Right-to-left shunt detection sensitivity with air–saline and air–succinil gelatin transcranial Doppler

Abstract

Background

Air–saline transcranial Doppler is nowadays the first-choice examination to identify right-to-left shunt. To increase right-to-left shunt detection in echocardiography, cardiologists also use air–gelatin mixtures, which are more stable, more echogenic, and easier to be prepared.

Aim

We assessed the sensitivity of air–gelatin compared with air–saline for transcranial Doppler right-to-left shunt detection.

Methods

Air–saline transcranial Doppler, during unilateral middle cerebral artery monitoring at rest and after Valsalva maneuver, was performed in patients referred to our neurosonology laboratory for right-to-left shunt detection. The same transcranial Doppler protocol was repeated with air–gelatin. To consider transcranial Doppler positive for cardiac right-to-left shunt, at least one embolic signal had to be detected within 20″ from contrast injection. Later signals were interpreted of pulmonary origin. Trans-thoracic echocardiography was repeated with both air–saline and air–gelatin.

Results

A total of 97 patients were enrolled; 46 had negative transcranial Doppler for cardiac right-to-left shunt with both air–saline and air–gelatin; out of these, four patients with air–saline plus two more patients with air–gelatin presented late, isolated microemboli, slightly more numerous with air–gelatin: these were interpreted as pulmonary shunts and confirmed with trans-thoracic echocardiography. In 28 patients with already early positive air–saline transcranial Doppler at rest, air–gelatin induced a marked right-to-left shunt increase, facilitating its visualization at trans-thoracic echocardiography. In 23 patients in whom air–saline transcranial Doppler was negative at rest and positive for cardiac right-to-left shunt only after Valsalva maneuver, air–gelatin was able to reveal shunt also at rest.

Conclusions

Air–gelatin increases right-to-left shunt detection sensitivity with transcranial Doppler in particular at rest, even in patients in whom air–saline mixture fails to identify the shunt. The choice of air–gelatin mixture should be considered for multicentric, clinical, and research trials.