Case History
A 25-year-old white female felt sharp left-sided chest pain and shortness of breath in a day and reported to the Emergency Room. She has been in good health status until the previous day. However, the sharp left-sided pain woke her from sleep. The pain persisted with movements and deep breathing. The pain has increased steadily, and the patient now suffers from a painful left shoulder. She also suffers shortness of breath and is anxious about death. She coughs. The patient is married and underwent a normal delivery three years ago before her current condition.
Currently, the patient uses birth control pills for family planning, and she has never been hospitalised except during labour and delivery. The review of her systems presented negative results. Moreover, the patient indicated that she had no history of venous conditions. Approximately a year ago, the patient experienced the same transitory minor case of chest pain when she went for a vacation in Michigan. She has a blood pressure of 114/80, a pulse of 118, and an oral temperature of 37.0 0C.
The patient exhibits signs of moderate respiratory distress. The patient has a well-developed physique and appears nourished. However, results indicated that the patient had a respiratory rate of 30 coupled with shallow breathing. She also exhibits dullness, diminished chest expansion, and breath sounds in the left base. The patient has egophony in her left base but does not exhibit any cases of rales or rubs. The patient’s heart shows PMI in the fifth intercostal space in MCL, and she has stressed the second sound in the pulmonic component. She has normal pelvic, abdomen, and rectal. According to extremities, there are no signs of oedema, cyanosis, or clubbing.
The test reveals negative signs on Homan’s Sign. The patient has a complete range of shoulder movement. She lacks any tenderness or warmth. Other parts of the joints are normal, and a chest X-ray done in the resuscitating room reveals a normal condition. There are high chances of pulmonary embolism (PE) based on the D-dimer test. Therefore, computer tomography angiography is necessary to rule out any condition of PE.
Pathology
PE affects the lungs, which has both airways and blood vessels that originate from the pulmonary arteries. Pulmonary arteries get blood from the right side of the heart. It branches to form small units known as capillaries (Grey and Ailinani 2003). Pulmonary embolism usually begins as a clot from the pelvic, legs, or abdominal vein. In some cases, PE may originate from the right side of the heart (Katz, Math, and Groskin 1998). Clots may reach the lung arteries through the bloodstream and lodge (embolism) lung, which interrupt blood supply to the artery (Katz, Math, and Groskin 1998). Therefore, that part of the lung cannot function due to an insufficient supply of air. There are different types of PE based on their sizes (Patel 1998).
Statistics on Pulmonary embolism
Post-mortem studies reveal that PE is common, but majorities do not show any signs. About 80% of PE cases are unrecognisable because they are small emboli, which do not result in major problems or stop blood flow to the lung. About 20 to 25 percent of hospitalised patients show signs of a pulmonary embolism while the signs are few in non-hospitalised cases (Ritchie et al. 2007).
Types of PE
Classifications of PE cases from a therapeutic perspective include the following subsets (Piazza & Goldhaber 2006):
- Massive pulmonary embolism: this occurs during cardiogenic shock or cardiac arrest (SBP < 90 mmHg) or when systolic blood pressure (SBP) falls by > 40 mmHg for at least 15 minutes. The main characteristics of massive PE are hypotension, tissue hypoperfusion, and hypoxemia.
- Sub-massive pulmonary embolism: the SBP may be >/= 90 mmHg, but the patient shows dysfunction in the right ventricular under echocardiography, CT scan, cardiac catheterization or raised biomarkers.
- Stable pulmonary embolism: occurs when SBP >/= 90 mmHg with no signs of right ventricular dysfunction.
Risk factors
The main risk factors of PE are surgery, trauma, and cancer diagnosis. However, almost half of patients with symptomatic PE lack noticeable risk factors. Signs of PE are dyspnoea or acute chest pain, tachycardia, tachypnoea. Other signs are cough or haemoptysis and right ventricular dysfunction (White, 2003).
These typical clinical symptoms are not unique to specific patients and vary in cases of confirmed PE. Therefore, further clinical diagnoses are necessary to confirm or reject the diagnosis results (Chunilal, 2003).
Patient preparation
The patient should have loose clothing during the CT examination. The hospital gown or apron is appropriate for examination. The patient should not have any metallic object. Therefore, they should remove all hairpins, jewellery, and eyeglasses. However, it depends on the part of the body under examination. Radiographers must advise patients not to consume meals or drink anything four hours before the examination. Female patients should inform the doctor of any existing pregnancy or a missed period.
The examination involves the use of an intravenous (IV) contrast medium. Therefore, it is necessary to establish cases of allergy to the administered contrast medium. Diabetic patients who take insulin must adjust their dosage before the examination.
