The foramen ovale is a remnant of the fetal circulation that remains patent in 20-25% of the adult population. Although long overlooked as a potential pathway that could produce pathologic conditions, the presence of a patent foramen ovale (PFO) has been associated with a higher than expected frequency in a variety of clinical syndromes including cryptogenic stroke, migraines, sleep apnea, platypnea-orthodeoxia, deep sea diving associated decompression illness, and high altitude pulmonary edema. A unifying hypothesis is that a chemical or particulate matter from the venous circulation crosses the PFO conduit between the right and left atria to produce a variety of clinical syndromes. Although observational studies suggest a therapeutic benefit of PFO closure compared to medical therapy alone in patients with cryptogenic stroke, 3 randomized controlled trials (RCTs) did not confirm the superiority of PFO closure for the secondary prevention of stroke. However, meta-analyses of these RCTs demonstrate a significant benefit of PFO closure over medical therapy alone. Similarly, observational studies provide support for PFO closure for symptomatic relief of migraines. But one controversial randomized study failed to replicate the results of the observational studies while another two demonstrated a partial benefit. The goal of this review is to discuss the clinical conditions associated with PFO and provide internists and primary care physicians with current data on PFO trials, and clinical insight to help guide their patients who are found to have a PFO on echocardiographic testing.

Background

Transcranial Doppler (TCD) with agitated saline has been shown to be an alternative for the detection of right-to-left shunts (RLS) with similar diagnostic accuracies as transesophageal echocardiography (TEE). It is hypothesized that the addition of blood to agitated saline increases the sensitivity of TCD for the detection of RLS. The aim of this meta-analysis was to determine whether agitated saline with blood increases the sensitivity of TCD for the detection of RLS compared to agitated saline alone and other contrast agents.

Method

A systematic review of Medline, Cochrane, and Embase was performed to look for all prospective studies assessing intracardiac RLS using TCD compared with TEE as the reference; both tests were performed with a contrast agent and a maneuver to provoke RLS in all studies.

Results

A total of 27 studies (29 comparisons) with 1,968 patients met the inclusion criteria. Of 29 comparisons, 10 (35%) used echovist contrast during TCD, 4 (14%) used a gelatin-based solution, 12 (41%) used agitated saline, and 3 (10%) utilized 2 different contrast agents. The addition of blood to agitated saline improved the sensitivity of TCD to 100% compared to agitated saline alone (96% sensitivity, P = 0.161), echovist (94% sensitivity, P = 0.044), and gelatin-based solutions (93% sensitivity, P = 0.041).

Conclusion

The addition of blood to agitated saline improves the sensitivity of TCD for the detection of RLS to 100% when compared to other conventional contrast agents; these findings support the addition of blood to agitated saline during TCD bubble studies.