Aortic arch branches are no longer a blind zone for transesophageal echocardiography: a new eye for aortic surgeons

The history of transesophageal echocardiography: the role of inspiration, innovation, and applications

Transesophageal echocardiography (TEE), which is commonly used for monitoring and diagnostic imaging during cardiovascular surgery, was originally developed by a strong desire to know what was taking place in the heart in the dark ages of cardiac surgery. The author was fortunate to be present in the midst of the development of TEE and have an opportunity to take a close look at the history of this innovation. Furthermore, the author believes that the history of TEE contains important lessons and tips for solving the problems we presently face in clinical practice. This article describes the history of TEE based on the reports in the early stage of development and discuss how inspiration and innovation was generated by a strong wish and passion to overcome problems. The development of TEE was based on the collaboration of colleagues in different fields, and an intense desire to convert ideas into reality.

The current role of echocardiography in acute aortic syndrome

Acute aortic syndrome (AAS) comprises a range of interrelated conditions caused by disruption of the medial layer of the aortic wall, including aortic dissection, intramural haematoma and penetrating aortic ulcer. Since mortality from AAS is high, a prompt and accurate diagnosis using imaging techniques is paramount. Both transthoracic (TTE) and transoesophageal echocardiography (TEE) are useful in the diagnosis of AAS. TTE should be the first imaging technique to evaluate patients with thoracic pain in the emergency room. Should AAS be suspected, contrast administration is recommended when images are not definitive. TEE allows high-quality images in thoracic aorta. The main drawback of this technique is that it is semi-invasive and the presence of a blind area that limits visualisation of the distal ascending aorta near. TEE identifies the location and size of the entry tear, secondary communications, true lumen compression and the dynamic flow pattern of false lumen. Although computed tomography (CT) is the most used imaging technique in the diagnosis of AAS, echocardiography offers complementary information relevant for its management. The best imaging strategy for appropriately diagnosing and assessing AAS is to combine CT, mainly ECG-gated contrast-enhanced CT, and TTE. Currently, TEE tends to be carried out in the operating theatre immediately before surgical or endovascular therapy and in monitoring their results. The aims of this review are to establish the current role of echocardiography in the diagnosis and management of AAS based on its advantages and limitations.

Transesophageal echocardiography evaluation of the aortic arch branches

Visualization of aortic arch branches by transesophageal echocardiography has been technically challenging. Visualizing these vessels helps in identifying the extent of dissection of the aorta, assessing the severity of carotid artery stenosis, presence of atheromatous plaques, patency of the left internal mammary artery graft, confirmation of subclavian artery cannulation, confirming holodiastolic flow reversal in the left subclavian artery by spectral Doppler imaging in case of severe aortic regurgitation, and confirming the optimal position of the intraaortic balloon perioperatively. The information obtained is helpful for diagnosis, monitoring, and decision-making during aortic surgery.

Triple ultrasonography for iatrogenic acute aortic dissection caused by axillary arterial perfusion

Iatrogenic aortic dissection caused by axillary arterial cannulation or perfusion becomes a fatal complication of cardiopulmonary bypass when surgeons do not recognize it in the surgical field of view immediately during surgery. Therefore, we routinely monitor the aorta using 'triple ultrasonography' during cardiovascular surgery. An 85-year-old woman underwent partial arch replacement for chronic type A aortic dissection. During cardiopulmonary bypass, acute aortic dissection was observed in the aortic arch from the right axillary artery on real-time transoesophageal echocardiography. Epiaortic and neck surface ultrasonography detected malperfusion of the carotid artery. During femoral arterial perfusion, the patient was rescued with partial aortic replacement. Axillary artery cannulation is useful for cardiopulmonary bypass but confers a risk of iatrogenic aortic dissection that cannot be confirmed by surgeons surgically. The transoesophageal echocardiography can guard the aorta while systemic perfusion is initiated. Furthermore, epiaortic and neck surface echography can be incorporated to transoesophageal echocardiography. Triple ultrasonography allows for the detection of iatrogenic aortic dissection.

Cerebral malperfusion in acute aortic dissection

Cerebral malperfusion in association with acute type A aortic dissection is uncommon but can have a considerable effect on the outcome of treatment. Successful treatment requires the individual and effective removal of each of the factors associated with malperfusion. In addition to the conventional surgical procedures, endovascular treatment has become an option for restoring perfusion. However, artificial perfusion and/or surgical procedures can lead to new malperfusion, which is not necessarily apparent to surgeons and which is difficult to predict. Thus, a number of modalities need to be applied to monitoring the current status of perfusion to enable timely treatment. Since each of the diagnostic modalities has its merits and demerits, one should use them effectively while being mindful of the pitfalls. In addition, a delay in the diagnosis in the pre-hospital stage is an important determinant of the surgical outcomes of aortic dissection. Portable echocardiography, which has been recently developed, may be useful for improving this situation. However, an early diagnosis largely depends on the physician's awareness and basic echocardiography skills. Surgeons should make general physicians aware of this message.

