- Pulmonary Embolism in Pregnancy: Facts
- Estimated incidence of 10.6 per 100,000
- Risk is highest in the post partum period
- Prevalence of PE in pregnant woman presenting with clinical symptoms is in the 3-6% range
- CT is a challenge in the pregnant patient due to physiologic changes including increased cardiac output and blood volume that result in decreased opacification - “ Pulmonary embolism (PE) is a leading cause of maternal mortality in the developed world. Along with appropriate prophylaxis and therapy, prevention of deaths from PE in pregnancy requires a high index of clinical suspicion followed by a timely and accurate diagnostic approach.”
American Thoracic Society Documents: An Official American Thoracic Society/Sociey of Thoracic radiology Clinical Practice Guideline-Evaluation of Suspected Pulmonary Embolism in Pregnancy
Leung AN et al.
Radiology 2012; 262:635-646 - Fetal and Maternal Doses Associated with Diagnostic Tests for PE
Executive Summary: Seven Recommendations
- “ In pregnant woman with suspected PE we suggest that D-dimer not be used to exclude PE.” (weak recommendation, very low quality evidence)
- “ In pregnant woman with suspected PE, we recommend a CXR as the first radiation associated procedure in the imaging workup.” (strong recommendation, low quality evidence)
- “ In pregnant woman with suspected PE and a normal CXR, we recommend lung scintigraphy as the next imaging test rather than CTPA.” (strong recommendation, low quality evidence) - Executive Summary: Seven Recommendations
- “ In pregnant woman with suspected PE and a nondiagnostic V/Q scan we suggest further diagnostic testing rather than clinical management alone (weak recommendation, low quality evidence). In patients with a nondiagnostic V/Q scan in whom a decision is made to further investigate, we recommend CTPA rather than DSA (strong recommendation, very low quality evidence)”
- “In pregnant woman with suspected PE and an abnormal CXR, we suggest CTPA as the next imaging test rather than lung scintigraphy (weak recommendation, very low qualiry evidence.” - Some Explanations for the Decision Process
- “ In pregnant woman with suspected PE and a normal CXR, we recommend lung scintigraphy as the next imaging test rather than CTPA.” (strong recommendation, low quality evidence)
- “ The recommendation puts a high value on minimizing radiation dose to the mother. It puts a lower value on rapidity of the diagnostic test and the possibility of alternate diagnoses afforded by CTPA.”
- “ In pregnant woman with suspected PE and a nondiagnostic V/Q scan we suggest further diagnostic testing rather than clinical management alone (weak recommendation, low quality evidence). In patients with a nondiagnostic V/Q scan in whom a decision is made to further investigate, we recommend CTPA rather than DSA (strong recommendation, very low quality evidence)”
- "This recommendation puts a high value on diagnostic certainty given the potential morbid consequences if PE is undiagnosed due to a nondiagnostic V/Q scan.”
- “ CTPA represents the current de facto clinical “gold standard” for PE Diagnosis. Clinical outcome studies have consistently shown the high negative predictive value of CTPA, as well as the low probability of subsequent thromboembolic events after a negative CTPA scan with 16-slice or higher CT scanners.”
CT imaging of acute pulmonary embolism
Henzler T et al.
J Cardiovascular Comput Tomogr (2011)5, 3-11 - Chronic Pulmonary Thromboembolism: Collateral Systemic Supply
-Dilated bronchial arteries
-Bronchial artery blood flow is usually 1-2% of cardiac output, in chronic thromboembolic pulmonary hypertension it is up to 30% of systemic blood flow - Chronic Pulmonary Thromboembolism: Pulmonary Hypertension
-Main pulmonary artery diameter of greater than 29 mm
-When the ratio of main pulmonary artery to the aorta is greater than 1:1 there is a strong correlation with elevated pulmonary artery pressure in patients younger than 50 years of age - Chronic Pulmonary Thromboembolism: Direct Pulmonary Arterial Signs
-Complete obstruction
-Partial filling defects
-Bands and webs
-Calcified thrombus - Chronic Pulmonary Thromboembolism: Vascular Signs
-Direct Pulmonary Arterial Signs
-Signs due to pulmonary hypertension
-Signs due to systemic collateral supply
"None of the patients with "dots" in our study also had DVT , compared to 58% of patients with classic PE (large tubular filling defects involving the proximal pulmonary vasculature." Dots are not clots: the over diagnosis and over treatment of PE
Suh JM et al.
Emerg Radiol (2010) 17:347-352 "We suggest that more in depth understanding about small peripheral PE is needed. The necessity of conventional anticoagulation should be critically reviewed in patients with subsegmental PE and minimal clot burden." Dots are not clots: the over diagnosis and over treatment of PE
Suh JM et al.
Emerg Radiol (2010) 17:347-352 "The peripheral clots measured 1.0-3.8 mm (mean 2.5 mm). These clots appeared focal and rounded with a "dot-like" appearance." Dots are not clots: the over diagnosis and over treatment of PE
Suh JM et al.