The examination is optimum in patients who have not eaten or drunk anything before the scan because of high rates of absorption of agents in the blood (RadiologyInfo.Org, n.d.). Patients receive an injection of 70ml to 100ml of a contrast agent in a supine position on the CT examination table. The injection goes through an intravenous line with a rate of flow of 5mL/s (CTisis.com, n.d.).
Scanning protocol of CTA
A radiographer scanned the patient in a supine position during one hold of breath. The radiographer must get images from the caudal to cranial and other areas that are sensitive to motion and near the diaphragm before the end of the phase. This is important to reduce the effects of venous inflow of the contrast medium along the brachiocephalic veins and superior vena cava.
The following table highlights the scan parameter used on the patient. The z-axis and field of view account for the whole thorax, which is 3cm above the aortic arch to the base of the lungs. The method used was a volume rendering of a 3D technique.
Contrast protocol for the examination
The scan parameters
- 80 ml of Omnipaque 370 administrated
- Rate of administering the agent of 4 ml/s with an automatic dual-chamber injector (Medrad)
- Start delay time with a test injection of 10 ml with a contrast material at a rate of 5 ml/s
Radiation dose reduction strategies
Experts have raised concerns about risks associated with high radiation doses during the scan since the invention of the multi-detector computed tomography (MDCT). A recent finding indicates that the dose of radiation can increase from 30% to 100% with the change in the slice thickness from 5mm to 1mm (Schoepf and Costello 2004). The change of slice thickness is necessary for getting the best diagnostic images with a low dose. The mAs changed from 140 to 120. The scan restricted the collimation from areas that are above the aortic arch and the diaphragm to irradiate only parts of interest.
The basic radiation protection methods were used to protect the patient against high doses of radiation. One way of protecting the patient involved the restriction of the scan to areas of interest only, which covered the diaphragm and the aortic arch. Thyroid and eye protection methods protected the patient against the effects of scattered radiation. A lead shield also protected the pelvis and abdomen of the patient. Moreover, the scan machine has automatic exposure control (AEC) that changes the tube current automatically depending on the size and the thickness of the body part under scanning. This technique maintains the quality of the image as it reduces the dose by up to 60 percent (Smith et al 2008). There is also the lower tube voltage for dose reduction. The normal tube output for cardiac scanning is 120 kV.
However, radiation absorption changes with the size of the tube voltage. Therefore, a change from 120 kV to 100 kV would reduce the dose by 50% theoretically (Park et al., 2009). A reduced kVp scanning results in high levels of noise due to an increment in the tube current. Such variations do not affect small or patients with average body size, like in this case (a body mass index less than 25 kg/m2 or weight under 85 to 95 kg) (Abada et al., 2006).
Image display, appearance, and analysis (2D/3D reconstructions)
Studies have proposed different methods of PE detection and visualisation to allow radiographers to identify PE successfully. Computer-aided detection (CAD) has been the most common in the display of emboli. However, it is necessary to develop additional emboli displays to support other forms that CAD cannot. The visualisation methods reduce the complexity of the detection process by limiting data presented for a review (Masutani, MacMahon and Doi 2002).
There are many proposed visualisation methods. We have maximum intensity projections (MIP) that rotate as slabs near the centre of the heart. Another approach limits the rotation of slab projections to various parts of the vascular tree. This enhances sensitivity as it reduces the number of images for examination simultaneously. However, these techniques need vessel tracking (Kiraly, Naidich, and Novak 2005).
We also have a proposed three-dimensional (3D) visualisation method. The 3D visualisation method shows the vascular tree with its surface colour as vessel contents show. It allows readers to see the vessel quickly. However, it needs navigation of the 3D because some parts of the vascular tree are not visible with a single view. Moreover, it is only appropriate to examine the vascular tree many times to ensure that all parts are viewed. This process requires vessel tracking and or complicated navigation processes, but it reduces workload (Pichon et al. 2004).
Kiraly, Naidich, and Novak (2005) suggest a new way of visualising the complete 3D tree structure by using a single and quite large 2D image. This method eliminates the need for vessel tracking and complicated 3D navigation. It only requires scanning through a 2D image, which is similar to reading a book, “from left to right and top to bottom”. This vessel has an easy-to-trace hierarchical order. This provides opportunities for a straightforward and systematic view of different parts of the vascular tree, which does not require multiple inspections of the vessel. Every method provides specific links to the main source of data.
