heart rate (commonly up to 10 to 15 bpm). Decrease in systemic vascular resistance caused by the low-resistance circuit of the placenta and vasodilatation contributes to decreases in blood pressure by 10 to 15 mm Hg.5 Decrease in the hematocrit level is due to an increase in plasma From the *Department of Radiology, Beth Israel Deaconess Medical Center, Boston, MA; and wDepartment of Radiology, Epicura Hospital, Baudour, Belgium. Diana E. Litmanovich is currently receiving grants from Radiological Society of North America and Society of Thoracic Radiology. Alexander A. Bankier is currently receiving a consult fee from Spiration/Olympus and has received royalties from Harvard Medical School-American Thoracic Society, Elsevier, and Amirsys. The remaining authors declare no conflicts of interest. Reprints: Diana E. Litmanovich, MD, Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave-Shapiro 4, Boston, MA 02215 (e-mail: [email protected]). Copyright r 2013 by Lippincott Williams & Wilkins
38 | www.thoracicimaging.com
volume (40% at 24 wk gestation, disproportional to increase in red cell mass). Finally, heart size increases by 30% by the end of the second trimester.4,5 In the third trimester, the supine position causes caval compression by the gravid uterus that may lead to a decrease in venous return, that is, decreased cardiac output with subsequent supine hypotension syndrome.5 Stroke volume decreases in the third trimester due to partial vena cava obstruction. In addition, the Virchow triad (hypercoagulability, venous stasis, and vascular damage) contributes to altered hemodynamics.6 For radiologists, cardiothoracic imaging of pregnant patients poses particular problems in terms of image quality. First, the physiological changes affect the quality of tissue/ vessel enhancement. Another challenge for imaging during pregnancy is the “2 in 1” setting, that is, the simultaneous imaging of the patient and the fetus, as imaging techniques optimal for the patient may be harmful for the fetus and vice versa. The “2 in 1” imaging implies unavoidable simultaneous exposure of the patient and the fetus to radiation, ultrasonographic (US) waves, or magnetic field, with all currently available techniques for cardiovascular and pulmonary imaging—US, computed tomography (CT) and magnetic resonance imaging (MRI)—having advantages and disadvantages when imaging pregnant women. The role of vascular US and echocardiography in cardiovascular imaging during pregnancy has been extensively discussed previously,7–9 and it is beyond the scope of this review. This manuscript will focus on 4 aspects of “2 in 1” imaging: CT safety, MRI safety, medico-legal issues, and practical algorithms.
SAFETY ASPECTS OF CT IMAGING General concerns of radiation exposure in diagnostic imaging (caused by substantial increase in CT utilization in the last decade) mainly focus on the relationship between radiation exposure and the associated lifetime attributable risk for cancer in the general population.10,11 In the context of female individuals of child-bearing age, several publications have addressed specific concerns, citing an increase in cancer risk of up to 0.8% for a 20-year-old woman undergoing chest CT angiography (CTA) and potential increase in relative risk for breast cancer of up to 4.2% per single cardiothoracic CTA.11,12 Relatively sparse and random scientific data in humans assessing radiation risks associated with imaging during pregnancy in both the radiology and nonradiology communities cause hesitation and apprehension.13–16 However, given the increase in imaging of pregnant patients for nonobstetric cardiopulmonary conditions, familiarity with the following topics is important: risk of CT radiation exposure to the patient, risk of direct and indirect CT radiation exposure to the fetus, fetal and maternal dosimetry, approach to CT imaging of pregnant J Thorac Imaging
Volume 29, Number 1, January 2014
J Thorac Imaging
Volume 29, Number 1, January 2014
Cardiovascular Imaging
patients in typical clinical scenarios, and the currently available options for CT radiation dose reduction. Safety of iodinated contrast administration during pregnancy and lactation must also be addressed. It is critical to understand that during pregnancy 2 individuals are exposed simultaneously, the woman and the fetus, and that the intensity of the exposure and potential consequences vary substantially between the 2. American College of Radiology (ACR) and American Congress of Obstetricians and Gynecologists agree that the necessary imaging examination should be performed after clinical workup, and the radiation level should be kept as low as reasonably achievable.17,18
Radiation Exposure to the Patient In pregnant women, all the organs exposed to diagnostic radiation as part of cardiopulmonary assessment are at risk for carcinogenesis: lung, heart, bone marrow, thyroid, and breast. For example, during most common cardiothoracic CT examinations, the radiation exposure to the lung approaches 18 to 25 mGy, even with modern scanners.19 Justifiably, radiation exposure of a pregnant woman is of higher concern than an age-matched nonpregnant female because of increased sensitivity of glandular breast tissue.11,12 Although minimal, radiation exposure to breasts exists even with a chest radiograph, at a range of 150 mGy (15 rad) such that, if reached, might require termination of pregnancy.24 Exposure to 100 to 500 mGy can induce spontaneous abortion, particularly at early stages of pregnancy. At exposures 1) can be used in the vast majority of CT examinations while maintaining diagnostic accuracy when GE and Toshiba scanners are used. With Siemens and Phillips scanners, careful selection of mAs is also recommended to decrease the effective tube current time product.32 (d) Appropriately limited length of the examination (z-axis) is important for both the patient and the fetus. Additional measures such as incorporation of novel reconstruction algorithms to reduce imaging noise and allow reduction in milliamperage and increasing the noise index when appropriate can substantially affect radiation dose.33,34 Imaging in multiple phases (such as noncontrast enhanced examination before contrast administration in patients with suspected aortic dissection) should be avoided. Appropriateness criteria, CT protocols, and radiation dose should be established and monitored on each clinical practice basis.
Intravenous Iodine Contrast Administration During Pregnancy and Lactation Iodine contrast agents are hydrophilic and of moderate molecular weight, thus they can cross the placenta by passive diffusion to be eventually excreted by fetal kidneys.35,36 No teratogenic effects have been reported with iodinated contrast agents.22 Although there is a potential to induce neonatal hypothyroidism by direct instillation into the amniotic sac37 or by maternal use of iodine-containing medications, no evidence exists of neonatal hypothyroidism induced by clinical doses of iodinated contrast media.38 Bourjeily et al39 have shown no clinical effect of in utero exposure to a single high dose of water-soluble iodinated contrast material on neonatal thyroid function. Owing to the lack of sufficient evidence that iodinated contrast material poses no risk to the fetus, the 2013 ACR Manual on Contrast Media states that iodinated contrast media may be given to the pregnant patient only if absolutely necessary.18 However, because of the theoretic concern that fetal thyroid function may be affected, neonates of all women exposed to iodinated contrast media during pregnancy should be screened for hypothyroidism.36 In many countries, including the United States and other industrialized countries, newborns routinely undergo this test. In cases in which a nursing patient was to undergo CT examination with an intravenous (IV) iodinated contrast agent, interruption of nursing was often suggested, usually for 12 to 24 hours. The theoretic risks are allergic sensitivity or reaction, neither of which has been reported.22 The estimated amount of iodinated contrast agent absorbed through the infant’s bowel is approximately 0.01% of the contrast agent administered to the patient, which is
