Two-dimensional and Doppler echocardiography are essential to the noninvasive assessment of patients with suspected PH. Echocardiography can demonstrate cardiac structural changes such as right atrial or right ventricular enlargement, right ventricular hypertrophy, and PA enlargement. Flattening or leftward shift of the interventricular septum can also be identified. If the shift occurs during systole, it suggests ventricular pressure overload. If it occurs during diastole, it suggests volume overload. Leftward shift of the septum throughout the cardiac cycle suggests both right ventricular pressure and volume overload (A, B). The left ventricle is often small and underfilled in PH, with normal systolic function (B).
Echocardiography is also useful to assess the severity of tricuspid regurgitation (TR) and estimate pulmonary artery systolic pressure (PASP). PASP is estimated by entering the peak velocity of the TR jet right into the modified Bernoulli equation and adding the right atrial pressure estimated by evaluating respiratory change in the inferior vena cava diameter (PASP = 4v2 + right atrial [RA] pressure) (C). Noninvasive PA pressure assessment is not only important in establishing a diagnosis of PH but also in monitoring response to therapy. Echocardiography-estimated PASP may by inaccurate when the peak velocity cannot be accurately assessed due to minimal TR, an eccentric TR jet, or severe TR. In patients with risk factors for PH and who have signs and symptoms concerning for PH, low estimated PASP may not exclude PH.
Echocardiography can also be helpful in detecting left-sided heart disease. A dilated, hypocontractile left ventricle, valvular disease, or left atrial myxoma can be identified or excluded on a routine echocardiogram. Color-flow and agitated saline injection can also be used to assess for the existence of congenital intracardiac or intrapulmonary shunts.