In emergency situations, particularly when treating pets in shock, quickly assessing left ventricular (LV) function is crucial for determining the best course of action and accurately diagnosing the type of shock (cardiogenic vs. hypovolemic vs. distributive vs. obstructive). A fast, reliable method that emergency veterinarians can use is Point-of-Care Ultrasound (POCUS). This “eyeball” approach allows us to evaluate LV contractility efficiently.
In this post, I’ll walk you through the three primary components of LV function assessment using POCUS, which can be easily applied by non-cardiologists. By mastering these techniques, you’ll be able to identify whether your patient’s LV function is hyperdynamic, normal, or depressed in just a few moments.
1. Endocardial Excursion: Measuring Heart Wall Movement
The first aspect of LV function to evaluate is the endocardial excursion, which refers to the movement of the endocardium (the inner lining of the heart) toward the center of the heart during contraction.
In a healthy heart, each portion of the endocardium moves significantly during systole (the heart’s contraction phase). This motion indicates that the heart is contracting effectively. On ultrasound, you should observe the heart walls moving inward toward the center. A lack of this movement suggests impaired contractility.
2. Myocardial Thickening: The LV Wall’s Vital Function
Next, check for myocardial thickening. The LV wall should visibly thicken during systole if the heart is functioning normally. This thickening is a key indicator that the LV is working as it should.
In cases where the walls don’t thicken appropriately, it may be a sign that the LV function is compromised. Lack of thickening typically signals reduced cardiac output, which is critical to identify in patients presenting with shock.
3. Septal Motion of the Anterior Mitral Valve Leaflet
The third component of your assessment focuses on the anterior mitral valve leaflet and its proximity to the interventricular septum during diastole (the heart’s relaxation phase).
In a healthy heart, the anterior leaflet should move closer to the septum because a lot of blood is flowing through the mitral valve during diastole. If the leaflet comes close to the septum, it’s a sign of good LV function. However, if there is a significant gap between the leaflet and the septum, the LV function is likely decreased.
Case Study: Normal LV Function in a Dog
Let’s look at a real-world example. In this case, a right parasternal long and short-axis views were obtained from a healthy dog. The LV shows good endocardial excursion, myocardial thickening, and the anterior mitral leaflet almost touches the interventricular septum at the end of diastole. Based on this assessment, we can confidently say the dog’s LV function is normal.
In a complementary right parasternal short-axis view (commonly called the “mushroom view”), we can appreciate two papillary muscles. This image shows a good-quality endocardial excursion and LV wall thickening during systole, confirming normal LV function.
Avoiding Common Pitfalls: The Cylinder Tangent Effect
When assessing LV function using ultrasound, it’s crucial to avoid oblique views, as they can distort the image and lead to misinterpretation. This distortion, known as the cylinder tangent effect, occurs when the ultrasound beam enters the heart or blood vessel at a tangent, making the walls appear thicker and the lumen smaller than they are.
For example, if the beam is directed incorrectly in a patient with impaired LV function, the oblique view could mislead you into thinking the LV is functioning normally or even hyperdynamically.
To avoid this, always aim to acquire classic “mushroom views” in the right parasternal short-axis plane. Additionally, when imaging blood vessels like the caudal vena cava, ensure that the ultrasound beam passes through the center of the vessel. Use both short- and long-axis views to get a clearer picture and prevent underestimating the vessel’s diameter.
Hyperdynamic LV: What It Means and When to Look for It
A hyperdynamic LV is characterized by a small LV lumen during systole and hyperkinetic contractions, often resulting in the papillary muscles touching or “kissing” during contraction. While this is commonly seen in cases of hypovolemic shock, it’s important to note that hyperdynamic LV doesn’t always mean volume depletion.
This condition can also occur in pets suffering from distributive shock due to reduced afterload (the pressure the heart must work against to pump blood) and increased LV contractility from elevated sympathetic tone. Essentially, the LV appears hyperdynamic because its workload is reduced, not necessarily because of hypovolemia.
Hypodynamic LV: Identifying a Weak Heart
On the other end of the spectrum is the hypodynamic LV, where the heart exhibits minimal endocardial excursion, poor wall thickening, and barely any movement of the anterior mitral leaflet. The result is a significant distance between the leaflet and the septum at the end of diastole, indicating severely depressed LV function.
In one case, a right parasternal long-axis view revealed minimal LV movement and little myocardial thickening, confirming hypodynamic function.
Conclusion: A Simple but Effective Tool for ER Vets
By mastering these three POCUS techniques—endocardial excursion, myocardial thickening, and septal motion of the anterior mitral valve leaflet—you can quickly and accurately assess left ventricular function in patients presenting with shock.
While these signs may seem subtle at first, with practice, they will become valuable tools in your emergency care arsenal.
Further Learning
Want to dive deeper into acid-base analysis or potassium supplementation in critically ill dogs and cats? Check out our free workshops and other educational materials:
- Free Workshop: Acid-base analysis
- RACE-Approved Course: Intravenous potassium supplementation
I appreciate you sharing this blog post. Thanks Again. Cool.