A Critical Review of Patent Foramen Ovale Detection Using Saline Contrast Echocardiography: When Bubbles Lie

Forame oval patente e acidente vascular cerebral isquêmico em jovens: associação causal ou estatística?

“…Several epidemiological studies, many of them cited here, point to this direction. Although the pressure in the right atrium is lower than the pressure in the left atrium, in several physiological situations (posture, inhalation, coughing, Valsalva maneuver) 36 there is an inversion of this gradient favoring right/left shunt in the presence of a patent foramen ovale. On the other hand, we know that patients with pulmonary artery hypertension and PFO waiting for a transplantation have a longer survival 37 .…”

Detection of Intracardiac and Intrapulmonary Shunts at Rest and During Exercise Using Saline Contrast Echocardiography

“…Echocardiography used as a technique for the detection of right-to-left shunts assumes that intravenously-infused saline contrast bubbles are filtered out by the pulmonary capillaries or collapse before reaching the left side of the heart (Yang, 1971;Yang et al, 1971a, b et al, 1980a;Meltzer et al, 1980b;Meltzer et al, 1981;Bommer et al, 1984;Woods & Patel, 2006). Thus, large diameter bubbles do not reach the left side of the heart unless they travel through large diameter pathways such as pulmonary arteriovenous malformations (PAVMs) or a PFO.…”

“…In general, if bubbles appear on the left side of the heart in ≤ 3 heart beats, then an intracardiac shunt is suspected, e.g. patent foramen ovale, atrial septal defect (Meltzer et al, 1980a;Woods & Patel, 2006). If an intracardiac shunt is suspected, then a second contrast injection should be performed upon the subject's release of a Valsalva maneuver (Woods & Patel, 2006).…”

“…patent foramen ovale, atrial septal defect (Meltzer et al, 1980a;Woods & Patel, 2006). If an intracardiac shunt is suspected, then a second contrast injection should be performed upon the subject's release of a Valsalva maneuver (Woods & Patel, 2006). Performing and releasing the Valsalva maneuver transiently elevates right heart pressure, which reverses the pressure gradient between the atria, creating conditions favorable for right-sided contrast to move to the left side of the heart across the intracardiac shunt.…”

“…Other diseases associated with arterial hypoxemia such as hepatopulmonary syndrome and hereditary hemorrhagic telangiectasia are known to have arteriovenous malformations that will allow for the transpulmonary passage of saline contrast bubbles under resting conditions (Woods & Patel, 2006). Thus, patients with underlying lung diseases and arterial hypoxemia, may desaturate further as a result of the opening of hypoxia-induced intrapulmonary arteriovenous anastomoses.…”