As a pediatric echosonographer, pulmonary hypertension is one of the most common problems that you will encounter, especially in babies born prematurely.
Systemic hypertension occurs when blood pressure is abnormally high in the aorta and its branches (left sided circulation). This pressure is obtained with a blood pressure machine and a cuff. Pulmonary hypertension occurs when there is abnormally high blood pressure in the pulmonary artery and its branches (right sided circulation). This pressure must be obtained in a more indirect way.
Most premature neonates (born before the normal gestational age of 40 weeks) will have pulmonary hypertension (PHTN), since the lungs are the last organs of the body to fully develop. Any other congenital defects in which blood flow is abnormally shunted from the left side of the heart to the right side of the heart are contributing factors. Any time a significant amount of blood shunts to the right side of the heart, volume and or pressure problems occur.
As the pressure in the lungs increase, the vasculature and the lungs will constrict in order to prevent pulmonary overflow. Eventually, this will lead to right ventricular hypertrophy and fibrosis of the vasculature of the lungs, a condition known as cor pulmonale.
As an echocariographer, it is extremely important that the right ventricle is evaluated completely, and its pressure is measured accurately. RVSP may be measured in three ways:
1) Measure the tricuspid regurgitation gradient. This gradient is the difference in pressure between the right ventricle and the right atrium. Add 5 mmHg to the gradient to compensate for central venous pressure (not 10 mmHg as in adults). The result is the RVSP.
2) Measure the PDA (patent ductus arteriosis) gradient. The PDA gradient is the difference in pressure between the aorta and the pulmonary artery. Subtract the PDA gradient from the systolic systemic blood pressure. The result is the RVSP.
3) Measure the VSD (ventricular septal defect) gradient. Note: this is only possible if there is a VSD present. The VSD gradient is the difference in pressure between the right and left ventricles. Subtract the VSD gradient from the systolic systemic pressure. The result is the RVSP.
Examples
Where the systemic blood pressure is 75/35 mmHg, systolic systemic blood pressure is 75 mmHg, and central venous pressure is assumed at 5 mmHg:
Tricuspid regurgitation gradient (TRg)= 20 mmHg
20 mmHg (TRg) + 5 mmHg (CVP) = 25 mmHg (RVSP)
VSD gradient (VSDg) = 50 mmHg
75 mmHg (SBP) – 50 mmHg (VSDg) = 25 mmHg (RVSP)
PDA gradient (PDAg) = 50 mmHg
75 mm Hg (SBP) – 50 mmHg (PDAg) = 25 mmHg (RVSP)
The best way to measure RVSP is to use the tricuspid regurgitation gradient. Keep in mind that it is important to get a good regurgitant envelope. This is very important and it can not be understated. A partial envelope or just a “valve click” will not do.
Be sure to Doppler tricuspid regurgitation in as many views as possible. Always use the highest gradient obtained and try to make the continuous wave curser as parallel to flw as possible. It is extremely important to provide the pediatric cardiologist or the neo-natologist with an accurate assessment of right ventricular pressures, as these can be life or death situations.
It is not always possible to measure (RVSP). If you can not do the measurement accurately, then specify this on the worksheet.