Utility of echocardiography in the diagnosis of aortic dissection involving the ascending aorta

Diagnostic Accuracy of Transthoracic Echocardiography for Acute Type A Aortic Syndrome: A Systematic Review and Meta-Analysis

BACKGROUND

Transthoracic echocardiography (TTE) is currently recognized as the potential first-line imaging test for patients with suspected acute type A aortic syndrome (AAAS). Direct TTE sign for detecting AAAS is positive if there is an intimal flap separating two aortic lumens or aortic wall thickening seen in the ascending aorta. Indirect TTE sign indicates high-risk features of AAAS, such as aortic root dilatation, pericardial effusion, and aortic regurgitation. Our aim is to summarize the existing clinical evidence regarding the diagnostic accuracy of TTE and to evaluate its potential role in the management of patients with suspected AAAS.

METHODS

We included prospective or retrospective diagnostic cohort studies, written in any language, that specifically focused on using TTE to diagnose AAAS from databases such as PubMed, EMBASE, MEDLINE, and the Cochrane Library. The pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio [1], and hierarchical summary receiver-operating characteristic (HSROC) curve were calculated for TTE in diagnosing AAAS. We applied Quality Assessment of Diagnostic Accuracy (QUADAS-2) tool and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) quality assessment criteria.

RESULTS

Ten studies (2886 patients) were included in the meta-analysis. The pooled sensitivity and specificity of direct TTE signs were 58% (95% CI, 38-76%) and 94% (95% CI, 89-97%). For any TTE signs, the pooled sensitivity and specificity were 91% (95% CI, 85-94%) and 74% (95% CI, 61-84%). The diagnostic accuracy of direct TTE signs was significantly higher than that of any TTE signs, as measured by the area under the HSROC curve [0.95 (95% CI, 0.92-0.96) vs. 0.87 (95% CI, 0.84-0.90)] in four studies.

CONCLUSIONS

Our study suggests that TTE could serve as the initial imaging test for patients with suspected AAAS. Given its high specificity, the presence of direct TTE signs may indicate AAAS, whereas the absence of any TTE signs, combined with low clinical suspicion, could suggest a lower likelihood of AAAS.

Diagnostic accuracy of transthoracic echocardiography for the identification of proximal aortic dissection: a systematic review and meta-analysis

This systematic review and meta-analysis evaluated the performance of transthoracic echocardiography (TTE) for diagnosis of proximal aortic dissections based on the identification of specific sonographic features. A systematic literature search of major databases was conducted on human studies investigating the diagnostic accuracy of TTE for proximal aortic dissection. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The quality of studies was evaluated using Quality Assessment of Diagnostic Accuracy Studies 2 tool. Data were gathered for the following sonographic findings: intimal flap, tear, or intramural hematoma; enlargement of aortic root or widening of aortic walls; aortic valve regurgitation; or pericardial effusion. Sensitivity, specificity, diagnostic odds ratio, number needed to diagnose values, and likelihood ratios were determined. Fourteen studies were included in our final analysis. More than half of the included studies demonstrated low risk of bias. The identification of intimal flap, tear, or intramural hematoma was shown to have an exceptional ability as a diagnostic tool to rule in proximal aortic dissections. TTE should be considered during the initial evaluation of patients presenting to the emergency department with suspected proximal aortic dissection. Positive sonographic findings on TTE may aid in rapid assessment, coordination of care, and treatment of individuals awaiting advanced imaging.

Bilateral blood pressure differential as a clinical marker for acute aortic dissection in the emergency department

INTRODUCTION

Interarm systolic BP differential is a classic sign of acute aortic dissection (AAD). All previous studies looking at the association of BP differential with AAD combine systolic BP differential >20 mm Hg with pulse deficit. Our aim was to assess the association of systolic BP differential with AAD, and its role in predicting AAD in the context of other signs and symptoms.