Transesophageal echocardiography estimation of coronary sinus blood flow for the adequacy of revascularization in patients undergoing off-pump coronary artery bypass graft

Aims and Objectives:

Physiologically coronary sinus (CS) drains the left coronary artery (LCA) territory. Stenosis of the branches of LCA may decrease the coronary sinus blood flow (CSBF). Any intervention that aims at restoring the flow of the stenosed vessel increases coronary artery flow that should consequently increase the CSBF. Hence, this study was undertaken to assess the CSBF before and after each branch of LCA to determine the adequacy of surgical revascularization in patients undergoing elective off pump coronary artery bypass grafting (OPCAB) using transesophageal echocardiography (TEE).

Materials and Methods:

Thirty consecutive patients scheduled for elective OPCAB were enrolled. CSBF was assessed before and after each branch of LCA revascularization using TEE. Left internal mammary artery (LIMA) Doppler was also obtained post LIMA to left anterior descending (LAD) grafting.

Results:

Hemodynamic and echocardiographic variables were compared by means of Student's t-test for paired data before and after revascularization. The CSBF per beat (1.28 ± 0.71), CSBF per minute (92.59 ± 59.32) and total velocity time integral (VTI) (8.93 ± 4.29) before LAD grafting showed statistically significant increase to CSBF per beat (1.70 ± 0.89), CSBF per minute (130.72 ± 74.22) and total VTI (11.96 ± 5.68) after LAD revascularization. The CSBF per beat (1.67 ± 1.03), CSBF per minute (131.91 ± 86.59) and total VTI (11.00 ± 5.53) before obtuse marginal (OM) grafting showed statistically significant increase to CSBF per beat (1.91 ± 1.03), CSBF per min (155.20 ± 88.70) and total VTI (12.09 ± 5.43) after OM revascularization. In 9 patients, color flow Doppler of LIMA could be demonstrated which showed diastolic predominant blood flow after LIMA to LAD grafting.

Conclusion:

Demonstration of CSBF was simple and monitoring the trend of CSBF values before and after each graft of LCA territory will guide to determine the adequacy of surgical revascularization.

Perioperative transesophageal echocardiography for aortic dissection

PURPOSE

Aortic dissection is an infrequent but serious condition that often requires immediate operative intervention. We explore recent developments in the classification of aortic dissection and perioperative transesophageal echocardiography that assist with quantifying the severity of disease and facilitate its management.

PRINCIPAL FINDINGS

We describe the pivotal role of echocardiography in relation to key surgical considerations such as cannulation, aortic root surgery, perfusion in the aortic arch vessels, stenting in hybrid arch repair, and timing of preventative surgery.

CONCLUSION

Developments in the classification of aortic dissection have improved our perspective and understanding of the key presenting features that affect mortality. Improvements in patient outcome may be achieved in part by appropriately timed echocardiography-guided surgery.

Acute type a aortic dissection: for further improvement of outcomes

Despite improved outcomes of acute type A aortic dissection (AAAD), many patients die at the moment of onset, and hospital mortality is still high. This article reviews the latest literature to seek the best possible way to optimize outcomes. Delayed diagnosis is caused by variation in or absence of typical symptoms, especially in patients with neurological symptoms. Misdiagnosis as acute myocardial infarction is another problem. Improved awareness by physicians is needed. On arrival, quick admission to the OR is desirable, followed by assessment with transesophageal echocardiography, and malperfusion already exists or newly develops in the OR; thus, timely diagnosis without delay with multimodality assessment is important. Although endovascular therapy is promising, careful introduction is mandatory so as not to cause complications. While various routes are used for the systemic perfusion, not a single route is perfect, and careful monitoring is essential. Surgical treatment on octogenarians is increasingly performed and produces better outcomes than conservative therapy. Complications are not rare, and consent from the family is essential. Prevention of AAAD is another important issue because more patients die at its onset than in the following treatment. In addition to hereditary diseases, including bicuspid aortic valve disease, the management of blood pressure is important.

Treatment strategy for acute type a aortic dissection complicated with organ ischemia

OBJECTIVE

We report our current treatment strategy for acute type A aortic dissection with organ ischemia as well as notable findings in our experience.