Emerg Radiol (2010) 17:347-352 "Peripheral, focal filling defects in the pulmonary arteries, which we termed "dots" are not traditional embolic clots, are not associated with detectable lower-extremity clot load, and may represent "normal" embolic activity originating from the lower extremity venous valves." Dots are not clots: the over diagnosis and over treatment of PE
Suh JM et al.
Emerg Radiol (2010) 17:347-352 - Studies for Detection of Pulmonary Embolism
- D-dimer
- Ventilation-perfusion scintigraphy (VQ scans)
- SPECT
- Pulmonary CT Angiography
- Pulmonary MR Angiography
- ECG Gated CT Angiography
- Dual Energy/Dual Source Pulmonary CTA - Pulmonary Embolism: Risk Factors
- Older age
- Prior venous thrombosis
- Active cancer
- Neurologic disease with extremity paresis
- Surgery
- Prolonged bed rest
- Congenital or acquired thrombophilia "The role of pulmonary CTA will continue to grow with the emergence of MDCT and dual energy CT and their improved capabilities. However, the need for any given CT examination should always be justified on the basis of the individual patient’s benefits and risks." Challenges, Controversies, and Hot Topics in Pulmonary Embolism Imaging
Sadigh G et al.
AJR 2011; 196:497-515 "Dual-energy CT could be an important tool for the diagnosis of various pulmonary diseases. Iodine perfusion maps and xenon ventilation imaging allow visualization of regional lung perfusion and ventilation and may facilitate the diagnosis of pulmonary embolisms and ventilation abnormalities." Dual-Energy CT: Clinical Applications in Various Pulmonary Diseases
Kang MJ et al.
RadioGraphics 2010; 30;685-698 - Pulmonary Artery Pseudoaneurysm: Clinical Presentation
- Hemoptysis (which may be brisk)
- Mass or rounded infiltrate on CXR
- Opacification of hemi-thorax on CXR or CT scan
- Management must be aggressive as 100% mortality with rupture Pulmonary Artery Pseudoaneurysm: Causes Vascular abnormality
- Behcet disease
- Marfan syndrome
- Takayasu disease
Other causes
- Septic emboli
- Neoplasm
- Pulmonary Artery Pseudoaneurysm: Causes
Trauma
- Improper insertion of Swan Ganz
- Penetrating trauma
Infection
- Mycotic aneurysm (direct extension from necrotizing pneumonia or endovascular seeding from endocarditis)
- Mycobacterial aneurysm (Rasmussen Aneurysm) "Interpretation time with MPR was significantly longer for two of the three specialists and significantly shorter for two of the three residents." Clinical Utility of Multiplanar Reformation in Pulmonary CT Angiography
Espinosa LA et al.
AJR 2010; 194:70-75 "Use of MPR for viewing increased the reader agreement and interpretation time of cardiothoracic specialists but increased reader agreement between residents and might have decreased interpretation time. All readers had a trend toward increased confidence." Clinical Utility of Multiplanar Reformation in Pulmonary CT Angiography
Espinosa LA et al.
AJR 2010; 194:70-75 "As in MDCT scanning with a smaller number of slices, the combination of CTV with CTPA in 64-MDCT results in a small but definitive increase in the percentage of patients with the diagnosis of thromboembolic disease." 64 MDCT Pulmonary Angiography and CT Venography in the Diagnosis of Thromboembolic Disease
Nazaroglu H et al.
AJR 2009;192:654-661 "Triple rule-out CT is feasible in patients with suspicion of PE, reveals a wide range of vascular and non-vascular chest disease, and offers an excellent overall diagnostic performance." Triple Rule-Out CT in Patients with Suspicion of Acute Pulmonary Embolism: Findings and Accuracy
Schertler T et al.
Acad Radiol 2009; 16:708-717 - Dual Source CT Scanner
- 110 ml of contrast injected at 4 cc/sec followed by 30 ml of saline
- Trigger set in ascending aorta
- Scanning was done in a cranial caudal direction
- Triple Rule-Out CT in Patients with Suspicion of Acute Pulmonary Embolism: Findings and Accuracy Schertler T et al. Acad Radiol 2009; 16:708-717
- "The use of bismuth breast shields together with a lower kVp and automatic tube current modulation will reduce the absorbed radiation dose to the breast and lungs without degradation of image quality to the organs of the thorax for CTA detection of PE."
Radiation Dose Savings for Adult Pulmonary Embolus 64-MDCT Using Bismuth Breast Shields, Lower Peak Kilovoltage, and Automatic Tube Current Modulation
Hurwitz LM et al.
AJR 2009; 192:244-253
- Chronic Pulmonary Thromboembolism: Collateral Systemic Supply
- Dilated bronchial arteries
- Bronchial artery blood flow is usually 1-2% of cardiac output, in chronic thromboembolic pulmonary hypertension it is up to 30% of systemic blood flow
- Chronic Pulmonary Thromboembolism: Pulmonary Hypertension
- Main pulmonary artery diameter of greater than 29 mm
- When the ratio of main pulmonary artery to the aorta is greater than 1:1 there is a strong correlation with elevated pulmonary artery pressure in patients younger than 50 years of age
- Chronic Pulmonary Thromboembolism: Direct Pulmonary Arterial Signs
- Complete obstruction
- Partial filling defects
- Bands and webs
- Calcified thrombus
- Chronic Pulmonary Thromboembolism: Vascular Signs
- Direct Pulmonary Arterial Signs
- Signs due to pulmonary hypertension
- Signs due to systemic collateral supply
“ A dedicated evaluation of the pulmonary arteries by the interpreting radiologist should be performed prospectively on all contrast enhance chest CT.”
