Saline Solution
The use of echo contrast improved the detection of the PFO relative to PW Doppler color. Recent studies have shown that a transthoracic echo contrast with a similar accuracy has a transesophageal echo.
Contrast is a mixture of 8 ml physiological saline (NaCl) with 0.5- 1.0ml air and 0.5- 1.0ml blood. First we look without the Valsalva maneuver, but no outcome is found, so we then use the Valsalva maneuver and this gives a result. A contrast echo is done with a AP4Ch or subcostale4Ch recording. The contrast is in the right atrium. In a positive test, it is seen crossing to the left atrium. The number of heart beats have to be counted. If there is seen in the LA contrast within 3 cardiac cycles, it is considered an intracardiac shunt. If it takes longer than three cardiac cycles are called an intrapulmonary shunt.
The risk of contrast ultrasound is very low, according to a study by the American Society of echocardiography there is about 0:06 % chance of a side effect of contrast by saline.
Example
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