Contrast-enhanced transthoracic echocardiography applied in evaluation of pulmonary right-to-left shunt: A preliminary study

Objective: To investigate the detection rate of patent foramen ovale-right to left shunt (PFO-RLS) and/or pulmonary-right to left shunt (P-RLS) via contrast-enhanced transthoracic echocardiography (c-TTE) in healthy participants, patients suffering from cryptogenic stroke and migraine with aura.

Methods: Initially, 20 healthy volunteers, 21 cases with cryptogenic stroke, and 18 cases with migraine aura were randomly selected, and all of them received c-TTE and transesophageal echocardiography (TEE) examinations. First of all, 0.9% sodium chloride solution was rapidly injected into upper extremiry vein, when these volunteers and patients were at rest or following a Valsalva maneuver with 40 mm Hg pressure exerted against a manometer. Secondly, c-TTE detection was carried out in order to distinguish PFO-RLS and P-RLS and make semi-quantitative classification of RLS from many different sources, according to the occurrence and duration time of microvesicles in left atrial after the developing of left atrium. In terms of c-TTE analyses, RLS could be diagnosed when micro bubbles were visualized in transition from the right atrium to the left atrium. Particularly, a small amounts of RLS was 1 level, indicating 1-10 microvesicles per frame could be seen in left atrium, moderate amounts of RLS was 2 level, indicating 11-30 microvesicles per frame could be seen in left atrium, and a large amounts of RLS was 3 level, indicating more than 30 microvesicles per frame, or the left atrium is filled with micro vesicles.

Results: A total of 20 healthy adult volunteers were identified into this research. RLS was detected in 7 cases, according to c-TTE method (7/20, 35%). In detail, 3 participants suffered from PFO-RLS and P-RSL (3/20, 15%) simultaneously, 5 cases suffered from PFO-RLS (5/20, 25%), and 5 cases suffered from P-RLS (5/20, 25%). Among 21 patients with cryptogenic stroke, RLS was detected in 14 cases, according to cTTE method (14/20, 67%), and then compared with healthy participants group, the difference between them was significant (χ² = 4.11, P = 0.04). Specifically, 2 participants suffered from PFO-RLS and P-RSL (2/21, 9.5%), 11 cases suffered from PFO-RLS (11/21, 52.4%), and 5 cases suffered from P-RLS (5/21, 23.8%). Among 21 patients suffering from migraine with aura, RLS was detected in 13 cases, according to c-TTE method (13/18, 72%), and then compared with healthy participants group, the difference of detection rate between them was significant (χ² = 5.2, P = 0.02). In detail, 3 participants suffered from PFO-RLS and P-RSL (3/18, 16.7%), 8 cases suffered from PFO-RLS (8/18, 44.4%), and 8 cases suffered from P-RLS (8/18, 44.4%). In addition, the grading of PFO-RLS in patients suffering from cryptogenic stroke and migraine with aura was mostly grade 2-grade 3. On the contrary, the grading of PFO-RLS in healthy adult volunteers was mostly grade 1-2. Besides, the semi-quantitative grading of P-RLS in each group was mostly grade 1 to grade 2, and difference between healthy volunteer group and cryptogenic stroke group was significant (Z = -2.77, P = 0.006).

Conclusion: P-RLS with lower semiquantitative grade is common in healthy individuals, patients with cryptogenic stroke and migraine aura. And P-RLS can be considered as a significant influencing factor in the pathogenesis of migraine with aura.