Rationale and Objectives
To retrospectively determine the value of a volumetric ventricle analysis for the assessment of right ventricular dysfunction in patients with suspected pulmonary embolism (PE) by using image data from non-electrocardiographically (ECG)-gated multidetector computed tomography angiography (CTA).
Materials and Methods
Hypothesizing that the presence of PE and the embolus location correlated with right ventricular dysfunction, we retrospectively analyzed 100 non–ECG-gated pulmonary CTA datasets of patients with central, peripheral, and without PE. Right ventricle/left ventricle (RV/LV) diameter ratio measured in transverse sections (RV/LV trans ), four-chamber view (RV/LV 4ch ), and RV/LV volume ratio (RV/LV vol ) were assessed on CT images. The results were correlated with the embolus location, the 30-day mortality rate, and the necessity of intensive care treatment.
Results
All CT parameters showed statistically significant differences between all patients groups depended on embolus location. The receiver operating characteristic analysis RV/LV vol showed the strongest discriminatory power to differ between patients with central and without PE and between patients with central and peripheral PE (central PE vs. no PE: RV/LV vol = 0.932, RV/LV trans = 0.880, and RV/LV 4ch = 0.811, central PE vs. peripheral PE: RV/LV vol = 0.950, RV/LV trans = 0.849, and RV/LV 4ch = 0.881), indicating a correlation with embolus location predisposing for RVD. For the identification of high-risk patients with PE all three CT parameters showed statistically significant values ( P < .0001), whereas in the receiver operating characteristic analysis, RV/LV vol had the strongest discriminatory power (RV/LV vol = 0.819, RV/LV trans = 0.799, and RV/LV 4ch = 0.758).
Conclusion
Ventricle volumetry of non–ECG-gated CTA allows the assessment of right ventricular dysfunction in patients with acute PE. Compared to unidimensional measurements, a volumetric analysis seems to be slightly superior to identify high-risk patients with adverse clinical outcome. However, the method is more time consuming and requires dedicated software tools compared to unidimensional parameters, which is disadvantageous in an emergency setting.
Acute pulmonary embolism (PE) is a common disease with a variable prognosis that ranges from incidental clinical unimportant small embolism to massive embolism with sudden death . If undiagnosed, PE is fatal in up to 30%, but even if diagnosed the 30-day mortality rate reaches 10% . Right ventricular dysfunction (RVD) is the major prognostic factor in patients with acute PE . Patients with RVD have a higher mortality rate than those without RVD, even if they are hemodynamically stable at clinical presentation . Therefore, the identification of patients with RVD is of major clinical importance, because these patients might benefit from intensive therapy with thrombolytic agents or surgery embolectomy . Echocardiography is the standard of reference for the assessment of RVD in patients with PE , but is operator dependent.
Multidetector computed tomography angiography (CTA) of the pulmonary arteries has become the accepted gold standard for the diagnosis of acute PE . In addition to the detection of PE, CTA also allows assessing the dimensions of the cardiac chambers, which are displayed in the same examination. Because of this, many investigators have tried to identify quantitative CT parameters for the assessment of RVD . Several studies have demonstrated that similar to echocardiography simple measurements of the maximum right ventricular (RV) to left ventricular (LV) dimension ratio (RV/LV) can be used to identify RVD in patients with acute PE .
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Materials and methods
Patients and Study Design
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Imaging Protocol
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CT Analysis
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Clinical Outcome
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Statistical Analysis
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Results
Clinical Outcome
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CT Parameters and Embolus Location
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Table 1
Clinical Characteristics of the 22 High-risk Patients
Death 4 Resuscitation 8 Systemic lysis therapy 8 Cardiogenic shock 10 Catecholamine dependent 10 Mechanical ventilation 10 Echocardiographic-confirmed severe right heart failure 16
Note: Some patients met several high risk criteria.
Table 2
Means, ▵ of Means, and t -test of Different CT Parameters to Differentiate Patient Groups Dependent on Embolus Location
Central vs. Peripheral PE Means ▵P Values RV/LV trans 1.25 vs. 0.88 0.37 <.0001 RV/LV 4ch 1.20 vs. 0.87 0.33 <.0001 RV/LV vol 1.65 vs. 0.86 0.79 <.0001 Central vs. no PE RV/LV trans 1.25 vs. 0.83 0.42 <.0001 1.20 vs. 0.84 0.36 <.0001 RV/LV vol 1.65 vs. 0.83 0.82 <.0001 Peripheral vs. no PE RV/LV trans 0.88 vs. 0.83 0.05 <.0001 RV/LV 4ch 0.87 vs. 0.84 0.03 <.0001 RV/LV vol 0.86 vs. 0.83 0.03 <.0001
CT: computed tomography; RV/LV trans : right ventricle/left ventricle diameter ratio measured in transverse sections; RV/LV 4ch : four-chamber view; RV/LV vol : RV/LV volume ratio; PE: pulmonary embolism.
Table 3
ROC Analysis of CT Parameters to Evaluate the Discriminatory Power to Differentiate Patient Groups Dependent on Embolus Location
Central vs. Peripheral Central vs. No Peripheral vs. No RV/LV trans 0.811 0.849 0.582 RV/LV 4ch 0.880 0.881 0.532 RV/LV vol 0.932 0.950 0.587
CT: computed tomography; RV/LV trans : right ventricle/left ventricle diameter ratio measured in transverse sections; RV/LV 4ch : four-chamber view; RV/LV vol : RV/LV volume ratio.
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CT Parameter and Patients Outcome
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Table 4
Means, ▵ of Means and t -test of Different CT Parameters to Identify High-risk Patients
Means High-risk Group vs. Other Patients ▵P Values RV/LV trans 1.27 vs. 0.89 0.38 <.0001 RV/LV 4ch 1.18 vs. 0.90 0.28 <.0001 RV/LV vol 1.68 vs. 0.93 0.79 <.0001
CT: computed tomography; RV/LV trans : right ventricle/left ventricle diameter ratio measured in transverse sections; RV/LV 4ch : four-chamber view; RV/LV vol : RV/LV volume ratio.
Table 5
ROC Analysis of the Different CT Parameters to Identify High-risk Patients
RV/LV trans 0.799 RV/LV 4ch 0.758 RV/LV vol 0.819
ROC: receiver operating characteristic; CT: computed tomography; RV/LV trans : right ventricle/left ventricle diameter ratio measured in transverse sections; RV/LV 4ch : four-chamber view; RV/LV vol : RV/LV volume ratio.
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Postprocessing Time for the Volumetric Analysis
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Radiation Dose
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Discussion
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