Patent foramen ovale is involved in many clinical situations, including cryptogenic stroke, decompression sickness, migraine, massive pulmonary embolism and acute cor pulmonale [3, 4]. Moreover, Boon et al. identified PFO as a risk factor for fatal outcome after severe asthma attack [5].
In the case here reported, the acute and transient increase in pulmonary pressure due to a severe asthma attack was probably responsible for the increased shunt through the foramen ovale, with low SpO2 values persisting for several days after the asthma attack was resolved.
Transthoracic echocardiographic evaluation (TTE) is the first approach in PFO diagnosis: transthoracic ultrasound both with color Doppler function and with microbubbles contrast has medium–high (46% to 78%) sensitivity, 99% of specificity in detecting PFO and its noninvasiveness and easiness to perform explains why it represents the first tool during diagnosis [6].
Transesophageal (TEE) evaluation increases sensitivity in PFO diagnosis up to 90% and represents the gold standard diagnostic technique; however, the acknowledged benefits should be weighed against the greater invasiveness and potentially complications [7, 8].
Transcranial Doppler is another diagnostic tool with high sensitivity and specificity of 97% and 93%, respectively, and could be used in addition to TEE examination to increase specificity and sensitivity while pre-operative studying before PFO closure [9].
Patent foramen ovale findings in the ICU could be asymptomatic or, as in the present case, the result of an adaptive response; however, PFO is a very frequent finding with uncertain significance in patients with severe ARDS and acute cor pulmonale [10].
It is also curiously reported that a right-to-left shunt can occur during normal right heart cameras’ pressures [11]. In the case here described, we did not find indirect signs of pulmonary hypertension such as abnormal TAPSE or right ventricular enlargement; however, we reasoned that PFO could have lowered right atrial pressure as well as a good left ventricular ejection fraction kept end diastolic pressure low, avoiding secondary pulmonary hypertension due to high left atrial pressure.
The question “What should I do if PFO is diagnosed?” often implies PFO closure in young patients after cryptogenic stroke. However, the debate about what to do when PFO occurs as an incidental finding is ongoing.
Ng et al. described the increased risk of peri-operative cerebral ischemic stroke in patients for whom PFO was diagnosed during a pre-operative examination [10].
Treatment options include medical therapy—mainly antiplatelet therapy or anticoagulants—and percutaneous PFO closure or via cardiac surgery if the atrium has to be opened as part of a scheduled surgical procedure. There remains a lack of strong evidence that the incidence of stroke is significantly reduced after PFO closure, although recent trials have shown several advantages to the procedure [12].
