Ultrasound Case of the Month
Case
This is a 56-year old female, with a PMH of breast cancer, who presented to the Emergency Department with shortness of breath and chest pain for one day. Her symptoms are not exertional or positional, and the pain is not pleuritic. There is no personal or family history of coronary artery disease. She denies having a history of similar symptoms in the past. She denies fevers, chills, abdominal pain, nausea, vomiting, or lower extremity edema.
Diagnosis
Saddle pulmonary embolism with evidence of right heart strain and left lower extremity deep vein thrombosis.
Video
Discussion
The above images demonstrate evidence of right heart strain from a saddle pulmonary embolism. A parasternal long axis view was obtained, and we are able to see enlargement of the right ventricle. In the parasternal long, the probe marker is pointed to the patients right shoulder, and the RV is the ventricle on the top of the screen, as it is the most anterior chamber in the heart and will be closest to the probe. In the parasternal long view, the RV, aortic outflow tract and the LA should all be approximately equal in size. In a patient with clinical suspicion of PE, a large RV is concerning. In the apical 4 chamber view, the RV/LV ratio should be about 0.6:1 measured across the base of the chambers. More simply, the RV should be small than the LV. If it is equal in size or larger, this represents RV enlargement.
Despite the fact that this patient did not report any lower extremity swelling, an ultrasound of the lower extremities was performed in order to find the potential source of the patient’s PE. Starting proximally in the inguinal region, locate the femoral vein at the greater saphenous junction. You should compress above at and below this junction, and then continue to compress in 1cm increments moving distally as far as you can, but at least until you see the split of the femoral vein and the deep femoral vein.
In the above ultrasound images, the left popliteal vein was non-compressible. We were able to visualize clot within the lumen of the vessel, confirming our diagnosis of a left lower extremity DVT when we were unable to compress the vessel.
While focused bedside echocardiography is less sensitive for peripheral pulmonary embolism, its sensitivity for centrally located PEs or PEs which result in hemodynamic instability is very high. Roughly 50% of patients with a PE will also have a DVT on US. Diagnosing a DVT early on at the bedside in a patient being evaluated for PE can enable earlier anticoagulation.
Key findings suggestive of PE on echo include
· McConnell’s sign: RV wall hypokinesis is highly specific for PE (in comparison to other causes of RV strain such as pulmonary hypertension). This is best seen on the apical four chamber view. There is akinesia of the free wall but normal motion at the apex.
· RV dilation: The ratio of RV to LV diameter is 0.6:1 measured at the base in the apical four chamber view (down close to the valves). Instead of taking a measurement, just eyeball this and make sure the RV doesn’t look bigger than the LV
· D-sign: This finding is seen in the parasternal short view when the LV takes on the shape of the letter “D”. In cases of right heart strain, the pressures in the RV are elevated which causes the interventricular septum to flatten out appearing like a “D”. In the normal PSS view the LV looks like a doughnut and the RV looks like a crescent.
Faculty Reviewer: Dr. Kristin Dwyer
Additional resources
http://rebelem.com/diagnosis-right-ventricular-strain-transthoracic-echocardiography/
http://blog.5minsono.com/rhs_1/
https://www.ncbi.nlm.nih.gov/pubmed/29174452