The prevalence of Symptomatic and Coincidental Pulmonary Embolism on Computed Tomography
Hui GC et al.
J Comput Assist Tomogr 2008;32:783-787
"The prevalence of symptomatic PE on dedicated CTPA was 11.8%, and the rate of coincidental PE on contrast enhanced CT was 1.8%. Coincidental PE was significantly higher in patients with progressive cancer or those receiving chemotherapy. A dedicated evaluation of the pulmonary arteries by the interpreting radiologist should be performed prospectively on all contrast enhance chest CT."
The prevalence of Symptomatic and Coincidental Pulmonary Embolism on Computed Tomography
Hui GC et al.
J Comput Assist Tomogr 2008;32:783-787
- "The prevalence of symptomatic PE on dedicated CTPA was 11.8%, and the rate of coincidental PE on contrast enhanced CT was 1.8%. Coincidental PE was significantly higher in patients with progressive cancer or those receiving chemotherapy."
The prevalence of Symptomatic and Coincidental Pulmonary Embolism on Computed Tomography
Hui GC et al.
J Comput Assist Tomogr 2008;32:783-787 - Facts
- Up to 25% of patients with untreated DVT develop PE
- Undiagnosed PE has a mortality as high as 30%, but falls to 0.7% if treated correctly
- CTPA has a sensitivity of 83% and specificity of 96% for detection of PE
- "Our data showed a suboptimal use of the Wells criteria and subjective overestimation of the probability of PE before ordering of CTA. Although a definitive acceptable PE positivity rate for CTA has not been established, the 10% yield represents overuse of CTA as a screening rather than a diagnostic examination."
CT Angiography in the Evaluation of Acute Pulmonary Embolus
Costantion MM et al.
AJR 2008; 191:471-474 - "Although a definitive acceptable PE positivity rate for CTA has not been established, the 10% yield represents overuse of CTA as a screening rather than a diagnostic examination."
CT Angiography in the Evaluation of Acute Pulmonary Embolus
Costantion MM et al.
AJR 2008; 191:471-474 - "More than 80% of deaths from PE occurring in the first 30 minutes, and 90% within the first 2.5 hours of the event."
CT Angiography in the Evaluation of Acute Pulmonary Embolus
Costantion MM et al.
AJR 2008; 191:471-474 - "The patients who survive to be referred for diagnostic evaluation are a very different subset of this population. It has been suggested that the mortality and recurrence rates in this population are likely as low as 5%, even if the patient is not treated ."
CT Angiography in the Evaluation of Acute Pulmonary Embolus
Costantion MM et al.
AJR 2008; 191:471-474 - D-Dimer Assay: facts
- D-dimer is a marker for the presence of stabilized fibrin
- D-dimer serves as an indirect indicator of thrombotic activity
- Reported to have a negative predictive value of 94% and a sensitivity of 97% for PE - D-Dimer Assay: facts
"In an oncologic population, D-dimer assay results have a high sensitivity (98%) and negative predictive value (97%) for pulmonary embolism but a low specificity (18%) and positive predictive value (25%)."
D-Dimer Assay to Exclude Pulmonary Embolism in High Risk Oncologic Population: Correlation with CT Pulmonary Angiography in an Urgent Care Setting
King V et al.
Radiology 2008; 247:854-861 - "The performance characteristics of CTV and deep venous sonography were similar when compared with a clinical standard. The results support the use of indirect CTV after CT pulmonary angiography as an alternative to sonography in the ICU patient."
Prospective Comparison of Indirect CT Venography Versus Venous Sonography in ICU Patients
Taffomi MJ et al.
AJR 2005; 185:457-462 - CTV: Scanning Protocol
- Scan delay is 180 sec after contrast bolus
- 10 mm axial sections at 20 mm intervals from the renal hilum thru the popliteal fossa
Prospective Comparison of Indirect CT Venography Versus Venous Sonography in ICU Patients
Taffomi MJ et al.
AJR 2005; 185:457-462 - "Most respondents (75%) perform CT angiography in pregnant patients suspected of having pulmonary embolism, but their policies and practices vary considerably."
Pulmomary Embolism in Pregnant Patients: A Survey of Practices and Policies for CT Pulmonary Angiography
Schuster ME et al.
AJR 2003; 181:1495-1498 - "The risk of pulmonary embolism at a mean of 9 months after negative MDCT pulmonary angiography findings is 1%."
Risk of Pulmonary Embolism After Negative MDCT Pulmonary Angiography Findings
Kavanagh EC et al.
AJR 2004; 182:499-504
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