Echocardiography is a non-invasive imaging technique that uses sound waves to create detailed images of the heart. It helps healthcare professionals assess the heart’s structure and function. The parasternal long axis (PLAX) view is a fundamental and frequently employed starting point in an echocardiographic examination. This view offers a specific cross-section of the heart, providing valuable insights into its mechanics.
Understanding the Parasternal Long Axis View
Obtaining the parasternal long axis (PLAX) view involves positioning the patient on their left side, often with their left arm raised. The ultrasound probe is placed on the left side of the chest, usually in the third or fourth intercostal space, adjacent to the sternum. The probe’s indicator is directed towards the patient’s right shoulder, typically at the 9 to 10 o’clock position. This placement and orientation allow the ultrasound beam to slice through the heart longitudinally, revealing its chambers and valves. The resulting image provides a clear perspective of structures from the base towards the apex.
Heart Structures Clearly Visible in PLAX
The parasternal long axis view provides clear visualization of several heart structures. The Left Ventricle (LV) is seen in its long axis, although its apex typically remains out of view. The Left Atrium (LA) appears posterior to the aortic root. Between these two chambers, the Mitral Valve is well-demonstrated, allowing assessment of its anterior and posterior leaflets.
Above the mitral valve, the Left Ventricular Outflow Tract (LVOT) is clearly visible, leading into the Aortic Valve. This valve, along with the proximal part of the Aorta (aortic root and ascending aorta), is also well-visualized. The Right Ventricular Outflow Tract (RVOT) is seen as the most anterior structure, located near the top of the image. The interventricular septum, which separates the left and right ventricles, is also clearly seen.
Limitations of the Parasternal Long Axis View
The parasternal long axis view does not provide a complete picture of all four heart chambers. The Right Atrium (RA) and the main body of the Right Ventricle (RV) are not well-visualized. The Tricuspid Valve, which separates the right atrium and right ventricle, is also largely obscured.
These limitations arise from the angle of the ultrasound beam and the heart’s anatomical orientation. The PLAX view primarily focuses on left-sided structures and outflow tracts, leaving the right atrium and most of the right ventricle outside the optimal imaging plane. Other echocardiographic views are necessary for a comprehensive evaluation of the entire heart.
Clinical Significance of the PLAX View
The parasternal long axis view is clinically important. This view allows assessment of the Left Ventricle’s size and function, including its wall thickness and internal diameter. Observing mitral valve leaflet movement offers insights into the heart’s pumping ability. For instance, a vigorous left ventricular contraction causes the mitral valve’s anterior leaflet to nearly touch the interventricular septum during diastole, indicating good function.
Healthcare providers use the PLAX view to evaluate the Mitral and Aortic Valves for issues like narrowing (stenosis) or leakage (regurgitation). Measurements of the aortic root and ascending aorta can be performed, aiding in detecting conditions like aneurysmal dilation. The PLAX view is often the initial view in a cardiac ultrasound examination due to its diagnostic yield and ease of acquisition, serving as a foundation for further, more specialized views.