**10. Role of V/Q SPECT in PE**

Given the high sensitivity associated with a low indeterminate rate, absence of contraindications and low radiation dose, V/Q SPECT seems ideally suited to be the initial

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screening test for PE in most clinical settings. It should be the test of choice in all cases with a clear chest x-ray (or minor alterations), and most probably in cases of X-rays with a single anomaly. It should be the test of choice in cases associated with pregnancy.

Consideration for CTPA as an initial test should be in cases of severe radiological anomalies or cases for which it is clear from the clinical presentation that a chest CT will be mandatory anyway (to exclude a non-embolic aetiology, when a chest X-ray is deemed insufficient). Cross over to the alternate technique (whether V/Q SPECT or CTPA was used first) should be considered for all equivocal cases and for cases with very strong disagreement between the imaging result and the clinical data. In those cases, lower limb Doppler studies may also be useful. For patients with moderate chest x-ray anomalies there is insufficient data for recommendations at this point but the performance of V/Q SPECT in that setting has been encouraging.

#### **11. Conclusion**

V/Q SPECT has proven its value in the setting of PE. It should totally replace planar V/Q scintigraphy in all settings, except in rare cases when a patient cannot tolerate supine imaging. It has significant advantages over CTPA in several common situations and its excellent sensitivity associated with a better safety profile and lower radiation dose makes it the ideal routine screening technique for PE.

#### **12. References**


screening test for PE in most clinical settings. It should be the test of choice in all cases with a clear chest x-ray (or minor alterations), and most probably in cases of X-rays with a single

Consideration for CTPA as an initial test should be in cases of severe radiological anomalies or cases for which it is clear from the clinical presentation that a chest CT will be mandatory anyway (to exclude a non-embolic aetiology, when a chest X-ray is deemed insufficient). Cross over to the alternate technique (whether V/Q SPECT or CTPA was used first) should be considered for all equivocal cases and for cases with very strong disagreement between the imaging result and the clinical data. In those cases, lower limb Doppler studies may also be useful. For patients with moderate chest x-ray anomalies there is insufficient data for recommendations at this point but the performance of V/Q SPECT in that setting has been

V/Q SPECT has proven its value in the setting of PE. It should totally replace planar V/Q scintigraphy in all settings, except in rare cases when a patient cannot tolerate supine imaging. It has significant advantages over CTPA in several common situations and its excellent sensitivity associated with a better safety profile and lower radiation dose makes it

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encouraging.

**11. Conclusion**

**12. References** 

70.

the ideal routine screening technique for PE.


**8** 

*Korea* 

**Risk Stratification of Submassive** 

**of Chest Computed Tomography as an Alternative to Echocardiography** 

Acute pulmonary embolism (PE) is a common and potentially fatal disease (Goldhaber et al., 1999). The most frequent cause of death within 30 days is right ventricular (RV) failure (Goldhaber & Elliott, 2003). Rapid risk stratification is paramount for identifying high-risk patients and for helping to select the appropriate treatment strategy. According to European guidelines (Torbicki et al., 2008), high-risk PE (formerly 'massive' PE) implies the presence of shock or hemodynamic instability (mortality >15%) (Goldhaber et al., 1999). Non highrisk PE can be further stratified by the presence of markers of RV dysfunction and/or myocardial injury as intermediate- and low-risk PE. Intermediate-risk PE (formerly 'submassive' PE) is diagnosed by the presence of at least one marker of RV dysfunction or myocardial injury. Low-risk PE (formerly 'non-massive' PE) is diagnosed when RV dysfunction markers are negative (mortality <1%). Reperfusion therapy, including thrombolysis or surgical embolectomy, is indicated for patients with high-risk PE. However, the risks and benefits of reperfusion therapy for patients with intermediate risk PE are less clear. Based on pathophysiological knowledge of the impact of RV dysfunction on acute PE, risk stratification is based on imaging modalities for the visualization of RV dysfunction. Therefore, echocardiographic assessment of RV dysfunction in acute PE may predict early mortality, and may guide decisions regarding reperfusion therapy (Grifoni et al., 2000; Kucher et al., 2005). Echocardiography, however, is time-consuming, operator-dependent, and not always available in an emergency situation, and echocardiographic criteria for assessing RV have not yet been determined. The development of narrow collimation, multi–detector row computed tomography (CT) imaging, and modern workstations for image postprocessing and analysis have made CT pulmonary angiography the modality of choice for the assessment of patients with pulmonary emboli (Ghaye et al., 2006; Schoepf & Costello, 2004). At times, CT is more rapidly accessible in emergency settings, and is more widely available than echocardiography. CT enables the direct visualization of emboli and provides information about cardiac morphology. CT findings, including RV enlargement, the ratio of RV diameter to the diameter of the left ventricle (LV) (RV/LV ratio), interventricular septal bowing, and pulmonary vascular obstruction score, have been associated with early mortality and clinical outcomes (Araoz et al., 2003; Collomb et al., 2003; Coutance et al., 2011; Ghuysen et al., 2005;

**1. Introduction** 

**Pulmonary Embolism: The Role** 

Won Young Kim, Shin Ahn and Choong Wook Lee *University of Ulsan College of Medicine; Asan Medical Center* 

