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Multidetector Computed Tomography for Acute Pulmonary Embolism: Diagnosis and Risk Stratification in a Single Test
Study Questions:
What is the diagnostic accuracy of multidetector computed tomography (MDCT) for identifying right ventricular dysfunction (RVD) in patients with acute pulmonary embolism (PE), and what are the prognostic implications of (RVD), as detected by MDCT, in the same patient population?
Methods:
MDCT and echocardiography data were available in 457 patients with acute PE. RVD was diagnosed on transthoracic echocardiography when a combination of at least two of the following were present: right-to-left ventricular (RV-LV) end-diastolic diameter ratio >0.9 in the apical four-chamber view, RV-LV ratio >0.7 in the parasternal long-axis view, presence of paradoxical septal motion, or pulmonary artery diastolic pressure >30 mm Hg. On MDCT, the ratio of RV-LV diameter was also determined and several thresholds were used for comparison. Endpoints included all-cause mortality death due to PE and clinical deterioration defined as shock, need for thrombolysis, need for intervention, need for pressor support, cardiopulmonary resuscitation, or recurrent PE.
Results:
Overall patient age was 67 ± 16 years, and 47.5% were male. Underlying medical illnesses included malignancy in 19.9%, heart failure in 4.6%, and immobilization in 38.9%. RVD was present by echocardiography in 230 (50%), and 177 (39%) had an elevated troponin. Diagnostic accuracy of MDCT was determined in the first 260 consecutive patients, and based on receiver operating characteristics, an MDCT RV-LV ratio ≥0.9 was identified as optimal threshold, with a sensitivity and specificity for RVD by echo of 92% and 56%. On follow-up, 52 patients (11.3%) had clinical deterioration in-hospital including 25 deaths, 17 of which were due to PE. RVD was detected by MDCT in 303 patients (66%), and 44 (14.5%) either died or had clinical deterioration compared to 854 (5.2%) without (hazard ratio, 3.5; p = 0.002). In-hospital death occurred in 5.6% of patients with RVD and in none without RVD on MDCT (p < 0.001), resulting in a negative predictive value of 100%. At the time of diagnosis of PE, 62 patients (63.7%) were hemodynamically stable and had RVD, 28 of whom died or who had clinical deterioration in-hospital (6.8%). On multivaried analysis, RVD of MDCT was associated with the increased development of death or clinical deterioration, as well as an increased risk of death due to PE.
Conclusions:
The authors concluded that MDCT can accurately diagnose RVD as compared to echocardiography, and also provides prognostic information with respect to death or clinical deterioration.
Perspective:
It is well recognized that prognosis in PE is related to several clinical factors; among them are hypotension, hypoxia, and clinical and echocardiographic evidence of RVD. RVD typically has been assessed with transthoracic echocardiography to evaluate RV size, wall motion, and systolic function and presence in magnitude regurgitation. Several studies have demonstrated that patients with RVD are at higher risk than those with preserved RV function, the obvious connection being the overall thrombus burden. MDCT has emerged as a front-line diagnostic tool for detection of acute PE, and in most centers, is the imaging procedure of choice for early evaluation of suspected pulmonary embolus. This study demonstrates that a simple measurement of RV size compared to LV size correlates well with similar echocardiographic assessment and, furthermore, provides significant prognostic information. The 100% negative predictive value of absence of RVD should be reassuring to clinicians. Conversely, detection of RVD correlates with DVD by echocardiography, and allows identification of a higher-risk patient subset for whom close scrutiny and/or alternate strategies may be warranted.
Keywords: Prognosis, Follow-Up Studies, Pulmonary Embolism, Cardiopulmonary Resuscitation, Multidetector Computed Tomography, Heart Failure, Hypotension, Ventricular Dysfunction, Right, Echocardiography
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