In this case, we have the image of the patient displayed on the CT console monitor in the axial plane. This scan shows “a pulmonary embolus in the pulmonary artery bifurcation site” that we viewed as an intraluminal filling defect. At the workstation, the image undergoes reconstruction and analysis by using a Multi-planar Reconstruction (MPR). This machine displays rotating maximum, minimum, and average intensity projections by relying on reformating tools like sagittal, coronal, and axial images. It simultaneously displays all these parts on the left side of the workstation of the monitor and separates other parts of the screen for a full display of any imaging plane.
Aftercare
In the ward, the nurse watched the patient for any allergic reaction from the contrast medium given to her. In the ward, physicians used a pulse oximeter, automated blood pressure, pulse measurement device and electro cardiography (ECG) to monitor the patient. The patient had a low-grade vena cava (IVC) filter after the scan due to her current condition of PE and the previous pelvic surgery.
Treatment
The first treatment requires a parenteral anticoagulant in cases where the patient has acute PE because of the delay in therapeutic consequences of the warfarin. Subcutaneous weight-based Low molecular weight heparin (LMWH) has shown effectiveness and safety as intravenous un-fractionated heparin in the treatment of PE. It also does not need therapeutic monitoring. As a result, LMWH has been effective in administering a fixed weight-based dose, which has made it favourable for the initial treatment of PE. Un-fractionated heparin is popular among PE patients with severe cases of renal impairment because of the renal clearance of LMWH. The treatment is also suitable for unstable patients who may require thrombolytic therapy (Quinlan, McQuillan and Eikelboom 2004).
Theoretically, LMWH may allow for outpatient therapy among PE patients. However, not much information exists on the effectiveness and safety of the approach among low-risk patients with PE (Squizzato et al 2009; Stein and Matta 2010). There are existing methods of identifying PE patients with low-risk cases of PE who may need outpatient therapy. However, there are no safety standards based on randomised studies of inpatient against outpatient therapy among PE patients (Trautmann and Seitz 2010).
Thrombolysis is common among patients with PE who have haemodynamic instability (systolic BP <90 mmHg) because of high rates of fatality associated with the standard anticoagulant therapy. There are proposals that patients who lack haemodynamic also comprise prognosis in the right ventricular dilatation or elevated troponin. Therefore, such patients should be a part of thrombolytic therapy (Petersen 2009).
Warfarin has been used for continual anticoagulation after the first treatment period with LMWH. Anticoagulation requires a minimum of three months for PE patients with symptomatic conditions because patients who receive short periods of therapy experience cases of recurrent thrombosis. The time of the first event remains the major predictor of recurrent risks among PE patients. PE patients who have a definite provoking risk factor like a major surgery have low cases of recurrence.
These patients require between three and six months for anticoagulant treatment. PE patients who exhibit unprovoked PE cases have high cases of recurrence and may need long-term anticoagulation. This is useful in cases where other prognostic factors like male gender, anti-thrombin, protein C and protein S deficiency or antiphospholipid antibody syndrome are present and influence recurrence of risk factors. It is necessary to consider specialists in venous thrombosis when making decisions about the time for anticoagulation in such patients (Rodger et al. 2010).
In this case, the patient received intravenous un-fractionated heparin immediately after the admission.
Prognosis
Under prognosis and therapy, we have two classifications of PE patients, which are “those who are hemodynamic insufficient (i.e., hypotension, cardiac arrest or shock) and those who are stable”. PE patients who have stable conditions also have a good prognosis concerning the low risk of PE in cases of mortality and morbidity when anticoagulant therapy is prompt. The first group has high risks of mortality and morbidity as indicated by thrombolytic therapy.
Furthermore, different forms of diagnostic and laboratory results have shown and defined various extents of subgroups among PE patients. However, hemodynamic stable can also rely on other progressive fibrinolytic therapy or surgery (embolectomy) to benefit PE patients. On the other hand, other groups of patients may also rely on normal therapy (Hartmann, Wittenberg and Schaefer-Prokop 2010).
Other studies have highlighted the right ventricular (RV) “roles, dilatation of the pulmonary trunk, bowing of the intraventricular septum and/or the extent of vascular obstruction as independent predictive factors in the outcome of PE patients who are hemodynamic stable” (Ghaye et al. 2006). The existence of the right ventricular dysfunction observed under echocardiography predicts low favourable results among normotensive patients. Ultrasound has been used to assess cardiac function for a long.
However, the existence of RV dilatation observed through an axial CT showed revealed a link to mortality among PE patients. CTA has become the popular method for scanning PE because it automatically provides information that can supersede the need for an extra ECG. Moreover, RV dilation observed on axial CT images indicated “comparable to reconstructed 4-chamber views,” which eliminate the requirement for extra reconstructions (Kamel et al. 2008).