METHODS

Historical matched case-control study using patient data collected between 2002 and 2014: participants were adults >18 years old with a bilateral BP measurement presenting to two tertiary care EDs or one regional cardiac referral centre in Canada. Cases were patients with diagnosed AAD; controls were those with a triage diagnosis of truncal pain (<14 days) and an absence of a clear diagnosis on basic investigation. Cases and controls were matched in a 1:1 ratio by sex and age. Bilateral BP differential and pulse deficit were compared between groups.

RESULTS

A total of 222 patients (111 cases and 111 controls) were analysed. On univariate analysis systolic BP differential >20 mm Hg (OR 2.7, 95% CI 1.39 to 5.25) was significantly associated with AAD. Pulse deficit (diagnostic OR (DOR) 28.9) in isolation had better diagnostic accuracy than systolic BP differential >20 mm Hg in isolation (DOR 2.71) or combined with systolic BP differential >20 mm Hg (DOR 4.2).

CONCLUSION

Bilateral systolic BP differentials >20 mm Hg are associated with non-traumatic AAD. However, the poor diagnostic accuracy and potential variability in measurement limits its clinical usefulness.

Clinical Examination for Acute Aortic Dissection: A Systematic Review and Meta-analysis

OBJECTIVES

Acute aortic dissection is a life-threatening condition due to a tear in the aortic wall. It is difficult to diagnose and if missed carries a significant mortality.

METHODS

We conducted a librarian-assisted systematic review of PubMed, MEDLINE, Embase, and the Cochrane database from 1968 to July 2016. Titles and abstracts were reviewed and data were extracted by two independent reviewers (agreement measured by kappa). Studies were combined if low clinical and statistical heterogeneity (I²  < 30%). Study quality was assessed using the QUADAS-2 tool. Bivariate random effects meta analyses using Revman 5 and SAS 9.3 were performed.

RESULTS

We identified 792 records: 60 were selected for full text review, nine studies with 2,400 participants were included (QUADAS-2 low risk of bias, κ = 0.89 [for full-text review]). Prevalence of aortic dissection ranged from 21.9% to 76.1% (mean ± SD = 39.1% ± 17.1%). The clinical findings increasing probability of aortic dissection were 1) neurologic deficit (n = 3, specificity = 95%, positive likelihood ratio [LR+] = 4.4, 95% confidence interval [CI] = 3.3-5.7, I²  = 0%) and 2) hypotension (n = 4, specificity = 95%, LR+ = 2.9 95% CI = 1.8-4.6, I²  = 42%), and decreasing probability were the absence of a widened mediastinum (n = 4, sensitivity = 76%-95%, negative likelihood ratio [LR-] = 0.14-0.60, I²  = 93%) and an American Heart Association aortic dissection detection (AHA ADD) risk score < 1 (n = 1, sensitivity = 91%, LR- = 0.22, 95% CI = 0.15-0.33).

CONCLUSIONS

Suspicion for acute aortic dissection should be raised with hypotension, pulse, or neurologic deficit. Conversely, a low AHA ADD score decreases suspicion. Clinical gestalt informed by high- and low-risk features together with an absence of an alternative diagnosis should drive investigation for acute aortic dissection.

Diagnostic performance of emergency transthoracic focus cardiac ultrasound in suspected acute type A aortic dissection

