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The Speed of Sound

The Speed of Sound

Small LV Shows Promise as an Indicator of PE during Pulse Checks in Cardiac Arrest

Butts, Christine MD

Emergency Medicine News: May 2020 - Volume 42 - Issue 5 - p 27
doi: 10.1097/01.EEM.0000666348.03522.b8
    pulse check, cardiac arrest, ultrasound. Parasternal long axis image. The LV myocardium (LV) appears thickened due to the small size of the chamber (C). The RV does not appear obviously enlarged in this view. Also in this image are the aortic valve and left atrium (LA). Watch a video of this that was taken just after initial ROSC at http://bit.ly/VideosSound. Note in the video that the contraction overall appears disorganized and irregular.
    Figure
    Figure

    A lot has been written about how to integrate ultrasound into the management of cardiac arrest. The lack of organized cardiac activity in patients with PEA correlated with very low rates of survival in the REASON trial. (Resuscitation. 2016;109:33.) Getting good images while limiting interruptions in CPR, however, is a challenge. Interpreting these images can be even more of a challenge, especially when it comes to the consideration of pulmonary embolism.

    A young woman who was having difficulty speaking and was clearly in distress presented to my ED recently. She was diaphoretic and vomiting. That morning in particular the ED was more chaotic than usual, and after examining her quickly, I was called away. Not long after, I heard the frantic calls of her nurse, stating that she wasn't breathing. CPR was in progress when I returned to her bedside. As we went through our PEA algorithm, we stopped for the first pulse check, where this image was obtained. The first thing that jumped out at us was the thickness of the left ventricle myocardium and the small size of the chamber. Several things were considered at this point, including hypovolemia and structural heart disease, and we administered volume to the patient.

    An enlarged RV has been proposed as an indicator of pulmonary embolism, with the caveat that the RV will naturally dilate in many cases of cardiac arrest. The RV enlarges as forward flow ceases. This has been demonstrated in multiple porcine studies. Other signs of massive PE, such as McConnell's sign or septal bowing, are best seen in other views, such as the apical four-chamber. These views can be next to impossible to obtain in a 10-second pulse check. Seeing these signs in a disorganized or irregularly beating heart can also be tough.

    At the next pulse check, the ultrasound remained unchanged, and we began to consider massive PE as a possible cause. We decided to give tPA, and we continued the code. The left ventricular chamber began to show more space within 10 minutes or so, and we got a pulse back within 20 minutes. Once she had a stable blood pressure, we took her to CT, which demonstrated an extensive PE throughout her lungs.

    What lessons did I learn? I had seen dilated and poorly functioning right ventricles in many cases of cardiac arrest, but I had never seen a case where the left ventricle showed such obvious signs of underfilling. When there is little blood return to the LV (either from lack of overall volume or from lack of forward flow from the RV), the chamber will appear small and will often appear to be contracting vigorously. Given the limitations inherent in scanning during pulse checks, seeing a small LV should prompt consideration of PE as a cause and thrombolysis as a treatment.

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    Dr. Buttsis the director of the division of emergency ultrasound and a clinical assistant professor of emergency medicine at Louisiana State University at New Orleans. Follow her on Twitter @EMNSpeedofSound, and read her past columns athttp://bit.ly/EMN-SpeedofSound.

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