Echocardiographic evaluation of the thoracic aorta

Pathophysiology, diagnosis, and management of aortic dissection

Aortic dissection is an uncommon but potentially fatal disease with catastrophic complications. A high level of suspicion is required for successful diagnosis as presenting symptoms are so variable that dissection may be overlooked in up to 39% of cases. It most commonly presents in the elderly population with a history of chronic hypertension. Rapid intervention is necessary as delay leads to higher mortality. Despite advances in diagnostic and therapeutic techniques, morbidity and mortality remains high. Advances in diagnostic imaging have raised the awareness of variants of aortic dissection, including intramural hemorrhage and penetrating aortic ulcer. This distinction is important as the clinical course of these variants differs from that of classical aortic dissection, and thus treatment may also differ. Understanding of these variants has also led to the recognition of markers that may help predict progression to classical aortic dissection and thus warrant closer vigilance in selected patient populations. The recognition that rapid diagnosis is required for management of aortic dissection has led to the investigation of serum tests as diagnostic aids. Serum smooth muscle myosin heavy chain, d-dimer, and serum soluble elastin fragments are promising tests that may help raise suspicion for the diagnosis of acute aortic dissection. The high mortality associated with surgical therapy has led to investigation of alternative approaches. Endovascular therapy has emerged as a viable option in patients with type B dissection who are too unstable for surgery. However, long-term follow up is required to validate this procedure.

MRI of the Thoracic Aorta

Diseases of the thoracic aorta cause significant morbidity and mortality and can result in potentially catastrophic consequences. Conventional digital subtraction angiography (DSA) has been the gold standard for imaging for many years; however, this is associated with adverse effects and provides only limited information about vessel morphology. DSA is used primarily as a first-line investigation in the setting of trauma. Several other techniques also have been used in recent years, including CT and MRI. This article focuses primarily on the latter.

Diagnostic Imaging for Aortic Dissection

Diagnostic imaging for aortic dissection has dramatically changed in recent years. Previously, imaging consisted of conventional X-ray radiography, followed by invasive catheter angiography. Now imaging of dissection is performed primarily with multidetector CT, and to a lesser extent, with ultrasound and MRI. Catheter angiography is used primarily as a means of treating complications. Which modality to choose depends on patient factors, physician preference, and differences in availability of state-of-the-art equipment. All three modalities are highly accurate in experienced hands and have revolutionized the detection and evaluation of this condition.

Thoracic aortic aneurysm with aortobronchial fistula: a thirteen-year experience

PURPOSE

This study investigated the causes of aortobronchial fistula, clinical features, diagnostic modalities, and prognostic factors.

PARTICIPANTS

A retrospective analysis of 17 patients with aortobronchial fistula secondary to thoracic aortic aneurysm was studied.

METHODS

Retrospective chart review was used.

RESULTS

Atherosclerosis (47.1%), infection (23.5%), and previous thoracic vascular surgery (17.6%) accounted for most causes. Most patients (94.1%) experienced at least 1 episode of hemoptysis. Chest computer tomography is the most useful tool and revealed hematoma or consolidation around the aneurysm in more than half of our patients. Bronchoscopy and aortoangiogram frequently did not demonstrate an aortobronchial fistula. The 6 patients in the surgery group all survived, in contrast to 100% mortality in the non-surgery group. The average interval between initial presentation of hemoptysis and surgical intervention in the surgery group is 68 days, in contrast to 170 days between initial presentation of hemoptysis and death in the non-surgery group.

CONCLUSIONS

A high index of suspicion will decrease delayed diagnosis. Early diagnosis and emergent surgery are 2 prognostic factors for survival.

MR imaging of the thoracic aorta

There are numerous pulse sequences available for evaluating the diverse pathology that affects the thoracic aorta. Preliminary imaging using TrueFISP and precontrast and postcontrast T1 GRE-FS is usually required to assess morphology of the aorta and adjacent structures. CE-MRA is the mainstay in the investigative approach. The addition of temporally resolved subsecond CE-MRA is particularly useful for assessing high-flow vascular lesions such as shunts, while at the same time not adding much to the overall contrast load. PC-MRA may help further characterize stenotic lesions and can be useful for monitoring progression of disease.