MATERIALS AND METHODS

Among 101 cases of acute type A aortic dissection, 25 had organ ischemia. Malperfusion was assessed at the aorta, proximal portion of the branch, organ parenchyma, and organ function by means of multiple modalities, including transesophageal echocardiography (TEE), near-infrared spectroscopy, and physical examinations. It was assessed every time the perfusion status was altered.

RESULTS

There were three operative deaths and one late hospital death. Uncertainty of symptoms and inadequate preoperative assessment in an emergent situation indicated the necessity of an overall check-up of organ ischemia in the operating room on a routine basis. Multi-modality assessment including TEE was helpful for this purpose. Two cases indicated that recovery of a true lumen could be inadequate despite true lumen perfusion including central cannulation. Thrombus in the false lumen appeared to be responsible.

CONCLUSIONS

To solve practical problems in treating acute type A dissection with organ ischemia, real-time information on organ perfusion is important for detecting the presence of malperfusion, making an appropriate strategy, and immediately assuring the efficacy of the means taken.

Recommendations for haemodynamic and neurological monitoring in repair of acute type a aortic dissection

During treatment of acute type A aortic dissection there is potential for both pre- and intra-operative malperfusion. There are a number of monitoring strategies that may allow for earlier detection of potentially catastrophic malperfusion (particularly cerebral malperfusion) phenomena available for the anaesthetist and surgeon. This review article sets out to discuss the benefits of the current standard monitoring techniques available as well as desirable/experimental techniques which may serve as adjuncts in the monitoring of these complex patients.

Assessment of internal thoracic artery patency with transesophageal echocardiography during coronary artery bypass graft surgery

OBJECTIVE

The purpose of this study was to evaluate intraoperative transesophageal echocardiography (TEE) for assessing patency of internal thoracic artery grafts.

DESIGN

A retrospective study.

SETTING

A university hospital.

PARTICIPANTS

Fifty-one consecutive patients who underwent coronary artery bypass graft (CABG) surgery using the left internal thoracic artery (LITA)-to-left coronary artery were examined postoperatively with coronary angiography (CAG).

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

The authors measured blood flow velocity using TEE after anastomosis of a LITA graft. Intraoperative TEE findings and routine CAG results were compared to evaluate the quality of TEE assessment. The LITA was detected in 45 of 51 patients (88%) intraoperatively with TEE. Peak and mean velocities and velocity time integral ratios were determined by dividing each diastolic value by its corresponding systolic value. The peak velocity ratio was 0.51 +/- 0.04 (range, 0.40-0.59) in the presence of stenosis and 1.14 +/- 0.10 (range, 0.58-3.87) in its absence (p = 0.0289), whereas mean velocity ratios were 0.62 +/- 0.05 (range, 0.45-0.72) and 1.27 +/- 0.10 (range, 0.66-4.08) (p = 0.0223), respectively, and velocity time integral ratios were 0.83 +/- 0.09 (range, 0.64-1.05) and 2.69 +/- 0.29 (range, 0.91-8.35) (p = 0.0224), respectively. The critical values for peak and mean velocities and velocity time integral ratios were 0.60, 0.73, and 1.06, respectively, whereas the sensitivity for each was 100% and the specificity was 92%, 94%, and 89%, respectively.

CONCLUSIONS

The authors concluded that the intraoperative assessment of LITA patency with TEE was a markedly useful and powerful tool for anesthesiologists during CABG surgery.

