Atheromatous plaque in the distal aortic arch creating the potential for cerebral embolism during cardiopulmonary bypass

Numerical Investigation of Blood Flow Characteristics through Cannulated Aorta

Cannulation of the aorta is done in order to provide oxygenation and circulatory function through the use of the heart lung machine during cardio-pulmonary bypass (CPB). The nature of the blood flow through the aorta and its ramifications during CPB is mostly linear as compared to the physiological flow, which is pulsatile in nature. This leads to the development of multiple morbidities caused by the development of emboli and atheromas. Perioperative postoperative care is necessitated by these conditions. As such the understanding of the blood flow characteristics is necessitated in order to effectively prevent the formation of emboli and to prevent the "Sandblasting" effect. The authors in this work seek to investigate the nature of blood flow through the aorta under such circumstances. The results obtained show the nature of blood flow in the cannulated aorta as well as the optimum angle of placement of the cannula with respect to the aortic wall.

Aortic Arch Atheroma: Stroke Reduction in Cardiac Surgical Patients

Cardiac surgery is increasingly performed on elderly patients with extensive coronary artery abnormalities who have impaired left ventricular function, decreased physiologic reserve, and multiple comorbid conditions. Considerable numbers of these patients develop perioperative neurologic complications ranging from subtle cognitive dysfunction to more evident postoperative confusion, delirium, and, less commonly, clinically apparent stroke. Magnetic resonance imaging studies have elucidated that a considerable number of patients have new ischemic brain infarcts, particularly after conventional coronary artery bypass graft surgery. Mechanisms of cerebral injury during and after cardiac surgery are discussed. Intraoperative transesophageal echocardiography and epiaortic scanning for detection of atheromatous disease of the proximal thoracic aorta is paramount in identifying patients at high risk from neurologic injury. It is important to recognize that our efforts to minimize neurologic injury should not be limited to the intraoperative period. Particular efforts should be directed to temperature management, glycemia control, and pharmacologic neuroprotection extending into the postoperative period. Preoperative magnetic resonance angiography may be of value for screening patients with significant atheroma of the proximal thoracic aorta. It is likely that for patients with no significant atheromatous disease, conventional coronary artery revascularization is the most effective long-term strategy, whereas patients with atheromatous thoracic aorta may be better managed with beating heart surgery, hybrid techniques, or medical therapy alone. Patient stratification based on the aortic atheromatic burden should be addressed in future trials designed to tailor treatment strategies to improve long-term outcomes of coronary heart disease and reduce the risks of perioperative neurologic injury.

Improved hydrodynamics of a new aortic cannula with a novel tip design

Background: Reduction of atheroembolic complications during cardiopulmonary bypass remains a major challenge in cardiac surgery. New cannula tip designs may help to attenuate this problem by improved hydrodynamics.

Methods: Pressure gradients and back pressures of a new aortic cannula tip design were measured and compared with the Medos X-Flow, Sarns Soft-Flow and Argyle THI cannulae at various flow rates in a mock circulation followed by flow visualization.

Results: Pressure gradients were the lowest for the new cannula. Back pressures of the new cannula were up to 84% lower than for the Argyle cannula. The back pressure profile and flow visualization of the new cannula showed broad centric flow dispersion with a transcannula increase of flow area from 38 mm2 to 139 mm2.

Conclusions: The new design of an aortic cannula tip provides improved hydrodynamics, with low pressure gradients, low back pressures and a uniform central dispersion of flow, reducing the sandblasting effect.

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.

Carotid atherosclerosis as a risk factor for complex aortic lesions in patients with ischemic cerebrovascular disease

Aortic arch atherosclerotic lesions can cause ischemic cerebrovascular disease (ICVD). The association between carotid and aortic atherosclerosis was examined, and it was investigated whether noninvasive carotid evaluation aids in the identification of aortic lesions as potential ICVD risk. The subjects comprised 147 patients with ICVD who had undergone carotid ultrasonography and transesophageal echocardiography. Carotid and aortic arch atherosclerosis was evaluated by measuring the maximum intima - media thickness (IMT), with aortic IMT of at least 4 mm, mobile plaques and/or ulcers defined as complex aortic lesions with potential ICVD risk. Carotid IMT was linearly associated with aortic IMT (r=0.53, p<0.001), and the association was independent of traditional cardiovascular risk factors (beta =0.36, p<0.001). Also, each 1 SD greater carotid IMT was associated with 4.2-fold (95% confidence interval: 2.5-7.0) higher likelihood of complex aortic lesions, with the likelihood little modified when controlling for cardiovascular risk factors. In particular, complex aortic lesions were found in 78% of patients with the highest carotid IMT tertile, compared with 14% of those with the lowest tertile (p<0.05). Based on these findings, carotid atherosclerosis is associated with aortic atherosclerosis, representing a risk factor for aortic lesions that are a potential ICVD risk.

Mallory - weiss tear complicating intraoperative transesophageal echocardiography

A Mallory - Weiss tear occurred as a complication of intraoperative transesophageal echocardiography carried out in a 62-year-old man who underwent coronary artery bypass grafting. Left ventricular function was monitored in the transgastric short-axis view. Postoperative esophagogastroscopy revealed a Mallory - Weiss tear at the gastroesophageal junction and erosions in the cardia, presumably secondary to contact pressure by the echoprobe and ultrasonic thermal injury. When not actively imaging, the echoprobe should be left free in the esophagus with the acoustic power off.