Type A aortic dissection (AD) is a deadly disease. Rapid identification of patients requiring immediate advanced aortic imaging or transfer to specialized centers is needed to improve outcomes. We evaluated the diagnostic performance of transthoracic focus cardiac ultrasound (FOCUS) performed by emergency physicians, alone and in combination with the aortic dissection detection (ADD) risk score in suspected type A AD. This was a prospective study performed on patients with suspected type A AD. FOCUS evaluated the presence of intimal flap/intramural hematoma (direct signs of AD), ascending aorta dilatation, aortic valve insufficiency or pericardial effusion/tamponade (indirect signs of AD). The ADD risk score of each patient was calculated according to guidelines. The final diagnosis was established after review of complete clinical data. 50 (18%) patients of 281 had a final diagnosis of type A AD. Detection of any FOCUS sign (direct or indirect) of AD had a sensitivity of 88% (95% CI 76-95%) for the diagnosis of type A AD. Presence of ADD risk score > 0 or detection of any FOCUS sign increased diagnostic sensitivity to 96% (95% CI 86-99%). Detection of direct FOCUS signs had a specificity of 94% (95% CI 90-97%), while combination of ADD risk score > 1 with detection of direct FOCUS signs had a specificity of 98% (95% CI 96-99%). FOCUS demonstrated acceptable accuracy as a triage tool to rapidly identify patients with suspected type A AD needing advanced aortic imaging or transfer, but it cannot be used as a stand-alone test even if combined with ADD risk score classification.

The role of transthoracic echocardiography in the diagnosis and management of acute type A aortic syndrome

BACKGROUND

Transthoracic echocardiography (TTE) has been traditionally considered inadequate for the diagnosis of acute type A aortic syndrome (AAAS). In the last decade, high-resolution probes and harmonic imaging have been implemented in new echocardiographic systems. However, studies assessing the diagnostic accuracy of TTE for the identification of AAAS in large populations using modern ultrasound technology are lacking.

METHODS

The diagnostic value of harmonic imaging TTE was assessed in 270 consecutive patients with suspected AAAS in whom TTE was the initial diagnostic test.

RESULTS

Acute type A aortic syndrome was diagnosed in 67 patients and excluded in 203 patients (disease prevalence 25%). Sixty-two patients had a classic acute type A aortic dissection, and 5, an acute type A intramural hematoma. Image quality achieved was considered optimal in 244 patients (90%). In the whole study population, TTE had sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of AAAS of 87%, 91%, 75%, and 95%, respectively. When evaluating only patients with optimal image quality, these values increased to 97%, 100%, 100%, and 99%, respectively. Forty-seven patients with clear-cut evidence of AAAS were transferred immediately to the operative room, where transesophageal echocardiography confirmed the diagnosis obtained by TTE in all patients.

CONCLUSIONS

Transthoracic echocardiography is a useful imaging modality for the diagnosis of classic acute type A aortic dissection. It cannot be used as the sole screening technique for detecting AAAS, but in the light of the predictive values observed, patients with optimal image quality and clear-cut diagnosis of AAAS should proceed to the operative room, whereas in patients with negative or indeterminate studies, other imaging techniques are needed to refine the diagnosis.

Gadolinium-enhanced MR angiography in the evaluation of congenital cardiovascular disease pre- and postoperative states in infants and children

The purpose of this study was to evaluate the utility of dynamic contrast magnetic resonance (MR) angiography under sedation for assessing congenital cardiovascular disease in infants and small children before and after cardiac surgery. In 38 patients with cardiovascular abnormalities, thoracic vasculatures were evaluated in either the preoperative (group 1; 23 patients, median age 9 months old) or the postoperative (group 2; 15 patients median age 1. 3 years old) state using gadolinium-enhanced dynamic MR angiography. Acquired data were processed with a multiprojection volume reconstruction. Image quality (grades 1-5, undiagnostic to excellent), presence or absence of the extracardiac vasculature, its pathology (group 1), and the patency of the postsurgical shunt or reconstructed vasculature (group 2) were evaluated. All images were of diagnostic image quality (mean grade 4.4-3.2). Recognition of the thoracic vasculature was correctly made in all cases (38/38, 100%). In group 1, anomalies and pathologic changes were correctly identified in 22 of 23 cases (95.7%). In one patient with dextrocardia and the cardiac type of total anomalous pulmonary venous return, the abnormality was not recognized. In group 2, the patency of the shunt flow after Glenn (n = 6), modified Fontan (n = 4), Rastelli (n = 1), and Blalock-Taussig (n = 3) operations was well demonstrated in each case. The reconstructed pulmonary artery (n = 1), veins (n = 2), and aorta (n = 1) were correctly visualized. In one case, stenosis of the reconstructed left pulmonary vein was missed by MR angiography. In 14 of 15 cases in group 2 (93.3%), MR angiography correctly gave information on the operated areas. In conclusion, dynamic contrast MR angiography under sedation is useful for evaluation of the thoracic vasculature of infants and small children in the pre- and postoperative states. J. Magn. Reson. Imaging 2000;12:1034-1042.

