Echocardiographic assessment of pulmonary hypertension
Echocardiography is the screening method of choice for suspected pulmonary hypertension. Echocardiography has two roles: one, to screen for causes of increased right-sided pressures, such as atrial and ventricular shunts, congenital abnormalities, valvular diseases, reduced LV function and more; two, to assess qualitatively and quantitatively the severity of pulmonary hypertension and to determine the patients' prognosis.
Transthoracic echocardiography is sufficient for initial screening and assessment of hemodynamic severity in many cases. Transesophageal echocardiography is recommended for a more precise identification (or exclusion) of structural abnormalities as cause of pulmonary hypertension, e. g. anomalous pulmonary veins.
In the presence of tricuspid regurgitation and pulmonary insufficiency Doppler echocardiography allows a rough estimation of systolic and diastolic pulmonary artery pressures. Measurement of tricuspid regurgitant (TR) jet velocity by continuous wave Doppler echocardiography gives an estimation of RV systolic pressure (PAP). The end-diastolic velocity of pulmonary regurgitation reflects the end-diastolic pressure gradient between pulmonary artery and right ventricle. Adding right atrial pressure to the gradient allows assessment of systolic and diastolic pulmonary artery pressures. The early diastolic peak pulmonary regurgitant velocity and the RV outflow acceleration time allows estimation of mean PAP [1,2,3,4].
All Doppler echocardiographic measurements should be performed at breathhold or endexpiration and over three cardiac cycles. An insufficient tricuspid regurgitation signal ca be enhanced by administration of agitated saline.
Echocardiograph assessment of systolic PAP has several limitations: In patients with severe TR Doppler echocardiography tends to overestimate PAP . The estimation of RAP is often a source of error [6,7]. As a consequence, estimation of systolic PAP based on Doppler echocardiography is not suitable for screening for mild, asymptomatic pulmonary hypertension .
In the echocardiography report we recommend to indicate the TR pressure gradient and systolic PAP. The assumed RAP should be indicated together with the method that was used for its estimation, e.g. height of jugular vein pressure. To document the hemodynamic implication cardiac output should be estimated.
Indirect signs of pulmonary hypertension
There are several signs which should raise the attention to a possible presence of pulmonary hypertension:
- Cardiac morphology
Increased dimensions of right heart chambers, abnormal shape and function of the interventricular septum, increased RV wall thickness and dilated main pulmonary artery . The shape of the interventricular septum allows an echocardiographic differentiation of RV pressure overload vs. volume overload, if right sided heart chambers are enlarged.
((to add: echo picture and clip of a severe cor pulmonare))Doppler echocardiographic signs
- A short acceleration time of RV ejection in the pulmonary artery, increased velocity of pulmonary valve regurgitation, notching of pulmonary valve (midsystolic closure of the pulmonary valve at high speed sweep), short isovolumic relaxation time (best measured on RV TDI), diminished or absent atrial wave (a-wave) of the pulmonary valve.
Hepatic vein velocity has a characteristic pattern in patients with pulmonary hypertension. Increased diastolic pressure and decreased compliance of the right ventricle results in a prominent atrial flow reversal in the hepatic vein.
There is a lack of confirmatory data whether stress Echocardiography is able to detect pulmonary hypertension present only under exercise. It is therefore not recommended for screening .