Sensitivity of brachial versus femoral vein injection of agitated saline to detect right-to-left shunts with Transcranial Doppler.

BACKGROUND: Transcranial Doppler (TCD) can detect a right-to-left shunt (RLS) with high sensitivity but has a 5% chance of a false negative study. TCD is usually performed with injection of agitated saline into an arm vein. We compared the sensitivity of TCD performed from the brachial versus femoral veins.
METHODS: Patients presenting to the cardiac catheterization laboratory for percutaneous closure of a patent foramen ovale (PFO) were enrolled. Power M-mode Transcranial Doppler (Terumo 150 PMD) was conducted. After injection of a mixture of 8 cc of agitated saline, 0.5 cc of air, and 1 cc of blood into the brachial vein, embolic tracks were counted over the middle cerebral arteries. The degree of RLS was evaluated by TCD at rest, and with Valsalva at 40 mmHg aided by visual feedback with a manometer device. The test was repeated using femoral venous injections.
RESULTS: Sixty five patients were enrolled, mean age 52, 43% male. TCD grades were significantly higher with femoral injections compared to brachial injections at rest (p<0.0001), and with the Valsalva maneuver (p<0.0001). The presence of a RLS was confirmed by intracardiac echocardiography (ICE) during cardiac catheterization in 62 (95.4%) patients.
CONCLUSION: The sensitivity of TCD for detection of RLS is increased when agitated saline injections are performed through the femoral vein. In patients with a high clinical suspicion for RLS, low TCD grades obtained with traditional brachial venous access should be interpreted with caution. When possible, a repeat study using femoral venous access may be considered.