Diseases of the aorta

The medical community has begun to realize the complexity of aortic pathology in vivo and its often iridescent and ambiguous clinical presentation. Diagnostic modalities such as transesophageal echocardiography, magnetic resonance imaging, and computed tomography have all been shown to be useful to investigate the aorta, both in chronic disease and in acute aortic syndromes. This article focuses on the possibilities and emerging advantages of magnetic resonance imaging with respect to a spectrum of aortic pathologies.

Detecting acute thoracic aortic dissection in the emergency department: time constraints and choice of the optimal diagnostic test

STUDY OBJECTIVES

To compare diagnostic strategies for the emergency assessment of patients with suspected acute thoracic aortic dissection and to measure the effect of delays related to the availability of these tests on the selection of the most appropriate one.

METHODS

We carried out a decision analysis representing the risks of performing one or two sequential tests, the tests' accuracy, the risks and benefits of treatment, and the time-dependent mortality rate in untreated patients with dissection (1%/hour). Data were drawn from a Medline search. Our subjects were patients who presented to the emergency department with chest pain in whom acute thoracic aortic dissection was suspected. For different clinical probabilities of aortic dissection, we compared the risks and benefits of testing using the following procedures (alone and in combinations): aortography, computed tomography (CT), magnetic resonance imaging (MRI), and both transesophageal (TEE) and transthoracic echocardiography (TTE). We then measured the effect of delays in these tests on the selection of the appropriate procedure. The outcome studied was 30-day survival.

RESULTS

We determined that the "threshold" clinical probability of aortic dissection above which the benefits of testing outweigh its risks is low. It ranges from 2% with the most reliable procedure (MRI) to 9% with the least (TTE). At low probability of dissection (< 15%), the accuracy of all tests except TTE is sufficient to rule out dissection. Delays have negligible effect on these results. When the likelihood of dissection is higher, the preferred option is to order a second diagnostic test if the results of the first are negative. The threshold probabilities above which to order a second test range from 15% (CT, then aortography) to 35% (MRI, then aortography). Excessive delays may affect the selection of tests when the likelihood of dissection is high (eg, 50%). Thus, although it is less accurate, a CT scan obtained within 2 hours or a TEE obtained within 6 hours of presentation to the ED yields a higher survival rate than an MRI obtained within 9 hours. Similarly, the benefits of ordering a second test, if the result of the first are negative, outweigh the risks only if the delay in obtaining the test does not exceed 10 hours.

CONCLUSION

All patients in whom aortic dissection is suspected, even if the index of suspicion is very low, should undergo one of the available diagnostic procedures (except TTE). A patient with a moderate to high probability of disease should undergo a second investigation if the findings of the first are negative. When the probability of dissection is high, the physician must consider delays in obtaining specific diagnostic tests and order those that will be the most quickly available.

Feasibility, accuracy and safety of magnetic resonance imaging in acute aortic dissection

Magnetic resonance imaging (MRI) is the most accurate method of defining the morphology and haemodynamic features of thoracic aortic dissection. However, because of doubts about its safety in acute situations, its use has so far been confined to imaging chronic dissections. We present a prospective study of 50 patients thought clinically to have acute thoracic aortic dissection in which a rapid diagnosis was made by MRI.

