Contrast echocardiographic visualization of cough-induced right to left shunt through a patent foramen ovale

In a series of 24 consecutive patients referred to the echocardiography laboratory because of suspected patent foramen ovale, contrast two-dimensional and M-mode echocardiographic studies were performed during normal breathing and during two provocative tests: the Valsalva maneuver and cough. A right to left shunt was visualized in 8 patients during normal breathing, in 11 patients during the Valsalva maneuver and in 17 patients during the cough test. Cardiac catheterization performed in all 24 patients and postmortem examination available in 3 patients confirmed the patency of the foramen ovale in only 15 patients. In these 15 patients, echo contrast appeared in the left heart cavities in early systole and almost simultaneously with complete right heart opacification. In contrast, for the two false positive results during the cough test, ultrasound contrast appeared at any time of the cardiac cycle when the right heart cavities had been partially cleared of contrast material. Right and left atrial pressures were simultaneously measured in four patients, and the normal interatrial pressure gradient was reversed during the Valsalva maneuver and the cough test. Echocardiography during both provocative tests showed that the interatrial septum flattened or became convex toward the left atrium. The cough test appears to be more reliable and easier to perform in critically ill patients than the Valsalva maneuver for the detection of right to left shunting through a patent foramen ovale.