epiaortic echocardiography in cardiac surgery
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epiaortic echocardiography in cardiac surgery
- 1. EPIAORTIC ECHOCARDIOGRAPHY Presenter : Dr Rajesh Munigial DM First Year Trainee Dept Of Cardiac Anaesthesiology JNMC , Belgaum
- 2. Topics Of Discussion Introduction Indications stroke Probes and technique Imaging planes Atherosclerotic plaque grading
- 3. INTRODUCTION Epiaortic ultrasound (EAU) is an imaging modality whereby a handheld transducer is placed directly upon a surgically exposed aorta EAU provides high-quality sonographic data depicting aortic anatomy and pathology Epicardial ultrasound was used in the 1980s at The Mount Sinai Medical Center and at Columbia University College of Physicians and Surgeons
- 4. Epiaortic ultrasound is a useful tool to assess diseased aorta, especially during its manipulation or instrumentation like aortic clamp placement and removal, insertion of the aortic cannula, the antegrade cardioplegia vent, the proximal anastomosis of coronary grafts, aortotomy It can identify diseased aortic segments containing atherosclerotic plaque, calcification, or thrombus that are at high risk for distal embolization It also helps in risk stratification for patients at risk of complications from distal embolization
- 5. Perioperative stroke is a major cause of morbidity and mortality in the cardiac surgery population Incidence : Off-pump CABG: 1.9% On pump CABG:3.8% Aortic valve surgery: 4.8% Mitral valve surgery: 8.8% Combined CABG and valve surgery:7.4%
- 6. Risk Factors For stroke in cardiac surgery Include : Advanced age Female gender Proximal aortic atherosclerosis Calcified aorta History of cerebrovascular disease Peripheral vascular disease Diabetes Hypertension Prior cardiac surgery Preoperative infection (including endocarditis), Urgent surgery Greater than 2-hour cardiopulmonary bypass (CPB) time, Intraoperative hemofiltration, and transfusion The presence of aortic plaque correlates well with postoperative stroke incidence. The more extensive and complex the plaque burden, the higher the risk of postoperative stroke
- 7. POSSIBLE MECHANISM OF STROKE : Arterial to arterial embolization of plaque or thrombus Embolization from intracardiac sources Paradoxical embolization from venous to arterial (through intra or extra-cardiac shunts ) Ischemic injury due to arterial thrombosis Air entrainment Cerebral hemorrhage Decreased cerebral venous drainage Prolonged seizure activity
- 8. Manipulation Of Aorta SANDBLASTING EFFECT
- 9. Intraoperative-3 methods of detection of plaque and calcificataion Surgical palpation of aorta LEAST SENSITIVE Transesophageal echocardiography EPIAORTIC ultrasound-MOST SENSITIVE
- 10. INDICATIONS OF EAU Increased risk of embolic stroke History of cerebrovascular disease Peripheral vascular disease Other imaging modalities demonstrating atherosclerosis It is recommende d to use in patients with
- 11. WHY EPIAORTIC ULTRASOUND ?? Easy to use Minimal time to perform Negligible complication rate High accuracy Provides direct and dynamic visualisation during surgery Surgical palpation is subjective
- 12. EAU SUPERIOR TO TEE Most surgical manipulation: in the region of ascending aorta (BLIND SPOT FOR TEE) (where the trachea and left mainstem bronchus interpose between the esophagus and aorta, causing disruption of ultrasound transmission) TEE unable to image the greatest area of interest of ascending aorta EAU is closer to the area of interest Enabling high transducer frequencies high quality images with fewer artifacts
- 13. How EAU alters surgical management Off pump CABG (as opposed to on pump ) No touch techniques Alteration in site of aortic instrumentation/manipulation Aortic endarterectomy/ aortic arch replacement
- 14. DISADVANTAGES Of EAU Need for sterility---potential for surgical field contamination Potential to cause arrythmias
- 16. PROBES AND TECHNIQUE Handheld transducer , sheathed in sterile covering , placed directly on ascending aorta with or without standoff Standoff refers to the distance between the probe and the object of interest Because of the wedge shape of the image, if the transducer is placed directly on the aorta, the anterior aortic wall (near field) will not be completely imaged; only a small section will be displayed while the rest will be outside the sector. To capture the near field in its entirety, the transducer is held at some distance away from the aorta (the standoff) This requires addition of a medium that conducts ultrasound waves-gel
- 17. Three types of probes available for imaging Linear probe rectangular image Phased array wedge shaped image Matrix array wedge shaped image
- 18. Linear array transducer Produces rectangular image Scans both anterior wall and posterior wall No need of standoff Larger foot print , larger surface area , difficult for probe manipulation Tunnelled view : entire left to right dimnesions not covered
- 19. Phased array transducer Ideally >7MHZ Small footprint Simultaneous left and right walls imaging Kept at a distance of 1cm away from aorta Need for standoff
- 20. Matrix array transducer Real time 3d images in form of pyramidal volume Simultaneous 2d images in 2 orthogonal planes Eliminates physical need to turn the the probe for SAX and LAX Improved spatial orientation Accurate volume estimation
- 21. IMAGING PLANES Most recent guidelines recommend 5 standard views to complete a comprehensive EAU examination from the sinotubular junction to the innominate artery and aortic arch. The ascending aorta is divided into proximal, mid-, and distal segments. Each segment of the ascending aorta can be described as having four walls: anterior (near field), posterior (far field), right, and left This leaves 12 total wall segments of the ascending aorta to characterize.
