Today’s didactic lecture on epiaortic ultrasonography was given by one of my wonderful cardiothoracic anesthesiology attendings – Dr. Jeff Swanson. As part of traditional cardiac surgeries, the aorta can be extensively manipulated – especially when performing arterial cannulation and applying the aortic cross-clamp. This can dislodge plaques systemically leading to strokes and other embolic phenomena. Epiaortic ultrasound (EAS) involves examining the aorta from the aortic root to to the aortic arch with ultrasound looking for dissections, atheromas, and other signs of pathology which may change operative management. In other words, you don’t want to be cannulating the aorta directly into an intimal plaque.
Roughly 45% of patients with an ascending plaque greater than 5 millimeters or a mobile component will have a stroke. Within the coronary artery bypass graft (CABG) cohort, there’s a 60% incidence of patients having an ascending atheroma greater than 3 millimeters.
EAS has been shown to be more sensitive than transesophageal echocardiography (TEE) and manual palpation of the aorta in detecting disease. This is, in part, due to TEE’s blind spot (the distal ascending aorta) being a common place for cannulation.
So how can EAS change management? Well, if we find something, we will likely change our cannulation strategy, try to do the surgery without a cross-clamp (ie, off pump CABG, hypothermic fibrillatory arrest, systemic potassium, deep hypothermic circulatory arrest to replace the diseased aortic segment, placing the vein grafts directly off the left internal mammary artery, etc.)
To perform the exam. we usually use a high frequency ultrasound probe (better resolution) in tandem with filling the mediastinal cavity with sterile saline as an acoustic medium. There are five views we try to obtain:
- Short axis
- Sinotubular junction to proximal interaction of the right pulmonary artery (RPA)
- Adjacent to the RPA
- Distal intersection of the RPA and innominate artery
- Long axis
- Ascending aorta
- Proximal aortic arch
When the surgeon is performing the EAS, I’m looking for plaque thickness, location, and any mobile components. Here’s an atheroma grading scale which I include in my report:
- Grade I: normal to mild intimal thickening
- Grade II: < 3 mm
- Grade III: 3 – 5 mm
- Grade IV: > 5 mm
- Grade V: any mobile component, regardless of size
So why do some places not routinely perform EAS? Is it the cost? Lack of equipment? Technical skills needed? Potential sterility issues? Finding pathology that could lead to a bigger operation that may cause more harm than if nothing was done? Honestly, I think at most academic centers, we should be performing EAS in every case. Cardiac anesthesiologists are trained extensively in ultrasound, and we are more than capable of interpreting the images in real-time. If this could even slightly decrease the risk of an embolic stoke post-operatively, I’m all for spending the extra two minutes to do it! 🙂
As always, drop me a comment below with questions! 🙂