Neonatal Aortic Arch Hemodynamics and Perfusion During Cardiopulmonary Bypass

The objective of this study is to quantify the detailed three-dimensional (3D) pulsatile hemodynamics, mechanical loading, and perfusion characteristics of a patient-specific neonatal aortic arch during cardiopulmonary bypass (CPB). The 3D cardiac magnetic resonance imaging (MRI) reconstruction of a pediatric patient with a normal aortic arch is modified based on clinical literature to represent the neonatal morphology and flow conditions. The anatomical dimensions are verified from several literature sources. The CPB is created virtually in the computer by clamping the ascending aorta and inserting the computer-aided design model of the 10 Fr tapered generic cannula. Pulsatile (130 bpm) 3D blood flow velocities and pressures are computed using the commercial computational fluid dynamics (CFD) software. Second order accurate CFD settings are validated against particle image velocimetry experiments in an earlier study with a complex cardiovascular unsteady benchmark. CFD results in this manuscript are further compared with the in vivo physiological CPB pressure waveforms and demonstrated excellent agreement. Cannula inlet flow waveforms are measured from in vivo PC-MRI and 3 kg piglet neonatal animal model physiological experiments, distributed equally between the head-neck vessels and the descending aorta. Neonatal 3D aortic hemodynamics is also compared with that of the pediatric and fetal aortic stages. Detailed 3D flow fields, blood damage, wall shear stress (WSS), pressure drop, perfusion, and hemodynamic parameters describing the pulsatile energetics are calculated for both the physiological neonatal aorta and for the CPB aorta assembly. The primary flow structure is the high-speed canulla jet flow (∼3.0 m/s at peak flow), which eventually stagnates at the anterior aortic arch wall and low velocity flow in the cross-clamp pouch. These structures contributed to the reduced flow pulsatility (85%), increased WSS (50%), power loss (28%), and blood damage (288%), compared with normal neonatal aortic physiology. These drastic hemodynamic differences and associated intense biophysical loading of the pathological CPB configuration necessitate urgent bioengineering improvements—in hardware design, perfusion flow waveform, and configuration. This study serves to document the baseline condition, while the methodology presented can be utilized in preliminary CPB cannula design and in optimization studies reducing animal experiments. Coupled to a lumped-parameter model the 3D hemodynamic characteristics will aid the surgical decision making process of the perfusion strategies in complex congenital heart surgeries.

A novel acoustic window for trans-oesophageal echocardiography by using a saline-filled endotracheal balloon

BACKGROUND

The main structures anterior to the trachea are frequently poorly visualized by trans-oesophageal echocardiography (TEE) because of the tracheal air column. We studied a new acoustic window for TEE imaging of large vessels anterior to the trachea by using a saline-filled endotracheal balloon.

METHODS

Cardiac surgery patients were studied. After ventilation was discontinued at the beginning of cardiopulmonary bypass, a saline-filled latex balloon was inserted into the trachea through the tracheal tube. The structures anterior to the trachea were imaged with and without the endotracheal balloon. TEE images of the proximal aortic arch and innominate artery were classified into three grades according to the quality of images: 1, vessel not visible; 2, part of vessel wall visible; 3, entire vessel wall visible. Grade 3 was categorized as good visualization while grades 1 and 2 were categorized as inadequate. TEE images with and without balloon were compared using the Mann-Whitney U-test and Chi-square analysis. P<0.05 was considered statistically significant.

RESULTS

In 20 patients, 84% had good visualization of proximal aortic arch with presence of endotracheal balloon compared with 11% without (P<0.001). A total of 94% had good visualization of the proximal innominate artery with presence of endotracheal balloon compared with 0% without (P<0.001).

CONCLUSIONS

A new 'TEE trans-tracheal acoustic window' was established by usage of a saline-filled endotracheal balloon. This window partially eliminates the TEE blind zone and provides improved visualization of the proximal aortic arch and innominate artery.

Detection and monitoring of complications associated with femoral or axillary arterial cannulation for surgical repair of aortic dissection

OBJECTIVES

Femoral arterial perfusion can be associated with complications, and axillary arterial perfusion is not free from risk. The purpose of this study was to describe the incidence and complications of femoral versus axillary artery cannulation for surgical repair of aortic dissection and to devise a strategy for early detection and monitoring of complications using transesophageal echocardiography, near-infrared spectroscopy, and orbital Doppler.

DESIGN

Retrospective and observational.

SETTING

University hospital.

PARTICIPANTS

Seventy-five consecutive patients with aortic dissection who underwent aortic repair between 1995 and 2004.

INTERVENTIONS

Aortic surgery.

MEASUREMENTS AND MAIN RESULTS

Among the 44 cases with femoral arterial perfusion, sudden onset of hypotension occurred in 3 cases but was immediately treated based on the TEE diagnosis (collapse of true lumen in the descending aorta). In another case, myocardial ischemia occurred because of occlusion of the coronary artery. These four cases comprised 57.1% of 7 patients with type III dissection with retrograde extension in whom femoral arterial perfusion was used. However, malperfusion was not encountered in 3 cases of the same type of dissection but with axillary arterial perfusion. Axillary artery perfusion (29 cases) led to malperfusion of the right frontal lobe and coronary artery in 1 case each.

CONCLUSIONS

Flexible management guided by real-time information is essential. Upon initiating femoral arterial perfusion, malperfusion should first be checked for in the descending aorta and then in the coronary and visceral arteries, especially in cases of type III dissection with retrograde extension. Attention should be paid to cerebral and coronary malperfusion when initiating axillary arterial perfusion.

Is it safe to initiate selective cerebral perfusion with normothermia?