Aorta: comprehensive evaluation by echocardiography and transesophageal echocardiography

The emergence of transesophageal echocardiography has made echocardiography a nearly ideal technique for evaluating the thoracic aorta. The echocardiographic anatomy of the aorta is reviewed. The role of echocardiography for evaluating aortic dissection, thoracic aortic aneurysm, aortic atherosclerosis, and thoracic aortic trauma is discussed. Comparison of echocardiography with other techniques for imaging the aorta (computed tomographic scan, nuclear magnetic resonance, and aortography) is presented.

Aortic dissection in the thrombolytic era: early recognition and optimal management is a prerequisite for increased survival

Based on two case reports, problems of diagnosis and treatment of aortic dissection are discussed. Thrombolytic treatment given to patients with aortic dissection presenting symptoms mimicking acute MI seems to have a fatal outcome. Indications, as well as contra-indications, for thrombolytic therapy are therefore of great importance, when this treatment is given to patients suspected of having acute myocardial infarction, especially where diagnosis is uncertain or as prehospital treatment. In patients with chest pain symptoms without typical history and electrocardiographic changes the diagnosis should be reconsidered within a few hours and, if possible, together with echocardiographic findings. In doing so patients with coronary heart disease will get all the benefits of thrombolytic treatment. Furthermore the importance of quick accurate diagnosis, especially in type A aortic dissection is pointed out, as emergency surgical intervention can be lifesaving. A more aggressive medical and surgical approach has contributed to the improved survival among patients with aortic dissections.

Echocardiography in the diagnosis of thoracic aortic pathology

Transthoracic two-dimensional and Doppler echocardiography has been well established as a useful technique for evaluating many pathologic processes affecting the thoracic aorta. However, the distance of the aortic arch and descending thoracic aorta from the chest wall and the interposition of highly attenuating lung and highly reflective mediastinal structures between the transducer and the aorta present unavoidable limitations. Transesophageal echocardiography is a relatively new technology that overcomes many of the inherent limitations with transthoracic imaging. Complete echocardiographic evaluation of the entire thoracic aorta can now be achieved in nearly all patients. This article will review the continually expanding role of echocardiography in the evaluation of thoracic aortic pathology, including the dramatic impact of transesophageal imaging on the diagnosis of life-threatening disorders such as aortic dissection.

The diagnostic value of imaging techniques for aortic dissection

Previous studies conducted in high-risk populations have reported high predictive values and accuracies for diagnostic imaging techniques for aortic dissection. To see how these techniques perform in low-risk populations, we used Bayes' theorem to calculate predictive values and accuracies for angiography, CT, MRI, and TEE. In high-risk populations (disease prevalence = 50%), positive predictive values were all greater than 85%. In intermediate risk populations (disease prevalence = 10%), positive predictive values were greater than or equal to 90% for CT, MRI, and TEE, but were 65% for angiography. In low-risk populations (disease prevalence = 1%), positive predictive values were 100% for MRI and less than or equal to 50% for angiography, CT, and TEE. In all three populations, negative predictive values and accuracies were greater than or equal to 85%. From these results we conclude that diagnostic imaging techniques for aortic dissection do not perform as well in low-risk populations as they do in high-risk populations.

Diagnosis of acute thoracic aortic dissection using combined echocardiography and computed tomography

Acute dissection of the thoracic aorta is a life-threatening emergency requiring a diagnosis which is rapid, accurate and safe, and which will distinguish between dissections involving the ascending and descending aorta. In the absence of any general agreement on the best method of making this diagnosis we studied the use of combined echocardiography and contrast-enhanced computed tomography (CT) to diagnose acute aortic dissection. Over a 3 year period 23 patients were investigated in this way. Aortic dissection was demonstrated in 18 cases, involving the ascending aorta in 15, and the descending aorta alone in three. The diagnosis of aortic dissection was confirmed in 13 patients at surgery, in one at aortography and in one at autopsy. Three patients died without surgery or autopsy being performed to confirm the diagnosis and the subsequently which accounted for their symptoms. This combined approach has proved a valuable and safe means of investigating aortic dissection.