- 22. Proximal ascending aorta: beginning of STJ , where it is common to see aortic valve and right pulmonary artery Mid ascending aorta: Defined by the part of the aorta that is juxtaposed with the right pulmonary artery Distal ascending aorta: from the distal right pulmonary artery to the innominate artery. More distally : proximal aortic arch
- 23. Short Axis Examination The ultrasound probe is positioned on the ascending aorta as proximally as possible, with the orientation marker directed toward the patients left shoulder. A significant difference between the antero-posterior and medial-lateral dimensions is an indicator of an orthogonal view. Measurements made in such a plane will be inaccurate. After identifying the proximal ascending aorta, where it is frequently possible to image the aortic valve, slowly advancing the probe distally in a cephalad direction along the aorta permits visualization of the mid ascending aorta, and finally the distal ascending aorta toward the aortic arch at the origin of the innominate artery. During the transit toward the innominate artery, it is necessary to rotate the probe in a clockwise fashion to maintain the SAX orientation. Advancing the probe slightly further permits examination of the proximal aortic arch
- 26. Epiaortic ultrasonographic image of the normal ascending (Asc) aorta in short-axis view obtained with phased-array transducer. Aortic wall areas that can be imaged in short axis include anterior (A), posterior (P), right lateral (RL), and left lateral (LL) walls. PA, Pulmonary artery; SVC, superior vena cava
- 27. LONG AXIS EXAMINATION The LAX orientation is achieved by rotating the probe 90 degrees from the SAX orientation . Proximally, the sinus of Valsalva, sinotubular junction, and aortic valve can be visualized The probe is then advanced in cephalad direction The aortic arch, with origins of the left common carotid and left subclavian artery, should be located as a final part of the examination
- 28. Epiaortic ultrasonographic image and accompanying diagram of normal ascending (Asc) aorta in long-axis view obtained with phased-array transducer. Aortic wall areas that can be imaged include anterior (A) and posterior (P) walls in each of proximal, mid, and distal segments. RPA, Right pulmonary artery
- 32. Doppler interrogation of ascending aorta and aortic valve Use of EAU for Doppler interrogation of the aortic valve is limited. In some cases, color Doppler may be useful to diagnose the presence or absence of dissections and hematomas. EAU has been used to guide aortic cannulation of patients with type A aortic dissections. In these cases, use of 2D EAU and color Doppler EAU helped identify true and false channels for successful arterial cannulation of the true lumen
- 33. It is difficult to obtain Doppler beam orientation parallel to aortic flow in many parts of the ascending aorta because more frequently than not, the orientation of the ultrasound probe to flow in the aorta will be perpendicular One must be careful to recognize that there is an element of error when the Doppler beam is not parallel to the direction of flow. The angle between the Doppler beam and the direction of flow within the aorta is called the insonation angle. It should be less than 30 degrees to maintain an error of less than 15%.
- 35. SUMMARY OF RECOMMENDATIONS 5 views for evaluation : 3 SAX(proximal,mid and doistal ascending aorta) , 1 LAX of ascending aorta and 1 LAX of proximal aortic arch 3 measurements to be recorded for each of 3 ascending aorta sax view and aortic arch 1. Maximal plaque height/thickness 2. location of the maximal plaque within the ascending aorta; and 3. presence of mobile components The maximal aortic diameter in SAX may also be recorded
- 36. Verbal report to be provided to surgical team before aortic manipulation written report documenting examination findings should be available in the patients chart within 24 hours of completion of the examination Trainees in perioperative echocardiography should participate in the evaluation of 25 EAU examinations, at least 5 of which must be personally directed by the individual under the direct supervision of an echocardiographer with advanced level training
- 44. REFERENCES 1. Glas KE, Swaminathan M, Reeves ST, Shanewise JS, Rubenson D, Smith PK, Mathew JP, Shernan SK; Council for Intraoperative Echocardiography of the American Society of Echocardiography; Society of Cardiovascular Anesthesiologists. Guidelines for the performance of a comprehensive intraoperative epiaortic ultrasonographic examination: recommendations of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists; endorsed by the Society of Thoracic Surgeons. J Am Soc Echocardiogr. 2007 Nov;20(11):1227-35. doi: 10.1016/j.echo.2007.09.001. PMID: 17983940. 2. Kaplans cardiac anaesthesia perioperative and critical care
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