OBJECTIVE

Preceding selective cerebral perfusion (P-SCP) is a method whereby SCP and systemic perfusion start simultaneously, and the arch vessels are clamped. Cerebral circulation is isolated from systemic circulation to avoid cerebral embolization due to detachment of atherosclerotic material from the aorta, caused by the "sandblasting" effect of high-velocity jets of blood exiting the aortic cannula. However, neither the safety of SCP at normothermia nor the influence of extended SCP time has been sufficiently clarified. To clarify the safety of P-SCP, the comparison study of P-SCP and conventional SCP (C-SCP) was performed retrospectively.

METHODS

Fifty-seven patients (C-SCP group: 29 patients; P-SCP: 28 patients) underwent surgery between 1992 and 2002.

RESULTS

Nine (15.8%) in-hospital death occurred; 4 in the C-SCP group (13.8%) and 5 in the P-SCP group (17.9%) (NS). The SCP time was 136.6 +/- 68.5 minutes in the C-SCP group and 195.8 +/- 30.7 minutes in the P-SCP group (p < 0.05). One patient in each group exhibited postoperative neurological dysfunction.

CONCLUSION

It may be little dangerous to initiate the SCP with normothermia. P-SCP may be useful in cases in which there is pedunculated atherosclerotic material, or mural thrombus in the ascending and arch aorta.

Thrombosed arch vessels after cardiac arrest because of pulmonary embolism

An unusual case of thrombus formation in the arch vessels after cardiac arrest because of pulmonary embolism is reported. A 67-year-old woman developed pulmonary embolism that soon led to cardiac arrest. Although percutaneous cardiopulmonary support was started, the blood pressure of her upper extremity was below 20 mm Hg and blood gas analysis showed marked metabolic and respiratory acidosis. Transesophageal echocardiography revealed thrombus in the right pulmonary artery, thrombus with floppy movement in the aortic arch, and 3 arch branch arteries filled with thrombus with little blood flow around it. After thrombolytic therapy, the thrombi gradually shrunk and perfusion in the upper extremities improved. The patient was successfully weaned from percutaneous cardiopulmonary support and was discharged alive. Thrombus formation can occur in the arch branch arteries after cardiac arrest, causing unusual laboratory data. Transesophageal echocardiography is useful for obtaining real-time information in the cardiovascular system at bedside in such a critically ill patient.

Left Internal Thoracic Artery Graft Assessed By Means of Intraoperative Transesophageal Echocardiography

BACKGROUND

We report a method of intraoperative assessment of left internal thoracic artery (LITA) graft with transesophageal echocardiography regarding patency, stenosis, and presence of remnant branch artery.

METHODS

In 52 consecutive coronary artery bypass grafting surgery patients, blood flow velocity was measured at the origin of the LITA after coronary artery bypass grafting by means of transesophageal echocardiography. The flow pattern and velocity change at temporary clamping of the graft was examined and was compared with the postoperative angiographic findings.

RESULTS

The LITA was visualized in 47 of 52 cases (90.4%). The LITA flow was diastolic dominant, systolic dominant, or equivalent in 41, 3, and 3 cases, respectively. The anastomosis was stenotic in 2 of 6 cases of the latter two groups, but in none of the 41 cases with diastolic dominant flow (p = 0.0139). The branch artery was present in 4 of 6 cases of the latter two groups, but in only 2 of 41 cases with diastolic dominant flow (p = 0.0012). Remnant branch artery was found in all three cases with systolic dominant flow. The LITA flow was instantaneously reduced at clamping and recovered at declamping in every case with graft occlusion but one. The ratio of velocity change at clamping was less than 0.50 in all 41 cases without remnant branch, whereas it was more than 0.50 in 5 of 6 cases with a branch (p < 0.0001).

CONCLUSIONS

The transesophageal echocardiographic assessment with the clamp test is feasible intraoperatively in the majority of patients, enabling us to assess LITA graft patency, stenosis, or presence of a remnant branch.

Three-dimensional transesophageal echocardiographic demonstration of innominate artery dissection

We describe an adult patient with type I aortic dissection in whom it was feasible to demonstrate the extension of the dissection into the innominate artery using color Doppler three-dimensional transesophageal echocardiography.

Transesophageal echocardiographic identification of bilateral vertebral artery ostial stenosis

We describe the usefulness of transesophageal echocardiography in correctly diagnosing severe ostial stenosis of both the left and right vertebral arteries in an adult patient. Although transesophageal echocardiography has been previously used to identify left vertebral artery stenosis, to our knowledge this study represents the first demonstration of its usefulness in detecting bilateral vertebral artery ostial stenosis.