Measurement of Pulmonary Hypertension

Is echo enough?

Pulmonary arterial hypertension is a common repercussion in valve diseases. When we have increased values for pulmonary arteries, there is much discussion around it. From situations in which a doctor thinks about contraindicating any intervention, even when determining a worse prognosis for a certain group of patients.

The gold standard for measuring pressure in the pulmonary artery trunk is cardiac catheterization on the right side, as it is able to measure the real pressure inside that cavity. However, it is an invasive method and is not without complications.

With the advent of echocardiography, a non-invasive method that manages to estimate intracavitary pressures through the speed of blood has been disseminated. We achieve it by using the modified Bernoulli equation (4v2), but as mentioned, it is an estimate.

Much is discussed about the correlation between the methods and whether the use of echocardiography would be sufficient to estimate the real value of pulmonary arterial pressure. Several studies have been conducted to try to find the right correlation and the results are very encouraging. The echocardiographic measurement through the speed of the tricuspid regurgitation jet brings very high sensitivity and specificity, around 85-90% when the vast majority of publications are observed. The correlation index is also very high, around r = 0.90.

However, the cardiologist who evaluates the patient must be aware of some limitations inherent in the method. Bernoulli’s equation uses the speed of blood flow during right ventricular systole that regurgitates into the right atrium. In this way, he estimates the pressure difference between these cavities. Faced with a common situation in valve diseases, a failure of coaptation of the tricuspid valve would lead to an equalization of the pressures between the right atrium and the right ventricle, since through the basic physical principle that communicating chambers tend to equalize pressures; we will see a value changed between the cavities.

Another point worth mentioning is the individual who does not have any tricuspid reflux. In this case, it is impossible to estimate the pressure difference between the cavities, since there is no reflux velocity to be measured.

We should also keep in mind that the echocardiogram is an examiner-dependent method, that is, the echocardiographer must respect the basic technical guidelines to obtain a reliable measurement, such as, for example, aligning the reflux jet with the continuous doppler guidance line, since deviations greater than 20 degrees lead to errors of at least 6% in the estimated values.

In regards to this aforementioned, echocardiography is an excellent non-invasive method for estimating pulmonary artery pressure, serving adequately for preoperative assessment, as well as for estimating prognosis and outcomes in a population of patients with heart valve disease.

Suggested literature:

1 – Sohrabi B, Kazemi B, Mehryar A, et al. Correlation between Pulmonary Artery Pressure Measured by Echocardiography and Right Heart Catheterization in Patients with Rheumatic Mitral Valve Stenosis (A Prospective Study). Echocardiography. 2016 Jan;33(1):7-13.

 

Download Paper