Echocardiography (echo) is a non-invasive imaging technique primarily used to assess the heart's structure and function. However, it also plays a crucial role in evaluating pulmonary hypertension (PH), a condition characterized by high blood pressure in the arteries of the lungs. Therefore, "pH on echo" refers to the estimation of pulmonary artery pressure using echocardiographic measurements. This is not a direct pH measurement (measuring acidity/alkalinity) but rather an indirect assessment of pressure within the pulmonary arteries.
Using Echo to Assess Pulmonary Hypertension
An echocardiogram can reveal several indicators of pulmonary hypertension, including:
- Elevated right ventricular systolic pressure (RVSP): This is a key indicator estimated from the echo. While not a direct measure of mean pulmonary arterial pressure (mPAP), RVSP provides a valuable clinical approximation. A right ventricular systolic pressure of 33 to 39 mm Hg, for example, is considered mild echocardiographic pulmonary hypertension and is associated with higher mortality (as noted in this JAMA Cardiology article).
- Right atrial and right ventricular enlargement: Increased pressure in the pulmonary arteries can lead to enlargement of the right side of the heart.
- Pulmonary artery dilation: The pulmonary arteries may appear wider than normal on the echo.
- Changes in tricuspid valve flow: The flow of blood across the tricuspid valve (between the right atrium and right ventricle) may show altered patterns indicative of increased pulmonary pressure.
Note: While echocardiography is an important screening tool for PH (LITFL article), a definitive diagnosis of PH, particularly for guiding treatment decisions, often requires right heart catheterization ([reference 1](Echocardiography should be used to assess the probability of PH being present. Confirmation with right heart catheterisation is warranted if a definitive diagnosis of PH is needed, particularly if pre-capillary PH-specific therapies may be indicated.)). This is because echocardiography provides an estimated pulmonary artery pressure, not a precise measurement. Pulmonary hypertension is defined as a mean arterial pressure of ≥25 mmHg as confirmed on right heart catheterisation (reference from NCBI).
Echo's Role in Differentiating Types of Pulmonary Hypertension
Echocardiography can also help differentiate between different types of PH, such as pre-capillary and post-capillary PH (reference). This distinction is crucial for appropriate treatment strategies.
In Summary
"pH on echo" isn't a literal pH value but rather a clinical shorthand referring to the estimation of pulmonary artery pressure through echocardiographic examination. This estimation helps screen for and assess the severity of pulmonary hypertension, a condition that requires further investigation using methods such as right heart catheterization for definitive diagnosis and treatment planning.
