Veterinary TOE Protocol

Introduction

Transthoracic echocardiography (TTE) in the hands of a skilled operator can provide stunning views of the heart in canines, which means that transoesophageal echocardiography (TOE) rarely provides any additional information that would change a diagnosis or course of treatment, making its utility within veterinary cardiology extremely limited. One very important application for TOE, however, is in the intraoperative setting.

The Royal Vet College (RVC) is one of only three centres worldwide which regularly performs mitral valve repair on dogs. Imaging of the mitral valve is one of the greatest strengths of TOE, being easily imaged from a number of planes from the transducer’s position within the oesophagus. Improvements in 3D imaging have expanded our knowledge further still, and the whole of the mitral valve and annulus can now be acquired and displayed in real time.

Above: Intraoperative 3D dataset demonstrating anterior leaflet prolapse in a human.

 

For TOE to deliver incremental benefit to the surgical team it is important to follow a protocol designed to methodically collect all of the relevant information. Much of the published literature on veterinary transosphageal echocardiography currently focuses on interventional procedures, particularly patent ductus arteriosus (PDA) closure.1,2 It is also important to communicate these findings effectively to the surgeons, using their terminology. The surgical team, for example, refer to “septal” and “mural” leaflets, while the cardiologists often refer to “anterior” and “posterior”3.

 

Knowledge of image optimisation basics such as depth and focal zone adjustment will be assumed.

 

Pre-operative imaging protocol (Anne to amend/approve):

 

4 chamber view – 0° 

[One of Anne’s images to illustrate this view]
  • With the angle set to 0°, gently advance the unlocked transducer until all four chambers of the heart are in view. You may need to apply slight flexion on the probe to lengthen out the left ventricle.
  • Turn on Colour Doppler, adjusting the box so that it covers the entire mitral valve and left atrium.
  • Zoom on the mitral valve, with and without Colour Doppler. You may wish to take a PISA from this view.
  • Take a pulsed and continuous wave Doppler trace of the mitral inflow, for later comparison with the post-operative trace.

 

2 chamber view – 90° 

 

5 chamber view 2D

5 chamber view colour over the mitral and aortic valves

4 chamber view, elongating the ventricle as much as possible, assessing systolic function. Take a mitral inflow at this view at the tips of the mitral valve.

Zoom over valve at 4 chamber level. Without and with colour. PISA? Make separate section below on performing a PISA + CW wave Doppler. Number of beats, scale, baseline.

2 chamber view. With and without colour. Zoom over valve. Nilesh’s sweeping thing – Nilesh to describe. Can we use some of the video clips from the dog last week to illustrate?

3 chamber view. With and without colour. Zoom over valve.

3D.

Transgastric short axis at papillary muscle level for LV function, at valve level to assess MR.

Transgastric long axis.

Withdraw; if time, colour over the tricuspid valve. CW Doppler.

 

Post-operative

Deairing

 

 

References

  1. Doocy, K., Nelson, D., Saunders, A. (2017). Real-time 3D transesophageal echocardiography-guided closure of a complicated patent ductus arteriosus in a dog. Journal of Veterinary Cardiology : the Official Journal of the European Society of Veterinary Cardiology, 19(3):287-292.
  2. Porciello, F., Caivano, D., Giorgi, M. et al. (2014). Transesophageal Echocardiography as the Sole Guidance for Occlusion of Patent Ductus Arteriosus using a Canine Ductal Occluder in Dogs. Journal of Veterinary Internal Medicine.
  3. Professor Daniel Brockman, personal communication. 18/05/2019.